Public API analyzer only works in Roslyn.sln if the API file is opened in the editor

[mavasani]

Version Used: Latest 16.6 dogfood build

Steps to Reproduce:

1. Open Roslyn.sln
2. Open any file, say Workspace.cs and add a new public API. You should see RS0016 error.
3. Ctrl + Dot to see that public code fix is shown and the preview also shows the correct change
4. Hit enter to attempt to apply the fix

Expected Behavior:
Unshipped public API file is changed

Actual Behavior:
Unshipped public API file is not changed. If you repeat the above steps with the public API already open in the editor, code fix does work. NOTE: I am unable to repro this behavior with couple other solutions I tried, but it does repro consistently on Roslyn.sln on both my machines.

I debugged this a bit, and it finally comes down the below code:

roslyn/src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioWorkspaceImpl.cs

Lines 1154 to 1167 in abd2fb0

	if (IsDocumentOpen(documentId))
	{
	var textBuffer = this.CurrentSolution.GetTextDocument(documentId).GetTextAsync(CancellationToken.None).WaitAndGetResult(CancellationToken.None).Container.TryGetTextBuffer();
	if (textBuffer != null)
	{
	TextEditApplication.UpdateText(newText, textBuffer, EditOptions.DefaultMinimalChange);
	return;
	}
	}
	// The document wasn't open in a normal way, so invisible editor time
	using var invisibleEditor = OpenInvisibleEditor(documentId);
	TextEditApplication.UpdateText(newText, invisibleEditor.TextBuffer, EditOptions.None);

It seems something from the InvisibleEditor code path is causing the scenario to fail, I don't see any exceptions - just the file change does not seem to get saved to disk. I am not sure which component or API does the actual write to disk in invisible editor code path.

[mavasani]

Tagging @jasonmalinowski, in case your upcoming PR is fixing anything on this code path.

[jasonmalinowski]

@mavasani I guess the changes I had in mind were the ones in 99dc680 which I guess isn't in that path. Hmm.

[sharwell]

This is caused by dotnet/project-system#2160 (failure of the SDK to add AdditionalFiles to AvailableItemName). I implemented a workaround for dotnet/roslyn in #42521.