Don't throw exceptions for file changes after a project is unloaded

src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioProject.cs

@@ -1148,10 +1148,13 @@ public void RemoveProjectReference(ProjectReference projectReference)
 
         public void RemoveFromWorkspace()
         {
-            _documentFileChangeContext.Dispose();
-
             using (_gate.DisposableWait())
             {
+                if (!_workspace.CurrentSolution.ContainsProject(Id))
+                {
+                    throw new InvalidOperationException("The project has already been removed.");
+                }
+
                 // clear tracking to external components
                 foreach (var provider in _eventSubscriptionTracker)
                 {
@@ -1161,6 +1164,8 @@ public void RemoveFromWorkspace()
                 _eventSubscriptionTracker.Clear();
             }
 
+            _documentFileChangeContext.Dispose();
+
             IReadOnlyList<MetadataReference>? remainingMetadataReferences = null;
 
             _workspace.ApplyChangeToWorkspace(w =>
@@ -1597,13 +1602,19 @@ public void ProcessFileChange(string projectSystemFilePath, string workspaceFile
             {
                 using (_project._gate.DisposableWait())
                 {
+                    // If our project has already been removed, this is a stale notification, and we can disregard.
+                    if (!_project._workspace.CurrentSolution.ContainsProject(_project.Id))
+                    {
+                        return;
+                    }
+
                     if (_documentPathsToDocumentIds.TryGetValue(workspaceFilePath, out var documentId))
                     {
                         // We create file watching prior to pushing the file to the workspace in batching, so it's
                         // possible we might see a file change notification early. In this case, toss it out. Since
                         // all adds/removals of documents for this project happen under our lock, it's safe to do this
-                        // check without taking the main workspace lock
-
+                        // check without taking the main workspace lock. We don't have to check for documents removed in
+                        // the batch, since those have already been removed out of _documentPathsToDocumentIds.
                         if (_documentsAddedInBatch.Any(d => d.Id == documentId))
                         {
                             return;

src/VisualStudio/Core/Test/ProjectSystemShim/VisualStudioProjectTests/FileChangeTests.vb

@@ -0,0 +1,63 @@
+' Licensed to the .NET Foundation under one or more agreements.
+' The .NET Foundation licenses this file to you under the MIT license.
+' See the LICENSE file in the project root for more information.
+
+Imports System.Threading
+Imports Microsoft.CodeAnalysis
+Imports Microsoft.CodeAnalysis.Test.Utilities
+Imports Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem
+Imports Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Framework
+Imports Roslyn.Test.Utilities
+
+Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim
+    <[UseExportProvider]>
+    Public Class FileChangeTests
+        <WpfTheory>
+        <CombinatorialData>
+        Public Async Function FileChangeAfterRemovalInUncommittedBatchIgnored(withDirectoryWatch As Boolean) As Task
+            Using environment = New TestEnvironment()
+                Dim projectInfo = New VisualStudioProjectCreationInfo
+
+                ' If we have a project directory, then we'll also have a watch for the entire directory;
+                ' test both cases
+                If withDirectoryWatch Then
+                    projectInfo.FilePath = "Z:\Project.csproj"
+                End If
+
+                Dim project = Await environment.ProjectFactory.CreateAndAddToWorkspaceAsync(
+                    "project", LanguageNames.CSharp, projectInfo, CancellationToken.None)
+
+                project.AddSourceFile("Z:\Foo.cs")
+
+                Using project.CreateBatchScope()
+                    ' This shouldn't throw
+                    Await environment.RaiseStaleFileChangeAsync("Z:\Foo.cs", Sub() project.RemoveSourceFile("Z:\Foo.cs"))
+                End Using
+            End Using
+        End Function
+
+        <WpfTheory>
+        <CombinatorialData>
+        Public Async Function FileChangeAfterRemoveOfProjectIgnored(withDirectoryWatch As Boolean) As Task
+            Using environment = New TestEnvironment()
+                Dim projectInfo = New VisualStudioProjectCreationInfo
+
+                ' If we have a project directory, then we'll also have a watch for the entire directory;
+                ' test both cases
+                If withDirectoryWatch Then
+                    projectInfo.FilePath = "Z:\Project.csproj"
+                End If
+
+                Dim project = Await environment.ProjectFactory.CreateAndAddToWorkspaceAsync(
+                    "project", LanguageNames.CSharp, projectInfo, CancellationToken.None)
+
+                project.AddSourceFile("Z:\Foo.cs")
+
+                Using project.CreateBatchScope()
+                    ' This shouldn't throw
+                    Await environment.RaiseStaleFileChangeAsync("Z:\Foo.cs", Sub() project.RemoveFromWorkspace())
+                End Using
+            End Using
+        End Function
+    End Class
+End Namespace

src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/MockVsFileChangeEx.vb

@@ -2,6 +2,7 @@
 ' The .NET Foundation licenses this file to you under the MIT license.
 ' See the LICENSE file in the project root for more information.
 
+Imports System.Collections.Immutable
 Imports System.Runtime.InteropServices
 Imports System.Threading
 Imports Microsoft.VisualStudio.Shell
@@ -14,8 +15,8 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
         Implements IVsAsyncFileChangeEx
 
         Private ReadOnly _lock As New Object
-        Private ReadOnly _watchedFiles As New List(Of WatchedEntity)
-        Private ReadOnly _watchedDirectories As New List(Of WatchedEntity)
+        Private _watchedFiles As ImmutableList(Of WatchedEntity) = ImmutableList(Of WatchedEntity).Empty
+        Private _watchedDirectories As ImmutableList(Of WatchedEntity) = ImmutableList(Of WatchedEntity).Empty
         Private _nextCookie As UInteger
 
         Public Function AdviseDirChange(pszDir As String, fWatchSubDir As Integer, pFCE As IVsFileChangeEvents, ByRef pvsCookie As UInteger) As Integer Implements IVsFileChangeEx.AdviseDirChange
@@ -36,13 +37,13 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
             Return VSConstants.S_OK
         End Function
 
-        Private Function AdviseDirectoryOrFileChange(watchedList As List(Of WatchedEntity),
+        Private Function AdviseDirectoryOrFileChange(ByRef watchedList As ImmutableList(Of WatchedEntity),
                                                      pszMkDocument As String,
                                                      pFCE As IVsFileChangeEvents) As UInteger
 
             SyncLock _lock
                 Dim cookie = _nextCookie
-                watchedList.Add(New WatchedEntity(cookie, pszMkDocument, DirectCast(pFCE, IVsFreeThreadedFileChangeEvents2)))
+                watchedList = watchedList.Add(New WatchedEntity(cookie, pszMkDocument, DirectCast(pFCE, IVsFreeThreadedFileChangeEvents2)))
                 _nextCookie += 1UI
 
                 Return cookie
@@ -59,40 +60,60 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
 
         Public Function UnadviseDirChange(VSCOOKIE As UInteger) As Integer Implements IVsFileChangeEx.UnadviseDirChange
             SyncLock _lock
-                _watchedDirectories.RemoveAll(Function(t) t.Cookie = VSCOOKIE)
+                _watchedDirectories = _watchedDirectories.RemoveAll(Function(t) t.Cookie = VSCOOKIE)
 
                 Return VSConstants.S_OK
             End SyncLock
         End Function
 
         Public Function UnadviseFileChange(VSCOOKIE As UInteger) As Integer Implements IVsFileChangeEx.UnadviseFileChange
             SyncLock _lock
-                _watchedFiles.RemoveAll(Function(t) t.Cookie = VSCOOKIE)
+                _watchedFiles = _watchedFiles.RemoveAll(Function(t) t.Cookie = VSCOOKIE)
 
                 Return VSConstants.S_OK
             End SyncLock
         End Function
 
         Public Sub FireUpdate(filename As String)
+            FireUpdate(filename, _watchedFiles, _watchedDirectories)
+        End Sub
+
+        ''' <summary>
+        ''' Raises a file change that raised after <paramref name="unsubscribingAction"/> is ran.
+        ''' </summary>
+        ''' <remarks>
+        ''' File change notifications are inherently asynchronous -- it's always possible that a file change
+        ''' notification may have been started for something we unsubscribe a moment later -- there's always a window of time
+        ''' between the final check and the entry into Roslyn code which is unavoidable as long as notifications aren't called
+        ''' by the shell under a lock, which they aren't for deadlock reasons.
+        ''' </remarks>
+        Public Sub FireStaleUpdate(filename As String, unsubscribingAction As Action)
+            Dim watchedFiles = _watchedFiles
+            Dim watchedDirectories = _watchedDirectories
+
+            unsubscribingAction()
+
+            FireUpdate(filename, watchedFiles, watchedDirectories)
+        End Sub
+
+        Private Shared Sub FireUpdate(filename As String, watchedFiles As ImmutableList(Of WatchedEntity), watchedDirectories As ImmutableList(Of WatchedEntity))
             Dim actionsToFire As List(Of Action) = New List(Of Action)()
 
-            SyncLock _lock
-                For Each watchedFile In _watchedFiles
-                    If String.Equals(watchedFile.Path, filename, StringComparison.OrdinalIgnoreCase) Then
-                        actionsToFire.Add(Sub()
-                                              watchedFile.Sink.FilesChanged(1, {watchedFile.Path}, {CType(_VSFILECHANGEFLAGS.VSFILECHG_Time, UInteger)})
-                                          End Sub)
-                    End If
-                Next
+            For Each watchedFile In watchedFiles
+                If String.Equals(watchedFile.Path, filename, StringComparison.OrdinalIgnoreCase) Then
+                    actionsToFire.Add(Sub()
+                                          watchedFile.Sink.FilesChanged(1, {watchedFile.Path}, {CType(_VSFILECHANGEFLAGS.VSFILECHG_Time, UInteger)})
+                                      End Sub)
+                End If
+            Next
 
-                For Each watchedDirectory In _watchedDirectories
-                    If FileNameMatchesFilter(filename, watchedDirectory) Then
-                        actionsToFire.Add(Sub()
-                                              watchedDirectory.Sink.DirectoryChangedEx2(watchedDirectory.Path, 1, {filename}, {CType(_VSFILECHANGEFLAGS.VSFILECHG_Time, UInteger)})
-                                          End Sub)
-                    End If
-                Next
-            End SyncLock
+            For Each watchedDirectory In watchedDirectories
+                If FileNameMatchesFilter(filename, watchedDirectory) Then
+                    actionsToFire.Add(Sub()
+                                          watchedDirectory.Sink.DirectoryChangedEx2(watchedDirectory.Path, 1, {filename}, {CType(_VSFILECHANGEFLAGS.VSFILECHG_Time, UInteger)})
+                                      End Sub)
+                End If
+            Next
 
             If actionsToFire.Count > 0 Then
                 For Each actionToFire In actionsToFire
@@ -103,7 +124,7 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
             End If
         End Sub
 
-        Private Function FileNameMatchesFilter(filename As String, watchedDirectory As WatchedEntity) As Boolean
+        Private Shared Function FileNameMatchesFilter(filename As String, watchedDirectory As WatchedEntity) As Boolean
             If Not filename.StartsWith(watchedDirectory.Path, StringComparison.OrdinalIgnoreCase) Then
                 Return False
             End If

src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/TestEnvironment.vb

@@ -274,12 +274,23 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
             End Function
         End Class
 
-        Friend Async Function RaiseFileChangeAsync(path As String) As Task
+        Friend Async Function GetFileChangeServiceAsync() As Task(Of MockVsFileChangeEx)
             ' Ensure we've pushed everything to the file change watcher
             Dim fileChangeProvider = ExportProvider.GetExportedValue(Of FileChangeWatcherProvider)
             Dim mockFileChangeService = Assert.IsType(Of MockVsFileChangeEx)(ServiceProvider.GetService(GetType(SVsFileChangeEx)))
             Await ExportProvider.GetExportedValue(Of AsynchronousOperationListenerProvider)().GetWaiter(FeatureAttribute.Workspace).ExpeditedWaitAsync()
-            mockFileChangeService.FireUpdate(path)
+            Return mockFileChangeService
+        End Function
+
+        Friend Async Function RaiseFileChangeAsync(path As String) As Task
+            Dim service = Await GetFileChangeServiceAsync()
+            service.FireUpdate(path)
+        End Function
+
+        ''' <inheritdoc cref="MockVsFileChangeEx.FireStaleUpdate(String, Action)" />
+        Friend Async Function RaiseStaleFileChangeAsync(path As String, unsubscribingAction As Action) As Task
+            Dim service = Await GetFileChangeServiceAsync()
+            service.FireStaleUpdate(path, unsubscribingAction)
         End Function
 
         Private Class MockVsSmartOpenScope