VisualStudio FileChangeWatcher doesn't correctly report changes for multiple projects #74716
Description
Version Used: VS 17.10.5, Roslyn main (d939cd6)
We have noticed that in Visual Studio our incremental source generator is not regenerating its output when an additional file (that's watched by the incremental generator) is modified by an external action (i.e. the file is changed while not being opened in VS).
I was able to trace this to Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem.FileChangeWatcher and specifically to the changes from #70936. Since that PR, it seems FileChangeWatcher is not reporting external changes to the correct project (files from multiple projects form a batch, and changes to these files are then all reported to the same sink, which corresponds to the first project in the batch), which is the cause of our source generator issue.
This can be seen by the following test (place it inside the Microsoft.VisualStudio..LanguageServices.UnitTests project):
Imports System.IO
Imports Microsoft.CodeAnalysis.Shared.TestHooks
Imports Microsoft.CodeAnalysis.Test.Utilities
Imports Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem
Imports Roslyn.Test.Utilities
Imports IVsAsyncFileChangeEx2 = Microsoft.VisualStudio.Shell.IVsAsyncFileChangeEx2
Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim
<UseExportProvider>
Public Class FileChangeWatcherTests
Implements IDisposable
Private ReadOnly _tempPath As String
Public Sub New()
_tempPath = Path.Combine(TempRoot.Root, Path.GetRandomFileName())
Directory.CreateDirectory(_tempPath)
End Sub
Private Sub Dispose() Implements IDisposable.Dispose
Directory.Delete(_tempPath, recursive:=True)
End Sub
<WpfFact>
Public Async Function WatchingMultipleContexts() As Task
Using workspace = New EditorTestWorkspace()
Dim fileChangeService = New MockVsFileChangeEx
Dim fileChangeWatcher = New FileChangeWatcher(workspace.GetService(Of IAsynchronousOperationListenerProvider)(), Task.FromResult(Of IVsAsyncFileChangeEx2)(fileChangeService))
Dim context1 = fileChangeWatcher.CreateContext()
Dim context2 = fileChangeWatcher.CreateContext()
Dim handler1Called As Boolean = False
Dim handler2Called As Boolean = False
AddHandler context1.FileChanged, Sub(sender, args) handler1Called = True
AddHandler context2.FileChanged, Sub(sender, args) handler2Called = True
Dim watchedFile1 = context1.EnqueueWatchingFile("file1.txt")
Dim watchedFile2 = context2.EnqueueWatchingFile("file2.txt")
Await workspace.GetService(Of AsynchronousOperationListenerProvider)().GetWaiter(FeatureAttribute.Workspace).ExpeditedWaitAsync()
fileChangeService.FireUpdate("file2.txt")
Assert.Equal("handler1Called=False, handler2Called=True", $"handler1Called={handler1Called}, handler2Called={handler2Called}")
End Using
End Function
End Class
End NamespaceExpected: handler1Called=False, handler2Called=True
Actual: handler1Called=True, handler2Called=False