Create new template engine when version changes

src/Microsoft.VisualStudio.LanguageServices.Razor/Editor/DefaultVisualStudioDocumentTracker.cs

@@ -3,6 +3,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
@@ -117,6 +121,52 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor.Editor
         {
             _project = project;
 
+            // Hack: When the context changes we want to replace the template engine held by the parser.
+            // This code isn't super well factored now - it's intended to be limited to one spot until
+            // we have time to a proper redesign.
+
+            if (TextBuffer.Properties.TryGetProperty(typeof(RazorEditorParser), out RazorEditorParser legacyParser) &&
+                legacyParser.TemplateEngine != null &&
+                _projectPath != null)
+            {
+                var factory = _workspace.Services.GetLanguageServices(RazorLanguage.Name).GetRequiredService<CodeAnalysis.Razor.RazorTemplateEngineFactoryService>();
+
+                var existingEngine = legacyParser.TemplateEngine;
+                var projectDirectory = Path.GetDirectoryName(_projectPath);
+                var templateEngine = factory.Create(projectDirectory, builder =>
+                {
+                    var existingVSParserOptions = existingEngine.Engine.Features.FirstOrDefault(
+                        feature => string.Equals(
+                            feature.GetType().Name,
+                            "VisualStudioParserOptionsFeature",
+                            StringComparison.Ordinal));
+
+                    if (existingVSParserOptions == null)
+                    {
+                        Debug.Fail("The VS Parser options should have been set.");
+                    }
+                    else
+                    {
+                        builder.Features.Add(existingVSParserOptions);
+                    }
+
+                    var existingTagHelperFeature = existingEngine.Engine.Features
+                        .OfType<ITagHelperFeature>()
+                        .FirstOrDefault();
+
+                    if (existingTagHelperFeature == null)
+                    {
+                        Debug.Fail("The VS TagHelperFeature should have been set.");
+                    }
+                    else
+                    {
+                        builder.Features.Add(existingTagHelperFeature);
+                    }
+                });
+
+                legacyParser.TemplateEngine = templateEngine;
+            }
+
             var handler = ContextChanged;
             if (handler != null)
             {

src/Microsoft.VisualStudio.LanguageServices.Razor/Legacy/RazorEditorParser.cs

@@ -15,6 +15,8 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
 {
     public class RazorEditorParser : IDisposable
     {
+        private RazorTemplateEngine _templateEngine;
+
         private AspNetCore.Razor.Language.Legacy.Span _lastChangeOwner;
         private AspNetCore.Razor.Language.Legacy.Span _lastAutoCompleteSpan;
         private BackgroundParser _parser;
@@ -41,7 +43,7 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
 
             TemplateEngine = templateEngine;
             FilePath = filePath;
-            _parser = new BackgroundParser(templateEngine, filePath);
+            _parser = new BackgroundParser(this, filePath);
             _parser.ResultsReady += (sender, args) => OnDocumentParseComplete(args);
             _parser.Start();
         }
@@ -51,7 +53,19 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
         /// </summary>
         public event EventHandler<DocumentParseCompleteEventArgs> DocumentParseComplete;
 
-        public RazorTemplateEngine TemplateEngine { get; }
+        public RazorTemplateEngine TemplateEngine
+        {
+            get => _templateEngine;
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                _templateEngine = value;
+            }
+        }
 
         public string FilePath { get; }
 
@@ -205,10 +219,10 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
             private MainThreadState _main;
             private BackgroundThread _bg;
 
-            public BackgroundParser(RazorTemplateEngine templateEngine, string filePath)
+            public BackgroundParser(RazorEditorParser parser, string filePath)
             {
                 _main = new MainThreadState(filePath);
-                _bg = new BackgroundThread(_main, templateEngine, filePath);
+                _bg = new BackgroundThread(_main, parser, filePath);
 
                 _main.ResultsReady += (sender, args) => OnResultsReady(args);
             }
@@ -454,17 +468,17 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
                 private MainThreadState _main;
                 private Thread _backgroundThread;
                 private CancellationToken _shutdownToken;
-                private RazorTemplateEngine _templateEngine;
+                private RazorEditorParser _parser;
                 private string _filePath;
                 private RazorSyntaxTree _currentSyntaxTree;
                 private IList<Edit> _previouslyDiscarded = new List<Edit>();
 
-                public BackgroundThread(MainThreadState main, RazorTemplateEngine templateEngine, string fileName)
+                public BackgroundThread(MainThreadState main, RazorEditorParser parser, string fileName)
                 {
                     // Run on MAIN thread!
                     _main = main;
                     _shutdownToken = _main.CancelToken;
-                    _templateEngine = templateEngine;
+                    _parser = parser;
                     _filePath = fileName;
 
                     _backgroundThread = new Thread(WorkerLoop);
@@ -567,12 +581,13 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
                 {
                     EnsureOnThread();
 
+                    var templateEngine = _parser.TemplateEngine;
                     var sourceDocument = new TextSnapshotSourceDocument(snapshot, _filePath);
-                    var imports = _templateEngine.GetImports(_filePath);
+                    var imports = templateEngine.GetImports(_filePath);
 
                     var codeDocument = RazorCodeDocument.Create(sourceDocument, imports);
 
-                    _templateEngine.GenerateCode(codeDocument);
+                    templateEngine.GenerateCode(codeDocument);
                     return codeDocument;
                 }
             }