Use thread context parameter for formatting handlers.

src/Features/LanguageServer/Protocol/Handler/Formatting/FormatDocumentHandler.cs

@@ -11,9 +11,10 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
     [ExportLspMethod(LSP.Methods.TextDocumentFormattingName)]
     internal class FormatDocumentHandler : FormatDocumentHandlerBase, IRequestHandler<LSP.DocumentFormattingParams, LSP.TextEdit[]>
     {
-        public async Task<LSP.TextEdit[]> HandleRequestAsync(Solution solution, LSP.DocumentFormattingParams request, LSP.ClientCapabilities clientCapabilities, CancellationToken cancellationToken)
+        public async Task<LSP.TextEdit[]> HandleRequestAsync(Solution solution, LSP.DocumentFormattingParams request, LSP.ClientCapabilities clientCapabilities,
+            CancellationToken cancellationToken, bool keepThreadContext = false)
         {
-            return await GetTextEdits(solution, request.TextDocument.Uri, cancellationToken).ConfigureAwait(false);
+            return await GetTextEdits(solution, request.TextDocument.Uri, keepThreadContext, cancellationToken).ConfigureAwait(keepThreadContext);
         }
     }
 }

src/Features/LanguageServer/Protocol/Handler/Formatting/FormatDocumentHandlerBase.cs

@@ -15,7 +15,7 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
 {
     internal class FormatDocumentHandlerBase
     {
-        protected async Task<LSP.TextEdit[]> GetTextEdits(Solution solution, Uri documentUri, CancellationToken cancellationToken, LSP.Range range = null)
+        protected async Task<LSP.TextEdit[]> GetTextEdits(Solution solution, Uri documentUri, bool keepThreadContext, CancellationToken cancellationToken, LSP.Range range = null)
         {
             var edits = new ArrayBuilder<LSP.TextEdit>();
             var document = solution.GetDocumentFromURI(documentUri);
@@ -23,14 +23,14 @@ protected async Task<LSP.TextEdit[]> GetTextEdits(Solution solution, Uri documen
             if (document != null)
             {
                 var formattingService = document.Project.LanguageServices.GetService<IEditorFormattingService>();
-                var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+                var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(keepThreadContext);
                 TextSpan? textSpan = null;
                 if (range != null)
                 {
                     textSpan = ProtocolConversions.RangeToTextSpan(range, text);
                 }
 
-                var textChanges = await formattingService.GetFormattingChangesAsync(document, textSpan, cancellationToken).ConfigureAwait(false);
+                var textChanges = await formattingService.GetFormattingChangesAsync(document, textSpan, cancellationToken).ConfigureAwait(keepThreadContext);
                 edits.AddRange(textChanges.Select(change => ProtocolConversions.TextChangeToTextEdit(change, text)));
             }
 

src/Features/LanguageServer/Protocol/Handler/Formatting/FormatDocumentOnTypeHandler.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System.Collections.Generic;
 using System.Composition;
@@ -17,14 +17,15 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
     [ExportLspMethod(Methods.TextDocumentOnTypeFormattingName)]
     internal class FormatDocumentOnTypeHandler : IRequestHandler<DocumentOnTypeFormattingParams, TextEdit[]>
     {
-        public async Task<TextEdit[]> HandleRequestAsync(Solution solution, DocumentOnTypeFormattingParams request, ClientCapabilities clientCapabilities, CancellationToken cancellationToken)
+        public async Task<TextEdit[]> HandleRequestAsync(Solution solution, DocumentOnTypeFormattingParams request, ClientCapabilities clientCapabilities,
+            CancellationToken cancellationToken, bool keepThreadContext = false)
         {
             var edits = new ArrayBuilder<TextEdit>();
             var document = solution.GetDocumentFromURI(request.TextDocument.Uri);
             if (document != null)
             {
                 var formattingService = document.Project.LanguageServices.GetService<IEditorFormattingService>();
-                var position = await document.GetPositionFromLinePositionAsync(ProtocolConversions.PositionToLinePosition(request.Position), cancellationToken).ConfigureAwait(false);
+                var position = await document.GetPositionFromLinePositionAsync(ProtocolConversions.PositionToLinePosition(request.Position), cancellationToken).ConfigureAwait(keepThreadContext);
 
                 if (string.IsNullOrEmpty(request.Character))
                 {
@@ -34,14 +35,14 @@ public async Task<TextEdit[]> HandleRequestAsync(Solution solution, DocumentOnTy
                 IList<TextChange> textChanges;
                 if (SyntaxFacts.IsNewLine(request.Character[0]))
                 {
-                    textChanges = await formattingService.GetFormattingChangesOnReturnAsync(document, position, cancellationToken).ConfigureAwait(false);
+                    textChanges = await formattingService.GetFormattingChangesOnReturnAsync(document, position, cancellationToken).ConfigureAwait(keepThreadContext);
                 }
                 else
                 {
-                    textChanges = await formattingService.GetFormattingChangesAsync(document, request.Character[0], position, cancellationToken).ConfigureAwait(false);
+                    textChanges = await formattingService.GetFormattingChangesAsync(document, request.Character[0], position, cancellationToken).ConfigureAwait(keepThreadContext);
                 }
 
-                var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+                var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(keepThreadContext);
                 if (textChanges != null)
                 {
                     edits.AddRange(textChanges.Select(change => ProtocolConversions.TextChangeToTextEdit(change, text)));

src/Features/LanguageServer/Protocol/Handler/Formatting/FormatDocumentRangeHandler.cs

@@ -11,9 +11,10 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
     [ExportLspMethod(Methods.TextDocumentRangeFormattingName)]
     internal class FormatDocumentRangeHandler : FormatDocumentHandlerBase, IRequestHandler<DocumentRangeFormattingParams, TextEdit[]>
     {
-        public async Task<TextEdit[]> HandleRequestAsync(Solution solution, DocumentRangeFormattingParams request, ClientCapabilities clientCapabilities, CancellationToken cancellationToken)
+        public async Task<TextEdit[]> HandleRequestAsync(Solution solution, DocumentRangeFormattingParams request, ClientCapabilities clientCapabilities,
+            CancellationToken cancellationToken, bool keepThreadContext = false)
         {
-            return await GetTextEdits(solution, request.TextDocument.Uri, cancellationToken, range: request.Range).ConfigureAwait(false);
+            return await GetTextEdits(solution, request.TextDocument.Uri, keepThreadContext, cancellationToken, range: request.Range).ConfigureAwait(keepThreadContext);
         }
     }
 }