Refactors classified span computation

Refactors the way classified spans are computed for Razor code documents intooling.

This change replaces the usage of legacy compiler APIs with a new `ClassifiedSpanVisitor`.
The new implementation is streamlined to only produce the information needed for the `GetLanguageKind()` API, improving performance and reducing dependencies.

This also includes changing the `ClassifiedSpanInternal` to `ClassifiedSpan` and removing the dependency on `Microsoft.AspNetCore.Razor.Language.Legacy`.

Author: DustinCampbell

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/RazorCodeDocumentExtensions.CachedData.cs

@@ -6,7 +6,6 @@
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Threading;
-using Microsoft.AspNetCore.Razor.Language.Legacy;
 using Microsoft.AspNetCore.Razor.Language.Syntax;
 using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.CodeAnalysis;
@@ -41,7 +40,7 @@ private sealed class CachedData(RazorCodeDocument codeDocument)
 
         private readonly SemaphoreSlim _stateLock = new(initialCount: 1);
         private SyntaxTree? _syntaxTree;
-        private ImmutableArray<ClassifiedSpanInternal>? _classifiedSpans;
+        private ImmutableArray<ClassifiedSpan>? _classifiedSpans;
         private ImmutableArray<SourceSpan>? _tagHelperSpans;
 
         public SyntaxTree GetOrParseCSharpSyntaxTree(CancellationToken cancellationToken)
@@ -63,7 +62,7 @@ static SyntaxTree ParseSyntaxTree(RazorCodeDocument codeDocument, CancellationTo
             }
         }
 
-        public ImmutableArray<ClassifiedSpanInternal> GetOrComputeClassifiedSpans(CancellationToken cancellationToken)
+        public ImmutableArray<ClassifiedSpan> GetOrComputeClassifiedSpans(CancellationToken cancellationToken)
         {
             if (_classifiedSpans is { } classifiedSpans)
             {
@@ -72,7 +71,7 @@ public ImmutableArray<ClassifiedSpanInternal> GetOrComputeClassifiedSpans(Cancel
 
             using (_stateLock.DisposableWait(cancellationToken))
             {
-                return _classifiedSpans ??= _codeDocument.GetRequiredSyntaxTree().GetClassifiedSpans();
+                return _classifiedSpans ??= ClassifiedSpanVisitor.VisitRoot(_codeDocument.GetRequiredSyntaxTree());
             }
         }
 

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/RazorCodeDocumentExtensions.cs

@@ -8,7 +8,7 @@
 using System.Linq;
 using System.Threading;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
-using Microsoft.AspNetCore.Razor.Language.Legacy;
+using Microsoft.AspNetCore.Razor.Language.Syntax;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor;
 using Microsoft.CodeAnalysis.Razor.Protocol;
@@ -150,14 +150,14 @@ public static RazorLanguageKind GetLanguageKind(this RazorCodeDocument codeDocum
         return GetLanguageKindCore(classifiedSpans, tagHelperSpans, hostDocumentIndex, documentLength, rightAssociative);
     }
 
-    private static ImmutableArray<ClassifiedSpanInternal> GetClassifiedSpans(RazorCodeDocument document)
+    private static ImmutableArray<ClassifiedSpan> GetClassifiedSpans(RazorCodeDocument document)
         => GetCachedData(document).GetOrComputeClassifiedSpans(CancellationToken.None);
 
     private static ImmutableArray<SourceSpan> GetTagHelperSpans(RazorCodeDocument document)
         => GetCachedData(document).GetOrComputeTagHelperSpans(CancellationToken.None);
 
     private static RazorLanguageKind GetLanguageKindCore(
-        ImmutableArray<ClassifiedSpanInternal> classifiedSpans,
+        ImmutableArray<ClassifiedSpan> classifiedSpans,
         ImmutableArray<SourceSpan> tagHelperSpans,
         int hostDocumentIndex,
         int hostDocumentLength,
@@ -178,7 +178,7 @@ private static RazorLanguageKind GetLanguageKindCore(
                     {
                         // We're at an edge.
 
-                        if (classifiedSpan.SpanKind is SpanKindInternal.MetaCode or SpanKindInternal.Transition)
+                        if (classifiedSpan.Kind is SpanKind.MetaCode or SpanKind.Transition)
                         {
                             // If we're on an edge of a transition of some kind (MetaCode representing an open or closing piece of syntax such as <|,
                             // and Transition representing an explicit transition to/from razor syntax, such as @|), prefer to classify to the span
@@ -236,13 +236,13 @@ private static RazorLanguageKind GetLanguageKindCore(
         // Default to Razor
         return RazorLanguageKind.Razor;
 
-        static RazorLanguageKind GetLanguageFromClassifiedSpan(ClassifiedSpanInternal classifiedSpan)
+        static RazorLanguageKind GetLanguageFromClassifiedSpan(ClassifiedSpan classifiedSpan)
         {
             // Overlaps with request
-            return classifiedSpan.SpanKind switch
+            return classifiedSpan.Kind switch
             {
-                SpanKindInternal.Markup => RazorLanguageKind.Html,
-                SpanKindInternal.Code => RazorLanguageKind.CSharp,
+                SpanKind.Markup => RazorLanguageKind.Html,
+                SpanKind.Code => RazorLanguageKind.CSharp,
 
                 // Content type was non-C# or Html or we couldn't find a classified span overlapping the request position.
                 // All other classified span kinds default back to Razor