Avoid suggesting a code fix for unknown entities

Author: sharwell

DocumentationAnalyzers/DocumentationAnalyzers.CodeFixes/StyleRules/DOC103CodeFixProvider.cs

@@ -42,33 +42,33 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
                     return;
                 }
 
+                string newText = token.ValueText;
+                if (newText == token.Text)
+                {
+                    // The entity is not recognized. Try decoding as an HTML entity.
+                    newText = WebUtility.HtmlDecode(token.Text);
+                }
+
+                if (newText == token.Text)
+                {
+                    // Unknown entity
+                    continue;
+                }
+
                 context.RegisterCodeFix(
                     CodeAction.Create(
                         StyleResources.DOC103CodeFix,
-                        cancellationToken => GetTransformedDocumentAsync(context.Document, diagnostic, cancellationToken),
+                        cancellationToken => GetTransformedDocumentAsync(context.Document, diagnostic, newText, cancellationToken),
                         nameof(DOC103CodeFixProvider)),
                     diagnostic);
             }
         }
 
-        private static async Task<Document> GetTransformedDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
+        private static async Task<Document> GetTransformedDocumentAsync(Document document, Diagnostic diagnostic, string newText, CancellationToken cancellationToken)
         {
             SyntaxNode root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
             SyntaxToken token = root.FindToken(diagnostic.Location.SourceSpan.Start, findInsideTrivia: true);
 
-            string newText = token.ValueText;
-            if (newText == token.Text)
-            {
-                // The entity is not recognized. Try decoding as an HTML entity.
-                newText = WebUtility.HtmlDecode(token.Text);
-            }
-
-            if (newText == token.Text)
-            {
-                // Unknown entity
-                return document;
-            }
-
             var newToken = SyntaxFactory.Token(token.LeadingTrivia, SyntaxKind.XmlTextLiteralToken, newText, newText, token.TrailingTrivia);
 
             return document.WithSyntaxRoot(root.ReplaceToken(token, newToken));

DocumentationAnalyzers/DocumentationAnalyzers.Test/StyleRules/DOC103UnitTests.cs

@@ -111,6 +111,35 @@ class TestClass
             }.RunAsync();
         }
 
+        [Fact]
+        public async Task TestUnknownEntityNotReplacedAsync()
+        {
+            var testCode = @"
+/// <summary>
+/// Unknown entity &myEntity;.
+/// </summary>
+class TestClass
+{
+}
+";
+            var fixedCode = testCode;
+
+            await new CSharpCodeFixTest<DOC103UseUnicodeCharacters, DOC103CodeFixProvider, XUnitVerifier>
+            {
+                TestState =
+                {
+                    Sources = { testCode },
+                    ExpectedDiagnostics = { DiagnosticResult.CompilerWarning("CS1570").WithSpan(3, 20, 3, 20).WithMessage("XML comment has badly formed XML -- 'Reference to undefined entity 'myEntity'.'") },
+                },
+                FixedState =
+                {
+                    Sources = { fixedCode },
+                    InheritanceMode = StateInheritanceMode.AutoInheritAll,
+                },
+                CompilerDiagnostics = CompilerDiagnostics.Warnings,
+            }.RunAsync();
+        }
+
         [Fact]
         public async Task TestHtmlEntityReplacementInInvalidXmlAsync()
         {