Update SA1129 CancellationToken handling to properly qualify member access

Author: nbarbettini

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/ReadabilityRules/SA1129CodeFixProvider.cs

@@ -58,13 +58,13 @@ private static async Task<Document> GetTransformedDocumentAsync(Document documen
         private static SyntaxNode GetReplacementNode(SyntaxNode node)
         {
             var newExpression = (ObjectCreationExpressionSyntax)node;
-            var identifierName = (newExpression.Type as IdentifierNameSyntax)
-                ?.Identifier.Text;
+            var nameSyntax = newExpression.Type as NameSyntax;
+            var identifierName = NameSyntaxHelpers.ToNormalizedString(nameSyntax);
 
             SyntaxNode replacement = null;
-            if (identifierName.Equals(nameof(CancellationToken), System.StringComparison.OrdinalIgnoreCase))
+            if (identifierName.EndsWith(nameof(CancellationToken), System.StringComparison.OrdinalIgnoreCase))
             {
-                replacement = GetCancellationTokenNoneSyntax();
+                replacement = GetCancellationTokenNoneSyntax(nameSyntax);
             }
             else
             {
@@ -76,11 +76,11 @@ private static SyntaxNode GetReplacementNode(SyntaxNode node)
                 .WithTrailingTrivia(newExpression.GetTrailingTrivia());
         }
 
-        private static SyntaxNode GetCancellationTokenNoneSyntax()
+        private static SyntaxNode GetCancellationTokenNoneSyntax(NameSyntax nameSyntax)
         {
             return SyntaxFactory.MemberAccessExpression(
                 SyntaxKind.SimpleMemberAccessExpression,
-                SyntaxFactory.IdentifierName(nameof(CancellationToken)),
+                nameSyntax,
                 SyntaxFactory.IdentifierName(nameof(CancellationToken.None)));
         }
 

StyleCop.Analyzers/StyleCop.Analyzers.Test/ReadabilityRules/SA1129UnitTests.cs

@@ -319,6 +319,44 @@ public void TestMethod()
             await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Verifies that <c>new CancellationToken()</c> is replaced by <c>CancellationToken.None</c>,
+        /// and a fully-qualified name is preserved correctly.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
+        [Fact]
+        public async Task VerifyQualifiedCancellationTokenFixUsesNoneSyntaxAsync()
+        {
+            var testCode = @"
+public class TestClass
+{
+    public void TestMethod()
+    {
+        var ct = new System.Threading.CancellationToken();
+    }
+}
+";
+
+            var fixedTestCode = @"
+public class TestClass
+{
+    public void TestMethod()
+    {
+        var ct = System.Threading.CancellationToken.None;
+    }
+}
+";
+
+            DiagnosticResult[] expected =
+            {
+                this.CSharpDiagnostic().WithLocation(6, 18),
+            };
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedTestCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
+        }
+
         /// <inheritdoc/>
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {