Use CancellationToken.None in the code fix for SA1129

Author: nbarbettini

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

@@ -58,12 +58,32 @@ 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;
 
-            return SyntaxFactory.DefaultExpression(newExpression.Type)
+            SyntaxNode replacement = null;
+            if (identifierName.Equals(nameof(CancellationToken), System.StringComparison.OrdinalIgnoreCase))
+            {
+                replacement = GetCancellationTokenNoneSyntax();
+            }
+            else
+            {
+                replacement = SyntaxFactory.DefaultExpression(newExpression.Type);
+            }
+
+            return replacement
                 .WithLeadingTrivia(newExpression.GetLeadingTrivia())
                 .WithTrailingTrivia(newExpression.GetTrailingTrivia());
         }
 
+        private static SyntaxNode GetCancellationTokenNoneSyntax()
+        {
+            return SyntaxFactory.MemberAccessExpression(
+                SyntaxKind.SimpleMemberAccessExpression,
+                SyntaxFactory.IdentifierName(nameof(CancellationToken)),
+                SyntaxFactory.IdentifierName(nameof(CancellationToken.None)));
+        }
+
         private class FixAll : DocumentBasedFixAllProvider
         {
             public static FixAllProvider Instance { get; } =

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

@@ -237,6 +237,47 @@ public T TestMethod2<T>()
             await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Verifies that <c>new CancellationTokenI()</c> is replaced by <c>CancellationToken.None</c>.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
+        [Fact]
+        public async Task VerifyCancellationTokenFixUsesNoneSyntaxAsync()
+        {
+            var testCode = @"
+using System.Threading;
+
+public class TestClass
+{
+    public void TestMethod()
+    {
+        var ct = new CancellationToken();
+    }
+}
+";
+
+            var fixedTestCode = @"
+using System.Threading;
+
+public class TestClass
+{
+    public void TestMethod()
+    {
+        var ct = CancellationToken.None;
+    }
+}
+";
+
+            DiagnosticResult[] expected =
+            {
+                this.CSharpDiagnostic().WithLocation(8, 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()
         {