Merge pull request #1461 from sharwell/fix-1456

Fix behavior of SA1506 code fix when a blank line follows a line comment

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1506UnitTests.cs

@@ -572,9 +572,14 @@ public class TestClass
     public void TestMethod1() { }
 
     /// <summary>more documentation.</summary>
-    
+
     /* another comment */
     public void TestMethod2() { }
+
+    /// <summary>more documentation.</summary>
+    // another comment (a specific regression test for https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/1456)
+
+    public void TestMethod3() { }
 }
 ";
 
@@ -592,6 +597,10 @@ public void TestMethod1() { }
     /// <summary>more documentation.</summary>
     /* another comment */
     public void TestMethod2() { }
+
+    /// <summary>more documentation.</summary>
+    // another comment (a specific regression test for https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/1456)
+    public void TestMethod3() { }
 }
 ";
 
@@ -600,6 +609,7 @@ public void TestMethod2() { }
                 this.CSharpDiagnostic().WithLocation(3, 1),
                 this.CSharpDiagnostic().WithLocation(10, 1),
                 this.CSharpDiagnostic().WithLocation(15, 1),
+                this.CSharpDiagnostic().WithLocation(20, 1),
             };
 
             await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TriviaHelper.cs

@@ -112,6 +112,53 @@ internal static int IndexOfTrailingWhitespace(IReadOnlyList<SyntaxTrivia> trivia
             return (whiteSpaceStartIndex < triviaList.Count) ? whiteSpaceStartIndex : -1;
         }
 
+        /// <summary>
+        /// Removes a range of elements from the <see cref="SyntaxTriviaList"/>.
+        /// </summary>
+        /// <param name="list">The list to remove elements from.</param>
+        /// <param name="index">The zero-based starting index of the range of elements to remove.</param>
+        /// <param name="count">The number of elements to remove.</param>
+        /// <returns>A copy of <paramref name="list"/> with the specified range of elements removed.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// <para>If <paramref name="index"/> is less than 0.</para>
+        /// <para>-or-</para>
+        /// <para>If <paramref name="count"/> is less than 0.</para>
+        /// </exception>
+        /// <exception cref="ArgumentException">
+        /// <para>If <paramref name="index"/> and <paramref name="count"/> do not denote a valid range of elements in
+        /// the <see cref="SyntaxTriviaList"/>.</para>
+        /// </exception>
+        internal static SyntaxTriviaList RemoveRange(this SyntaxTriviaList list, int index, int count)
+        {
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count));
+            }
+
+            if (index > list.Count - count)
+            {
+                throw new ArgumentException("The specified range of elements does not exist in the list.");
+            }
+
+            SyntaxTrivia[] trivia = new SyntaxTrivia[list.Count - count];
+            for (int i = 0; i < index; i++)
+            {
+                trivia[i] = list[i];
+            }
+
+            for (int i = index; i + count < list.Count; i++)
+            {
+                trivia[i] = list[i + count];
+            }
+
+            return SyntaxFactory.TriviaList(trivia);
+        }
+
         /// <summary>
         /// Returns the index of the last trivia of a specified kind in the trivia list.
         /// </summary>

StyleCop.Analyzers/StyleCop.Analyzers/LayoutRules/SA1506CodeFixProvider.cs

@@ -52,32 +52,46 @@ private static async Task<Document> GetTransformedDocumentAsync(Document documen
             var triviaList = token.LeadingTrivia;
 
             var index = triviaList.IndexOf(SyntaxKind.SingleLineDocumentationCommentTrivia);
-            for (; index < triviaList.Count - 1; index++)
-            {
-                if (triviaList[index].IsKind(SyntaxKind.SingleLineCommentTrivia)
-                    || triviaList[index].IsKind(SyntaxKind.MultiLineCommentTrivia))
-                {
-                    break;
-                }
-            }
 
-            while (!triviaList[index].IsKind(SyntaxKind.EndOfLineTrivia))
+            int currentLineStart = index + 1;
+            bool onBlankLine = true;
+            for (int currentIndex = currentLineStart; currentIndex < triviaList.Count; currentIndex++)
             {
-                index--;
-            }
+                switch (triviaList[currentIndex].Kind())
+                {
+                case SyntaxKind.EndOfLineTrivia:
+                    if (onBlankLine)
+                    {
+                        triviaList = triviaList.RemoveRange(currentLineStart, currentIndex - currentLineStart + 1);
+                        currentIndex = currentLineStart - 1;
+                        continue;
+                    }
+                    else
+                    {
+                        currentLineStart = currentIndex + 1;
+                        onBlankLine = true;
+                        break;
+                    }
 
-            var lastEndOfLine = index;
+                case SyntaxKind.WhitespaceTrivia:
+                    break;
 
-            while (!triviaList[index].IsKind(SyntaxKind.SingleLineDocumentationCommentTrivia))
-            {
-                index--;
+                default:
+                    if (triviaList[currentIndex].HasBuiltinEndLine())
+                    {
+                        currentLineStart = currentIndex + 1;
+                        onBlankLine = true;
+                        break;
+                    }
+                    else
+                    {
+                        onBlankLine = false;
+                        break;
+                    }
+                }
             }
 
-            var lastDocumentation = index;
-
-            var newLeadingTrivia = triviaList.Take(lastDocumentation + 1).Concat(triviaList.Skip(lastEndOfLine + 1));
-            var newSyntaxRoot = syntaxRoot.ReplaceToken(token, token.WithLeadingTrivia(newLeadingTrivia));
-
+            var newSyntaxRoot = syntaxRoot.ReplaceToken(token, token.WithLeadingTrivia(triviaList));
             return document.WithSyntaxRoot(newSyntaxRoot);
         }
     }