Expose breakable range handler to Razor (#76629)

Roslyn side of dotnet/razor#11337

src/LanguageServer/Protocol/Handler/Breakpoints/ValidateBreakableRangeHandler.cs

@@ -28,12 +28,13 @@ internal sealed class ValidateBreakableRangeHandler() : ILspServiceDocumentReque
         public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.VSInternalValidateBreakableRangeParams request)
             => request.TextDocument;
 
-        public async Task<LSP.Range?> HandleRequestAsync(LSP.VSInternalValidateBreakableRangeParams request, RequestContext context, CancellationToken cancellationToken)
-        {
-            var document = context.GetRequiredDocument();
+        public Task<LSP.Range?> HandleRequestAsync(LSP.VSInternalValidateBreakableRangeParams request, RequestContext context, CancellationToken cancellationToken)
+            => GetBreakableRangeAsync(context.GetRequiredDocument(), request.Range, cancellationToken);
 
+        public static async Task<LSP.Range?> GetBreakableRangeAsync(Document document, LSP.Range range, CancellationToken cancellationToken)
+        {
             var text = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
-            var span = ProtocolConversions.RangeToTextSpan(request.Range, text);
+            var span = ProtocolConversions.RangeToTextSpan(range, text);
             var breakpointService = document.Project.Services.GetRequiredService<IBreakpointResolutionService>();
 
             if (span.Length > 0)
@@ -62,7 +63,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.VSInternalValidateBr
                     if (tree.GetDiagnostics(cancellationToken).Any(d => d.Severity == DiagnosticSeverity.Error))
                     {
                         // Keep the span as is.
-                        return request.Range;
+                        return range;
                     }
                 }
             }
@@ -93,7 +94,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.VSInternalValidateBr
             // BP: int a = $$ GetData();
             //
             // If the user types "1;" we'd shrink the breakpoint, so stick to the end of the range.
-            if (!result.IsLineBreakpoint && BreakpointRangeIsSmaller(breakpointRange, request.Range))
+            if (!result.IsLineBreakpoint && BreakpointRangeIsSmaller(breakpointRange, range))
             {
                 var secondResult = await breakpointService.ResolveBreakpointAsync(document, new TextSpan(span.End, length: 0), cancellationToken).ConfigureAwait(false);
                 if (secondResult is not null)

src/Tools/ExternalAccess/Razor/Cohost/Handlers/ValidateBreakableRange.cs

@@ -0,0 +1,27 @@
+// 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.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.LanguageServer;
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost.Handlers;
+
+internal static class ValidateBreakableRange
+{
+    public static async Task<LinePositionSpan?> GetBreakableRangeAsync(Document document, LinePositionSpan span, CancellationToken cancellationToken)
+    {
+        var range = ProtocolConversions.LinePositionToRange(span);
+        var result = await ValidateBreakableRangeHandler.GetBreakableRangeAsync(document, range, cancellationToken).ConfigureAwait(false);
+
+        if (result is null)
+        {
+            return null;
+        }
+
+        return ProtocolConversions.RangeToLinePositionSpan(result);
+    }
+}

src/Tools/ExternalAccess/Razor/ITextBufferExtensions.cs

@@ -0,0 +1,18 @@
+// 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.Diagnostics.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.Text;
+
+namespace Microsoft.CodeAnalysis.ExternalAccess.Razor;
+
+internal static class ITextBufferExtensions
+{
+    public static bool TryGetTextDocument(this ITextBuffer textBuffer, [NotNullWhen(true)] out TextDocument? textDocument)
+    {
+        textDocument = textBuffer.CurrentSnapshot.AsText().GetOpenTextDocumentInCurrentContextWithChanges();
+        return textDocument is not null;
+    }
+}