Update filenames in file banners when moving a type to a new file.

src/Analyzers/CSharp/Analyzers/FileHeaders/CSharpFileHeaderHelper.cs

@@ -12,15 +12,10 @@ namespace Microsoft.CodeAnalysis.CSharp.FileHeaders;
 /// <summary>
 /// Helper class used for working with file headers.
 /// </summary>
-internal sealed class CSharpFileHeaderHelper : AbstractFileHeaderHelper
+internal sealed class CSharpFileHeaderHelper() : AbstractFileHeaderHelper(CSharpSyntaxKinds.Instance)
 {
     public static readonly CSharpFileHeaderHelper Instance = new();
 
-    private CSharpFileHeaderHelper()
-        : base(CSharpSyntaxKinds.Instance)
-    {
-    }
-
     public override string CommentPrefix => "//";
 
     protected override ReadOnlyMemory<char> GetTextContextOfComment(SyntaxTrivia commentTrivia)

src/Analyzers/Core/Analyzers/FileHeaders/AbstractFileHeaderHelper.cs

@@ -9,16 +9,8 @@
 
 namespace Microsoft.CodeAnalysis.FileHeaders;
 
-internal abstract class AbstractFileHeaderHelper
+internal abstract class AbstractFileHeaderHelper(ISyntaxKinds syntaxKinds)
 {
-    protected AbstractFileHeaderHelper(ISyntaxKinds syntaxKinds)
-    {
-        SingleLineCommentTriviaKind = syntaxKinds.SingleLineCommentTrivia;
-        MultiLineCommentTriviaKind = syntaxKinds.MultiLineCommentTrivia;
-        WhitespaceTriviaKind = syntaxKinds.WhitespaceTrivia;
-        EndOfLineTriviaKind = syntaxKinds.EndOfLineTrivia;
-    }
-
     /// <summary>
     /// Gets the text prefix indicating a single-line comment.
     /// </summary>
@@ -27,16 +19,16 @@ protected AbstractFileHeaderHelper(ISyntaxKinds syntaxKinds)
     protected abstract ReadOnlyMemory<char> GetTextContextOfComment(SyntaxTrivia commentTrivia);
 
     /// <inheritdoc cref="ISyntaxKinds.SingleLineCommentTrivia"/>
-    private int SingleLineCommentTriviaKind { get; }
+    private int SingleLineCommentTriviaKind { get; } = syntaxKinds.SingleLineCommentTrivia;
 
     /// <inheritdoc cref="ISyntaxKinds.MultiLineCommentTrivia"/>
-    private int? MultiLineCommentTriviaKind { get; }
+    private int? MultiLineCommentTriviaKind { get; } = syntaxKinds.MultiLineCommentTrivia;
 
     /// <inheritdoc cref="ISyntaxKinds.WhitespaceTrivia"/>
-    private int WhitespaceTriviaKind { get; }
+    private int WhitespaceTriviaKind { get; } = syntaxKinds.WhitespaceTrivia;
 
     /// <inheritdoc cref="ISyntaxKinds.EndOfLineTrivia"/>
-    private int EndOfLineTriviaKind { get; }
+    private int EndOfLineTriviaKind { get; } = syntaxKinds.EndOfLineTrivia;
 
     public FileHeader ParseFileHeader(SyntaxNode root)
     {

src/EditorFeatures/CSharpTest/CodeActions/MoveType/MoveTypeTests.MoveToNewFile.cs

@@ -105,7 +105,7 @@ class Class1 { }
 
         await TestMoveTypeToNewFileAsync(
             code, codeAfterMove, expectedDocumentName,
-            destinationDocumentText, destinationDocumentContainers: ImmutableArray.Create("A", "B"));
+            destinationDocumentText, destinationDocumentContainers: ["A", "B"]);
     }
 
     [WpfFact]
@@ -2012,4 +2012,37 @@ partial interface I
             """;
         await TestMoveTypeToNewFileAsync(code, codeAfterMove, expectedDocumentName, destinationDocumentText);
     }
+
+    [WpfFact, WorkItem("https://github.com/dotnet/roslyn/issues/74703")]
+    public async Task TestUpdateFileName()
+    {
+        var code =
+            """
+
+            <Workspace>
+                <Project Language="C#" AssemblyName="Assembly1" CommonReferences="true">
+                    <Document Folders="A\B" FilePath="Goo.cs">// This is a banner referencing Goo.cs
+            [||]class Class1 { }
+            class Class2 { }
+                    </Document>
+                </Project>
+            </Workspace>
+            """;
+        var codeAfterMove = """
+            // This is a banner referencing Goo.cs
+            class Class2 { }
+
+            """;
+
+        var expectedDocumentName = "Class1.cs";
+        var destinationDocumentText = """
+            // This is a banner referencing Class1.cs
+            class Class1 { }
+
+            """;
+
+        await TestMoveTypeToNewFileAsync(
+            code, codeAfterMove, expectedDocumentName,
+            destinationDocumentText, destinationDocumentContainers: ["A", "B"]);
+    }
 }

src/Features/CSharp/Portable/AddFileBanner/CSharpAddFileBannerCodeRefactoringProvider.cs

@@ -11,28 +11,10 @@ namespace Microsoft.CodeAnalysis.CSharp.AddFileBanner;
 
 [ExportCodeRefactoringProvider(LanguageNames.CSharp,
     Name = PredefinedCodeRefactoringProviderNames.AddFileBanner), Shared]
-internal class CSharpAddFileBannerCodeRefactoringProvider : AbstractAddFileBannerCodeRefactoringProvider
+[method: ImportingConstructor]
+[method: SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
+internal sealed class CSharpAddFileBannerCodeRefactoringProvider() : AbstractAddFileBannerCodeRefactoringProvider
 {
-    [ImportingConstructor]
-    [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
-    public CSharpAddFileBannerCodeRefactoringProvider()
-    {
-    }
-
     protected override bool IsCommentStartCharacter(char ch)
         => ch == '/';
-
-    protected override SyntaxTrivia CreateTrivia(SyntaxTrivia trivia, string text)
-    {
-        switch (trivia.Kind())
-        {
-            case SyntaxKind.SingleLineCommentTrivia:
-            case SyntaxKind.MultiLineCommentTrivia:
-            case SyntaxKind.SingleLineDocumentationCommentTrivia:
-            case SyntaxKind.MultiLineDocumentationCommentTrivia:
-                return SyntaxFactory.Comment(text);
-        }
-
-        return trivia;
-    }
 }

src/Features/CSharp/Portable/AddFileBanner/CSharpAddFileBannerNewDocumentFormattingProvider.cs

@@ -15,14 +15,10 @@
 namespace Microsoft.CodeAnalysis.CSharp.AddFileBanner;
 
 [ExportNewDocumentFormattingProvider(LanguageNames.CSharp), Shared]
-internal class CSharpAddFileBannerNewDocumentFormattingProvider : AbstractAddFileBannerNewDocumentFormattingProvider
+[method: ImportingConstructor]
+[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+internal sealed class CSharpAddFileBannerNewDocumentFormattingProvider() : AbstractAddFileBannerNewDocumentFormattingProvider
 {
-    [ImportingConstructor]
-    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-    public CSharpAddFileBannerNewDocumentFormattingProvider()
-    {
-    }
-
     protected override SyntaxGenerator SyntaxGenerator => CSharpSyntaxGenerator.Instance;
     protected override SyntaxGeneratorInternal SyntaxGeneratorInternal => CSharpSyntaxGeneratorInternal.Instance;
     protected override AbstractFileHeaderHelper FileHeaderHelper => CSharpFileHeaderHelper.Instance;

src/Features/Core/Portable/AddFileBanner/AbstractAddFileBannerCodeRefactoringProvider.cs

@@ -27,8 +27,6 @@ internal abstract class AbstractAddFileBannerCodeRefactoringProvider : SyntaxEdi
 
     protected abstract bool IsCommentStartCharacter(char ch);
 
-    protected abstract SyntaxTrivia CreateTrivia(SyntaxTrivia trivia, string text);
-
     protected sealed override ImmutableArray<FixAllScope> SupportedFixAllScopes { get; }
         = [FixAllScope.Project, FixAllScope.Solution];
 
@@ -53,15 +51,10 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
         var position = span.Start;
         var firstToken = root.GetFirstToken();
         if (!firstToken.FullSpan.IntersectsWith(position))
-        {
             return;
-        }
 
         if (HasExistingBanner(document, root))
-        {
-            // Already has a banner.
             return;
-        }
 
         // Process the other documents in this document's project.  Look at the
         // ones that we can get a root from (without having to parse).  Then
@@ -86,9 +79,10 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
                 context.RegisterRefactoring(
                     CodeAction.Create(
                         CodeFixesResources.Add_file_header,
-                        _ => AddBannerAsync(document, root, siblingDocument, siblingBanner),
+                        cancellationToken => AddFileBannerHelpers.CopyBannerAsync(
+                            destinationDocument: document, document.FilePath, sourceDocument: siblingDocument, cancellationToken),
                         equivalenceKey: GetEquivalenceKey(siblingDocument, siblingBanner)),
-                    new Text.TextSpan(position, length: 0));
+                    new TextSpan(position, length: 0));
                 return;
             }
         }
@@ -125,38 +119,6 @@ private static ImmutableArray<SyntaxTrivia> GetBannerFromEquivalenceKey(string e
         return bannerService.GetFileBanner(token);
     }
 
-    private Task<Document> AddBannerAsync(
-        Document document, SyntaxNode root,
-        Document siblingDocument, ImmutableArray<SyntaxTrivia> banner)
-    {
-        banner = UpdateEmbeddedFileNames(siblingDocument, document, banner);
-
-        var newRoot = root.WithPrependedLeadingTrivia(new SyntaxTriviaList(banner));
-        return Task.FromResult(document.WithSyntaxRoot(newRoot));
-    }
-
-    /// <summary>
-    /// Looks at <paramref name="banner"/> to see if it contains the name of <paramref name="sourceDocument"/>
-    /// in it.  If so, those names will be replaced with <paramref name="destinationDocument"/>'s name.
-    /// </summary>
-    private ImmutableArray<SyntaxTrivia> UpdateEmbeddedFileNames(
-        Document sourceDocument, Document destinationDocument, ImmutableArray<SyntaxTrivia> banner)
-    {
-        var sourceName = IOUtilities.PerformIO(() => Path.GetFileName(sourceDocument.FilePath));
-        var destinationName = IOUtilities.PerformIO(() => Path.GetFileName(destinationDocument.FilePath));
-        if (string.IsNullOrEmpty(sourceName) || string.IsNullOrEmpty(destinationName))
-            return banner;
-
-        var result = new FixedSizeArrayBuilder<SyntaxTrivia>(banner.Length);
-        foreach (var trivia in banner)
-        {
-            var updated = CreateTrivia(trivia, trivia.ToFullString().Replace(sourceName, destinationName));
-            result.Add(updated);
-        }
-
-        return result.MoveToImmutable();
-    }
-
     private async Task<ImmutableArray<SyntaxTrivia>> TryGetBannerAsync(
         Document document, SyntaxNode? root, CancellationToken cancellationToken)
     {

src/Features/Core/Portable/AddFileBanner/AbstractAddFileBannerNewDocumentFormattingProvider.cs

@@ -29,12 +29,12 @@ public async Task<Document> FormatNewDocumentAsync(Document document, Document?
         {
             var newLineTrivia = SyntaxGeneratorInternal.EndOfLine(options.FormattingOptions.NewLine);
             var rootWithFileHeader = await AbstractFileHeaderCodeFixProvider.GetTransformedSyntaxRootAsync(
-                    SyntaxGenerator.SyntaxFacts,
-                    FileHeaderHelper,
-                    newLineTrivia,
-                    document,
-                    fileHeaderTemplate,
-                    cancellationToken).ConfigureAwait(false);
+                SyntaxGenerator.SyntaxFacts,
+                FileHeaderHelper,
+                newLineTrivia,
+                document,
+                fileHeaderTemplate,
+                cancellationToken).ConfigureAwait(false);
 
             return document.WithSyntaxRoot(rootWithFileHeader);
         }

src/Features/Core/Portable/AddFileBanner/AddFileBannerHelpers.cs

@@ -0,0 +1,68 @@
+// 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;
+using System.Collections.Immutable;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.Utilities;
+
+namespace Microsoft.CodeAnalysis.AddFileBanner;
+
+internal static class AddFileBannerHelpers
+{
+    public static async Task<Document> CopyBannerAsync(
+        Document destinationDocument,
+        string? destinationFilePath,
+        Document sourceDocument,
+        CancellationToken cancellationToken)
+    {
+        var bannerService = destinationDocument.GetRequiredLanguageService<IFileBannerFactsService>();
+
+        var fromRoot = await sourceDocument.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+        var sourceBanner = bannerService.GetFileBanner(fromRoot);
+
+        sourceBanner = UpdateEmbeddedFileNames(
+            sourceDocument, destinationFilePath, sourceBanner, bannerService.CreateTrivia);
+
+        var destinationRoot = await destinationDocument.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+        var destinationBanner = bannerService.GetFileBanner(destinationRoot);
+
+        var firstToken = destinationRoot.GetFirstToken();
+        var newRoot = destinationRoot.ReplaceToken(
+            firstToken,
+            firstToken.WithLeadingTrivia(
+                sourceBanner.Concat(firstToken.LeadingTrivia.Skip(destinationBanner.Length))));
+        return destinationDocument.WithSyntaxRoot(newRoot);
+    }
+
+    /// <summary>
+    /// Looks at <paramref name="banner"/> to see if it contains the name of <paramref name="sourceDocument"/>
+    /// in it.  If so, those names will be replaced with <paramref name="destinationFilePath"/>.
+    /// </summary>
+    private static ImmutableArray<SyntaxTrivia> UpdateEmbeddedFileNames(
+        Document sourceDocument,
+        string? destinationFilePath,
+        ImmutableArray<SyntaxTrivia> banner,
+        Func<SyntaxTrivia, string, SyntaxTrivia> createTrivia)
+    {
+        var sourceName = IOUtilities.PerformIO(() => Path.GetFileName(sourceDocument.FilePath));
+        var destinationName = IOUtilities.PerformIO(() => Path.GetFileName(destinationFilePath));
+        if (string.IsNullOrEmpty(sourceName) || string.IsNullOrEmpty(destinationName))
+            return banner;
+
+        var result = new FixedSizeArrayBuilder<SyntaxTrivia>(banner.Length);
+        foreach (var trivia in banner)
+        {
+            var updated = createTrivia(trivia, trivia.ToFullString().Replace(sourceName, destinationName));
+            result.Add(updated);
+        }
+
+        return result.MoveToImmutable();
+    }
+}

src/Features/Core/Portable/CodeRefactorings/MoveType/AbstractMoveTypeService.MoveTypeEditor.cs

@@ -10,6 +10,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.AddFileBanner;
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.LanguageService;
@@ -27,7 +28,6 @@ private sealed class MoveTypeEditor(
         string fileName,
         CancellationToken cancellationToken) : Editor(service, state, fileName, cancellationToken)
     {
-
         /// <summary>
         /// Given a document and a type contained in it, moves the type
         /// out to its own document. The new document's name typically
@@ -111,8 +111,7 @@ private async Task<Solution> RemoveUnnecessaryImportsAsync(
         private async Task<Document> AddNewDocumentWithSingleTypeDeclarationAsync(DocumentId newDocumentId)
         {
             var document = SemanticDocument.Document;
-            Debug.Assert(document.Name != FileName,
-                         $"New document name is same as old document name:{FileName}");
+            Debug.Assert(document.Name != FileName, $"New document name is same as old document name:{FileName}");
 
             var root = SemanticDocument.Root;
             var projectToBeUpdated = document.Project;
@@ -146,7 +145,10 @@ private async Task<Document> AddNewDocumentWithSingleTypeDeclarationAsync(Docume
             // get the updated document, give it the minimal set of imports that the type
             // inside it needs.
             var newDocument = solutionWithNewDocument.GetRequiredDocument(newDocumentId);
-            return newDocument;
+            var newDocumentWithUpdatedBanner = await AddFileBannerHelpers.CopyBannerAsync(
+                newDocument, FileName, document, this.CancellationToken).ConfigureAwait(false);
+
+            return newDocumentWithUpdatedBanner;
         }
 
         /// <summary>
@@ -194,6 +196,7 @@ private async Task<Solution> RemoveTypeFromSourceDocumentAsync(Document sourceDo
             documentEditor.RemoveNode(State.TypeNode, SyntaxRemoveOptions.KeepUnbalancedDirectives);
 
             var updatedDocument = documentEditor.GetChangedDocument();
+            updatedDocument = await AddFileBannerHelpers.CopyBannerAsync(updatedDocument, sourceDocument.FilePath, sourceDocument, this.CancellationToken).ConfigureAwait(false);
 
             return updatedDocument.Project.Solution;
         }