Expose registered project file extensions

.github/instructions/IDE.instructions.md

@@ -104,3 +104,4 @@ var methodDecl = generator.MethodDeclaration("MyMethod", ...);
 - **ImportingConstructor must be marked `[Obsolete]`** with `MefConstruction.ImportingConstructorMessage`
 - **Language services must be exported with a specific language name** — don't use generic exports for both C#/VB
 - **Workspace changes must use immutable updates** — `Workspace.SetCurrentSolution()`
+- **MSBuild project extensions are stored with a leading `.`.** `ProjectFileExtensionRegistry` accepts registration and lookup values with or without the dot, but its enumeration API returns the canonical dot-prefixed form.

src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/FileBasedPrograms/FileBasedProgramsEntryPointDiscovery.cs

@@ -77,7 +77,7 @@ public Task OnInitializedAsync(ClientCapabilities clientCapabilities, RequestCon
         return Task.CompletedTask;
     }
 
-    private void OnWorkspaceFoldersChanged(ImmutableHashSet<string> _)
+    private void OnWorkspaceFoldersChanged()
         => _discoveryQueue.AddWork();
 
     public void Dispose()

src/LanguageServer/Protocol/Handler/IWorkspaceFolderTracker.cs

@@ -10,7 +10,7 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler;
 
 internal interface IWorkspaceFolderTracker : ILspService
 {
-    event Action<ImmutableHashSet<string>>? WorkspaceFoldersChanged;
+    event Action? WorkspaceFoldersChanged;
 
     ImmutableHashSet<string> GetRequiredWorkspaceFolderPaths();
 

src/LanguageServer/Protocol/Handler/WorkspaceFolderTracker.cs

@@ -12,11 +12,13 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler;
 
 internal sealed class WorkspaceFolderTracker : IWorkspaceFolderTracker
 {
-    // Mutations are serialized by the request queue, but non-mutating requests may read the current folders concurrently.
+    /// <summary>
+    /// Mutations are serialized by the request queue, but non-mutating requests may read the current folders concurrently.
+    /// </summary>
     private readonly object _gate = new();
-    private ImmutableHashSet<string> _workspaceFolderPaths = ImmutableHashSet.Create(PathUtilities.Comparer);
+    private volatile ImmutableHashSet<string> _workspaceFolderPaths = ImmutableHashSet.Create(PathUtilities.Comparer);
 
-    public event Action<ImmutableHashSet<string>>? WorkspaceFoldersChanged;
+    public event Action? WorkspaceFoldersChanged;
 
     public void Update(WorkspaceFolder[]? addedFolders, WorkspaceFolder[]? removedFolders)
     {
@@ -52,16 +54,11 @@ public void Update(WorkspaceFolder[]? addedFolders, WorkspaceFolder[]? removedFo
             _workspaceFolderPaths = updatedWorkspaceFolderPaths;
         }
 
-        WorkspaceFoldersChanged?.Invoke(updatedWorkspaceFolderPaths);
+        WorkspaceFoldersChanged?.Invoke();
     }
 
     public ImmutableHashSet<string> GetRequiredWorkspaceFolderPaths()
-    {
-        lock (_gate)
-        {
-            return _workspaceFolderPaths;
-        }
-    }
+        => _workspaceFolderPaths;
 
     private static string? GetNormalizedFilePath(WorkspaceFolder workspaceFolder)
         => workspaceFolder.DocumentUri.ParsedDocumentUri?.IsFile == true

src/LanguageServer/ProtocolUnitTests/HandlerTests.cs

@@ -49,7 +49,7 @@ public void WorkspaceFolderTrackerPreservesSetForEquivalentUpdate()
         var workspaceFolder = new WorkspaceFolder { DocumentUri = new("file:///Workspace"), Name = "Workspace" };
         var equivalentWorkspaceFolder = new WorkspaceFolder { DocumentUri = new("file:///Workspace/"), Name = "Workspace" };
         var eventCount = 0;
-        tracker.WorkspaceFoldersChanged += _ => eventCount++;
+        tracker.WorkspaceFoldersChanged += () => eventCount++;
 
         tracker.Update([workspaceFolder], removedFolders: null);
         var workspaceFolders = tracker.GetRequiredWorkspaceFolderPaths();

src/Workspaces/MSBuild/Core/MSBuild/ProjectFileExtensionRegistry.cs

@@ -4,7 +4,7 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
+using System.Collections.Immutable;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using Microsoft.CodeAnalysis.FileBasedPrograms;
@@ -26,9 +26,9 @@ public ProjectFileExtensionRegistry(DiagnosticReporter diagnosticReporter, IFile
 
         _extensionToLanguageMap = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
         {
-            { "csproj", LanguageNames.CSharp },
-            { "vbproj", LanguageNames.VisualBasic },
-            { "fsproj", LanguageNames.FSharp }
+            { ".csproj", LanguageNames.CSharp },
+            { ".vbproj", LanguageNames.VisualBasic },
+            { ".fsproj", LanguageNames.FSharp }
         };
 
         _dataGuard = new NonReentrantLock();
@@ -41,38 +41,58 @@ public void AssociateFileExtensionWithLanguage(string fileExtension, string lang
     {
         using (_dataGuard.DisposableWait())
         {
-            _extensionToLanguageMap[fileExtension] = language;
+            _extensionToLanguageMap[AddLeadingDot(fileExtension)] = language;
         }
     }
 
-    public bool TryGetLanguageNameFromProjectPath(string? projectFilePath, DiagnosticReportingMode mode, [NotNullWhen(true)] out string? languageName)
+    /// <summary>
+    /// Gets the registered project file extensions with a leading '.'.
+    /// </summary>
+    public ImmutableArray<string> GetRegisteredProjectFileExtensions()
     {
-        return TryGetLanguageNameFromProjectPath(projectFilePath, mode, out languageName, out _);
+        using (_dataGuard.DisposableWait())
+        {
+            return [.. _extensionToLanguageMap.Keys];
+        }
     }
 
-    public bool TryGetLanguageNameFromProjectPath(string? projectFilePath, DiagnosticReportingMode mode, [NotNullWhen(true)] out string? languageName, out bool isFileBasedApp)
+    /// <summary>
+    /// Tries to get the language registered for an extension, with or without a leading '.'.
+    /// </summary>
+    public bool TryGetLanguageNameFromExtension(string extension, [NotNullWhen(true)] out string? languageName)
     {
-        var extension = Path.GetExtension(projectFilePath);
-        if (extension is null)
+        using (_dataGuard.DisposableWait())
+        {
+            return _extensionToLanguageMap.TryGetValue(AddLeadingDot(extension), out languageName);
+        }
+    }
+
+    private static string AddLeadingDot(string extension)
+        => extension.Length == 0 || extension[0] == '.' ? extension : "." + extension;
+
+    public bool TryGetLanguageNameFromProjectPath(string? projectFilePath, DiagnosticReportingMode mode, [NotNullWhen(true)] out string? languageName)
+        => TryGetLanguageNameFromProjectPath(projectFilePath, mode, out languageName, out _);
+
+    public bool TryGetLanguageNameFromProjectPath(
+        string? projectFilePath,
+        DiagnosticReportingMode mode,
+        [NotNullWhen(true)] out string? languageName,
+        out bool isFileBasedApp)
+    {
+        if (projectFilePath is null)
         {
             languageName = null;
             isFileBasedApp = false;
-            _diagnosticReporter.Report(mode, $"Project file path was 'null'");
+            _diagnosticReporter.Report(mode, "Project file path is null.");
             return false;
         }
 
-        Debug.Assert(projectFilePath != null);
-
-        if (extension is ['.', .. var rest])
-            extension = rest;
+        var projectFileExtension = Path.GetExtension(projectFilePath);
 
-        using (_dataGuard.DisposableWait())
+        if (TryGetLanguageNameFromExtension(projectFileExtension, out languageName))
         {
-            if (_extensionToLanguageMap.TryGetValue(extension, out languageName))
-            {
-                isFileBasedApp = false;
-                return true;
-            }
+            isFileBasedApp = false;
+            return true;
         }
 
         if (_fileBasedProgramService?.IsValidEntryPointPath(projectFilePath) == true)
@@ -83,7 +103,7 @@ public bool TryGetLanguageNameFromProjectPath(string? projectFilePath, Diagnosti
         }
 
         isFileBasedApp = false;
-        _diagnosticReporter.Report(mode, string.Format(WorkspacesResources.Cannot_open_project_0_because_the_file_extension_1_is_not_associated_with_a_language, projectFilePath, Path.GetExtension(projectFilePath)));
+        _diagnosticReporter.Report(mode, string.Format(WorkspacesResources.Cannot_open_project_0_because_the_file_extension_1_is_not_associated_with_a_language, projectFilePath, projectFileExtension));
         return false;
     }
 }

src/Workspaces/MSBuild/Test/NetCoreTests.cs

@@ -747,7 +747,7 @@ public async Task TestOpenProject_FileBasedApp_AssociateFileExtensionWithLanguag
         var sourceFilePath = GetSolutionFileName("Program.cs");
 
         using var workspace = CreateMSBuildWorkspace();
-        workspace.AssociateFileExtensionWithLanguage("cs", LanguageNames.CSharp);
+        workspace.AssociateFileExtensionWithLanguage(".cs", LanguageNames.CSharp);
         await workspace.OpenProjectAsync(sourceFilePath);
 
         // [Failure] Msbuild failed when processing the file 'Program.cs' with message:
@@ -756,6 +756,29 @@ public async Task TestOpenProject_FileBasedApp_AssociateFileExtensionWithLanguag
         Assert.Contains("Program.cs", diagnostic.Message);
     }
 
+    [Fact]
+    public void ProjectFileExtensionRegistryUsesLeadingDots()
+    {
+        using var workspace = new AdhocWorkspace();
+        var registry = new ProjectFileExtensionRegistry(new DiagnosticReporter(workspace), fileBasedProgramService: null);
+
+        var registeredExtensions = registry.GetRegisteredProjectFileExtensions();
+        Assert.Equal(3, registeredExtensions.Length);
+        Assert.Contains(".csproj", registeredExtensions);
+        Assert.Contains(".vbproj", registeredExtensions);
+        Assert.Contains(".fsproj", registeredExtensions);
+
+        Assert.True(registry.TryGetLanguageNameFromExtension(".csproj", out var languageName));
+        Assert.Equal(LanguageNames.CSharp, languageName);
+        Assert.True(registry.TryGetLanguageNameFromExtension("csproj", out languageName));
+        Assert.Equal(LanguageNames.CSharp, languageName);
+
+        registry.AssociateFileExtensionWithLanguage(".", "Dot");
+        Assert.True(registry.TryGetLanguageNameFromExtension(".", out languageName));
+        Assert.Equal("Dot", languageName);
+        Assert.False(registry.TryGetLanguageNameFromExtension("", out _));
+    }
+
     [ConditionalFact(typeof(DotNetSdkMSBuildInstalled))]
     [Trait(Traits.Feature, Traits.Features.MSBuildWorkspace)]
     [Trait(Traits.Feature, Traits.Features.NetCore)]