Don't put breakpoints on component start tags, end tags or attributes (#12422)

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Debugging/RemoteDebugInfoService.cs

@@ -5,9 +5,9 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Syntax;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
-using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Razor.Remote;
 using Microsoft.CodeAnalysis.Remote.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Text;
@@ -113,27 +113,48 @@ protected override IRemoteDebugInfoService CreateService(in ServiceArgs args)
 
     private bool TryGetUsableProjectedIndex(RazorCodeDocument codeDocument, LinePosition hostDocumentPosition, out int projectedIndex)
     {
-        var hostDocumentIndex = codeDocument.Source.Text.GetPosition(hostDocumentPosition);
-
         projectedIndex = 0;
-        var languageKind = codeDocument.GetLanguageKind(hostDocumentIndex, rightAssociative: false);
-        // For C#, we just map
-        if (languageKind == RazorLanguageKind.CSharp &&
-            !_documentMappingService.TryMapToCSharpDocumentPosition(codeDocument.GetRequiredCSharpDocument(), hostDocumentIndex, out _, out projectedIndex))
-        {
-            return false;
-        }
-        // Otherwise see if there is more C# on the line to map to. This is for situations like "$$<p>@DateTime.Now</p>"
-        else if (languageKind == RazorLanguageKind.Html &&
-            !_documentMappingService.TryMapToCSharpPositionOrNext(codeDocument.GetRequiredCSharpDocument(), hostDocumentIndex, out _, out projectedIndex))
-        {
-            return false;
-        }
-        else if (languageKind == RazorLanguageKind.Razor)
+
+        var sourceText = codeDocument.Source.Text;
+        var hostDocumentIndex = sourceText.GetPosition(hostDocumentPosition);
+        var syntaxRoot = codeDocument.GetRequiredSyntaxRoot();
+        var csharpDocument = codeDocument.GetRequiredCSharpDocument();
+
+        // We want to find a position that maps to C# on the same line as the original request, but we might have to skip over
+        // some Razor/HTML nodes to find valid C#.
+        while (sourceText.GetLinePosition(hostDocumentIndex).Line == hostDocumentPosition.Line)
         {
-            return false;
+            if (_documentMappingService.TryMapToCSharpPositionOrNext(csharpDocument, hostDocumentIndex, out _, out projectedIndex))
+            {
+                if (syntaxRoot.FindInnermostNode(hostDocumentIndex) is not { } node)
+                {
+                    return false;
+                }
+
+                // We want to avoid component tags and component attributes, where we map to C#, but they're not valid breakpoint locations
+                if (!node.IsAnyAttributeSyntax() && node is not (MarkupTagHelperStartTagSyntax or MarkupEndTagSyntax))
+                {
+                    // Found something valid!
+                    return true;
+                }
+
+                // It's C#, but not valid, so skip past it so we can try to find more C#
+                hostDocumentIndex = node.Span.End + 1;
+            }
+
+            // See if there is more C# on the line to map to, for example "$$<p>@DateTime.Now</p>"
+            if (!_documentMappingService.TryMapToCSharpPositionOrNext(csharpDocument, hostDocumentIndex, out _, out projectedIndex))
+            {
+                return false;
+            }
+
+            // We found some C# later on the line, so map that back to Razor so we can loop around and check the node type
+            if (!_documentMappingService.TryMapToRazorDocumentPosition(csharpDocument, projectedIndex, out _, out hostDocumentIndex))
+            {
+                return false;
+            }
         }
 
-        return true;
+        return false;
     }
 }

src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RemoteDebugInfoServiceTest.cs

@@ -174,6 +174,104 @@ public async Task ResolveBreakpointRangeAsync_OutsideImplicitExpression()
         await VerifyBreakpointRangeAsync(input);
     }
 
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentStartTag()
+    {
+        var input = """
+                <div></div>
+
+                <Page$$Title>Hello</PageTitle>
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentAttribute()
+    {
+        var input = """
+                <div></div>
+
+                @{
+                    var caption = "Hello";
+                }
+
+                <InputText Val$$ue="@caption" />
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentContent()
+    {
+        var input = """
+                <div></div>
+
+                @{
+                    var caption = "Hello";
+                }
+
+                <PageTitle>@[|cap$$tion|]</PageTitle>
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentContent_FromStartOfLine()
+    {
+        var input = """
+                <div></div>
+
+                @{
+                    var caption = "Hello";
+                }
+
+                $$<PageTitle>@[|caption|]</PageTitle>
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentContent_FromStartOfLine_WithAttribute()
+    {
+        var input = """
+                <div></div>
+
+                @{
+                    var caption = "Hello";
+                }
+
+                $$<InputText Value="@caption" />@[|caption|]
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
+    [Fact]
+    public async Task ResolveBreakpointRangeAsync_ComponentContent_FromStartTag()
+    {
+        var input = """
+                <div></div>
+
+                @{
+                    var caption = "Hello";
+                }
+
+                <PageT$$itle>@[|caption|]</PageTitle>
+
+                """;
+
+        await VerifyBreakpointRangeAsync(input);
+    }
+
     private async Task VerifyProximityExpressionsAsync(TestCode input, string[] extraExpressions)
     {
         var document = CreateProjectAndRazorDocument(input.Text);