Fix handling of both a header and a separated comment

When a comment preceding a set of using directives is separated from the first
using directive by a blank line, that comment is associated with the list of
using directives as opposed to specifically tied to the first one. This means
after reordering the separated comment will continue to be separated and placed
before the first using directive of the sorted result.

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/OrderingRules/UsingCodeFixProvider.UsingsSorter.cs

@@ -173,6 +173,7 @@ private List<UsingDirectiveSyntax> GenerateUsings(List<UsingDirectiveSyntax> usi
 
                     // when there is a directive trivia, add it (and any trivia before it) to the triviaToMove collection.
                     // when there are leading blank lines for the first entry, add them to the triviaToMove collection.
+                    int triviaToMoveCount = triviaToMove.Count;
                     var previousIsEndOfLine = false;
                     for (var m = leadingTrivia.Count - 1; m >= 0; m--)
                     {
@@ -188,7 +189,8 @@ private List<UsingDirectiveSyntax> GenerateUsings(List<UsingDirectiveSyntax> usi
                         {
                             if (previousIsEndOfLine)
                             {
-                                triviaToMove.Insert(0, leadingTrivia[m]);
+                                triviaToMove.InsertRange(0, leadingTrivia.Take(m + 2));
+                                break;
                             }
 
                             previousIsEndOfLine = true;
@@ -202,6 +204,43 @@ private List<UsingDirectiveSyntax> GenerateUsings(List<UsingDirectiveSyntax> usi
                     // preserve leading trivia (excluding directive trivia), indenting each line as appropriate
                     var newLeadingTrivia = leadingTrivia.Except(triviaToMove).ToList();
 
+                    // indent the triviaToMove if necessary so it behaves correctly later
+                    bool atStartOfLine = triviaToMoveCount == 0 || triviaToMove.Last().HasBuiltinEndLine();
+                    for (int m = triviaToMoveCount; m < triviaToMove.Count; m++)
+                    {
+                        bool currentAtStartOfLine = atStartOfLine;
+                        atStartOfLine = triviaToMove[m].HasBuiltinEndLine();
+                        if (!currentAtStartOfLine)
+                        {
+                            continue;
+                        }
+
+                        if (triviaToMove[m].IsKind(SyntaxKind.EndOfLineTrivia))
+                        {
+                            // This is a blank line; indenting it would only add trailing whitespace
+                            continue;
+                        }
+
+                        if (triviaToMove[m].IsDirective)
+                        {
+                            // Only #region and #endregion directives get indented
+                            if (!triviaToMove[m].IsKind(SyntaxKind.RegionDirectiveTrivia) && !triviaToMove[m].IsKind(SyntaxKind.EndRegionDirectiveTrivia))
+                            {
+                                // This is a preprocessor line that doesn't need to be indented
+                                continue;
+                            }
+                        }
+
+                        if (triviaToMove[m].IsKind(SyntaxKind.DisabledTextTrivia))
+                        {
+                            // This is text in a '#if false' block; just ignore it
+                            continue;
+                        }
+
+                        triviaToMove.Insert(m, SyntaxFactory.Whitespace(indentation));
+                        m++;
+                    }
+
                     // strip any leading whitespace on each line (and also blank lines)
                     var k = 0;
                     var startOfLine = true;

StyleCop.Analyzers/StyleCop.Analyzers.Test/OrderingRules/SA1200UnitTests.cs

@@ -194,6 +194,44 @@ namespace TestNamespace
             await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
         }
 
+        [Fact]
+        [WorkItem(2363, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2363")]
+        public async Task TestInvalidUsingStatementsWithSeparatedFileHeaderAndTriviaAsync()
+        {
+            var testCode = @"// File Header
+
+// Leading Comment
+
+using System;
+using System.Threading;
+
+namespace TestNamespace
+{
+}
+";
+
+            var fixedTestCode = @"// File Header
+
+namespace TestNamespace
+{
+    // Leading Comment
+
+    using System;
+    using System.Threading;
+}
+";
+
+            DiagnosticResult[] expectedResults =
+            {
+                this.CSharpDiagnostic(SA1200UsingDirectivesMustBePlacedCorrectly.DescriptorInside).WithLocation(5, 1),
+                this.CSharpDiagnostic(SA1200UsingDirectivesMustBePlacedCorrectly.DescriptorInside).WithLocation(6, 1),
+            };
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expectedResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedTestCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
+        }
+
         [Fact]
         [WorkItem(2363, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2363")]
         public async Task TestInvalidUsingStatementsWithTriviaAsync()