Don't add already known documents to the misc files project (#10753)

Noticed in the logs that we were double-compiling files, and it was
causing issues in my "self versioned documents" branch. Separated out of
that to make it easier to review.

RCA is because we now share a project manager across VS and LSP server,
so we get real project information much sooner than before, which beats
file watchers etc.

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/ProjectSystem/RazorProjectService.cs

@@ -159,24 +159,24 @@ internal partial class RazorProjectService : IRazorProjectService, IRazorProject
     private void AddDocumentToMiscProjectCore(ProjectSnapshotManager.Updater updater, string filePath)
     {
         var textDocumentPath = FilePathNormalizer.Normalize(filePath);
+        _logger.LogDebug($"Asked to add {textDocumentPath} to the miscellaneous files project, because we don't have project info (yet?)");
 
-        _logger.LogDebug($"Adding {filePath} to the miscellaneous files project, because we don't have project info (yet?)");
-        var miscFilesProject = _projectManager.GetMiscellaneousProject();
-
-        if (miscFilesProject.GetDocument(FilePathNormalizer.Normalize(textDocumentPath)) is not null)
+        if (_projectManager.TryResolveDocumentInAnyProject(textDocumentPath, _logger, out var document))
         {
-            // Document already added. This usually occurs when VSCode has already pre-initialized
-            // open documents and then we try to manually add all known razor documents.
+            // Already in a known project, so we don't want it in the misc files project
+            _logger.LogDebug($"File {textDocumentPath} is already in {document.Project.Key}, so we're not adding it to the miscellaneous files project");
             return;
         }
 
+        var miscFilesProject = _projectManager.GetMiscellaneousProject();
+
         // Representing all of our host documents with a re-normalized target path to workaround GetRelatedDocument limitations.
         var normalizedTargetFilePath = textDocumentPath.Replace('/', '\\').TrimStart('\\');
 
         var hostDocument = new HostDocument(textDocumentPath, normalizedTargetFilePath);
         var textLoader = _remoteTextLoaderFactory.Create(textDocumentPath);
 
-        _logger.LogInformation($"Adding document '{filePath}' to project '{miscFilesProject.Key}'.");
+        _logger.LogInformation($"Adding document '{textDocumentPath}' to project '{miscFilesProject.Key}'.");
 
         updater.DocumentAdded(miscFilesProject.Key, hostDocument, textLoader);
     }

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/RazorProjectServiceTest.cs

@@ -733,6 +733,47 @@ public class RazorProjectServiceTest(ITestOutputHelper testOutput) : LanguageSer
         Assert.False(_projectManager.IsDocumentOpen(DocumentFilePath));
     }
 
+    [Fact]
+    public async Task AddDocumentToMiscProjectAsync_IgnoresKnownDocument()
+    {
+        // Arrange
+        const string ProjectFilePath = "C:/path/to/project.csproj";
+        const string IntermediateOutputPath = "C:/path/to/obj";
+        const string RootNamespace = "TestRootNamespace";
+        const string DocumentFilePath = "C:/path/to/document.cshtml";
+
+        await _projectService.AddProjectAsync(
+            ProjectFilePath, IntermediateOutputPath, RazorConfiguration.Default, RootNamespace, displayName: null, DisposalToken);
+        await _projectService.AddDocumentToPotentialProjectsAsync(DocumentFilePath, DisposalToken);
+
+        // Act
+        using var listener = _projectManager.ListenToNotifications();
+
+        // Act
+        await _projectService.AddDocumentToMiscProjectAsync(DocumentFilePath, DisposalToken);
+
+        // Assert
+        listener.AssertNoNotifications();
+    }
+
+    [Fact]
+    public async Task AddDocumentToMiscProjectAsync_IgnoresKnownDocument_InMiscFiles()
+    {
+        // Arrange
+        const string DocumentFilePath = "C:/path/to/document.cshtml";
+
+        await _projectService.AddDocumentToMiscProjectAsync(DocumentFilePath, DisposalToken);
+
+        // Act
+        using var listener = _projectManager.ListenToNotifications();
+
+        // Act
+        await _projectService.AddDocumentToMiscProjectAsync(DocumentFilePath, DisposalToken);
+
+        // Assert
+        listener.AssertNoNotifications();
+    }
+
     [Fact]
     public async Task RemoveDocument_RemovesDocumentFromOwnerProject()
     {