Use merge linked file api properly instead of manually de-duping.

src/Features/LanguageServer/Protocol/Extensions/TextEditEqualityComparer.cs

-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System.Collections.Generic;
-using Microsoft.VisualStudio.LanguageServer.Protocol;
-
-namespace Microsoft.CodeAnalysis.LanguageServer
-{
-    internal class TextEditEqualityComparer : IEqualityComparer<TextEdit>
-    {
-        public bool Equals(TextEdit x, TextEdit y)
-        {
-            return EqualityComparer<Range>.Default.Equals(x.Range, y.Range) &&
-                   x.NewText == y.NewText;
-        }
-
-        public int GetHashCode(TextEdit obj)
-        {
-            var hashCode = -1114201889;
-            hashCode = (hashCode * -1521134295) + EqualityComparer<Range>.Default.GetHashCode(obj.Range);
-            hashCode = (hashCode * -1521134295) + EqualityComparer<string>.Default.GetHashCode(obj.NewText);
-            return hashCode;
-        }
-    }
-}

src/Features/LanguageServer/Protocol/Handler/Rename/RenameHandler.cs

@@ -12,6 +12,7 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editor;
 using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Roslyn.Utilities;
@@ -22,8 +23,6 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
     [ExportLspMethod(LSP.Methods.TextDocumentRenameName), Shared]
     internal class RenameHandler : IRequestHandler<LSP.RenameParams, WorkspaceEdit?>
     {
-        private static TextEditEqualityComparer s_textEditEqualityComparer = new TextEditEqualityComparer();
-
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public RenameHandler()
@@ -48,43 +47,38 @@ public RenameHandler()
                 var renameLocationSet = await renameInfo.FindRenameLocationsAsync(solution.Workspace.Options, cancellationToken).ConfigureAwait(false);
                 var renameReplacementInfo = await renameLocationSet.GetReplacementsAsync(request.NewName, solution.Workspace.Options, cancellationToken).ConfigureAwait(false);
 
-                var newSolution = renameReplacementInfo.NewSolution;
-                var solutionChanges = newSolution.GetChanges(solution);
+                var renamedSolution = renameReplacementInfo.NewSolution;
+                var solutionChanges = renamedSolution.GetChanges(solution);
 
-                var solutionWithLinkedFileChangesMerged = newSolution.WithMergedLinkedFileChangesAsync(solution, solutionChanges, cancellationToken: cancellationToken).Result;
-                var changedDocuments = solutionWithLinkedFileChangesMerged.GetChanges(solution).GetProjectChanges().SelectMany(p => p.GetChangedDocuments(onlyGetDocumentsWithTextChanges: true));
+                // Linked files can correspond to multiple roslyn documents each with changes.  W merge the changes in the linked files so that all linked documents have the same text.
+                // Then we can just take the text changes from the first document to avoid returning duplicate edits.
+                var solutionWithLinkedFileChangesMerged = await renamedSolution.WithMergedLinkedFileChangesAsync(solution, solutionChanges, cancellationToken: cancellationToken).ConfigureAwait(false);
+                solutionChanges = solutionWithLinkedFileChangesMerged.GetChanges(solution);
+                var changedDocuments = solutionChanges
+                    .GetProjectChanges()
+                    .SelectMany(p => p.GetChangedDocuments(onlyGetDocumentsWithTextChanges: true))
+                    .GroupBy(docId => solutionWithLinkedFileChangesMerged.GetRequiredDocument(docId).FilePath, StringComparer.OrdinalIgnoreCase).Select(group => group.First());
 
-                // Linked files will create multiple documents with duplicate edits for the same actual file.
-                // So take only the unique edits per URI to avoid returning duplicate edits.
-                var textEdits = new Dictionary<Uri, List<TextEdit>>();
-                foreach (var changedDocument in changedDocuments)
+                using var _ = ArrayBuilder<TextDocumentEdit>.GetInstance(out var documentEdits);
+                foreach (var docId in changedDocuments)
                 {
-                    var documentUri = newSolution.GetRequiredDocument(changedDocument).GetURI();
-                    var textChangesForUri = textEdits.GetOrValue(documentUri, new List<TextEdit>());
-                    textChangesForUri.AddRange(await GetTextChangesAsync(changedDocument, newSolution, solution, cancellationToken).ConfigureAwait(false));
-                    textEdits[documentUri] = textChangesForUri.Distinct(s_textEditEqualityComparer).ToList();
-                }
+                    var oldDoc = solution.GetRequiredDocument(docId);
+                    var newDoc = solutionWithLinkedFileChangesMerged.GetRequiredDocument(docId);
 
-                var documentEdits = textEdits.Select(kvp => new TextDocumentEdit
-                {
-                    TextDocument = new VersionedTextDocumentIdentifier { Uri = kvp.Key },
-                    Edits = kvp.Value.ToArray()
-                }).ToArray();
+                    var textChanges = await newDoc.GetTextChangesAsync(oldDoc, cancellationToken).ConfigureAwait(false);
+                    var oldText = await oldDoc.GetTextAsync(cancellationToken).ConfigureAwait(false);
+                    var textDocumentEdit = new TextDocumentEdit
+                    {
+                        TextDocument = new VersionedTextDocumentIdentifier { Uri = newDoc.GetURI() },
+                        Edits = textChanges.Select(tc => ProtocolConversions.TextChangeToTextEdit(tc, oldText)).ToArray()
+                    };
+                    documentEdits.Add(textDocumentEdit);
+                }
 
-                workspaceEdit = new WorkspaceEdit { DocumentChanges = documentEdits };
+                workspaceEdit = new WorkspaceEdit { DocumentChanges = documentEdits.ToArray() };
             }
 
             return workspaceEdit;
-
-            static async Task<IEnumerable<TextEdit>> GetTextChangesAsync(DocumentId documentId, Solution newSolution, Solution oldSolution, CancellationToken cancellationToken)
-            {
-                var oldDoc = oldSolution.GetRequiredDocument(documentId);
-                var newDoc = newSolution.GetRequiredDocument(documentId);
-
-                var textChanges = await newDoc.GetTextChangesAsync(oldDoc, cancellationToken).ConfigureAwait(false);
-                var oldText = await oldDoc.GetTextAsync(cancellationToken).ConfigureAwait(false);
-                return textChanges.Select(textChange => ProtocolConversions.TextChangeToTextEdit(textChange, oldText));
-            }
         }
     }
 }