Skip past whitespace on the same line when wrapping with tag

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/WrapWithTag/WrapWithTagEndpoint.cs

@@ -47,13 +47,30 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(WrapWithTagParams reques
             return null;
         }
 
-        var sourceText = await documentContext.GetSourceTextAsync(cancellationToken).ConfigureAwait(false);
+        var sourceText = codeDocument.Source.Text;
         if (request.Range?.Start is not { } start ||
             !sourceText.TryGetAbsoluteIndex(start, out var hostDocumentIndex))
         {
             return null;
         }
 
+        // First thing we do is make sure we start at a non-whitespace character. This is important because in some
+        // situations the whitespace can be technically C#, but move one character to the right and it's HTML. eg
+        //
+        // @if (true) {
+        //   |   <p></p>
+        // }
+        //
+        // Limiting this to only whitespace on the same line, as it's not clear what user expectation would be otherwise.
+        var requestSpan = sourceText.GetTextSpan(request.Range);
+        if (sourceText.TryGetFirstNonWhitespaceOffset(requestSpan, out var offset, out var newLineCount) &&
+            newLineCount == 0)
+        {
+            request.Range.Start.Character += offset;
+            requestSpan = sourceText.GetTextSpan(request.Range);
+            hostDocumentIndex += offset;
+        }
+
         // Since we're at the start of the selection, lets prefer the language to the right of the cursor if possible.
         // That way with the following situation:
         //
@@ -89,7 +106,6 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(WrapWithTagParams reques
             // <p>[|@currentCount|]</p>
 
             var tree = await documentContext.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
-            var requestSpan = sourceText.GetTextSpan(request.Range);
             var node = tree.Root.FindNode(requestSpan, includeWhitespace: false, getInnermostNodeForTie: true);
             if (node?.FirstAncestorOrSelf<CSharpImplicitExpressionSyntax>() is { Parent: CSharpCodeBlockSyntax codeBlock } &&
                 (requestSpan == codeBlock.FullSpan || requestSpan.Length == 0))

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/WrapWithTag/WrapWithTagEndpointTests.cs

@@ -146,6 +146,114 @@ public async Task Handle_RazorBlockStart_ReturnsResult()
         Mock.Get(clientConnection).Verify();
     }
 
+    [Fact]
+    public async Task Handle_HtmlInCSharp()
+    {
+        // Arrange
+        var input = new TestCode("""
+            @if (true)
+            {
+                [|<p></p>|]
+            }
+            """);
+        var codeDocument = CreateCodeDocument(input.Text);
+        var uri = new Uri("file://path/test.razor");
+        var documentContext = CreateDocumentContext(uri, codeDocument);
+        var response = new WrapWithTagResponse();
+
+        var clientConnection = TestMocks.CreateClientConnection(builder =>
+        {
+            builder.SetupSendRequest<WrapWithTagParams, WrapWithTagResponse>(LanguageServerConstants.RazorWrapWithTagEndpoint, response: new(), verifiable: true);
+        });
+
+        var endpoint = new WrapWithTagEndpoint(clientConnection, LoggerFactory);
+
+        var range = codeDocument.Source.Text.GetRange(input.Span);
+        var wrapWithDivParams = new WrapWithTagParams(new TextDocumentIdentifier { Uri = uri })
+        {
+            Range = range
+        };
+        var requestContext = CreateRazorRequestContext(documentContext);
+
+        // Act
+        var result = await endpoint.HandleRequestAsync(wrapWithDivParams, requestContext, DisposalToken);
+
+        // Assert
+        Assert.NotNull(result);
+        Mock.Get(clientConnection).Verify();
+    }
+
+    [Fact]
+    public async Task Handle_HtmlInCSharp_WithWhitespace()
+    {
+        // Arrange
+        var input = new TestCode("""
+            @if (true)
+            {
+               [| <p></p>|]
+            }
+            """);
+        var codeDocument = CreateCodeDocument(input.Text);
+        var uri = new Uri("file://path/test.razor");
+        var documentContext = CreateDocumentContext(uri, codeDocument);
+        var response = new WrapWithTagResponse();
+
+        var clientConnection = TestMocks.CreateClientConnection(builder =>
+        {
+            builder.SetupSendRequest<WrapWithTagParams, WrapWithTagResponse>(LanguageServerConstants.RazorWrapWithTagEndpoint, response: new(), verifiable: true);
+        });
+
+        var endpoint = new WrapWithTagEndpoint(clientConnection, LoggerFactory);
+
+        var range = codeDocument.Source.Text.GetRange(input.Span);
+        var wrapWithDivParams = new WrapWithTagParams(new TextDocumentIdentifier { Uri = uri })
+        {
+            Range = range
+        };
+        var requestContext = CreateRazorRequestContext(documentContext);
+
+        // Act
+        var result = await endpoint.HandleRequestAsync(wrapWithDivParams, requestContext, DisposalToken);
+
+        // Assert
+        Assert.NotNull(result);
+        Mock.Get(clientConnection).Verify();
+    }
+
+    [Fact]
+    public async Task Handle_HtmlInCSharp_WithNewline()
+    {
+        // Arrange
+        var input = new TestCode("""
+            @if (true)
+            {[|
+                <p></p>|]
+            }
+            """);
+        var codeDocument = CreateCodeDocument(input.Text);
+        var uri = new Uri("file://path/test.razor");
+        var documentContext = CreateDocumentContext(uri, codeDocument);
+        var response = new WrapWithTagResponse();
+
+        var clientConnection = TestMocks.CreateClientConnection(builder => { });
+
+        var endpoint = new WrapWithTagEndpoint(clientConnection, LoggerFactory);
+
+        var range = codeDocument.Source.Text.GetRange(input.Span);
+        var wrapWithDivParams = new WrapWithTagParams(new TextDocumentIdentifier { Uri = uri })
+        {
+            Range = range
+        };
+        var requestContext = CreateRazorRequestContext(documentContext);
+
+        // Act
+        var result = await endpoint.HandleRequestAsync(wrapWithDivParams, requestContext, DisposalToken);
+
+        // Assert
+        Assert.Null(result);
+        Mock.Get(clientConnection).Verify();
+    }
+
     [Fact]
     public async Task Handle_CSharp_PartOfImplicitStatement_ReturnsNull()
     {