Merge pull request #2653 from vweijsters/fix-2649

Fixed issue in FileHeaderHelpers with incomplete multiline comments

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/SA1633UnitTests.cs

@@ -7,6 +7,7 @@ namespace StyleCop.Analyzers.Test.DocumentationRules
     using System.Threading.Tasks;
     using Microsoft.CodeAnalysis.CodeFixes;
     using StyleCop.Analyzers.DocumentationRules;
+    using TestHelper;
     using Xunit;
 
     /// <summary>
@@ -344,6 +345,43 @@ public async Task TestValidFileHeaderWithLeadingBlankLinesAsync(string prefix)
             await this.VerifyCSharpDiagnosticAsync(testCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Verifies that incomplete multiline comment at the start of the file is handled correctly.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
+        [Fact]
+        [WorkItem(2649, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2649")]
+        public async Task TestIncompleteMultilineCommentAsync()
+        {
+            this.useNoXmlSettings = true;
+
+            var testCode = @"/*
+ * copyright (c) FooCorp. All rights reserved.
+";
+
+            var fixedCode = @"// copyright (c) FooCorp. All rights reserved.
+
+/*
+ * copyright (c) FooCorp. All rights reserved.
+";
+
+            DiagnosticResult[] expectedDiagnostics =
+            {
+                this.CSharpCompilerError("CS1035").WithMessage("End-of-file found, '*/' expected").WithLocation(1, 1),
+                this.CSharpDiagnostic(FileHeaderAnalyzers.SA1633DescriptorMissing).WithLocation(1, 1),
+            };
+
+            // The fixed code will still have the incomplete comment, as there is no certainty that the incomplete comment was intended as file header.
+            DiagnosticResult[] expectedFixedDiagnostics =
+            {
+                this.CSharpCompilerError("CS1035").WithMessage("End-of-file found, '*/' expected").WithLocation(3, 1),
+            };
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expectedDiagnostics, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, expectedFixedDiagnostics, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, numberOfFixAllIterations: 2).ConfigureAwait(false);
+        }
+
         /// <inheritdoc/>
         protected override string GetSettings()
         {

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/FileHeaderHelpers.cs

@@ -65,6 +65,12 @@ internal static FileHeader ParseFileHeader(SyntaxNode root)
 
                         var startIndex = triviaString.IndexOf("/*", StringComparison.Ordinal) + 2;
                         var endIndex = triviaString.LastIndexOf("*/", StringComparison.Ordinal);
+                        if (endIndex == -1)
+                        {
+                            // While editing, it is possible to have a multiline comment trivia that does not contain the closing '*/' yet.
+                            return FileHeader.MissingFileHeader;
+                        }
+
                         var commentContext = triviaString.Substring(startIndex, endIndex - startIndex).Trim();
 
                         var triviaStringParts = commentContext.Replace("\r\n", "\n").Split('\n');