Ensure unique file paths for non-file Uris (#12037)

Bug: microsoft/vscode-dotnettools#2151
(deliberately not marking this PR as a fix due to DevKit process)

When an active agent chat session is open, VS Code will send LSP
requests for files with the `chat-editing-text-model://` scheme, similar
to how the left hand side of a diff view uses `git://`. This causes
problems during editing because we end up getting didChange messages for
Uris with that scheme, and Uris with the file scheme, which means we end
up with two didChanges for the same physical file.

This PR expands the fix we previously had specifically for `git://`
Uris, to apply to any non-file Uri. It essentially ensures these
documents are always in the misc files project, so we'll still be able
to generally deal with them, we just won't get confused by them. As I
noted in a comment, a better fix would be to stop using file paths, but
instead use the Uris provided by the LSP client as the source of truth,
but given the size and risk of that change (would mean Uri/DocumentUri
as a key in `ProjectSnapshotManager`) and the fact that cohosting
effectively delivers this via Roslyn anyway, it didn't seem prudent or
worth it for this specific issue.

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/UriExtensions.cs

@@ -37,25 +37,36 @@ public static string GetAbsoluteOrUNCPath(this Uri uri)
         // Absolute paths are usually encoded.
         var absolutePath = uri.AbsolutePath.Contains("%") ? WebUtility.UrlDecode(uri.AbsolutePath) : uri.AbsolutePath;
 
-        if (string.Equals(uri.Scheme, "git", StringComparison.OrdinalIgnoreCase))
-        {
-            // return a normalized path when we want to add to a fake git directory path (hacky fix for https://github.com/dotnet/razor/issues/9365)
-            return AddToFakeGitDirectoryAtRoot(absolutePath);
-        }
-
-        return absolutePath;
+        return EnsureUniquePathForScheme(uri.Scheme, absolutePath);
     }
 
-    private static string AddToFakeGitDirectoryAtRoot(string decodedAbsolutePath)
+    private static string EnsureUniquePathForScheme(string scheme, string decodedAbsolutePath)
     {
+        // File Uris we leave untouched, as they represent the actual files on disk
+        if (scheme == Uri.UriSchemeFile)
+        {
+            return decodedAbsolutePath;
+        }
+
         var normalizedPath = FilePathNormalizer.Normalize(decodedAbsolutePath);
         var firstSeparatorIndex = normalizedPath.IndexOf('/');
         if (firstSeparatorIndex < 0)
         {
-            // no-op
+            // A path without a separator is unlikely, but we can't add our unique-ness marker anyway, so just return as is
+            // and hope for the best.
             return decodedAbsolutePath;
         }
 
-        return normalizedPath.Insert(firstSeparatorIndex + 1, "_git_/");
+        // For any non-file Uri, we add a marker to the path to ensure things won't conflict with the real file on disk.
+        // This is a somewhat hacky fix to ensure things like a git diff view will work, where the left hand side is a
+        // Uri like "git://path/to/file.razor" and the right hand side is "file://path/to/file.razor". If we mapped both
+        // of those to the same file path, then one side would be sending line and character positions that don't match
+        // our understanding of the document.
+        // A true fix would be to move away from using file paths in the first place, but instead use the Uris as provided
+        // by the LSP client as the source of truth.
+        // See https://github.com/dotnet/razor/issues/9365 and https://github.com/microsoft/vscode-dotnettools/issues/2151
+        // for examples.
+
+        return normalizedPath.Insert(firstSeparatorIndex + 1, $"_{scheme}_/");
     }
 }

src/Razor/test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/UriExtensionsTest.cs

@@ -60,6 +60,7 @@ public void GetAbsoluteOrUNCPath_AbsolutePath_HandlesSpacePaths()
     [InlineData(@"git:/c%3A/path/to/dir/Index.cshtml", @"c:/_git_/path/to/dir/Index.cshtml")]
     [InlineData(@"git:/c:/path%2Fto/dir/Index.cshtml?%7B%22p", @"c:/_git_/path/to/dir/Index.cshtml")]
     [InlineData(@"git:/c:/path/to/dir/Index.cshtml", @"c:/_git_/path/to/dir/Index.cshtml")]
+    [InlineData(@"chat-editing-text-model:/c:/path/to/dir/Index.cshtml", @"c:/_chat-editing-text-model_/path/to/dir/Index.cshtml")]
     public void GetAbsoluteOrUNCPath_AbsolutePath_HandlesGitScheme(string filePath, string expected)
     {
         // Arrange