Better support for _Imports.razor (dotnet/aspnetcore-tooling#357)

* Better support for _Imports.razor

* Special case component imports when generating code

* Prevent a future VS crash

* Rebased and updated

* update

* Removed unnecessary newline
\n\nCommit migrated from abbfe00bdc

src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.Designer.cs

@@ -223,7 +223,7 @@ namespace Microsoft.AspNetCore.Razor.Language {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to The &apos;@{0}&apos; directive specified in {1} file will not be imported. The directive must appear at the top of each Razor cshtml file.
+        ///   Looks up a localized string similar to The &apos;@{0}&apos; directive specified in {1} file will not be imported. The directive must appear at the top of each Razor file.
         /// </summary>
         internal static string PageDirectiveCannotBeImported {
             get {

src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.resx

@@ -163,7 +163,7 @@
     <value>TypeName</value>
   </data>
   <data name="PageDirectiveCannotBeImported" xml:space="preserve">
-    <value>The '@{0}' directive specified in {1} file will not be imported. The directive must appear at the top of each Razor cshtml file</value>
+    <value>The '@{0}' directive specified in {1} file will not be imported. The directive must appear at the top of each Razor file</value>
   </data>
   <data name="PageDirective_Description" xml:space="preserve">
     <value>Mark the page as a routable component.</value>

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDiagnosticFactory.cs

@@ -17,7 +17,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
         public static readonly RazorDiagnosticDescriptor UnsupportedTagHelperDirective = new RazorDiagnosticDescriptor(
             $"{DiagnosticPrefix}9978",
             () => 
-                "The directives @addTagHelper, @removeTagHelper and @tagHelperPrefix are not valid in a component document." +
+                "The directives @addTagHelper, @removeTagHelper and @tagHelperPrefix are not valid in a component document. " +
                 "Use '@using <namespace>' directive instead.",
             RazorDiagnosticSeverity.Error);
 
@@ -321,5 +321,16 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
         {
             return RazorDiagnostic.Create(ChildContentHasInvalidParameterOnComponent, source ?? SourceSpan.Undefined, attribute, element);
         }
+
+        public static readonly RazorDiagnosticDescriptor UnsupportedComponentImportContent =
+            new RazorDiagnosticDescriptor(
+                $"{DiagnosticPrefix}10003",
+                () => "Markup, code and block directives are not valid in component imports.",
+                RazorDiagnosticSeverity.Error);
+
+        public static RazorDiagnostic Create_UnsupportedComponentImportContent(SourceSpan? source)
+        {
+            return RazorDiagnostic.Create(UnsupportedComponentImportContent, source ?? SourceSpan.Undefined);
+        }
     }
 }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDocumentClassifierPass.cs

@@ -70,47 +70,63 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             }
 
             @namespace.Content = computedNamespace;
-
-            @class.BaseType = ComponentsApi.ComponentBase.FullTypeName;
             @class.ClassName = computedClass;
             @class.Modifiers.Clear();
             @class.Modifiers.Add("public");
 
-            var documentNode = codeDocument.GetDocumentIntermediateNode();
-            var typeParamReferences = documentNode.FindDirectiveReferences(ComponentTypeParamDirective.Directive);
-            for (var i = 0; i < typeParamReferences.Count; i++)
+            if (FileKinds.IsComponentImport(codeDocument.GetFileKind()))
             {
-                var typeParamNode = (DirectiveIntermediateNode)typeParamReferences[i].Node;
-                if (typeParamNode.HasDiagnostics)
+                // We don't want component imports to be considered as real component.
+                // But we still want to generate code for it so we can get diagnostics.
+                @class.BaseType = typeof(object).FullName;
+
+                method.ReturnType = "void";
+                method.MethodName = "Execute";
+                method.Modifiers.Clear();
+                method.Modifiers.Add("protected");
+
+                method.Parameters.Clear();
+            }
+            else
+            {
+                @class.BaseType = ComponentsApi.ComponentBase.FullTypeName;
+
+                var documentNode = codeDocument.GetDocumentIntermediateNode();
+                var typeParamReferences = documentNode.FindDirectiveReferences(ComponentTypeParamDirective.Directive);
+                for (var i = 0; i < typeParamReferences.Count; i++)
                 {
-                    continue;
+                    var typeParamNode = (DirectiveIntermediateNode)typeParamReferences[i].Node;
+                    if (typeParamNode.HasDiagnostics)
+                    {
+                        continue;
+                    }
+
+                    @class.TypeParameters.Add(new TypeParameter() { ParameterName = typeParamNode.Tokens.First().Content, });
                 }
 
-                @class.TypeParameters.Add(new TypeParameter() { ParameterName = typeParamNode.Tokens.First().Content, });
+                method.ReturnType = "void";
+                method.MethodName = ComponentsApi.ComponentBase.BuildRenderTree;
+                method.Modifiers.Clear();
+                method.Modifiers.Add("protected");
+                method.Modifiers.Add("override");
+
+                method.Parameters.Clear();
+                method.Parameters.Add(new MethodParameter()
+                {
+                    ParameterName = "builder",
+                    TypeName = ComponentsApi.RenderTreeBuilder.FullTypeName,
+                });
+
+                // We need to call the 'base' method as the first statement.
+                var callBase = new CSharpCodeIntermediateNode();
+                callBase.Annotations.Add(BuildRenderTreeBaseCallAnnotation, true);
+                callBase.Children.Add(new IntermediateToken
+                {
+                    Kind = TokenKind.CSharp,
+                    Content = $"base.{ComponentsApi.ComponentBase.BuildRenderTree}(builder);"
+                });
+                method.Children.Insert(0, callBase);
             }
-
-            method.ReturnType = "void";
-            method.MethodName = ComponentsApi.ComponentBase.BuildRenderTree;
-            method.Modifiers.Clear();
-            method.Modifiers.Add("protected");
-            method.Modifiers.Add("override");
-
-            method.Parameters.Clear();
-            method.Parameters.Add(new MethodParameter()
-            {
-                ParameterName = "builder",
-                TypeName = ComponentsApi.RenderTreeBuilder.FullTypeName,
-            });
-
-            // We need to call the 'base' method as the first statement.
-            var callBase = new CSharpCodeIntermediateNode();
-            callBase.Annotations.Add(BuildRenderTreeBaseCallAnnotation, true);
-            callBase.Children.Add(new IntermediateToken
-            {
-                Kind = TokenKind.CSharp,
-                Content = $"base.{ComponentsApi.ComponentBase.BuildRenderTree}(builder);"
-            });
-            method.Children.Insert(0, callBase);
         }
 
         internal static bool IsBuildRenderTreeBaseCall(CSharpCodeIntermediateNode node)

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentInjectDirective.cs

@@ -29,7 +29,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(FileKinds.Component, Directive);
+            builder.AddDirective(Directive, FileKinds.Component, FileKinds.ComponentImport);
             builder.Features.Add(new ComponentInjectDirectivePass());
         }
     }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentLayoutDirective.cs

@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(FileKinds.Component, Directive);
+            builder.AddDirective(Directive, FileKinds.Component, FileKinds.ComponentImport);
             builder.Features.Add(new ComponentLayoutDirectivePass());
         }
     }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentLayoutDirectivePass.cs

@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             attributeNode.Children.Add(new IntermediateToken()
             {
                 Kind = TokenKind.CSharp,
-                Content = $"[{ComponentsApi.LayoutAttribute.FullTypeName}(typeof({token.Content}))]" + Environment.NewLine,
+                Content = $"[{ComponentsApi.LayoutAttribute.FullTypeName}(typeof({token.Content}))]",
             });
             
             // Insert the new attribute on top of the class

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentPageDirective.cs

@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(FileKinds.Component, Directive);
+            builder.AddDirective(Directive, FileKinds.Component, FileKinds.ComponentImport);
             builder.Features.Add(new ComponentPageDirectivePass());
             return builder;
         }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentPageDirectivePass.cs

@@ -38,7 +38,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             for (var i = 0; i < directives.Count; i++)
             {
                 var directive = directives[i];
-                if (directive.Node.IsImported())
+                if (FileKinds.IsComponentImport(codeDocument.GetFileKind()) || directive.Node.IsImported())
                 {
                     directive.Node.Diagnostics.Add(ComponentDiagnosticFactory.CreatePageDirective_CannotBeImported(directive.Node.Source.Value));
                 }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentTypeParamDirective.cs

@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(FileKinds.Component, Directive);
+            builder.AddDirective(Directive, FileKinds.Component, FileKinds.ComponentImport);
             return builder;
         }
     }

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

@@ -9,7 +9,21 @@ namespace Microsoft.AspNetCore.Razor.Language
 {
     internal class DefaultRazorDirectiveFeature : RazorEngineFeatureBase, IRazorDirectiveFeature, IConfigureRazorParserOptionsFeature
     {
-        public ICollection<DirectiveDescriptor> Directives { get; } = new List<DirectiveDescriptor>();
+        // To maintain backwards compatibility, adding to this list will default to legacy file kind.
+        public ICollection<DirectiveDescriptor> Directives
+        {
+            get
+            {
+                ICollection<DirectiveDescriptor> result;
+                if (!DirectivesByFileKind.TryGetValue(FileKinds.Legacy, out result))
+                {
+                    result = new List<DirectiveDescriptor>();
+                    DirectivesByFileKind.Add(FileKinds.Legacy, result);
+                }
+
+                return result;
+            }
+        }
 
         public IDictionary<string, ICollection<DirectiveDescriptor>> DirectivesByFileKind { get; } = new Dictionary<string, ICollection<DirectiveDescriptor>>(StringComparer.OrdinalIgnoreCase);
 
@@ -24,22 +38,11 @@ namespace Microsoft.AspNetCore.Razor.Language
 
             options.Directives.Clear();
 
-            foreach (var directive in Directives)
-            {
-                options.Directives.Add(directive);
-            }
-
-            if (options.FileKind != null && DirectivesByFileKind.TryGetValue(options.FileKind, out var directives))
+            var fileKind = options.FileKind ?? FileKinds.Legacy;
+            if (DirectivesByFileKind.TryGetValue(fileKind, out var directives))
             {
                 foreach (var directive in directives)
                 {
-                    // Replace any non-file-kind-specific directives
-                    var replaces = options.Directives.Where(d => string.Equals(d.Directive, directive.Directive, StringComparison.Ordinal)).ToArray();
-                    foreach (var replace in replaces)
-                    {
-                        options.Directives.Remove(replace);
-                    }
-
                     options.Directives.Add(directive);
                 }
             }

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

@@ -45,7 +45,17 @@ namespace Microsoft.AspNetCore.Razor.Language
             // We need to decide up front if this document is a "component" file. This will affect how
             // lowering behaves.
             LoweringVisitor visitor;
-            if (FileKinds.IsComponent(codeDocument.GetFileKind()) &&
+            if (FileKinds.IsComponentImport(codeDocument.GetFileKind()) &&
+                syntaxTree.Options.FeatureFlags.AllowComponentFileKind)
+            {
+                visitor = new ComponentImportFileKindVisitor(document, builder, syntaxTree.Options.FeatureFlags)
+                {
+                    SourceDocument = syntaxTree.Source,
+                };
+
+                visitor.Visit(syntaxTree.Root);
+            }
+            else if (FileKinds.IsComponent(codeDocument.GetFileKind()) &&
                 syntaxTree.Options.FeatureFlags.AllowComponentFileKind)
             {
                 visitor = new ComponentFileKindVisitor(document, builder, syntaxTree.Options.FeatureFlags)
@@ -1856,6 +1866,58 @@ namespace Microsoft.AspNetCore.Razor.Language
             }
         }
 
+        private class ComponentImportFileKindVisitor : LoweringVisitor
+        {
+            public ComponentImportFileKindVisitor(
+                DocumentIntermediateNode document,
+                IntermediateNodeBuilder builder,
+                RazorParserFeatureFlags featureFlags)
+                : base(document, builder, featureFlags)
+            {
+            }
+
+            public override void DefaultVisit(SyntaxNode node)
+            {
+                base.DefaultVisit(node);
+            }
+
+            public override void VisitMarkupElement(MarkupElementSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+
+            public override void VisitMarkupCommentBlock(MarkupCommentBlockSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+
+            public override void VisitMarkupTagHelperElement(MarkupTagHelperElementSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+
+            public override void VisitCSharpImplicitExpression(CSharpImplicitExpressionSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+
+            public override void VisitCSharpExplicitExpression(CSharpExplicitExpressionSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+
+            public override void VisitCSharpStatement(CSharpStatementSyntax node)
+            {
+                _document.Diagnostics.Add(
+                    ComponentDiagnosticFactory.Create_UnsupportedComponentImportContent(BuildSourceSpanFromNode(node)));
+            }
+        }
+
         private class ImportsVisitor : LoweringVisitor
         {
             public ImportsVisitor(DocumentIntermediateNode document, IntermediateNodeBuilder builder, RazorParserFeatureFlags featureFlags)

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

@@ -37,7 +37,9 @@ namespace Microsoft.AspNetCore.Razor.Language
             // The imports come logically before the main razor file and are in the order they
             // should be processed.
             DirectiveVisitor visitor = null;
-            if (FileKinds.IsComponent(codeDocument.GetFileKind()))
+            var parserOptions = codeDocument.GetParserOptions();
+            if (FileKinds.IsComponent(codeDocument.GetFileKind()) &&
+                (parserOptions == null || parserOptions.FeatureFlags.AllowComponentFileKind))
             {
                 codeDocument.TryComputeNamespaceAndClass(out var currentNamespace, out var _);
                 visitor = new ComponentDirectiveVisitor(codeDocument.Source.FilePath, descriptors, currentNamespace);

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Extensions/FunctionsDirective.cs

@@ -23,7 +23,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(Directive);
+            builder.AddDirective(Directive, FileKinds.Legacy, FileKinds.Component);
             builder.Features.Add(new FunctionsDirectivePass());
         }
 

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Extensions/ImplementsDirective.cs

@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(Directive);
+            builder.AddDirective(Directive, FileKinds.Legacy, FileKinds.Component, FileKinds.ComponentImport);
             builder.Features.Add(new ImplementsDirectivePass());
         }
     }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Extensions/InheritsDirective.cs

@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(Directive);
+            builder.AddDirective(Directive, FileKinds.Legacy, FileKinds.Component, FileKinds.ComponentImport);
             builder.Features.Add(new InheritsDirectivePass());
         }
 

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Extensions/SectionDirective.cs

@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            builder.AddDirective(Directive);
+            builder.AddDirective(Directive, FileKinds.Legacy, FileKinds.Component);
             builder.Features.Add(new SectionDirectivePass());
             builder.AddTargetExtension(new SectionTargetExtension());
         }

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

@@ -27,6 +27,23 @@ namespace Microsoft.AspNetCore.Razor.Language
             return string.Equals(fileKind, FileKinds.ComponentImport, StringComparison.OrdinalIgnoreCase);
         }
 
+        public static string GetComponentFileKindFromFilePath(string filePath)
+        {
+            if (filePath == null)
+            {
+                throw new ArgumentNullException(nameof(filePath));
+            }
+
+            if (string.Equals(ComponentMetadata.ImportsFileName, Path.GetFileName(filePath), StringComparison.Ordinal))
+            {
+                return FileKinds.ComponentImport;
+            }
+            else
+            {
+                return FileKinds.Component;
+            }
+        }
+
         public static string GetFileKindFromFilePath(string filePath)
         {
             if (filePath == null)

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

@@ -166,35 +166,38 @@ namespace Microsoft.AspNetCore.Razor.Language
         /// Adds the specified <see cref="DirectiveDescriptor"/> for the provided file kind.
         /// </summary>
         /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
-        /// <param name="fileKind">The file kind, for which to register the directive. See <see cref="FileKinds"/>.</param>
         /// <param name="directive">The <see cref="DirectiveDescriptor"/> to add.</param>
+        /// <param name="fileKinds">The file kinds, for which to register the directive. See <see cref="FileKinds"/>.</param>
         /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
-        public static RazorProjectEngineBuilder AddDirective(this RazorProjectEngineBuilder builder, string fileKind, DirectiveDescriptor directive)
+        public static RazorProjectEngineBuilder AddDirective(this RazorProjectEngineBuilder builder, DirectiveDescriptor directive, params string[] fileKinds)
         {
             if (builder == null)
             {
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            if (fileKind == null)
-            {
-                throw new ArgumentNullException(nameof(fileKind));
-            }
-
             if (directive == null)
             {
                 throw new ArgumentNullException(nameof(directive));
             }
 
-            var directiveFeature = GetDirectiveFeature(builder);
-
-            if (!directiveFeature.DirectivesByFileKind.TryGetValue(fileKind, out var directives))
+            if (fileKinds == null)
             {
-                directives = new List<DirectiveDescriptor>();
-                directiveFeature.DirectivesByFileKind.Add(fileKind, directives);
+                throw new ArgumentNullException(nameof(fileKinds));
             }
 
-            directives.Add(directive);
+            var directiveFeature = GetDirectiveFeature(builder);
+
+            foreach (var fileKind in fileKinds)
+            {
+                if (!directiveFeature.DirectivesByFileKind.TryGetValue(fileKind, out var directives))
+                {
+                    directives = new List<DirectiveDescriptor>();
+                    directiveFeature.DirectivesByFileKind.Add(fileKind, directives);
+                }
+
+                directives.Add(directive);
+            }
 
             return builder;
         }

src/Razor/Microsoft.AspNetCore.Razor.Tools/src/GenerateCommand.cs

@@ -7,6 +7,7 @@ using System.Diagnostics;
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Components;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Razor;
 using Microsoft.Extensions.CommandLineUtils;
@@ -286,6 +287,10 @@ namespace Microsoft.AspNetCore.Razor.Tools
             {
                 var outputPath = Path.Combine(projectDirectory, outputs[i]);
                 var fileKind = fileKinds.Count > 0 ? fileKinds[i] : "mvc";
+                if (Language.FileKinds.IsComponent(fileKind))
+                {
+                    fileKind = Language.FileKinds.GetComponentFileKindFromFilePath(sources[i]);
+                }
 
                 items[i] = new SourceItem(sources[i], outputs[i], relativePath[i], fileKind);
             }

src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/RazorIntegrationTestBase.cs

@@ -59,6 +59,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
         {
             AdditionalSyntaxTrees = new List<SyntaxTree>();
             AdditionalRazorItems = new List<RazorProjectItem>();
+            ImportItems = new List<RazorProjectItem>();
 
             BaseCompilation = DefaultBaseCompilation;
             Configuration = RazorConfiguration.Default;
@@ -72,6 +73,8 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
 
         internal List<RazorProjectItem> AdditionalRazorItems { get; }
 
+        internal List<RazorProjectItem> ImportItems { get; }
+
         internal List<SyntaxTree> AdditionalSyntaxTrees { get; }
 
         internal virtual CSharpCompilation BaseCompilation { get; }
@@ -118,6 +121,8 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
                 // Turn off checksums, we're testing code generation.
                 b.Features.Add(new SuppressChecksum());
 
+                b.Features.Add(new TestImportProjectFeature(ImportItems));
+
                 if (LineEnding != null)
                 {
                     b.Phases.Insert(0, new ForceLineEndingPhase(LineEnding));
@@ -135,7 +140,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
             });
         }
 
-        internal RazorProjectItem CreateProjectItem(string cshtmlRelativePath, string cshtmlContent)
+        internal RazorProjectItem CreateProjectItem(string cshtmlRelativePath, string cshtmlContent, string fileKind = null)
         {
             var fullPath = WorkingDirectory + PathSeparator + cshtmlRelativePath;
 
@@ -156,7 +161,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
                 physicalPath: fullPath,
                 relativePhysicalPath: cshtmlRelativePath,
                 basePath: WorkingDirectory,
-                fileKind: FileKind)
+                fileKind: fileKind ?? FileKind)
             {
                 Content = cshtmlContent.TrimStart(),
             };
@@ -167,7 +172,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
             return CompileToCSharp(DefaultFileName, cshtmlContent, throwOnFailure);
         }
 
-        protected CompileToCSharpResult CompileToCSharp(string cshtmlRelativePath, string cshtmlContent, bool throwOnFailure = true)
+        protected CompileToCSharpResult CompileToCSharp(string cshtmlRelativePath, string cshtmlContent, bool throwOnFailure = true, string fileKind = null)
         {
             if (DeclarationOnly && DesignTime)
             {
@@ -197,7 +202,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
                 }
 
                 // Result of generating declarations
-                var projectItem = CreateProjectItem(cshtmlRelativePath, cshtmlContent);
+                var projectItem = CreateProjectItem(cshtmlRelativePath, cshtmlContent, fileKind);
                 codeDocument = projectEngine.ProcessDeclarationOnly(projectItem);
                 var declaration = new CompileToCSharpResult
                 {
@@ -243,7 +248,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
                 // This will include the built-in components.
                 var projectEngine = CreateProjectEngine(Configuration, BaseCompilation.References.ToArray());
 
-                var projectItem = CreateProjectItem(cshtmlRelativePath, cshtmlContent);
+                var projectItem = CreateProjectItem(cshtmlRelativePath, cshtmlContent, fileKind);
 
                 RazorCodeDocument codeDocument;
                 if (DeclarationOnly)
@@ -456,5 +461,22 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
                 codeDocument.Items[key] = LineEnding;
             }
         }
+
+        private class TestImportProjectFeature : IImportProjectFeature
+        {
+            private List<RazorProjectItem> _imports;
+
+            public TestImportProjectFeature(List<RazorProjectItem> imports)
+            {
+                _imports = imports;
+            }
+
+            public RazorProjectEngine ProjectEngine { get; set; }
+
+            public IReadOnlyList<RazorProjectItem> GetImports(RazorProjectItem projectItem)
+            {
+                return _imports;
+            }
+        }
     }
 }