Merge pull request microsoft#171 from Microsoft/dev/andarno/fix168

Preserve leading trivia in VSTHRD103 code fix
snalexp · Jul 31, 2017 · a6e4c82 · a6e4c82
2 parents 43ea43b + 92825b0
commit a6e4c82
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Showing 2 changed files with 94 additions and 2 deletions.
diff --git a/src/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD103UseAsyncOptionAnalyzerTests.cs b/src/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD103UseAsyncOptionAnalyzerTests.cs
@@ -923,6 +923,94 @@ internal static void Foo<T>() { }
             this.VerifyCSharpFix(test, withFix);
         }
 
+        [Fact]
+        public void AsyncAlternative_CodeFixRespectsTrivia()
+        {
+            var test = @"
+using System;
+using System.Threading.Tasks;
+
+class Test {
+    void Foo() { }
+    Task FooAsync() => Task.CompletedTask;
+
+    async Task DoWorkAsync()
+    {
+        await Task.Yield();
+        Console.WriteLine(""Foo"");
+
+        // Some comment
+        Foo(/*argcomment*/); // another comment
+    }
+}
+";
+            var withFix = @"
+using System;
+using System.Threading.Tasks;
+
+class Test {
+    void Foo() { }
+    Task FooAsync() => Task.CompletedTask;
+
+    async Task DoWorkAsync()
+    {
+        await Task.Yield();
+        Console.WriteLine(""Foo"");
+
+        // Some comment
+        await FooAsync(/*argcomment*/); // another comment
+    }
+}
+";
+            this.expect.Locations = new[] { new DiagnosticResultLocation("Test0.cs", 15, 9, 15, 12) };
+            this.VerifyCSharpDiagnostic(test, this.expect);
+            this.VerifyCSharpFix(test, withFix);
+        }
+
+        [Fact]
+        public void AwaitRatherThanWait_CodeFixRespectsTrivia()
+        {
+            var test = @"
+using System;
+using System.Threading.Tasks;
+
+class Test {
+    void Foo() { }
+    Task FooAsync() => Task.CompletedTask;
+
+    async Task DoWorkAsync()
+    {
+        await Task.Yield();
+        Console.WriteLine(""Foo"");
+
+        // Some comment
+        FooAsync(/*argcomment*/).Wait(); // another comment
+    }
+}
+";
+            var withFix = @"
+using System;
+using System.Threading.Tasks;
+
+class Test {
+    void Foo() { }
+    Task FooAsync() => Task.CompletedTask;
+
+    async Task DoWorkAsync()
+    {
+        await Task.Yield();
+        Console.WriteLine(""Foo"");
+
+        // Some comment
+        await FooAsync(/*argcomment*/); // another comment
+    }
+}
+";
+            this.expect.Locations = new[] { new DiagnosticResultLocation("Test0.cs", 15, 34, 15, 38) };
+            this.VerifyCSharpDiagnostic(test, this.expect);
+            this.VerifyCSharpFix(test, withFix);
+        }
+
         [Fact]
         public void XunitThrowAsyncNotSuggestedInAsyncTestMethod()
         {

diff --git a/src/Microsoft.VisualStudio.Threading.Analyzers/VSTHRD103UseAsyncOptionCodeFix.cs b/src/Microsoft.VisualStudio.Threading.Analyzers/VSTHRD103UseAsyncOptionCodeFix.cs
@@ -135,8 +135,11 @@ protected override async Task<Solution> GetChangedSolutionAsync(CancellationToke
                 if (this.AlternativeAsyncMethod != string.Empty)
                 {
                     // Replace the member being called and await the invocation expression.
+                    // While doing so, move leading trivia to the surrounding await expression.
                     var asyncMethodName = syncMethodName.WithIdentifier(SyntaxFactory.Identifier(this.diagnostic.Properties[AsyncMethodKeyName]));
-                    awaitExpression = SyntaxFactory.AwaitExpression(syncExpression.ReplaceNode(syncMethodName, asyncMethodName));
+                    awaitExpression = SyntaxFactory.AwaitExpression(
+                        syncExpression.ReplaceNode(syncMethodName, asyncMethodName).WithoutLeadingTrivia())
+                        .WithLeadingTrivia(syncExpression.GetLeadingTrivia());
                     if (!(syncExpression.Parent is ExpressionStatementSyntax))
                     {
                         awaitExpression = SyntaxFactory.ParenthesizedExpression(awaitExpression)
@@ -156,7 +159,8 @@ protected override async Task<Solution> GetChangedSolutionAsync(CancellationToke
                         syncMemberStrippedExpression = expressionMethodCall.Expression;
                     }
 
-                    awaitExpression = SyntaxFactory.AwaitExpression(syncMemberStrippedExpression);
+                    awaitExpression = SyntaxFactory.AwaitExpression(syncMemberStrippedExpression.WithoutLeadingTrivia())
+                        .WithLeadingTrivia(syncMemberStrippedExpression.GetLeadingTrivia());
                 }
 
                 updatedMethod = updatedMethod