Filter all html diagnostics out if they're reported in a comment (#12002)

Noticed while I was testing an old formatting issue, that we would
report diagnostics when Razor comments appear in CSS tags. In general,
there is no reason to report a diagnostic in a comment.

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorTranslateDiagnosticsService.cs

@@ -102,6 +102,7 @@ private static LspDiagnostic[] FilterHTMLDiagnostics(
 
         var filteredDiagnostics = unmappedDiagnostics
             .Where(d =>
+                !InRazorComment(d, sourceText, syntaxTree) &&
                 !InCSharpLiteral(d, sourceText, syntaxTree) &&
                 !InAttributeContainingCSharp(d, sourceText, syntaxTree, processedAttributes) &&
                 !AppliesToTagHelperTagName(d, sourceText, syntaxTree) &&
@@ -146,6 +147,18 @@ private LspDiagnostic[] MapDiagnostics(
         return mappedDiagnostics.ToArray();
     }
 
+    private static bool InRazorComment(
+        LspDiagnostic d,
+        SourceText sourceText,
+        RazorSyntaxTree syntaxTree)
+    {
+        // If the diagnostic is within a Razor comment block, we don't want to show it.
+        // Razor comments are not part of the Html document, so diagnostics within them stem from misinterpretation
+        // of the "~" and comments that are generated by the compiler.
+        return d.Range is not null &&
+            syntaxTree.Root.FindNode(sourceText.GetTextSpan(d.Range), getInnermostNodeForTie: true) is RazorCommentBlockSyntax;
+    }
+
     private static bool InCSharpLiteral(
         LspDiagnostic d,
         SourceText sourceText,
@@ -496,7 +509,7 @@ private bool TryGetOriginalDiagnosticRange(LspDiagnostic diagnostic, RazorCodeDo
             // for mapping when a user reports not seeing an error they thought they should
             if (diagnostic.Severity == LspDiagnosticSeverity.Error)
             {
-                this._logger.LogWarning($"Dropping diagnostic {diagnostic.Code}:{diagnostic.Message} at csharp range {diagnostic.Range}");
+                _logger.LogWarning($"Dropping diagnostic {diagnostic.Code}:{diagnostic.Message} at csharp range {diagnostic.Range}");
             }
 
             return false;

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

@@ -109,6 +109,60 @@ public Task FilterEscapedAtFromCss()
             }]);
     }
 
+    [Fact]
+    public Task FilterRazorCommentsFromCss()
+    {
+        TestCode input = """
+            <div>
+
+            <style>
+                @* This is a Razor comment *@
+            </style>
+
+            </div>
+            """;
+
+        return VerifyDiagnosticsAsync(input,
+            htmlResponse: [new VSInternalDiagnosticReport
+            {
+                Diagnostics =
+                [
+                    new Diagnostic
+                    {
+                        Code = CSSErrorCodes.MissingSelectorBeforeCombinatorCode,
+                        Range = SourceText.From(input.Text).GetRange(new TextSpan(input.Text.IndexOf("@*"), 1))
+                    }
+                ]
+            }]);
+    }
+
+    [Fact]
+    public Task FilterRazorCommentsFromCss_Inside()
+    {
+        TestCode input = """
+            <div>
+
+            <style>
+                @* This is a Razor comment *@
+            </style>
+
+            </div>
+            """;
+
+        return VerifyDiagnosticsAsync(input,
+            htmlResponse: [new VSInternalDiagnosticReport
+            {
+                Diagnostics =
+                [
+                    new Diagnostic
+                    {
+                        Code = CSSErrorCodes.MissingSelectorBeforeCombinatorCode,
+                        Range = SourceText.From(input.Text).GetRange(new TextSpan(input.Text.IndexOf("Ra"), 1))
+                    }
+                ]
+            }]);
+    }
+
     [Fact]
     public Task CombinedAndNestedDiagnostics()
         => VerifyDiagnosticsAsync("""
@@ -170,6 +224,15 @@ private async Task VerifyDiagnosticsAsync(TestCode input, VSInternalDiagnosticRe
                     Diagnostics = await endpoint.GetTestAccessor().HandleRequestAsync(document, DisposalToken)
                 }];
 
+        Assert.NotNull(result);
+
+        if (result is [{ Diagnostics: null }])
+        {
+            // No diagnostics found, make sure none were expected
+            AssertEx.Equal(input.OriginalInput, input.Text);
+            return;
+        }
+
         var markers = result!.SelectMany(d => d.Diagnostics.AssumeNotNull()).SelectMany(d =>
             new[] {
                 (index: inputText.GetTextSpan(d.Range).Start, text: $"{{|{d.Code!.Value.Second}:"),