Make Foreground dispatchable methods noop if parser is disposed.

- Added tests to validate each of the new noopable methods.

#1750

src/Microsoft.VisualStudio.Editor.Razor/DefaultVisualStudioRazorParser.cs

@@ -38,6 +38,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         private RazorTemplateEngine _templateEngine;
         private RazorCodeDocument _codeDocument;
         private ITextSnapshot _snapshot;
+        private bool _disposed;
 
         // For testing only
         internal DefaultVisualStudioRazorParser(RazorCodeDocument codeDocument)
@@ -127,6 +128,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
             _documentTracker.ContextChanged -= DocumentTracker_ContextChanged;
 
             StopIdleTimer();
+
+            _disposed = true;
         }
 
         // Internal for testing
@@ -264,10 +267,16 @@ namespace Microsoft.VisualStudio.Editor.Razor
             }
         }
 
-        private void OnIdle(object state)
+        // Internal for testing
+        internal void OnIdle(object state)
         {
             _dispatcher.AssertForegroundThread();
 
+            if (_disposed)
+            {
+                return;
+            }
+
             OnNotifyForegroundIdle();
 
             foreach (var textView in _documentTracker.TextViews)
@@ -283,13 +292,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
             QueueReparse();
         }
 
-        private void ReparseOnForeground(object state)
+        // Internal for testing
+        internal void ReparseOnForeground(object state)
         {
             _dispatcher.AssertForegroundThread();
 
-            if (_parser == null)
+            if (_disposed)
             {
-                Debug.Fail("Reparse being attempted after the parser has been disposed.");
                 return;
             }
 
@@ -354,6 +363,11 @@ namespace Microsoft.VisualStudio.Editor.Razor
         {
             _dispatcher.AssertForegroundThread();
 
+            if (_disposed)
+            {
+                return;
+            }
+
             var args = (DocumentStructureChangedEventArgs)state;
             if (_latestChangeReference == null || // extra hardening
                 !_latestChangeReference.IsAssociatedWith(args))

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

@@ -27,6 +27,54 @@ namespace Microsoft.VisualStudio.Editor.Razor
             return documentTracker;
         }
 
+        [ForegroundFact]
+        public void ReparseOnForeground_NoopsIfDisposed()
+        {
+            // Arrange
+            var parser = new DefaultVisualStudioRazorParser(
+                Dispatcher,
+                CreateDocumentTracker(),
+                Mock.Of<RazorTemplateEngineFactoryService>(),
+                new DefaultErrorReporter(),
+                Mock.Of<ICompletionBroker>());
+            parser.Dispose();
+
+            // Act & Assert
+            parser.ReparseOnForeground(null);
+        }
+
+        [ForegroundFact]
+        public void OnIdle_NoopsIfDisposed()
+        {
+            // Arrange
+            var parser = new DefaultVisualStudioRazorParser(
+                Dispatcher,
+                CreateDocumentTracker(),
+                Mock.Of<RazorTemplateEngineFactoryService>(),
+                new DefaultErrorReporter(),
+                Mock.Of<ICompletionBroker>());
+            parser.Dispose();
+
+            // Act & Assert
+            parser.OnIdle(null);
+        }
+
+        [ForegroundFact]
+        public void OnDocumentStructureChanged_NoopsIfDisposed()
+        {
+            // Arrange
+            var parser = new DefaultVisualStudioRazorParser(
+                Dispatcher,
+                CreateDocumentTracker(),
+                Mock.Of<RazorTemplateEngineFactoryService>(),
+                new DefaultErrorReporter(),
+                Mock.Of<ICompletionBroker>());
+            parser.Dispose();
+
+            // Act & Assert
+            parser.OnDocumentStructureChanged(new object());
+        }
+
         [ForegroundFact]
         public void OnDocumentStructureChanged_IgnoresEditsThatAreOld()
         {