Add and process notifications for Imports (#2656)

This builds support for tracking the effect of changes to imports on
other documents, and completes our model for being able to keep
generated code up to date.

benchmarks/Microsoft.AspNetCore.Razor.Performance/ProjectSystem/ProjectSnapshotManagerBenchmarkBase.cs

@@ -132,14 +132,6 @@ namespace Microsoft.AspNetCore.Razor.Performance
 
         private class StaticProjectSnapshotProjectEngineFactory : ProjectSnapshotProjectEngineFactory
         {
-            public override RazorProjectEngine Create(ProjectSnapshot project, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
-            {
-                return RazorProjectEngine.Create(project.Configuration, fileSystem, b =>
-                {
-                    RazorExtensions.Register(b);
-                });
-            }
-
             public override IProjectEngineFactory FindFactory(ProjectSnapshot project)
             {
                 throw new NotImplementedException();
@@ -149,6 +141,14 @@ namespace Microsoft.AspNetCore.Razor.Performance
             {
                 throw new NotImplementedException();
             }
+
+            public override RazorProjectEngine Create(RazorConfiguration configuration, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
+            {
+                return RazorProjectEngine.Create(configuration, fileSystem, b =>
+                {
+                    RazorExtensions.Register(b);
+                });
+            }
         }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/DefaultRazorProjectFileSystem.cs

@@ -49,6 +49,10 @@ namespace Microsoft.AspNetCore.Razor.Language
             var absolutePath = NormalizeAndEnsureValidPath(path);
 
             var file = new FileInfo(absolutePath);
+            if (!absolutePath.StartsWith(absoluteBasePath))
+            {
+                throw new InvalidOperationException($"The file '{file.FullName}' is not a descendent of the base path '{absoluteBasePath}'.");
+            }
 
             var relativePhysicalPath = file.FullName.Substring(absoluteBasePath.Length + 1); // Include leading separator
             var filePath = "/" + relativePhysicalPath.Replace(Path.DirectorySeparatorChar, '/');

src/Microsoft.CodeAnalysis.Razor.Workspaces/DefaultProjectSnapshotProjectEngineFactory.cs

@@ -32,13 +32,8 @@ namespace Microsoft.CodeAnalysis.Razor
             _factories = factories;
         }
 
-        public override RazorProjectEngine Create(ProjectSnapshot project, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
+        public override RazorProjectEngine Create(RazorConfiguration configuration, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
         {
-            if (project == null)
-            {
-                throw new ArgumentNullException(nameof(project));
-            }
-
             if (fileSystem == null)
             {
                 throw new ArgumentNullException(nameof(fileSystem));
@@ -55,7 +50,7 @@ namespace Microsoft.CodeAnalysis.Razor
             //
             // We typically want this because the language adds features over time - we don't want to a bunch of errors
             // to show up when a document is first opened, and then go away when the configuration loads, we'd prefer the opposite.
-            var configuration = project.Configuration ?? DefaultConfiguration;
+            configuration = configuration ?? DefaultConfiguration;
 
             // If there's no factory to handle the configuration then fall back to a very basic configuration.
             //

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSnapshotProjectEngineFactory.cs

@@ -45,7 +45,36 @@ namespace Microsoft.CodeAnalysis.Razor
             return Create(project, RazorProjectFileSystem.Create(Path.GetDirectoryName(project.FilePath)), configure);
         }
 
-        public abstract RazorProjectEngine Create(ProjectSnapshot project, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure);
+        public RazorProjectEngine Create(ProjectSnapshot project, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
+        {
+            if (project == null)
+            {
+                throw new ArgumentNullException(nameof(project));
+            }
 
+            if (fileSystem == null)
+            {
+                throw new ArgumentNullException(nameof(fileSystem));
+            }
+
+            return Create(project.Configuration, fileSystem, configure);
+        }
+
+        public RazorProjectEngine Create(RazorConfiguration configuration, string directoryPath, Action<RazorProjectEngineBuilder> configure)
+        {
+            if (configuration == null)
+            {
+                throw new ArgumentNullException(nameof(configuration));
+            }
+
+            if (directoryPath == null)
+            {
+                throw new ArgumentNullException(nameof(directoryPath));
+            }
+
+            return Create(configuration, RazorProjectFileSystem.Create(directoryPath), configure);
+        }
+
+        public abstract RazorProjectEngine Create(RazorConfiguration configuration, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure);
     }
 }

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/DefaultProjectSnapshot.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
 
@@ -58,9 +59,37 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             }
         }
 
+        public override bool IsImportDocument(DocumentSnapshot document)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+            
+            return State.ImportsToRelatedDocuments.ContainsKey(document.TargetPath);
+        }
+
+        public override IEnumerable<DocumentSnapshot> GetRelatedDocuments(DocumentSnapshot document)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+
+            if (State.ImportsToRelatedDocuments.TryGetValue(document.TargetPath, out var relatedDocuments))
+            {
+                lock (_lock)
+                {
+                    return relatedDocuments.Select(GetDocument).ToArray();
+                }
+            }
+
+            return Array.Empty<DocumentSnapshot>();
+        }
+
         public override RazorProjectEngine GetProjectEngine()
         {
-            return State.ProjectEngine.GetProjectEngine(this);
+            return State.ProjectEngine.GetProjectEngine(this.State);
         }
 
         public override Task<IReadOnlyList<TagHelperDescriptor>> GetTagHelpersAsync()

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/DefaultProjectSnapshotManager.cs

@@ -90,12 +90,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 var projects = new ProjectSnapshot[_projects.Count];
                 foreach (var entry in _projects)
                 {
-                    if (entry.Value.Snapshot == null)
+                    projects[i++] = entry.Value.GetSnapshot();
-                    {
-                        entry.Value.Snapshot = new DefaultProjectSnapshot(entry.Value.State);
-                    }
-
-                    projects[i++] = entry.Value.Snapshot;
                 }
 
                 return projects;
@@ -115,12 +110,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             if (_projects.TryGetValue(filePath, out var entry))
             {
-                if (entry.Snapshot == null)
+                return entry.GetSnapshot();
-                {
-                    entry.Snapshot = new DefaultProjectSnapshot(entry.State);
-                }
-
-                return entry.Snapshot;
             }
 
             return null;
@@ -175,8 +165,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[hostProject.FilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(hostProject.FilePath, document.FilePath, ProjectChangeKind.DocumentAdded));
+                    entry = new Entry(state);
+                    _projects[hostProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), document.FilePath, ProjectChangeKind.DocumentAdded));
                 }
             }
         }
@@ -201,8 +193,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[hostProject.FilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(hostProject.FilePath, document.FilePath, ProjectChangeKind.DocumentRemoved));
+                    entry = new Entry(state);
+                    _projects[hostProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), document.FilePath, ProjectChangeKind.DocumentRemoved));
                 }
             }
         }
@@ -229,12 +223,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 entry.State.Documents.TryGetValue(documentFilePath, out var older))
             {
                 ProjectState state;
-                SourceText olderText;
-                VersionStamp olderVersion;
 
                 var currentText = sourceText;
-                if (older.TryGetText(out olderText) && 
+                if (older.TryGetText(out var olderText) &&
-                    older.TryGetTextVersion(out olderVersion))
+                    older.TryGetTextVersion(out var olderVersion))
                 {
                     var version = currentText.ContentEquals(olderText) ? olderVersion : olderVersion.GetNewerVersion();
                     state = entry.State.WithChangedHostDocument(older.HostDocument, currentText, version);
@@ -256,8 +248,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[projectFilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(projectFilePath, documentFilePath, ProjectChangeKind.DocumentChanged));
+                    entry = new Entry(state);
+                    _projects[projectFilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), documentFilePath, ProjectChangeKind.DocumentChanged));
                 }
             }
         }
@@ -293,8 +287,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[projectFilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(projectFilePath, documentFilePath, ProjectChangeKind.DocumentChanged));
+                    entry = new Entry(state);
+                    _projects[projectFilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), documentFilePath, ProjectChangeKind.DocumentChanged));
                 }
             }
         }
@@ -321,12 +317,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 entry.State.Documents.TryGetValue(documentFilePath, out var older))
             {
                 ProjectState state;
-                SourceText olderText;
-                VersionStamp olderVersion;
 
                 var currentText = sourceText;
-                if (older.TryGetText(out olderText) &&
+                if (older.TryGetText(out var olderText) &&
-                    older.TryGetTextVersion(out olderVersion))
+                    older.TryGetTextVersion(out var olderVersion))
                 {
                     var version = currentText.ContentEquals(olderText) ? olderVersion : olderVersion.GetNewerVersion();
                     state = entry.State.WithChangedHostDocument(older.HostDocument, currentText, version);
@@ -346,8 +340,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[projectFilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(projectFilePath, documentFilePath, ProjectChangeKind.DocumentChanged));
+                    entry = new Entry(state);
+                    _projects[projectFilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), documentFilePath, ProjectChangeKind.DocumentChanged));
                 }
             }
         }
@@ -381,8 +377,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // Document updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[projectFilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-                    NotifyListeners(new ProjectChangeEventArgs(projectFilePath, documentFilePath, ProjectChangeKind.DocumentChanged));
+                    entry = new Entry(state);
+                    _projects[projectFilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), documentFilePath, ProjectChangeKind.DocumentChanged));
                 }
             }
         }
@@ -407,10 +405,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             var workspaceProject = GetWorkspaceProject(hostProject.FilePath);
 
             var state = ProjectState.Create(Workspace.Services, hostProject, workspaceProject);
-            _projects[hostProject.FilePath] = new Entry(state);
+            var entry = new Entry(state);
+            _projects[hostProject.FilePath] = entry;
 
             // We need to notify listeners about every project add.
-            NotifyListeners(new ProjectChangeEventArgs(hostProject.FilePath, ProjectChangeKind.ProjectAdded));
+            NotifyListeners(new ProjectChangeEventArgs(null, entry.GetSnapshot(), ProjectChangeKind.ProjectAdded));
         }
 
         public override void HostProjectChanged(HostProject hostProject)
@@ -429,9 +428,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 // HostProject updates can no-op.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[hostProject.FilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-
+                    entry = new Entry(state);
-                    NotifyListeners(new ProjectChangeEventArgs(hostProject.FilePath, ProjectChangeKind.ProjectChanged));
+                    _projects[hostProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), ProjectChangeKind.ProjectChanged));
                 }
             }
         }
@@ -445,12 +445,12 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             _foregroundDispatcher.AssertForegroundThread();
 
-            if (_projects.TryGetValue(hostProject.FilePath, out var snapshot))
+            if (_projects.TryGetValue(hostProject.FilePath, out var entry))
             {
-                _projects.Remove(hostProject.FilePath);
-
                 // We need to notify listeners about every project removal.
-                NotifyListeners(new ProjectChangeEventArgs(hostProject.FilePath, ProjectChangeKind.ProjectRemoved));
+                var oldSnapshot = entry.GetSnapshot();
+                _projects.Remove(hostProject.FilePath);
+                NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, null, ProjectChangeKind.ProjectRemoved));
             }
         }
 
@@ -477,9 +477,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 if (entry.State.WorkspaceProject == null)
                 {
                     var state = entry.State.WithWorkspaceProject(workspaceProject);
-                    _projects[workspaceProject.FilePath] = new Entry(state);
 
-                    NotifyListeners(new ProjectChangeEventArgs(workspaceProject.FilePath, ProjectChangeKind.ProjectChanged));
+                    var oldSnapshot = entry.GetSnapshot();
+                    entry = new Entry(state);
+                    _projects[workspaceProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), ProjectChangeKind.ProjectChanged));
                 }
             }
         }
@@ -505,14 +507,15 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 (entry.State.WorkspaceProject == null || entry.State.WorkspaceProject.Version.GetNewerVersion(workspaceProject.Version) == workspaceProject.Version))
             {
                 var state = entry.State.WithWorkspaceProject(workspaceProject);
-                
+
                 // WorkspaceProject updates can no-op. This can be the case if a build is triggered, but we've
                 // already seen the update.
                 if (!object.ReferenceEquals(state, entry.State))
                 {
-                    _projects[workspaceProject.FilePath] = new Entry(state);
+                    var oldSnapshot = entry.GetSnapshot();
-
+                    entry = new Entry(state);
-                    NotifyListeners(new ProjectChangeEventArgs(workspaceProject.FilePath, ProjectChangeKind.ProjectChanged));
+                    _projects[workspaceProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), ProjectChangeKind.ProjectChanged));
                 }
             }
         }
@@ -549,17 +552,21 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 {
                     // OK there's another WorkspaceProject, use that.
                     state = entry.State.WithWorkspaceProject(otherWorkspaceProject);
-                    _projects[otherWorkspaceProject.FilePath] = new Entry(state);
 
-                    NotifyListeners(new ProjectChangeEventArgs(otherWorkspaceProject.FilePath, ProjectChangeKind.ProjectChanged));
+                    var oldSnapshot = entry.GetSnapshot();
+                    entry = new Entry(state);
+                    _projects[otherWorkspaceProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), ProjectChangeKind.ProjectChanged));
                 }
                 else
                 {
-                    state = entry.State.WithWorkspaceProject(null);
-                    _projects[workspaceProject.FilePath] = new Entry(state);
-
                     // Notify listeners of a change because we've removed computed state.
-                    NotifyListeners(new ProjectChangeEventArgs(workspaceProject.FilePath, ProjectChangeKind.ProjectChanged));
+                    state = entry.State.WithWorkspaceProject(null);
+
+                    var oldSnapshot = entry.GetSnapshot();
+                    entry = new Entry(state);
+                    _projects[workspaceProject.FilePath] = entry;
+                    NotifyListeners(new ProjectChangeEventArgs(oldSnapshot, entry.GetSnapshot(), ProjectChangeKind.ProjectChanged));
                 }
             }
         }
@@ -601,7 +608,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             {
                 throw new ArgumentNullException(nameof(exception));
             }
-            
+
             _errorReporter.ReportError(exception, workspaceProject);
         }
 
@@ -644,13 +651,18 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private class Entry
         {
-            public ProjectSnapshot Snapshot;
+            public ProjectSnapshot SnapshotUnsafe;
             public readonly ProjectState State;
 
             public Entry(ProjectState state)
             {
                 State = state;
             }
+
+            public ProjectSnapshot GetSnapshot()
+            {
+                return SnapshotUnsafe ?? (SnapshotUnsafe = new DefaultProjectSnapshot(State));
+            }
         }
     }
 }

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/DocumentState.cs

@@ -183,6 +183,18 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             return state;
         }
 
+        public virtual DocumentState WithImportsChange()
+        {
+            var state = new DocumentState(Services, HostDocument, _sourceText, _version, _loader);
+
+            // The source could not have possibly changed.
+            state._sourceText = _sourceText;
+            state._version = _version;
+            state._loaderTask = _loaderTask;
+
+            return state;
+        }
+
         public virtual DocumentState WithWorkspaceProjectChange()
         {
             var state = new DocumentState(Services, HostDocument, _sourceText, _version, _loader);

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/EphemeralProjectSnapshot.cs

@@ -56,6 +56,26 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             return null;
         }
 
+        public override bool IsImportDocument(DocumentSnapshot document)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+
+            return false;
+        }
+
+        public override IEnumerable<DocumentSnapshot> GetRelatedDocuments(DocumentSnapshot document)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+
+            return Array.Empty<DocumentSnapshot>();
+        }
+
         public override RazorProjectEngine GetProjectEngine()
         {
             return _projectEngine.Value;

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/LiveShareProjectSnapshotBase.cs

@@ -27,6 +27,10 @@ namespace Microsoft.CodeAnalysis.Razor.Workspaces.ProjectSystem
 
         public override DocumentSnapshot GetDocument(string filePath) => throw new NotImplementedException();
 
+        public override bool IsImportDocument(DocumentSnapshot document) => throw new NotImplementedException();
+
+        public override IEnumerable<DocumentSnapshot> GetRelatedDocuments(DocumentSnapshot document) => throw new NotImplementedException();
+
         public override RazorProjectEngine GetProjectEngine() => throw new NotImplementedException();
 
         public override Task<IReadOnlyList<TagHelperDescriptor>> GetTagHelpersAsync() => throw new NotImplementedException();

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ProjectChangeEventArgs.cs

@@ -7,29 +7,39 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
     internal class ProjectChangeEventArgs : EventArgs
     {
-        public ProjectChangeEventArgs(string projectFilePath, ProjectChangeKind kind)
+        public ProjectChangeEventArgs(ProjectSnapshot older, ProjectSnapshot newer, ProjectChangeKind kind)
         {
-            if (projectFilePath == null)
+            if (older == null && newer == null)
             {
-                throw new ArgumentNullException(nameof(projectFilePath));
+                throw new ArgumentException("Both projects cannot be null.");
             }
 
-            ProjectFilePath = projectFilePath;
+            Older = older;
+            Newer = newer;
             Kind = kind;
+
+            ProjectFilePath = older?.FilePath ?? newer.FilePath;
         }
 
-        public ProjectChangeEventArgs(string projectFilePath, string documentFilePath, ProjectChangeKind kind)
+        public ProjectChangeEventArgs(ProjectSnapshot older, ProjectSnapshot newer, string documentFilePath, ProjectChangeKind kind)
         {
-            if (projectFilePath == null)
+            if (older == null && newer == null)
             {
-                throw new ArgumentNullException(nameof(projectFilePath));
+                throw new ArgumentException("Both projects cannot be null.");
             }
 
-            ProjectFilePath = projectFilePath;
+            Older = older;
+            Newer = newer;
             DocumentFilePath = documentFilePath;
             Kind = kind;
+
+            ProjectFilePath = older?.FilePath ?? newer.FilePath;
         }
 
+        public ProjectSnapshot Older { get; }
+
+        public ProjectSnapshot Newer { get; }
+
         public string ProjectFilePath { get; }
 
         public string DocumentFilePath { get; }

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ProjectEngineTracker.cs

@@ -2,6 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.IO;
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis.Host;
 
@@ -41,11 +45,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             return this;
         }
 
-        public RazorProjectEngine GetProjectEngine(ProjectSnapshot snapshot)
+        public RazorProjectEngine GetProjectEngine(ProjectState state)
         {
-            if (snapshot == null)
+            if (state == null)
             {
-                throw new ArgumentNullException(nameof(snapshot));
+                throw new ArgumentNullException(nameof(state));
             }
 
             if (_projectEngine == null)
@@ -55,12 +59,30 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                     if (_projectEngine == null)
                     {
                         var factory = _services.GetRequiredService<ProjectSnapshotProjectEngineFactory>();
-                        _projectEngine = factory.Create(snapshot);
+                        _projectEngine = factory.Create(state.HostProject.Configuration, Path.GetDirectoryName(state.HostProject.FilePath), configure: null);
                     }
                 }
             }
 
             return _projectEngine;
         }
+
+        public List<string> GetImportDocumentTargetPaths(ProjectState state, string targetPath)
+        {
+            var projectEngine = GetProjectEngine(state);
+            var importFeature = projectEngine.ProjectFeatures.OfType<IImportProjectFeature>().FirstOrDefault();
+            var projectItem = projectEngine.FileSystem.GetItem(targetPath);
+            var importItems = importFeature?.GetImports(projectItem).Where(i => i.FilePath != null);
+
+            // Target path looks like `Foo\\Bar.cshtml`
+            var targetPaths = new List<string>();
+            foreach (var importItem in importItems)
+            {
+                var itemTargetPath = importItem.FilePath.Replace('/', '\\').TrimStart('\\');
+                targetPaths.Add(itemTargetPath);
+            }
+
+            return targetPaths;
+        }
     }
 }

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ProjectSnapshot.cs

@@ -25,6 +25,17 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         public abstract DocumentSnapshot GetDocument(string filePath);
 
+        public abstract bool IsImportDocument(DocumentSnapshot document);
+
+        /// <summary>
+        /// If the provided document is an import document, gets the other documents in the project
+        /// that include directives specified by the provided document. Otherwise returns an empty
+        /// list.
+        /// </summary>
+        /// <param name="document">The document.</param>
+        /// <returns>A list of related documents.</returns>
+        public abstract IEnumerable<DocumentSnapshot> GetRelatedDocuments(DocumentSnapshot document);
+
         public abstract Task<IReadOnlyList<TagHelperDescriptor>> GetTagHelpersAsync();
 
         public abstract bool TryGetTagHelpers(out IReadOnlyList<TagHelperDescriptor> result);

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ProjectState.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Text;
@@ -12,10 +13,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
     // Internal tracker for DefaultProjectSnapshot
     internal class ProjectState
     {
-        private static readonly IReadOnlyDictionary<string, DocumentState> EmptyDocuments = new Dictionary<string, DocumentState>();
+        private static readonly ImmutableDictionary<string, DocumentState> EmptyDocuments = ImmutableDictionary.Create<string, DocumentState>(FilePathComparer.Instance);
-
+        private static readonly ImmutableDictionary<string, ImmutableArray<string>> EmptyImportsToRelatedDocuments = ImmutableDictionary.Create<string, ImmutableArray<string>>(FilePathComparer.Instance);
         private readonly object _lock;
-
+        
         private ProjectEngineTracker _projectEngine;
         private ProjectTagHelperTracker _tagHelpers;
 
@@ -43,6 +44,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             HostProject = hostProject;
             WorkspaceProject = workspaceProject;
             Documents = EmptyDocuments;
+            ImportsToRelatedDocuments = EmptyImportsToRelatedDocuments;
             Version = VersionStamp.Create();
 
             _lock = new object();
@@ -53,7 +55,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ProjectDifference difference,
             HostProject hostProject,
             Project workspaceProject,
-            IReadOnlyDictionary<string, DocumentState> documents)
+            ImmutableDictionary<string, DocumentState> documents,
+            ImmutableDictionary<string, ImmutableArray<string>> importsToRelatedDocuments)
         {
             if (older == null)
             {
@@ -70,12 +73,18 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 throw new ArgumentNullException(nameof(documents));
             }
 
+            if (importsToRelatedDocuments == null)
+            {
+                throw new ArgumentNullException(nameof(importsToRelatedDocuments));
+            }
+
             Services = older.Services;
             Version = older.Version.GetNewerVersion();
 
             HostProject = hostProject;
             WorkspaceProject = workspaceProject;
             Documents = documents;
+            ImportsToRelatedDocuments = importsToRelatedDocuments;
 
             _lock = new object();
 
@@ -84,7 +93,10 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
         }
 
         // Internal set for testing.
-        public IReadOnlyDictionary<string, DocumentState> Documents { get; internal set; }
+        public ImmutableDictionary<string, DocumentState> Documents { get; internal set; }
+
+        // Internal set for testing.
+        public ImmutableDictionary<string, ImmutableArray<string>> ImportsToRelatedDocuments { get; internal set; }
 
         public HostProject HostProject { get; }
 
@@ -152,17 +164,24 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             {
                 return this;
             }
-
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
-            foreach (var kvp in Documents)
-            {
-                documents.Add(kvp.Key, kvp.Value);
-            }
             
-            documents.Add(hostDocument.FilePath, DocumentState.Create(Services, hostDocument, loader));
+            var documents = Documents.Add(hostDocument.FilePath, DocumentState.Create(Services, hostDocument, loader));
 
-            var difference = ProjectDifference.DocumentAdded;
+            // Compute the effect on the import map
-            var state = new ProjectState(this, difference, HostProject, WorkspaceProject, documents);
+            var importTargetPaths = ProjectEngine.GetImportDocumentTargetPaths(this, hostDocument.TargetPath);
+            var importsToRelatedDocuments = AddToImportsToRelatedDocuments(ImportsToRelatedDocuments, hostDocument, importTargetPaths);
+            
+            // Now check if the updated document is an import - it's important this this happens after
+            // updating the imports map.
+            if (importsToRelatedDocuments.TryGetValue(hostDocument.TargetPath, out var relatedDocuments))
+            {
+                foreach (var relatedDocument in relatedDocuments)
+                {
+                    documents = documents.SetItem(relatedDocument, documents[relatedDocument].WithImportsChange());
+                }
+            }
+
+            var state = new ProjectState(this, ProjectDifference.DocumentAdded, HostProject, WorkspaceProject, documents, importsToRelatedDocuments);
             return state;
         }
 
@@ -177,17 +196,24 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             {
                 return this;
             }
+            
+            var documents = Documents.Remove(hostDocument.FilePath);
 
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
+            // First check if the updated document is an import - it's important that this happens
-            foreach (var kvp in Documents)
+            // before updating the imports map.
+            if (ImportsToRelatedDocuments.TryGetValue(hostDocument.TargetPath, out var relatedDocuments))
             {
-                documents.Add(kvp.Key, kvp.Value);
+                foreach (var relatedDocument in relatedDocuments)
+                {
+                    documents = documents.SetItem(relatedDocument, documents[relatedDocument].WithImportsChange());
+                }
             }
 
-            documents.Remove(hostDocument.FilePath);
+            // Compute the effect on the import map
+            var importTargetPaths = ProjectEngine.GetImportDocumentTargetPaths(this, hostDocument.TargetPath);
+            var importsToRelatedDocuments = RemoveFromImportsToRelatedDocuments(ImportsToRelatedDocuments, hostDocument, importTargetPaths);
 
-            var difference = ProjectDifference.DocumentRemoved;
+            var state = new ProjectState(this, ProjectDifference.DocumentRemoved, HostProject, WorkspaceProject, documents, importsToRelatedDocuments);
-            var state = new ProjectState(this, difference, HostProject, WorkspaceProject, documents);
             return state;
         }
 
@@ -198,23 +224,22 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 throw new ArgumentNullException(nameof(hostDocument));
             }
 
-            if (!Documents.ContainsKey(hostDocument.FilePath))
+            if (!Documents.TryGetValue(hostDocument.FilePath, out var document))
             {
                 return this;
             }
 
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
+            var documents = Documents.SetItem(hostDocument.FilePath, document.WithText(sourceText, version));
-            foreach (var kvp in Documents)
+
+            if (ImportsToRelatedDocuments.TryGetValue(hostDocument.TargetPath, out var relatedDocuments))
             {
-                documents.Add(kvp.Key, kvp.Value);
+                foreach (var relatedDocument in relatedDocuments)
+                {
+                    documents = documents.SetItem(relatedDocument, documents[relatedDocument].WithImportsChange());
+                }
             }
 
-            if (documents.TryGetValue(hostDocument.FilePath, out var document))
+            var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, WorkspaceProject, documents, ImportsToRelatedDocuments);
-            {
-                documents[hostDocument.FilePath] = document.WithText(sourceText, version);
-            }
-
-            var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, WorkspaceProject, documents);
             return state;
         }
 
@@ -225,23 +250,22 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 throw new ArgumentNullException(nameof(hostDocument));
             }
 
-            if (!Documents.ContainsKey(hostDocument.FilePath))
+            if (!Documents.TryGetValue(hostDocument.FilePath, out var document))
             {
                 return this;
             }
 
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
+            var documents = Documents.SetItem(hostDocument.FilePath, document.WithTextLoader(loader));
-            foreach (var kvp in Documents)
+
+            if (ImportsToRelatedDocuments.TryGetValue(hostDocument.TargetPath, out var relatedDocuments))
             {
-                documents.Add(kvp.Key, kvp.Value);
+                foreach (var relatedDocument in relatedDocuments)
+                {
+                    documents = documents.SetItem(relatedDocument, documents[relatedDocument].WithImportsChange());
+                }
             }
 
-            if (documents.TryGetValue(hostDocument.FilePath, out var document))
+            var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, WorkspaceProject, documents, ImportsToRelatedDocuments);
-            {
-                documents[hostDocument.FilePath] = document.WithTextLoader(loader);
-            }
-
-            var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, WorkspaceProject, documents);
             return state;
         }
 
@@ -256,15 +280,20 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             {
                 return this;
             }
+            
+            var documents = Documents.ToImmutableDictionary(kvp => kvp.Key, kvp => kvp.Value.WithConfigurationChange(), FilePathComparer.Instance);
 
-            var difference = ProjectDifference.ConfigurationChanged;
+            // If the host project has changed then we need to recompute the imports map
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
+            var importsToRelatedDocuments = EmptyImportsToRelatedDocuments;
-            foreach (var kvp in Documents)
+
+            foreach (var document in documents)
             {
-                documents.Add(kvp.Key, kvp.Value.WithConfigurationChange());
+                var importTargetPaths = ProjectEngine.GetImportDocumentTargetPaths(this, document.Value.HostDocument.TargetPath);
+                importsToRelatedDocuments = AddToImportsToRelatedDocuments(ImportsToRelatedDocuments, document.Value.HostDocument, importTargetPaths);
             }
 
-            var state = new ProjectState(this, difference, hostProject, WorkspaceProject, documents);
+
+            var state = new ProjectState(this, ProjectDifference.ConfigurationChanged, hostProject, WorkspaceProject, documents, importsToRelatedDocuments);
             return state;
         }
 
@@ -291,14 +320,52 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 return this;
             }
 
-            var documents = new Dictionary<string, DocumentState>(FilePathComparer.Instance);
+            var documents = Documents.ToImmutableDictionary(kvp => kvp.Key, kvp => kvp.Value.WithWorkspaceProjectChange(), FilePathComparer.Instance);
-            foreach (var kvp in Documents)
+            var state = new ProjectState(this, difference, HostProject, workspaceProject, documents, ImportsToRelatedDocuments);
+            return state;
+        }
+
+        private static ImmutableDictionary<string, ImmutableArray<string>> AddToImportsToRelatedDocuments(
+            ImmutableDictionary<string, ImmutableArray<string>> importsToRelatedDocuments,
+            HostDocument hostDocument,
+            List<string> importTargetPaths)
+        {
+            foreach (var importTargetPath in importTargetPaths)
             {
-                documents.Add(kvp.Key, kvp.Value.WithWorkspaceProjectChange());
+                if (!importsToRelatedDocuments.TryGetValue(importTargetPath, out var relatedDocuments))
+                {
+                    relatedDocuments = ImmutableArray.Create<string>();
+                }
+
+                relatedDocuments = relatedDocuments.Add(hostDocument.FilePath);
+                importsToRelatedDocuments = importsToRelatedDocuments.SetItem(importTargetPath, relatedDocuments);
             }
 
-            var state = new ProjectState(this, difference, HostProject, workspaceProject, documents);
+            return importsToRelatedDocuments;
-            return state;
+        }
+
+        private static ImmutableDictionary<string, ImmutableArray<string>> RemoveFromImportsToRelatedDocuments(
+            ImmutableDictionary<string, ImmutableArray<string>> importsToRelatedDocuments,
+            HostDocument hostDocument,
+            List<string> importTargetPaths)
+        {
+            foreach (var importTargetPath in importTargetPaths)
+            {
+                if (importsToRelatedDocuments.TryGetValue(importTargetPath, out var relatedDocuments))
+                {
+                    relatedDocuments = relatedDocuments.Remove(hostDocument.FilePath);
+                    if (relatedDocuments.Length > 0)
+                    {
+                        importsToRelatedDocuments = importsToRelatedDocuments.SetItem(importTargetPath, relatedDocuments);
+                    }
+                    else
+                    {
+                        importsToRelatedDocuments = importsToRelatedDocuments.Remove(importTargetPath);
+                    }
+                }
+            }
+
+            return importsToRelatedDocuments;
         }
     }
 }

src/Microsoft.CodeAnalysis.Remote.Razor/RazorServiceBase.cs

@@ -76,6 +76,16 @@ namespace Microsoft.CodeAnalysis.Remote.Razor
                 return null;
             }
 
+            public override bool IsImportDocument(DocumentSnapshot document)
+            {
+                throw new NotImplementedException();
+            }
+
+            public override IEnumerable<DocumentSnapshot> GetRelatedDocuments(DocumentSnapshot document)
+            {
+                throw new NotImplementedException();
+            }
+
             public override RazorProjectEngine GetProjectEngine()
             {
                 throw new NotImplementedException();

src/Microsoft.VisualStudio.LanguageServices.Razor/BackgroundDocumentGenerator.cs

@@ -237,7 +237,7 @@ namespace Microsoft.CodeAnalysis.Razor
             {
                 case ProjectChangeKind.ProjectAdded:
                     {
-                        var projectSnapshot = _projectManager.GetLoadedProject(e.ProjectFilePath);
+                        var projectSnapshot = e.Newer;
                         foreach (var documentFilePath in projectSnapshot.DocumentFilePaths)
                         {
                             Enqueue(projectSnapshot, projectSnapshot.GetDocument(documentFilePath));
@@ -247,7 +247,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     }
                 case ProjectChangeKind.ProjectChanged:
                     {
-                        var projectSnapshot = _projectManager.GetLoadedProject(e.ProjectFilePath);
+                        var projectSnapshot = e.Newer;
                         foreach (var documentFilePath in projectSnapshot.DocumentFilePaths)
                         {
                             Enqueue(projectSnapshot, projectSnapshot.GetDocument(documentFilePath));
@@ -257,23 +257,35 @@ namespace Microsoft.CodeAnalysis.Razor
                     }
 
                 case ProjectChangeKind.DocumentAdded:
+                case ProjectChangeKind.DocumentChanged:
                     {
-                        var project = _projectManager.GetLoadedProject(e.ProjectFilePath);
+                        var project = e.Newer;
-                        Enqueue(project, project.GetDocument(e.DocumentFilePath));
+                        var document = project.GetDocument(e.DocumentFilePath);
+
+                        Enqueue(project, document);
+                        foreach (var relatedDocument in project.GetRelatedDocuments(document))
+                        {
+                            Enqueue(project, document);
+                        }
 
                         break;
                     }
 
-                case ProjectChangeKind.DocumentChanged:
+                case ProjectChangeKind.DocumentRemoved:
                     {
-                        var project = _projectManager.GetLoadedProject(e.ProjectFilePath);
+                        // For removals use the old snapshot to find the removed document, so we can figure out 
-                        Enqueue(project, project.GetDocument(e.DocumentFilePath));
+                        // what the imports were in the new snapshot.
+                        var document = e.Older.GetDocument(e.DocumentFilePath);
+
+                        foreach (var relatedDocument in e.Newer.GetRelatedDocuments(document))
+                        {
+                            Enqueue(e.Newer, document);
+                        }
 
                         break;
                     }
 
                 case ProjectChangeKind.ProjectRemoved:
-                case ProjectChangeKind.DocumentRemoved:
                     {
                         // ignore
                         break;

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/ProjectSystem/DefaultDocumentSnapshotTest.cs

@@ -1,36 +1,28 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Collections.Generic;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Text;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class DefaultDocumentSnapshotTest
+    public class DefaultDocumentSnapshotTest : WorkspaceTestBase
     {
         public DefaultDocumentSnapshotTest()
         {
-            var services = TestServices.Create(
+            var projectState = ProjectState.Create(Workspace.Services, TestProjectData.SomeProject);
-                new[] { new TestProjectSnapshotProjectEngineFactory() },
-                new[] { new TestTagHelperResolver() });
-            Workspace = TestWorkspace.Create(services);
-            var hostProject = new HostProject("C:/some/path/project.csproj", RazorConfiguration.Default);
-            var projectState = ProjectState.Create(Workspace.Services, hostProject);
             var project = new DefaultProjectSnapshot(projectState);
-            HostDocument = new HostDocument("C:/some/path/file.cshtml", "C:/some/path/file.cshtml");
+            HostDocument = TestProjectData.SomeProjectFile1;
-            SourceText = Text.SourceText.From("<p>Hello World</p>");
+            SourceText = SourceText.From("<p>Hello World</p>");
             Version = VersionStamp.Default.GetNewerVersion();
             var textAndVersion = TextAndVersion.Create(SourceText, Version);
             var documentState = DocumentState.Create(Workspace.Services, HostDocument, () => Task.FromResult(textAndVersion));
             Document = new DefaultDocumentSnapshot(project, documentState);
-
         }
 
-        private Workspace Workspace { get; }
-
         private SourceText SourceText { get; }
 
         private VersionStamp Version { get; }
@@ -39,6 +31,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private DefaultDocumentSnapshot Document { get; }
 
+        protected override void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+            services.Add(new TestTagHelperResolver());
+        }
+
         [Fact]
         public async Task GetGeneratedOutputAsync_SetsHostDocumentOutput()
         {

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/ProjectSystem/DefaultProjectSnapshotTest.cs

@@ -1,35 +1,23 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.CodeAnalysis.Host;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Host;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class DefaultProjectSnapshotTest
+    public class DefaultProjectSnapshotTest : WorkspaceTestBase
     {
         public DefaultProjectSnapshotTest()
         {
             TagHelperResolver = new TestTagHelperResolver();
 
-            HostServices = TestServices.Create(
+            HostProject = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
-                new IWorkspaceService[]
+            HostProjectWithConfigurationChange = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-                {
-                    new TestProjectSnapshotProjectEngineFactory(),
-                },
-                new ILanguageService[]
-                {
-                    TagHelperResolver,
-                });
-
-            HostProject = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_2_0);
-            HostProjectWithConfigurationChange = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_1_0);
-
-            Workspace = TestWorkspace.Create(HostServices);
 
             var projectId = ProjectId.CreateNewId("Test");
             var solution = Workspace.CurrentSolution.AddProject(ProjectInfo.Create(
@@ -38,19 +26,21 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 "Test",
                 "Test",
                 LanguageNames.CSharp,
-                "c:\\MyProject\\Test.csproj"));
+                TestProjectData.SomeProject.FilePath));
             WorkspaceProject = solution.GetProject(projectId);
 
-            SomeTagHelpers = new List<TagHelperDescriptor>();
+            SomeTagHelpers = new List<TagHelperDescriptor>
-            SomeTagHelpers.Add(TagHelperDescriptorBuilder.Create("Test1", "TestAssembly").Build());
+            {
+                TagHelperDescriptorBuilder.Create("Test1", "TestAssembly").Build()
+            };
 
             Documents = new HostDocument[]
             {
-                new HostDocument("c:\\MyProject\\File.cshtml", "File.cshtml"),
+                TestProjectData.SomeProjectFile1,
-                new HostDocument("c:\\MyProject\\Index.cshtml", "Index.cshtml"),
+                TestProjectData.SomeProjectFile2,
 
                 // linked file
-                new HostDocument("c:\\SomeOtherProject\\Index.cshtml", "Pages\\Index.cshtml"),
+                TestProjectData.AnotherProjectNestedFile3,
             };
         }
 
@@ -64,12 +54,25 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private TestTagHelperResolver TagHelperResolver { get; }
 
-        private HostServices HostServices { get; }
-
-        private Workspace Workspace { get; }
-
         private List<TagHelperDescriptor> SomeTagHelpers { get; }
 
+        private void Configure(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Remove(builder.Features.OfType<IImportProjectFeature>().Single());
+            builder.Features.Add(new TestImportProjectFeature());
+        }
+
+        protected override void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+            services.Add(TagHelperResolver);
+        }
+
+        protected override void ConfigureProjectEngine(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Remove(builder.Features.OfType<IImportProjectFeature>().Single());
+            builder.Features.Add(new TestImportProjectFeature());
+        }
+
         [Fact]
         public void ProjectSnapshot_CachesDocumentSnapshots()
         {
@@ -114,5 +117,79 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 TagHelperResolver.CompletionSource.SetCanceled();
             }
         }
+
+        [Fact]
+        public void IsImportDocument_NonImportDocument_ReturnsFalse()
+        {
+            // Arrange
+            var state = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(Documents[0], DocumentState.EmptyLoader);
+            var snapshot = new DefaultProjectSnapshot(state);
+
+            var document = snapshot.GetDocument(Documents[0].FilePath);
+
+            // Act
+            var result = snapshot.IsImportDocument(document);
+
+            // Assert
+            Assert.False(result);
+        }
+
+        [Fact]
+        public void IsImportDocument_ImportDocument_ReturnsTrue()
+        {
+            // Arrange
+            var state = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(Documents[0], DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectImportFile, DocumentState.EmptyLoader);
+            var snapshot = new DefaultProjectSnapshot(state);
+
+            var document = snapshot.GetDocument(TestProjectData.SomeProjectImportFile.FilePath);
+
+            // Act
+            var result = snapshot.IsImportDocument(document);
+
+            // Assert
+            Assert.True(result);
+        }
+
+        [Fact]
+        public void GetRelatedDocuments_NonImportDocument_ReturnsEmpty()
+        {
+            // Arrange
+            var state = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(Documents[0], DocumentState.EmptyLoader);
+            var snapshot = new DefaultProjectSnapshot(state);
+
+            var document = snapshot.GetDocument(Documents[0].FilePath);
+
+            // Act
+            var documents = snapshot.GetRelatedDocuments(document);
+
+            // Assert
+            Assert.Empty(documents);
+        }
+
+        [Fact]
+        public void GetRelatedDocuments_ImportDocument_ReturnsRelated()
+        {
+            // Arrange
+            var state = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(Documents[0], DocumentState.EmptyLoader)
+                .WithAddedHostDocument(Documents[1], DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectImportFile, DocumentState.EmptyLoader);
+            var snapshot = new DefaultProjectSnapshot(state);
+
+            var document = snapshot.GetDocument(TestProjectData.SomeProjectImportFile.FilePath);
+
+            // Act
+            var documents = snapshot.GetRelatedDocuments(document);
+
+            // Assert
+            Assert.Collection(
+                documents.OrderBy(d => d.FilePath),
+                d => Assert.Equal(Documents[0].FilePath, d.FilePath),
+                d => Assert.Equal(Documents[1].FilePath, d.FilePath));
+        }
     }
 }

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/ProjectSystem/DocumentStateTest.cs

@@ -3,37 +3,22 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Text;
-using Moq;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class DocumentStateTest
+    public class DocumentStateTest : WorkspaceTestBase
     {
         public DocumentStateTest()
         {
             TagHelperResolver = new TestTagHelperResolver();
-
+            
-            HostServices = TestServices.Create(
+            HostProject = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
-                new IWorkspaceService[]
+            HostProjectWithConfigurationChange = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-                {
-                    new TestProjectSnapshotProjectEngineFactory(),
-                },
-                new ILanguageService[]
-                {
-                    TagHelperResolver,
-                });
-
-            HostProject = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_2_0);
-            HostProjectWithConfigurationChange = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_1_0);
-
-            Workspace = TestWorkspace.Create(HostServices);
 
             var projectId = ProjectId.CreateNewId("Test");
             var solution = Workspace.CurrentSolution.AddProject(ProjectInfo.Create(
@@ -42,13 +27,13 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 "Test",
                 "Test",
                 LanguageNames.CSharp,
-                "c:\\MyProject\\Test.csproj"));
+                TestProjectData.SomeProject.FilePath));
             WorkspaceProject = solution.GetProject(projectId);
 
             SomeTagHelpers = new List<TagHelperDescriptor>();
             SomeTagHelpers.Add(TagHelperDescriptorBuilder.Create("Test1", "TestAssembly").Build());
 
-            Document = new HostDocument("c:\\MyProject\\File.cshtml", "File.cshtml");
+            Document = TestProjectData.SomeProjectFile1;
 
             Text = SourceText.From("Hello, world!");
             TextLoader = () => Task.FromResult(TextAndVersion.Create(Text, VersionStamp.Create()));
@@ -64,16 +49,17 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private TestTagHelperResolver TagHelperResolver { get; }
 
-        private HostServices HostServices { get; }
-
-        private Workspace Workspace { get; }
-
         private List<TagHelperDescriptor> SomeTagHelpers { get; }
 
         private Func<Task<TextAndVersion>> TextLoader { get; }
 
         private SourceText Text { get; }
 
+        protected override void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+            services.Add(TagHelperResolver);
+        }
+
         [Fact]
         public async Task DocumentState_CreatedNew_HasEmptyText()
         {
@@ -145,6 +131,38 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             Assert.True(state.TryGetTextVersion(out _));
         }
 
+        [Fact]
+        public void DocumentState_WithImportsChange_CachesSnapshotText()
+        {
+            // Arrange
+            var original = DocumentState.Create(Workspace.Services, Document, DocumentState.EmptyLoader)
+                .WithText(Text, VersionStamp.Create());
+
+            // Act
+            var state = original.WithImportsChange();
+
+            // Assert
+            Assert.True(state.TryGetText(out _));
+            Assert.True(state.TryGetTextVersion(out _));
+        }
+
+        [Fact]
+        public async Task DocumentState_WithImportsChange_CachesLoadedText()
+        {
+            // Arrange
+            var original = DocumentState.Create(Workspace.Services, Document, DocumentState.EmptyLoader)
+                .WithTextLoader(TextLoader);
+
+            await original.GetTextAsync();
+
+            // Act
+            var state = original.WithImportsChange();
+
+            // Assert
+            Assert.True(state.TryGetText(out _));
+            Assert.True(state.TryGetTextVersion(out _));
+        }
+
         [Fact]
         public void DocumentState_WithWorkspaceProjectChange_CachesSnapshotText()
         {
@@ -160,7 +178,6 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             Assert.True(state.TryGetTextVersion(out _));
         }
 
-
         [Fact]
         public async Task DocumentState_WithWorkspaceProjectChange_CachesLoadedText()
         {

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/ProjectSystem/ProjectStateTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
@@ -12,26 +13,14 @@ using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class ProjectStateTest
+    public class ProjectStateTest : WorkspaceTestBase
     {
         public ProjectStateTest()
         {
             TagHelperResolver = new TestTagHelperResolver();
 
-            HostServices = TestServices.Create(
+            HostProject = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
-                new IWorkspaceService[]
+            HostProjectWithConfigurationChange = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-                {
-                    new TestProjectSnapshotProjectEngineFactory(),
-                },
-                new ILanguageService[]
-                {
-                    TagHelperResolver,
-                });
-
-            HostProject = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_2_0);
-            HostProjectWithConfigurationChange = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_1_0);
-
-            Workspace = TestWorkspace.Create(HostServices);
 
             var projectId = ProjectId.CreateNewId("Test");
             var solution = Workspace.CurrentSolution.AddProject(ProjectInfo.Create(
@@ -40,7 +29,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 "Test",
                 "Test",
                 LanguageNames.CSharp,
-                "c:\\MyProject\\Test.csproj"));
+                TestProjectData.SomeProject.FilePath));
             WorkspaceProject = solution.GetProject(projectId);
 
             SomeTagHelpers = new List<TagHelperDescriptor>();
@@ -48,11 +37,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             Documents = new HostDocument[]
             {
-                new HostDocument("c:\\MyProject\\File.cshtml", "File.cshtml"),
+                TestProjectData.SomeProjectFile1,
-                new HostDocument("c:\\MyProject\\Index.cshtml", "Index.cshtml"),
+                TestProjectData.SomeProjectFile2,
 
                 // linked file
-                new HostDocument("c:\\SomeOtherProject\\Index.cshtml", "Pages\\Index.cshtml"),
+                TestProjectData.AnotherProjectNestedFile3,
             };
 
             Text = SourceText.From("Hello, world!");
@@ -69,16 +58,23 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private TestTagHelperResolver TagHelperResolver { get; }
 
-        private HostServices HostServices { get; }
-
-        private Workspace Workspace { get; }
-
         private List<TagHelperDescriptor> SomeTagHelpers { get; }
 
         private Func<Task<TextAndVersion>> TextLoader { get; }
 
         private SourceText Text { get; }
 
+        protected override void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+            services.Add(TagHelperResolver);
+        }
+
+        protected override void ConfigureProjectEngine(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Remove(builder.Features.OfType<IImportProjectFeature>().Single());
+            builder.Features.Add(new TestImportProjectFeature());
+        }
+
         [Fact]
         public void ProjectState_ConstructedNew()
         {
@@ -139,9 +135,93 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             Assert.Collection(
                 state.Documents.OrderBy(kvp => kvp.Key),
+                d => Assert.Same(Documents[2], d.Value.HostDocument),
                 d => Assert.Same(Documents[0], d.Value.HostDocument),
-                d => Assert.Same(Documents[1], d.Value.HostDocument),
+                d => Assert.Same(Documents[1], d.Value.HostDocument));
-                d => Assert.Same(Documents[2], d.Value.HostDocument));
+        }
+
+        [Fact]
+        public void ProjectState_AddHostDocument_TracksImports()
+        {
+            // Arrange
+            
+            // Act
+            var state = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile1, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile2, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectNestedFile3, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.AnotherProjectNestedFile4, DocumentState.EmptyLoader);
+            
+            // Assert
+            Assert.Collection(
+                state.ImportsToRelatedDocuments.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                            TestProjectData.SomeProjectFile1.FilePath,
+                            TestProjectData.SomeProjectFile2.FilePath,
+                            TestProjectData.SomeProjectNestedFile3.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                },
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectNestedImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                            TestProjectData.SomeProjectNestedFile3.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                });
+        }
+
+        [Fact]
+        public void ProjectState_AddHostDocument_TracksImports_AddImportFile()
+        {
+            // Arrange
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile1, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile2, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectNestedFile3, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.AnotherProjectNestedFile4, DocumentState.EmptyLoader);
+
+            // Act
+            var state = original
+                .WithAddedHostDocument(TestProjectData.AnotherProjectImportFile, DocumentState.EmptyLoader);
+
+            // Assert
+            Assert.Collection(
+                state.ImportsToRelatedDocuments.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                            TestProjectData.SomeProjectFile1.FilePath,
+                            TestProjectData.SomeProjectFile2.FilePath,
+                            TestProjectData.SomeProjectNestedFile3.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                },
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectNestedImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                            TestProjectData.SomeProjectNestedFile3.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                });
         }
 
         [Fact]
@@ -311,6 +391,68 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 d => Assert.Same(Documents[2], d.Value.HostDocument));
         }
 
+        [Fact]
+        public void ProjectState_RemoveHostDocument_TracksImports()
+        {
+            // Arrange
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile1, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile2, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectNestedFile3, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.AnotherProjectNestedFile4, DocumentState.EmptyLoader);
+
+            // Act
+            var state = original.WithRemovedHostDocument(TestProjectData.SomeProjectNestedFile3);
+
+            // Assert
+            Assert.Collection(
+                state.ImportsToRelatedDocuments.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                            TestProjectData.SomeProjectFile1.FilePath,
+                            TestProjectData.SomeProjectFile2.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                },
+                kvp =>
+                {
+                    Assert.Equal(TestProjectData.SomeProjectNestedImportFile.TargetPath, kvp.Key);
+                    Assert.Equal(
+                        new string[]
+                        {
+                            TestProjectData.AnotherProjectNestedFile4.FilePath,
+                        },
+                        kvp.Value.OrderBy(f => f));
+                });
+        }
+
+        [Fact]
+        public void ProjectState_RemoveHostDocument_TracksImports_RemoveAllDocuments()
+        {
+            // Arrange
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile1, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectFile2, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.SomeProjectNestedFile3, DocumentState.EmptyLoader)
+                .WithAddedHostDocument(TestProjectData.AnotherProjectNestedFile4, DocumentState.EmptyLoader);
+
+            // Act
+            var state = original
+                .WithRemovedHostDocument(TestProjectData.SomeProjectFile1)
+                .WithRemovedHostDocument(TestProjectData.SomeProjectFile2)
+                .WithRemovedHostDocument(TestProjectData.SomeProjectNestedFile3)
+                .WithRemovedHostDocument(TestProjectData.AnotherProjectNestedFile4);
+
+            // Assert
+            Assert.Empty(state.Documents);
+            Assert.Empty(state.ImportsToRelatedDocuments);
+        }
+
         [Fact]
         public void ProjectState_RemoveHostDocument_RetainsComputedState()
         {
@@ -398,13 +540,13 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
         {
             // Arrange
             var callCount = 0;
-
+            
-            var documents = new Dictionary<string, DocumentState>();
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
             documents[Documents[1].FilePath] = TestDocumentState.Create(Workspace.Services, Documents[1], onConfigurationChange: () => callCount++);
             documents[Documents[2].FilePath] = TestDocumentState.Create(Workspace.Services, Documents[2], onConfigurationChange: () => callCount++);
 
             var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
-            original.Documents = documents;
+            original.Documents = documents.ToImmutable();
 
             var changed = WorkspaceProject.WithAssemblyName("Test1");
 
@@ -503,12 +645,12 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             // Arrange
             var callCount = 0;
 
-            var documents = new Dictionary<string, DocumentState>();
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
             documents[Documents[1].FilePath] = TestDocumentState.Create(Workspace.Services, Documents[1], onWorkspaceProjectChange: () => callCount++);
             documents[Documents[2].FilePath] = TestDocumentState.Create(Workspace.Services, Documents[2], onWorkspaceProjectChange: () => callCount++);
 
             var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
-            original.Documents = documents;
+            original.Documents = documents.ToImmutable();
 
             var changed = WorkspaceProject.WithAssemblyName("Test1");
 
@@ -520,6 +662,231 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             Assert.Equal(2, callCount);
         }
 
+        [Fact]
+        public void ProjectState_WhenImportDocumentAdded_CallsImportsChanged()
+        {
+            // Arrange
+            var callCount = 0;
+            
+            var document1 = TestProjectData.SomeProjectFile1;
+            var document2 = TestProjectData.SomeProjectFile2;
+            var document3 = TestProjectData.SomeProjectNestedFile3;
+            var document4 = TestProjectData.AnotherProjectNestedFile4;
+
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
+            documents[document1.FilePath] = TestDocumentState.Create(Workspace.Services, document1, onImportsChange: () => callCount++);
+            documents[document2.FilePath] = TestDocumentState.Create(Workspace.Services, document2, onImportsChange: () => callCount++);
+            documents[document3.FilePath] = TestDocumentState.Create(Workspace.Services, document3, onImportsChange: () => callCount++);
+            documents[document4.FilePath] = TestDocumentState.Create(Workspace.Services, document4, onImportsChange: () => callCount++);
+
+            var importsToRelatedDocuments = ImmutableDictionary.CreateBuilder<string, ImmutableArray<string>>(FilePathComparer.Instance);
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectImportFile.TargetPath, 
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectFile1.FilePath,
+                    TestProjectData.SomeProjectFile2.FilePath,
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectNestedImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
+            original.Documents = documents.ToImmutable();
+            original.ImportsToRelatedDocuments = importsToRelatedDocuments.ToImmutable();
+
+            // Act
+            var state = original.WithAddedHostDocument(TestProjectData.AnotherProjectImportFile, DocumentState.EmptyLoader);
+
+            // Assert
+            Assert.NotEqual(original.Version, state.Version);
+            Assert.Equal(4, callCount);
+        }
+
+        [Fact]
+        public void ProjectState_WhenImportDocumentAdded_CallsImportsChanged_Nested()
+        {
+            // Arrange
+            var callCount = 0;
+
+            var document1 = TestProjectData.SomeProjectFile1;
+            var document2 = TestProjectData.SomeProjectFile2;
+            var document3 = TestProjectData.SomeProjectNestedFile3;
+            var document4 = TestProjectData.AnotherProjectNestedFile4;
+
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
+            documents[document1.FilePath] = TestDocumentState.Create(Workspace.Services, document1, onImportsChange: () => callCount++);
+            documents[document2.FilePath] = TestDocumentState.Create(Workspace.Services, document2, onImportsChange: () => callCount++);
+            documents[document3.FilePath] = TestDocumentState.Create(Workspace.Services, document3, onImportsChange: () => callCount++);
+            documents[document4.FilePath] = TestDocumentState.Create(Workspace.Services, document4, onImportsChange: () => callCount++);
+
+            var importsToRelatedDocuments = ImmutableDictionary.CreateBuilder<string, ImmutableArray<string>>(FilePathComparer.Instance);
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectFile1.FilePath,
+                    TestProjectData.SomeProjectFile2.FilePath,
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectNestedImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
+            original.Documents = documents.ToImmutable();
+            original.ImportsToRelatedDocuments = importsToRelatedDocuments.ToImmutable();
+
+            // Act
+            var state = original.WithAddedHostDocument(TestProjectData.AnotherProjectNestedImportFile, DocumentState.EmptyLoader);
+
+            // Assert
+            Assert.NotEqual(original.Version, state.Version);
+            Assert.Equal(2, callCount);
+        }
+
+        [Fact]
+        public void ProjectState_WhenImportDocumentChangedTextLoader_CallsImportsChanged()
+        {
+            // Arrange
+            var callCount = 0;
+
+            var document1 = TestProjectData.SomeProjectFile1;
+            var document2 = TestProjectData.SomeProjectFile2;
+            var document3 = TestProjectData.SomeProjectNestedFile3;
+            var document4 = TestProjectData.AnotherProjectNestedFile4;
+            var document5 = TestProjectData.AnotherProjectNestedImportFile;
+
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
+            documents[document1.FilePath] = TestDocumentState.Create(Workspace.Services, document1, onImportsChange: () => callCount++);
+            documents[document2.FilePath] = TestDocumentState.Create(Workspace.Services, document2, onImportsChange: () => callCount++);
+            documents[document3.FilePath] = TestDocumentState.Create(Workspace.Services, document3, onImportsChange: () => callCount++);
+            documents[document4.FilePath] = TestDocumentState.Create(Workspace.Services, document4, onImportsChange: () => callCount++);
+            documents[document5.FilePath] = TestDocumentState.Create(Workspace.Services, document5, onImportsChange: () => callCount++);
+
+            var importsToRelatedDocuments = ImmutableDictionary.CreateBuilder<string, ImmutableArray<string>>(FilePathComparer.Instance);
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectFile1.FilePath,
+                    TestProjectData.SomeProjectFile2.FilePath,
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath,
+                    TestProjectData.AnotherProjectNestedImportFile.FilePath));
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectNestedImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
+            original.Documents = documents.ToImmutable();
+            original.ImportsToRelatedDocuments = importsToRelatedDocuments.ToImmutable();
+
+            // Act
+            var state = original.WithChangedHostDocument(document5, DocumentState.EmptyLoader);
+
+            // Assert
+            Assert.NotEqual(original.Version, state.Version);
+            Assert.Equal(2, callCount);
+        }
+
+        [Fact]
+        public void ProjectState_WhenImportDocumentChangedSnapshot_CallsImportsChanged()
+        {
+            // Arrange
+            var callCount = 0;
+
+            var document1 = TestProjectData.SomeProjectFile1;
+            var document2 = TestProjectData.SomeProjectFile2;
+            var document3 = TestProjectData.SomeProjectNestedFile3;
+            var document4 = TestProjectData.AnotherProjectNestedFile4;
+            var document5 = TestProjectData.AnotherProjectNestedImportFile;
+
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
+            documents[document1.FilePath] = TestDocumentState.Create(Workspace.Services, document1, onImportsChange: () => callCount++);
+            documents[document2.FilePath] = TestDocumentState.Create(Workspace.Services, document2, onImportsChange: () => callCount++);
+            documents[document3.FilePath] = TestDocumentState.Create(Workspace.Services, document3, onImportsChange: () => callCount++);
+            documents[document4.FilePath] = TestDocumentState.Create(Workspace.Services, document4, onImportsChange: () => callCount++);
+            documents[document5.FilePath] = TestDocumentState.Create(Workspace.Services, document5, onImportsChange: () => callCount++);
+
+            var importsToRelatedDocuments = ImmutableDictionary.CreateBuilder<string, ImmutableArray<string>>(FilePathComparer.Instance);
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectFile1.FilePath,
+                    TestProjectData.SomeProjectFile2.FilePath,
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath,
+                    TestProjectData.AnotherProjectNestedImportFile.FilePath));
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectNestedImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
+            original.Documents = documents.ToImmutable();
+            original.ImportsToRelatedDocuments = importsToRelatedDocuments.ToImmutable();
+
+            // Act
+            var state = original.WithChangedHostDocument(document5, Text, VersionStamp.Create());
+
+            // Assert
+            Assert.NotEqual(original.Version, state.Version);
+            Assert.Equal(2, callCount);
+        }
+
+
+        [Fact]
+        public void ProjectState_WhenImportDocumentRemoved_CallsImportsChanged()
+        {
+            // Arrange
+            var callCount = 0;
+
+            var document1 = TestProjectData.SomeProjectFile1;
+            var document2 = TestProjectData.SomeProjectFile2;
+            var document3 = TestProjectData.SomeProjectNestedFile3;
+            var document4 = TestProjectData.AnotherProjectNestedFile4;
+            var document5 = TestProjectData.AnotherProjectNestedImportFile;
+
+            var documents = ImmutableDictionary.CreateBuilder<string, DocumentState>(FilePathComparer.Instance);
+            documents[document1.FilePath] = TestDocumentState.Create(Workspace.Services, document1, onImportsChange: () => callCount++);
+            documents[document2.FilePath] = TestDocumentState.Create(Workspace.Services, document2, onImportsChange: () => callCount++);
+            documents[document3.FilePath] = TestDocumentState.Create(Workspace.Services, document3, onImportsChange: () => callCount++);
+            documents[document4.FilePath] = TestDocumentState.Create(Workspace.Services, document4, onImportsChange: () => callCount++);
+            documents[document5.FilePath] = TestDocumentState.Create(Workspace.Services, document5, onImportsChange: () => callCount++);
+
+            var importsToRelatedDocuments = ImmutableDictionary.CreateBuilder<string, ImmutableArray<string>>(FilePathComparer.Instance);
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectFile1.FilePath,
+                    TestProjectData.SomeProjectFile2.FilePath,
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath,
+                    TestProjectData.AnotherProjectNestedImportFile.FilePath));
+            importsToRelatedDocuments.Add(
+                TestProjectData.SomeProjectNestedImportFile.TargetPath,
+                ImmutableArray.Create(
+                    TestProjectData.SomeProjectNestedFile3.FilePath,
+                    TestProjectData.AnotherProjectNestedFile4.FilePath));
+
+            var original = ProjectState.Create(Workspace.Services, HostProject, WorkspaceProject);
+            original.Documents = documents.ToImmutable();
+            original.ImportsToRelatedDocuments = importsToRelatedDocuments.ToImmutable();
+
+            // Act
+            var state = original.WithRemovedHostDocument(document5);
+
+            // Assert
+            Assert.NotEqual(original.Version, state.Version);
+            Assert.Equal(2, callCount);
+        }
+
         private class TestDocumentState : DocumentState
         {
             public static TestDocumentState Create(
@@ -529,15 +896,27 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 Action onTextChange = null,
                 Action onTextLoaderChange = null,
                 Action onConfigurationChange = null,
+                Action onImportsChange = null,
                 Action onWorkspaceProjectChange = null)
             {
-                return new TestDocumentState(services, hostDocument, null, null, loader, onTextChange, onTextLoaderChange, onConfigurationChange, onWorkspaceProjectChange);
+                return new TestDocumentState(
+                    services, 
+                    hostDocument, 
+                    null, 
+                    null, 
+                    loader, 
+                    onTextChange, 
+                    onTextLoaderChange, 
+                    onConfigurationChange, 
+                    onImportsChange,
+                    onWorkspaceProjectChange);
             }
 
-            Action _onTextChange;
+            private readonly Action _onTextChange;
-            Action _onTextLoaderChange;
+            private readonly Action _onTextLoaderChange;
-            Action _onConfigurationChange;
+            private readonly Action _onConfigurationChange;
-            Action _onWorkspaceProjectChange;
+            private readonly Action _onImportsChange;
+            private readonly Action _onWorkspaceProjectChange;
 
             private TestDocumentState(
                 HostWorkspaceServices services,
@@ -548,12 +927,14 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 Action onTextChange,
                 Action onTextLoaderChange,
                 Action onConfigurationChange,
+                Action onImportsChange,
                 Action onWorkspaceProjectChange)
                 : base(services, hostDocument, text, version, loader)
             {
                 _onTextChange = onTextChange;
                 _onTextLoaderChange = onTextLoaderChange;
                 _onConfigurationChange = onConfigurationChange;
+                _onImportsChange = onImportsChange;
                 _onWorkspaceProjectChange = onWorkspaceProjectChange;
             }
 
@@ -575,6 +956,12 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 return base.WithConfigurationChange();
             }
 
+            public override DocumentState WithImportsChange()
+            {
+                _onImportsChange?.Invoke();
+                return base.WithImportsChange();
+            }
+
             public override DocumentState WithWorkspaceProjectChange()
             {
                 _onWorkspaceProjectChange?.Invoke();

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Shared/TestImportProjectFeature.cs

@@ -0,0 +1,32 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public class TestImportProjectFeature : RazorProjectEngineFeatureBase, IImportProjectFeature
+    {
+        public IReadOnlyList<RazorProjectItem> GetImports(RazorProjectItem projectItem)
+        {
+            if (projectItem == null)
+            {
+                throw new ArgumentNullException(nameof(projectItem));
+            }
+
+            var imports = new List<RazorProjectItem>();
+            AddHierarchicalImports(projectItem, imports);
+
+            return imports;
+        }
+
+        private void AddHierarchicalImports(RazorProjectItem projectItem, List<RazorProjectItem> imports)
+        {
+            // We want items in descending order. FindHierarchicalItems returns items in ascending order.
+            var importProjectItems = ProjectEngine.FileSystem.FindHierarchicalItems(projectItem.FilePath, "_Imports.cshtml").Reverse();
+            imports.AddRange(importProjectItems);
+        }
+    }
+}

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Shared/TestProjectData.cs

@@ -0,0 +1,56 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+using System.Runtime.InteropServices;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Razor.ProjectSystem;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    // Used to abstract away platform-specific file/directory path information.
+    //
+    // The System.IO.Path methods don't processes Windows paths in a Windows way 
+    // on *nix (rightly so), so we need to use platform-specific paths.
+    //
+    // Target paths are always Windows style.
+    internal static class TestProjectData
+    {
+        static TestProjectData()
+        {
+            var baseDirectory = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "c:\\users\\example\\src" : "/home/example";
+
+            SomeProject = new HostProject(Path.Combine(baseDirectory, "SomeProject", "SomeProject.csproj"), RazorConfiguration.Default);
+            SomeProjectFile1 = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "File1.cshtml"), "File1.cshtml");
+            SomeProjectFile2 = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "File2.cshtml"), "File2.cshtml");
+            SomeProjectImportFile = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "_Imports.cshtml"), "_Imports.cshtml");
+            SomeProjectNestedFile3 = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "Nested", "File3.cshtml"), "Nested\\File1.cshtml");
+            SomeProjectNestedFile4 = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "Nested", "File4.cshtml"), "Nested\\File2.cshtml");
+            SomeProjectNestedImportFile = new HostDocument(Path.Combine(baseDirectory, "SomeProject", "Nested", "_Imports.cshtml"), "Nested\\_Imports.cshtml");
+
+            AnotherProject = new HostProject(Path.Combine(baseDirectory, "AnotherProject", "AnotherProject.csproj"), RazorConfiguration.Default);
+            AnotherProjectFile1 = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "File1.cshtml"), "File1.cshtml");
+            AnotherProjectFile2 = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "File2.cshtml"), "File2.cshtml");
+            AnotherProjectImportFile = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "_Imports.cshtml"), "_Imports.cshtml");
+            AnotherProjectNestedFile3 = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "Nested", "File3.cshtml"), "Nested\\File1.cshtml");
+            AnotherProjectNestedFile4 = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "Nested", "File4.cshtml"), "Nested\\File2.cshtml");
+            AnotherProjectNestedImportFile = new HostDocument(Path.Combine(baseDirectory, "AnotherProject", "Nested", "_Imports.cshtml"), "Nested\\_Imports.cshtml");
+        }
+
+        public static readonly HostProject SomeProject;
+        public static readonly HostDocument SomeProjectFile1;
+        public static readonly HostDocument SomeProjectFile2;
+        public static readonly HostDocument SomeProjectImportFile;
+        public static readonly HostDocument SomeProjectNestedFile3;
+        public static readonly HostDocument SomeProjectNestedFile4;
+        public static readonly HostDocument SomeProjectNestedImportFile;
+
+        public static readonly HostProject AnotherProject;
+        public static readonly HostDocument AnotherProjectFile1;
+        public static readonly HostDocument AnotherProjectFile2;
+        public static readonly HostDocument AnotherProjectImportFile;
+        public static readonly HostDocument AnotherProjectNestedFile3;
+        public static readonly HostDocument AnotherProjectNestedFile4;
+        public static readonly HostDocument AnotherProjectNestedImportFile;
+    }
+}

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Shared/TestProjectSnapshotProjectEngineFactory.cs

@@ -8,11 +8,13 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
     internal class TestProjectSnapshotProjectEngineFactory : ProjectSnapshotProjectEngineFactory
     {
+        public Action<RazorProjectEngineBuilder> Configure { get; set; }
+
         public RazorProjectEngine Engine { get; set; }
 
-        public override RazorProjectEngine Create(ProjectSnapshot project, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
+        public override RazorProjectEngine Create(RazorConfiguration configuration, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
         {
-            return Engine ?? RazorProjectEngine.Create(project.Configuration, fileSystem, configure);
+            return Engine ?? RazorProjectEngine.Create(configuration, fileSystem, configure ?? Configure);
         }
 
         public override IProjectEngineFactory FindFactory(ProjectSnapshot project)

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Shared/WorkspaceTestBase.cs

@@ -0,0 +1,79 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Razor.ProjectSystem;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public abstract class WorkspaceTestBase
+    {
+        private bool _initialized;
+        private HostServices _hostServices;
+        private Workspace _workspace;
+
+        protected WorkspaceTestBase()
+        {
+        }
+
+        protected HostServices HostServices
+        {
+            get
+            {
+                EnsureInitialized();
+                return _hostServices;
+            }
+        }
+
+        protected Workspace Workspace
+        {
+            get
+            {
+                EnsureInitialized();
+                return _workspace;
+            }
+        }
+        
+        protected virtual void ConfigureWorkspaceServices(List<IWorkspaceService> services)
+        {
+        }
+
+        protected virtual void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+        }
+
+        protected virtual void ConfigureWorkspace(AdhocWorkspace workspace)
+        {
+        }
+
+        protected virtual void ConfigureProjectEngine(RazorProjectEngineBuilder builder)
+        {
+        }
+
+        private void EnsureInitialized()
+        {
+            if (_initialized)
+            {
+                return;
+            }
+
+            var workspaceServices = new List<IWorkspaceService>()
+            {
+                new TestProjectSnapshotProjectEngineFactory()
+                {
+                    Configure = ConfigureProjectEngine,
+                },
+            };
+            ConfigureWorkspaceServices(workspaceServices);
+
+            var languageServices = new List<ILanguageService>();
+            ConfigureLanguageServices(languageServices);
+
+            _hostServices = TestServices.Create(workspaceServices, languageServices);
+            _workspace = TestWorkspace.Create(_hostServices, ConfigureWorkspace);
+            _initialized = true;
+        }
+    }
+}

test/Microsoft.VisualStudio.Editor.Razor.Test.Common/SingleThreadedForegroundDispatcher.cs

@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    internal class SingleThreadedForegroundDispatcher : ForegroundDispatcher
+    {
+        public SingleThreadedForegroundDispatcher()
+        {
+            ForegroundScheduler = SynchronizationContext.Current == null ? new ThrowingTaskScheduler() : TaskScheduler.FromCurrentSynchronizationContext();
+            BackgroundScheduler = TaskScheduler.Default;
+        }
+
+        public override TaskScheduler ForegroundScheduler { get; }
+
+        public override TaskScheduler BackgroundScheduler { get; }
+
+        private Thread Thread { get; } = Thread.CurrentThread;
+
+        public override bool IsForegroundThread => Thread.CurrentThread == Thread;
+
+        private class ThrowingTaskScheduler : TaskScheduler
+        {
+            protected override IEnumerable<Task> GetScheduledTasks()
+            {
+                return Enumerable.Empty<Task>();
+            }
+
+            protected override void QueueTask(Task task)
+            {
+                throw new InvalidOperationException($"Use [{nameof(ForegroundFactAttribute)}]");
+            }
+
+            protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+            {
+                throw new InvalidOperationException($"Use [{nameof(ForegroundFactAttribute)}]");
+            }
+        }
+    }
+}

test/Microsoft.VisualStudio.Editor.Razor.Test.Common/Xunit/ForegroundDispatcherTestBase.cs

@@ -1,11 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Razor;
 
 namespace Xunit
@@ -13,40 +8,5 @@ namespace Xunit
     public abstract class ForegroundDispatcherTestBase
     {
         internal ForegroundDispatcher Dispatcher { get; } = new SingleThreadedForegroundDispatcher();
-
-        private class SingleThreadedForegroundDispatcher : ForegroundDispatcher
-        {
-            public SingleThreadedForegroundDispatcher()
-            {
-                ForegroundScheduler = SynchronizationContext.Current == null ? new ThrowingTaskScheduler() : TaskScheduler.FromCurrentSynchronizationContext();
-                BackgroundScheduler = TaskScheduler.Default;
-            }
-
-            public override TaskScheduler ForegroundScheduler { get; }
-
-            public override TaskScheduler BackgroundScheduler { get; }
-
-            private Thread Thread { get; } = Thread.CurrentThread;
-
-            public override bool IsForegroundThread => Thread.CurrentThread == Thread;
-        }
-
-        private class ThrowingTaskScheduler : TaskScheduler
-        {
-            protected override IEnumerable<Task> GetScheduledTasks()
-            {
-                return Enumerable.Empty<Task>();
-            }
-
-            protected override void QueueTask(Task task)
-            {
-                throw new InvalidOperationException($"Use [{nameof(ForegroundFactAttribute)}]");
-            }
-
-            protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
-            {
-                throw new InvalidOperationException($"Use [{nameof(ForegroundFactAttribute)}]");
-            }
-        }
     }
 }

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultImportDocumentManagerIntegrationTest.cs

@@ -14,7 +14,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
     {
         public DefaultImportDocumentManagerIntegrationTest()
         {
-            ProjectPath = "C:\\path\\to\\project\\project.csproj";
+            ProjectPath = TestProjectData.SomeProject.FilePath;
+            DirectoryPath = Path.GetDirectoryName(ProjectPath);
 
             FileSystem = RazorProjectFileSystem.Create(Path.GetDirectoryName(ProjectPath));
             ProjectEngine = RazorProjectEngine.Create(FallbackRazorConfiguration.MVC_2_1, FileSystem, b =>
@@ -24,7 +25,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             });
         }
 
-        private string FilePath { get; }
+        private string DirectoryPath { get; }
 
         private string ProjectPath { get; }
 
@@ -36,15 +37,15 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         public void Changed_TrackerChanged_ResultsInChangedHavingCorrectArgs()
         {
             // Arrange
-            var testImportsPath = "C:\\path\\to\\project\\_ViewImports.cshtml";
+            var testImportsPath = Path.Combine(DirectoryPath, "_ViewImports.cshtml");
-
+            
             var tracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\Views\\Home\\file.cshtml" &&
+                t => t.FilePath == Path.Combine(DirectoryPath, "Views", "Home", "_ViewImports.cshtml") &&
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
             var anotherTracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\anotherFile.cshtml" &&
+                t => t.FilePath == Path.Combine(DirectoryPath, "anotherFile.cshtml") &&
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
@@ -56,12 +57,12 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             fileChangeTrackerFactory
                 .Setup(f => f.Create(testImportsPath))
                 .Returns(fileChangeTracker.Object);
-
+            
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\Views\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "Views", "_ViewImports.cshtml")))
                 .Returns(Mock.Of<FileChangeTracker>());
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\Views\\Home\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "Views", "Home", "_ViewImports.cshtml")))
                 .Returns(Mock.Of<FileChangeTracker>());
 
             var called = false;
@@ -76,8 +77,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
                 Assert.Equal(FileChangeKind.Changed, args.Kind);
                 Assert.Collection(
                     args.AssociatedDocuments,
-                    f => Assert.Equal("C:\\path\\to\\project\\Views\\Home\\file.cshtml", f),
+                    f => Assert.Equal(Path.Combine(DirectoryPath, "Views", "Home", "_ViewImports.cshtml"), f),
-                    f => Assert.Equal("C:\\path\\to\\project\\anotherFile.cshtml", f));
+                    f => Assert.Equal(Path.Combine(DirectoryPath, "anotherFile.cshtml"), f));
             };
 
             // Act

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultImportDocumentManagerTest.cs

@@ -16,7 +16,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
     {
         public DefaultImportDocumentManagerTest()
         {
-            ProjectPath = "C:\\path\\to\\project\\project.csproj";
+            ProjectPath = TestProjectData.SomeProject.FilePath;
+            DirectoryPath = Path.GetDirectoryName(ProjectPath);
 
             FileSystem = RazorProjectFileSystem.Create(Path.GetDirectoryName(ProjectPath));
             ProjectEngine = RazorProjectEngine.Create(FallbackRazorConfiguration.MVC_2_1, FileSystem, b =>
@@ -26,10 +27,10 @@ namespace Microsoft.VisualStudio.Editor.Razor
             });
         }
 
-        private string FilePath { get; }
-
         private string ProjectPath { get; }
 
+        private string DirectoryPath { get; }
+
         private RazorProjectFileSystem FileSystem { get; }
 
         private RazorProjectEngine ProjectEngine { get; }
@@ -39,17 +40,17 @@ namespace Microsoft.VisualStudio.Editor.Razor
         {
             // Arrange
             var tracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\Views\\Home\\file.cshtml" && 
+                t => t.FilePath == Path.Combine(DirectoryPath, "Views", "Home", "file.cshtml") && 
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
-
+            
             var fileChangeTrackerFactory = new Mock<FileChangeTrackerFactory>();
             var fileChangeTracker1 = new Mock<FileChangeTracker>();
             fileChangeTracker1
                 .Setup(f => f.StartListening())
                 .Verifiable();
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\Views\\Home\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "Views", "Home", "_ViewImports.cshtml")))
                 .Returns(fileChangeTracker1.Object)
                 .Verifiable();
             var fileChangeTracker2 = new Mock<FileChangeTracker>();
@@ -57,13 +58,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 .Setup(f => f.StartListening())
                 .Verifiable();
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\Views\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "Views", "_ViewImports.cshtml")))
                 .Returns(fileChangeTracker2.Object)
                 .Verifiable();
             var fileChangeTracker3 = new Mock<FileChangeTracker>();
             fileChangeTracker3.Setup(f => f.StartListening()).Verifiable();
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "_ViewImports.cshtml")))
                 .Returns(fileChangeTracker3.Object)
                 .Verifiable();
 
@@ -84,12 +85,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
         {
             // Arrange
             var tracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\file.cshtml" &&
+                t => t.FilePath == Path.Combine(DirectoryPath, "file.cshtml") &&
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
             var anotherTracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\anotherFile.cshtml" && 
+                t => t.FilePath == Path.Combine(DirectoryPath, "anotherFile.cshtml") && 
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
@@ -115,7 +116,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         {
             // Arrange
             var tracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\file.cshtml" &&
+                t => t.FilePath == Path.Combine(DirectoryPath, "file.cshtml") &&
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
@@ -125,7 +126,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 .Setup(f => f.StopListening())
                 .Verifiable();
             fileChangeTrackerFactory
-                .Setup(f => f.Create("C:\\path\\to\\project\\_ViewImports.cshtml"))
+                .Setup(f => f.Create(Path.Combine(DirectoryPath, "_ViewImports.cshtml")))
                 .Returns(fileChangeTracker.Object)
                 .Verifiable();
 
@@ -145,12 +146,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
         {
             // Arrange
             var tracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\file.cshtml" && 
+                t => t.FilePath == Path.Combine(DirectoryPath, "file.cshtml") && 
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 
             var anotherTracker = Mock.Of<VisualStudioDocumentTracker>(
-                t => t.FilePath == "C:\\path\\to\\project\\anotherFile.cshtml" &&
+                t => t.FilePath == Path.Combine(DirectoryPath, "anotherFile.cshtml") &&
                 t.ProjectPath == ProjectPath &&
                 t.ProjectSnapshot == Mock.Of<ProjectSnapshot>(p => p.GetProjectEngine() == ProjectEngine));
 

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultVisualStudioDocumentTrackerTest.cs

@@ -26,8 +26,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
             RazorCoreContentType = Mock.Of<IContentType>(c => c.IsOfType(RazorLanguage.ContentType) == true);
             TextBuffer = Mock.Of<ITextBuffer>(b => b.ContentType == RazorCoreContentType);
 
-            FilePath = "C:/Some/Path/TestDocumentTracker.cshtml";
+            FilePath = TestProjectData.SomeProjectFile1.FilePath;
-            ProjectPath = "C:/Some/Path/TestProject.csproj";
+            ProjectPath = TestProjectData.SomeProject.FilePath;
 
             ImportDocumentManager = Mock.Of<ImportDocumentManager>();
             WorkspaceEditorSettings = new DefaultWorkspaceEditorSettings(Mock.Of<ForegroundDispatcher>(), Mock.Of<EditorSettingsManager>());
@@ -56,7 +56,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
             ProjectManager = new TestProjectSnapshotManager(Dispatcher, Workspace) { AllowNotifyListeners = true };
 
             HostProject = new HostProject(ProjectPath, FallbackRazorConfiguration.MVC_2_1);
-            OtherHostProject = new HostProject(ProjectPath, FallbackRazorConfiguration.MVC_2_0);
+            UpdatedHostProject = new HostProject(ProjectPath, FallbackRazorConfiguration.MVC_2_0);
+            OtherHostProject = new HostProject(TestProjectData.AnotherProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
 
             DocumentTracker = new DefaultVisualStudioDocumentTracker(
                 Dispatcher,
@@ -79,6 +80,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
         private HostProject HostProject { get; }
 
+        private HostProject UpdatedHostProject { get; }
+
         private HostProject OtherHostProject { get; }
 
         private Project WorkspaceProject { get; set; }
@@ -191,7 +194,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             ProjectManager.HostProjectAdded(HostProject);
             ProjectManager.WorkspaceProjectAdded(WorkspaceProject);
 
-            var e = new ProjectChangeEventArgs(ProjectPath, ProjectChangeKind.ProjectAdded);
+            var e = new ProjectChangeEventArgs(null, ProjectManager.GetLoadedProject(HostProject.FilePath), ProjectChangeKind.ProjectAdded);
 
             var called = false;
             DocumentTracker.ContextChanged += (sender, args) =>
@@ -215,8 +218,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
             // Arrange
             ProjectManager.HostProjectAdded(HostProject);
             ProjectManager.WorkspaceProjectAdded(WorkspaceProject);
-
+            
-            var e = new ProjectChangeEventArgs(ProjectPath, ProjectChangeKind.ProjectChanged);
+            var e = new ProjectChangeEventArgs(null, ProjectManager.GetLoadedProject(HostProject.FilePath), ProjectChangeKind.ProjectChanged);
 
             var called = false;
             DocumentTracker.ContextChanged += (sender, args) =>
@@ -238,7 +241,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
         public void ProjectManager_Changed_ProjectRemoved_TriggersContextChanged_WithEphemeralProject()
         {
             // Arrange
-            var e = new ProjectChangeEventArgs(ProjectPath, ProjectChangeKind.ProjectRemoved);
+            ProjectManager.HostProjectAdded(HostProject);
+            ProjectManager.WorkspaceProjectAdded(WorkspaceProject);
+
+            var project = ProjectManager.GetLoadedProject(HostProject.FilePath);
+            ProjectManager.HostProjectRemoved(HostProject);
+
+            var e = new ProjectChangeEventArgs(project, null, ProjectChangeKind.ProjectRemoved);
 
             var called = false;
             DocumentTracker.ContextChanged += (sender, args) =>
@@ -260,7 +269,9 @@ namespace Microsoft.VisualStudio.Editor.Razor
         public void ProjectManager_Changed_IgnoresUnknownProject()
         {
             // Arrange
-            var e = new ProjectChangeEventArgs("c:/OtherPath/OtherProject.csproj", ProjectChangeKind.ProjectChanged);
+            ProjectManager.HostProjectAdded(OtherHostProject);
+
+            var e = new ProjectChangeEventArgs(null, ProjectManager.GetLoadedProject(OtherHostProject.FilePath), ProjectChangeKind.ProjectChanged);
 
             var called = false;
             DocumentTracker.ContextChanged += (sender, args) =>
@@ -488,13 +499,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
             DocumentTracker.ContextChanged += (sender, e) => { args.Add(e); };
             
             // Act
-            ProjectManager.HostProjectChanged(OtherHostProject);
+            ProjectManager.HostProjectChanged(UpdatedHostProject);
             await DocumentTracker.PendingTagHelperTask;
 
             // Assert
             var snapshot = Assert.IsType<DefaultProjectSnapshot>(DocumentTracker.ProjectSnapshot);
 
-            Assert.Same(OtherHostProject, snapshot.HostProject);
+            Assert.Same(UpdatedHostProject, snapshot.HostProject);
 
             Assert.Collection(
                 args,

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultVisualStudioRazorParserTest.cs

@@ -24,7 +24,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var engine = RazorProjectEngine.Create(RazorConfiguration.Default, RazorProjectFileSystem.Empty);
             ProjectEngineFactory = Mock.Of<ProjectSnapshotProjectEngineFactory>(
                 f => f.Create(
-                    It.IsAny<ProjectSnapshot>(),
+                    It.IsAny<RazorConfiguration>(),
                     It.IsAny<RazorProjectFileSystem>(),
                     It.IsAny<Action<RazorProjectEngineBuilder>>()) == engine);
         }

test/Microsoft.VisualStudio.Editor.Razor.Test/Documents/EditorDocumentManagerBaseTest.cs

@@ -21,13 +21,13 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
 
         private TestEditorDocumentManager Manager { get; }
 
-        public string Project1 => "c:\\Project1";
+        public string Project1 => TestProjectData.SomeProject.FilePath;
 
-        public string Project2 => "c:\\Project2";
+        public string Project2 => TestProjectData.AnotherProject.FilePath;
 
-        public string File1 => "c:\\Project1\\File1.cshtml";
+        public string File1 => TestProjectData.SomeProjectFile1.FilePath;
 
-        public string File2 => "c:\\Project2\\File2.cshtml";
+        public string File2 => TestProjectData.AnotherProjectFile2.FilePath;
 
         public TestTextBuffer TextBuffer => new TestTextBuffer(new StringTextSnapshot("HI"));
 
@@ -113,8 +113,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             // Assert
             Assert.Collection(
                 documents.OrderBy(d => d.ProjectFilePath),
-                d => Assert.Same(document1, d),
+                d => Assert.Same(document2, d),
-                d => Assert.Same(document2, d));
+                d => Assert.Same(document1, d));
         }
 
         [ForegroundFact]
@@ -147,8 +147,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             // Assert
             Assert.Collection(
                 Manager.Opened.OrderBy(d => d.ProjectFilePath),
-                d => Assert.Same(document1, d),
+                d => Assert.Same(document2, d),
-                d => Assert.Same(document2, d));
+                d => Assert.Same(document1, d));
         }
 
         [ForegroundFact]
@@ -165,8 +165,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             // Assert
             Assert.Collection(
                 Manager.Closed.OrderBy(d => d.ProjectFilePath),
-                d => Assert.Same(document1, d),
+                d => Assert.Same(document2, d),
-                d => Assert.Same(document2, d));
+                d => Assert.Same(document1, d));
         }
 
         private class TestEditorDocumentManager : EditorDocumentManagerBase

test/Microsoft.VisualStudio.Editor.Razor.Test/Documents/EditorDocumentManagerListenerTest.cs

@@ -17,8 +17,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
     {
         public EditorDocumentManagerListenerTest()
         {
-            ProjectFilePath = "C:\\project1\\project.csproj";
+            ProjectFilePath = TestProjectData.SomeProject.FilePath;
-            DocumentFilePath = "c:\\project1\\file1.cshtml";
+            DocumentFilePath = TestProjectData.SomeProjectFile1.FilePath;
             TextLoader = TextLoader.From(TextAndVersion.Create(SourceText.From("FILE"), VersionStamp.Default));
             FileChangeTracker = new DefaultFileChangeTracker(DocumentFilePath);
 
@@ -58,8 +58,10 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
 
             var listener = new EditorDocumentManagerListener(editorDocumentManger.Object, changedOnDisk, changedInEditor, opened, closed);
 
+            var project = Mock.Of<ProjectSnapshot>(p => p.FilePath == "/Path/to/project.csproj");
+
             // Act & Assert
-            listener.ProjectManager_Changed(null, new ProjectChangeEventArgs("/Path/to/project.csproj", ProjectChangeKind.DocumentAdded));
+            listener.ProjectManager_Changed(null, new ProjectChangeEventArgs(project, project, ProjectChangeKind.DocumentAdded));
         }
 
         [Fact]
@@ -76,8 +78,10 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
 
             var listener = new EditorDocumentManagerListener(editorDocumentManger.Object, onChangedOnDisk: null, onChangedInEditor: null, onOpened: opened, onClosed: null);
 
+            var project = Mock.Of<ProjectSnapshot>(p => p.FilePath == "/Path/to/project.csproj");
+
             // Act
-            listener.ProjectManager_Changed(null, new ProjectChangeEventArgs("/Path/to/project.csproj", ProjectChangeKind.DocumentAdded));
+            listener.ProjectManager_Changed(null, new ProjectChangeEventArgs(project, project, ProjectChangeKind.DocumentAdded));
 
             // Assert
             Assert.True(called);

test/Microsoft.VisualStudio.Editor.Razor.Test/Documents/EditorDocumentTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Razor;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.Test;
 using Microsoft.VisualStudio.Text;
@@ -16,8 +17,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         public EditorDocumentTest()
         {
             DocumentManager = Mock.Of<EditorDocumentManager>();
-            ProjectFilePath = "C:\\project1\\project.csproj";
+            ProjectFilePath = TestProjectData.SomeProject.FilePath;
-            DocumentFilePath = "c:\\project1\\file1.cshtml";
+            DocumentFilePath = TestProjectData.SomeProjectFile1.FilePath;
             TextLoader = TextLoader.From(TextAndVersion.Create(SourceText.From("FILE"), VersionStamp.Default));
             FileChangeTracker = new DefaultFileChangeTracker(DocumentFilePath);
 

test/Microsoft.VisualStudio.Editor.Razor.Test/Shared/ForegroundDispatcherWorkspaceTestBase.cs

@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.CodeAnalysis.Razor;
+
+namespace Xunit
+{
+    public abstract class ForegroundDispatcherWorkspaceTestBase : WorkspaceTestBase
+    {
+        internal ForegroundDispatcher Dispatcher { get; } = new SingleThreadedForegroundDispatcher();
+    }
+}

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DocumentGenerator/BackgroundDocumentGeneratorTest.cs

@@ -5,6 +5,8 @@ using System;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Host;
 using Moq;
 using Xunit;
 
@@ -12,20 +14,18 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
     // These tests are really integration tests. There isn't a good way to unit test this functionality since
     // the only thing in here is threading.
-    public class BackgroundDocumentGeneratorTest : ForegroundDispatcherTestBase
+    public class BackgroundDocumentGeneratorTest : ForegroundDispatcherWorkspaceTestBase
     {
         public BackgroundDocumentGeneratorTest()
         {
             Documents = new HostDocument[]
             {
-                new HostDocument("c:\\Test1\\Index.cshtml", "Index.cshtml"),
+                TestProjectData.SomeProjectFile1,
-                new HostDocument("c:\\Test1\\Components\\Counter.cshtml", "Components\\Counter.cshtml"),
+                TestProjectData.AnotherProjectFile1,
             };
 
-            HostProject1 = new HostProject("c:\\Test1\\Test1.csproj", FallbackRazorConfiguration.MVC_1_0);
+            HostProject1 = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-            HostProject2 = new HostProject("c:\\Test2\\Test2.csproj", FallbackRazorConfiguration.MVC_1_0);
+            HostProject2 = new HostProject(TestProjectData.AnotherProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-
-            Workspace = TestWorkspace.Create();
 
             var projectId1 = ProjectId.CreateNewId("Test1");
             var projectId2 = ProjectId.CreateNewId("Test2");
@@ -37,14 +37,14 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                     "Test1",
                     "Test1",
                     LanguageNames.CSharp,
-                    "c:\\Test1\\Test1.csproj"))
+                    TestProjectData.SomeProject.FilePath))
                 .AddProject(ProjectInfo.Create(
                     projectId2,
                     VersionStamp.Default,
                     "Test2",
                     "Test2",
                     LanguageNames.CSharp,
-                    "c:\\Test2\\Test2.csproj")); ;
+                    TestProjectData.AnotherProject.FilePath)); ;
 
             WorkspaceProject1 = solution.GetProject(projectId1);
             WorkspaceProject2 = solution.GetProject(projectId2);
@@ -60,7 +60,11 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private Project WorkspaceProject2 { get; }
 
-        private Workspace Workspace { get; }
+        protected override void ConfigureProjectEngine(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Remove(builder.Features.OfType<IImportProjectFeature>().Single());
+            builder.Features.Add(new TestImportProjectFeature());
+        }
 
         [ForegroundFact]
         public async Task Queue_ProcessesNotifications_AndGoesBackToSleep()

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Documents/VisualStudioFileChangeTrackerTest.cs

@@ -23,7 +23,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
                 .Setup(f => f.AdviseFileChange(It.IsAny<string>(), It.IsAny<uint>(), It.IsAny<IVsFileChangeEvents>(), out cookie))
                 .Returns(VSConstants.S_OK)
                 .Verifiable();
-            var tracker = new VisualStudioFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher, ErrorReporter, fileChangeService.Object);
+            var tracker = new VisualStudioFileChangeTracker(TestProjectData.SomeProjectImportFile.FilePath, Dispatcher, ErrorReporter, fileChangeService.Object);
 
             // Act
             tracker.StartListening();
@@ -43,7 +43,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
                 .Setup(f => f.AdviseFileChange(It.IsAny<string>(), It.IsAny<uint>(), It.IsAny<IVsFileChangeEvents>(), out cookie))
                 .Returns(VSConstants.S_OK)
                 .Callback(() => callCount++);
-            var tracker = new VisualStudioFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher, ErrorReporter, fileChangeService.Object);
+            var tracker = new VisualStudioFileChangeTracker(TestProjectData.SomeProjectImportFile.FilePath, Dispatcher, ErrorReporter, fileChangeService.Object);
             tracker.StartListening();
 
             // Act
@@ -67,7 +67,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
                 .Setup(f => f.UnadviseFileChange(cookie))
                 .Returns(VSConstants.S_OK)
                 .Verifiable();
-            var tracker = new VisualStudioFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher, ErrorReporter, fileChangeService.Object);
+            var tracker = new VisualStudioFileChangeTracker(TestProjectData.SomeProjectImportFile.FilePath, Dispatcher, ErrorReporter, fileChangeService.Object);
             tracker.StartListening(); // Start listening for changes.
 
             // Act
@@ -86,7 +86,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             fileChangeService
                 .Setup(f => f.UnadviseFileChange(cookie))
                 .Throws(new InvalidOperationException());
-            var tracker = new VisualStudioFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher, ErrorReporter, fileChangeService.Object);
+            var tracker = new VisualStudioFileChangeTracker(TestProjectData.SomeProjectImportFile.FilePath, Dispatcher, ErrorReporter, fileChangeService.Object);
 
             // Act & Assert
             tracker.StopListening();
@@ -100,7 +100,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         public void FilesChanged_WithSpecificFlags_InvokesChangedHandler_WithExpectedArguments(uint fileChangeFlag, int expectedKind)
         {
             // Arrange
-            var filePath = "C:\\path\\to\\project\\_ViewImports.cshtml";
+            var filePath = TestProjectData.SomeProjectImportFile.FilePath;
             uint cookie;
             var fileChangeService = new Mock<IVsFileChangeEx>();
             fileChangeService

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Microsoft.VisualStudio.LanguageServices.Razor.Test.csproj

@@ -14,6 +14,9 @@
     <Compile Include="..\Microsoft.CodeAnalysis.Razor.Workspaces.Test\Shared\**\*.cs">
       <Link>Shared\%(RecursiveDir)%(FileName)%(Extension)</Link>
     </Compile>
+    <Compile Include="..\Microsoft.VisualStudio.Editor.Razor.Test\Shared\**\*.cs">
+      <Link>Shared\%(RecursiveDir)%(FileName)%(Extension)</Link>
+    </Compile>
   </ItemGroup>
 
   <ItemGroup>

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/ProjectSystem/DefaultProjectSnapshotManagerTest.cs

@@ -13,35 +13,24 @@ using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class DefaultProjectSnapshotManagerTest : ForegroundDispatcherTestBase
+    public class DefaultProjectSnapshotManagerTest : ForegroundDispatcherWorkspaceTestBase
     {
         public DefaultProjectSnapshotManagerTest()
         {
             TagHelperResolver = new TestTagHelperResolver();
 
-            HostServices = TestServices.Create(
-                new IWorkspaceService[]
-                {
-                    new TestProjectSnapshotProjectEngineFactory(),
-                },
-                new ILanguageService[]
-                {
-                    TagHelperResolver,
-                });
-
             Documents = new HostDocument[]
             {
-                new HostDocument("c:\\MyProject\\File.cshtml", "File.cshtml"),
+                TestProjectData.SomeProjectFile1,
-                new HostDocument("c:\\MyProject\\Index.cshtml", "Index.cshtml"),
+                TestProjectData.SomeProjectFile2,
 
                 // linked file
-                new HostDocument("c:\\SomeOtherProject\\Index.cshtml", "Pages\\Index.cshtml"),
+                TestProjectData.AnotherProjectNestedFile3,
             };
 
-            HostProject = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_2_0);
+            HostProject = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
-            HostProjectWithConfigurationChange = new HostProject("c:\\MyProject\\Test.csproj", FallbackRazorConfiguration.MVC_1_0);
+            HostProjectWithConfigurationChange = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-
+            
-            Workspace = TestWorkspace.Create(HostServices);
             ProjectManager = new TestProjectSnapshotManager(Dispatcher, Enumerable.Empty<ProjectSnapshotChangeTrigger>(), Workspace);
 
             var projectId = ProjectId.CreateNewId("Test");
@@ -51,7 +40,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 "Test",
                 "Test",
                 LanguageNames.CSharp,
-                "c:\\MyProject\\Test.csproj"));
+                TestProjectData.SomeProject.FilePath));
             WorkspaceProject = solution.GetProject(projectId);
 
             var vbProjectId = ProjectId.CreateNewId("VB");
@@ -81,7 +70,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 "Test (Different TFM)",
                 "Test",
                 LanguageNames.CSharp,
-                "c:\\MyProject\\Test.csproj"));
+                TestProjectData.SomeProject.FilePath));
             WorkspaceProjectWithDifferentTfm = solution.GetProject(projectIdWithDifferentTfm);
 
             SomeTagHelpers = TagHelperResolver.TagHelpers;
@@ -108,14 +97,15 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private TestProjectSnapshotManager ProjectManager { get; }
 
-        private HostServices HostServices { get; }
-
-        private Workspace Workspace { get; }
-
         private SourceText SourceText { get; }
 
         private IList<TagHelperDescriptor> SomeTagHelpers { get; }
 
+        protected override void ConfigureLanguageServices(List<ILanguageService> services)
+        {
+            services.Add(TagHelperResolver);
+        }
+
         [ForegroundFact]
         public void DocumentAdded_AddsDocument()
         {
@@ -129,7 +119,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert
             var snapshot = ProjectManager.GetSnapshot(HostProject);
-            Assert.Collection(snapshot.DocumentFilePaths, d => Assert.Equal(Documents[0].FilePath, d));
+            Assert.Collection(snapshot.DocumentFilePaths.OrderBy(f => f), d => Assert.Equal(Documents[0].FilePath, d));
 
             Assert.Equal(ProjectChangeKind.DocumentAdded, ProjectManager.ListenersNotifiedOf);
         }
@@ -148,7 +138,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert
             var snapshot = ProjectManager.GetSnapshot(HostProject);
-            Assert.Collection(snapshot.DocumentFilePaths, d => Assert.Equal(Documents[0].FilePath, d));
+            Assert.Collection(snapshot.DocumentFilePaths.OrderBy(f => f), d => Assert.Equal(Documents[0].FilePath, d));
 
             Assert.Null(ProjectManager.ListenersNotifiedOf);
         }
@@ -262,9 +252,9 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             // Assert
             var snapshot = ProjectManager.GetSnapshot(HostProject);
             Assert.Collection(
-                snapshot.DocumentFilePaths, 
+                snapshot.DocumentFilePaths.OrderBy(f => f), 
-                d => Assert.Equal(Documents[0].FilePath, d),
+                d => Assert.Equal(Documents[2].FilePath, d),
-                d => Assert.Equal(Documents[2].FilePath, d));
+                d => Assert.Equal(Documents[0].FilePath, d));
 
             Assert.Equal(ProjectChangeKind.DocumentRemoved, ProjectManager.ListenersNotifiedOf);
         }

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/ProjectSystem/DefaultRazorProjectHostTest.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
@@ -15,11 +16,10 @@ using ItemCollection = Microsoft.VisualStudio.ProjectSystem.ItemCollection;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class DefaultRazorProjectHostTest : ForegroundDispatcherTestBase
+    public class DefaultRazorProjectHostTest : ForegroundDispatcherWorkspaceTestBase
     {
         public DefaultRazorProjectHostTest()
         {
-            Workspace = new AdhocWorkspace();
             ProjectManager = new TestProjectSnapshotManager(Dispatcher, Workspace);
 
             ConfigurationItems = new ItemCollection(Rules.RazorConfiguration.SchemaName);
@@ -38,8 +38,6 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private TestProjectSnapshotManager ProjectManager { get; }
 
-        private Workspace Workspace { get; }
-
         [Fact]
         public void TryGetDefaultConfiguration_FailsIfNoRule()
         {
@@ -612,7 +610,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
         public async Task DefaultRazorProjectHost_ForegroundThread_CreateAndDispose_Succeeds()
         {
             // Arrange
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
             // Act & Assert
@@ -627,7 +625,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
         public async Task DefaultRazorProjectHost_BackgroundThread_CreateAndDispose_Succeeds()
         {
             // Arrange
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
             // Act & Assert
@@ -646,7 +644,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             {
             };
 
-            var services = new TestProjectSystemServices("Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
             // Act & Assert
@@ -670,8 +668,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ExtensionItems.Item("MVC-2.1");
             ExtensionItems.Item("Another-Thing");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
-            DocumentItems.Property("File.cshtml", Rules.RazorGenerateWithTargetPath.TargetPathProperty, "File.cshtml");
+            DocumentItems.Property(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath), Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.SomeProjectFile1.TargetPath);
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -681,7 +679,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -693,7 +691,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert
             var snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
 
             Assert.Equal(RazorLanguageVersion.Version_2_1, snapshot.Configuration.LanguageVersion);
             Assert.Equal("MVC-2.1", snapshot.Configuration.ConfigurationName);
@@ -707,8 +705,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 d =>
                 {
                     var document = snapshot.GetDocument(d);
-                    Assert.Equal("c:\\MyProject\\File.cshtml", document.FilePath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.FilePath, document.FilePath);
-                    Assert.Equal("File.cshtml", document.TargetPath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.TargetPath, document.TargetPath);
                 });
 
             await Task.Run(async () => await host.DisposeAsync());
@@ -726,7 +724,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             ExtensionItems.Item("TestExtension");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -736,7 +734,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -766,8 +764,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ExtensionItems.Item("MVC-2.1");
             ExtensionItems.Item("Another-Thing");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
-            DocumentItems.Property("File.cshtml", Rules.RazorGenerateWithTargetPath.TargetPathProperty, "File.cshtml");
+            DocumentItems.Property(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath), Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.SomeProjectFile1.TargetPath);
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -777,7 +775,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -789,7 +787,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert - 1
             var snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
 
             Assert.Equal(RazorLanguageVersion.Version_2_1, snapshot.Configuration.LanguageVersion);
             Assert.Equal("MVC-2.1", snapshot.Configuration.ConfigurationName);
@@ -803,8 +801,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 d => 
                 {
                     var document = snapshot.GetDocument(d);
-                    Assert.Equal("c:\\MyProject\\File.cshtml", document.FilePath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.FilePath, document.FilePath);
-                    Assert.Equal("File.cshtml", document.TargetPath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.TargetPath, document.TargetPath);
                 });
 
             // Act - 2
@@ -813,9 +811,9 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ConfigurationItems.RemoveItem("MVC-2.1");
             ConfigurationItems.Item("MVC-2.0", new Dictionary<string, string>() { { "Extensions", "MVC-2.0;Another-Thing" }, });
             ExtensionItems.Item("MVC-2.0");
-            DocumentItems.Item("c:\\AnotherProject\\AnotherFile.cshtml", new Dictionary<string, string>()
+            DocumentItems.Item(TestProjectData.AnotherProjectNestedFile3.FilePath, new Dictionary<string, string>()
             {
-                { Rules.RazorGenerateWithTargetPath.TargetPathProperty, "Pages\\AnotherFile.cshtml" },
+                { Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.AnotherProjectNestedFile3.TargetPath },
             });
 
             changes = new TestProjectChangeDescription[]
@@ -830,7 +828,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert - 2
             snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
 
             Assert.Equal(RazorLanguageVersion.Version_2_0, snapshot.Configuration.LanguageVersion);
             Assert.Equal("MVC-2.0", snapshot.Configuration.ConfigurationName);
@@ -844,14 +842,14 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 d =>
                 {
                     var document = snapshot.GetDocument(d);
-                    Assert.Equal("c:\\AnotherProject\\AnotherFile.cshtml", document.FilePath);
+                    Assert.Equal(TestProjectData.AnotherProjectNestedFile3.FilePath, document.FilePath);
-                    Assert.Equal("Pages\\AnotherFile.cshtml", document.TargetPath);
+                    Assert.Equal(TestProjectData.AnotherProjectNestedFile3.TargetPath, document.TargetPath);
                 },
                 d =>
                 {
                     var document = snapshot.GetDocument(d);
-                    Assert.Equal("c:\\MyProject\\File.cshtml", document.FilePath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.FilePath, document.FilePath);
-                    Assert.Equal("File.cshtml", document.TargetPath);
+                    Assert.Equal(TestProjectData.SomeProjectFile1.TargetPath, document.TargetPath);
                 });
 
             await Task.Run(async () => await host.DisposeAsync());
@@ -871,8 +869,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ExtensionItems.Item("MVC-2.1");
             ExtensionItems.Item("Another-Thing");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
-            DocumentItems.Property("File.cshtml", Rules.RazorGenerateWithTargetPath.TargetPathProperty, "File.cshtml");
+            DocumentItems.Property(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath), Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.SomeProjectFile1.TargetPath);
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -882,7 +880,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -894,7 +892,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert - 1
             var snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
 
             Assert.Equal(RazorLanguageVersion.Version_2_1, snapshot.Configuration.LanguageVersion);
             Assert.Equal("MVC-2.1", snapshot.Configuration.ConfigurationName);
@@ -937,8 +935,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ExtensionItems.Item("MVC-2.1");
             ExtensionItems.Item("Another-Thing");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
-            DocumentItems.Property("File.cshtml", Rules.RazorGenerateWithTargetPath.TargetPathProperty, "File.cshtml");
+            DocumentItems.Property(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath), Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.SomeProjectFile1.TargetPath);
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -948,7 +946,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -960,7 +958,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert - 1
             var snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
 
             Assert.Equal(RazorLanguageVersion.Version_2_1, snapshot.Configuration.LanguageVersion);
             Assert.Equal("MVC-2.1", snapshot.Configuration.ConfigurationName);
@@ -1007,8 +1005,8 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
             ExtensionItems.Item("MVC-2.1");
             ExtensionItems.Item("Another-Thing");
 
-            DocumentItems.Item("File.cshtml");
+            DocumentItems.Item(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath));
-            DocumentItems.Property("File.cshtml", Rules.RazorGenerateWithTargetPath.TargetPathProperty, "File.cshtml");
+            DocumentItems.Property(Path.GetFileName(TestProjectData.SomeProjectFile1.FilePath), Rules.RazorGenerateWithTargetPath.TargetPathProperty, TestProjectData.SomeProjectFile1.TargetPath);
 
             var changes = new TestProjectChangeDescription[]
             {
@@ -1018,7 +1016,7 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
                 DocumentItems.ToChange(),
             };
 
-            var services = new TestProjectSystemServices("c:\\MyProject\\Test.csproj");
+            var services = new TestProjectSystemServices(TestProjectData.SomeProject.FilePath);
 
             var host = new DefaultRazorProjectHost(services, Workspace, ProjectManager);
 
@@ -1030,16 +1028,16 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
             // Assert - 1
             var snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\MyProject\\Test.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.SomeProject.FilePath, snapshot.FilePath);
             Assert.Same("MVC-2.1", snapshot.Configuration.ConfigurationName);
 
             // Act - 2
-            services.UnconfiguredProject.FullPath = "c:\\AnotherProject\\Test2.csproj";
+            services.UnconfiguredProject.FullPath = TestProjectData.AnotherProject.FilePath;
             await Task.Run(async () => await host.OnProjectRenamingAsync());
 
             // Assert - 1
             snapshot = Assert.Single(ProjectManager.Projects);
-            Assert.Equal("c:\\AnotherProject\\Test2.csproj", snapshot.FilePath);
+            Assert.Equal(TestProjectData.AnotherProject.FilePath, snapshot.FilePath);
             Assert.Same("MVC-2.1", snapshot.Configuration.ConfigurationName);
 
             await Task.Run(async () => await host.DisposeAsync());

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/ProjectSystem/FallbackRazorProjectHostTest.cs

@@ -12,11 +12,10 @@ using ItemReference = Microsoft.CodeAnalysis.Razor.ProjectSystem.ManagedProjectS
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class FallbackRazorProjectHostTest : ForegroundDispatcherTestBase
+    public class FallbackRazorProjectHostTest : ForegroundDispatcherWorkspaceTestBase
     {
         public FallbackRazorProjectHostTest()
         {
-            Workspace = new AdhocWorkspace();
             ProjectManager = new TestProjectSnapshotManager(Dispatcher, Workspace);
 
             ReferenceItems = new ItemCollection(ManagedProjectSystemSchema.ResolvedCompilationReference.SchemaName);
@@ -32,8 +31,6 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private ItemCollection NoneItems { get; }
 
-        private Workspace Workspace { get; }
-
         [Fact]
         public void GetChangedAndRemovedDocuments_ReturnsChangedContentAndNoneItems()
         {

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/ProjectSystem/WorkspaceProjectSnapshotChangeTriggerTest.cs

@@ -9,11 +9,10 @@ using Xunit;
 
 namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 {
-    public class WorkspaceProjectSnapshotChangeTriggerTest : ForegroundDispatcherTestBase
+    public class WorkspaceProjectSnapshotChangeTriggerTest : ForegroundDispatcherWorkspaceTestBase
     {
         public WorkspaceProjectSnapshotChangeTriggerTest()
         {
-            Workspace = TestWorkspace.Create();
             EmptySolution = Workspace.CurrentSolution.GetIsolatedSolution();
 
             var projectId1 = ProjectId.CreateNewId("One");
@@ -72,8 +71,6 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem
 
         private Project ProjectNumberThree { get; }
 
-        private Workspace Workspace { get; }
-
         [ForegroundTheory]
         [InlineData(WorkspaceChangeKind.SolutionAdded)]
         [InlineData(WorkspaceChangeKind.SolutionChanged)]

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/VsSolutionUpdatesProjectSnapshotChangeTriggerTest.cs

@@ -2,8 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Razor;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.VisualStudio.Editor.Razor;
 using Microsoft.VisualStudio.Shell.Interop;
@@ -16,8 +16,8 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
     {
         public VsSolutionUpdatesProjectSnapshotChangeTriggerTest()
         {
-            SomeProject = new HostProject("c:\\SomeProject\\SomeProject.csproj", FallbackRazorConfiguration.MVC_1_0);
+            SomeProject = new HostProject(TestProjectData.SomeProject.FilePath, FallbackRazorConfiguration.MVC_1_0);
-            SomeOtherProject = new HostProject("c:\\SomeOtherProject\\SomeOtherProject.csproj", FallbackRazorConfiguration.MVC_2_0);
+            SomeOtherProject = new HostProject(TestProjectData.AnotherProject.FilePath, FallbackRazorConfiguration.MVC_2_0);
 
             Workspace = TestWorkspace.Create(w =>
             {

test/Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test/Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test.csproj

@@ -8,6 +8,9 @@
     <Compile Include="..\Microsoft.CodeAnalysis.Razor.Workspaces.Test\Shared\**\*.cs">
       <Link>Shared\%(RecursiveDir)%(FileName)%(Extension)</Link>
     </Compile>
+    <Compile Include="..\Microsoft.VisualStudio.Editor.Razor.Test\Shared\**\*.cs">
+      <Link>Shared\%(RecursiveDir)%(FileName)%(Extension)</Link>
+    </Compile>
   </ItemGroup>
 
   <ItemGroup>