Fixed ArgumentOutOfRangeException in SA1120

Author: vweijsters

StyleCop.Analyzers/StyleCop.Analyzers.Test/ReadabilityRules/SA1120UnitTests.cs

@@ -6,6 +6,7 @@ namespace StyleCop.Analyzers.Test.ReadabilityRules
     using System.Collections.Generic;
     using System.Threading;
     using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis;
     using Microsoft.CodeAnalysis.CodeFixes;
     using Microsoft.CodeAnalysis.Diagnostics;
     using StyleCop.Analyzers.ReadabilityRules;
@@ -404,6 +405,41 @@ public async Task VerifyThatEmptyCommentAtFileEndWillBeHandledProperlyAsync()
             await this.VerifyCSharpFixAsync(testCode, fixedTestCode).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Verifies that an unclosed multiline comment at the end of a source file will be handled correctly.
+        /// This is a regression test for #2056
+        /// </summary>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
+        [Fact]
+        public async Task VerifyThatUnclosedCommentAtFileEndWillBeHandledProperlyAsync()
+        {
+            var testCode = @"public class TestClass
+{
+}
+/*";
+
+            var fixedTestCode = @"public class TestClass
+{
+}
+";
+
+            DiagnosticResult[] expected =
+            {
+                new DiagnosticResult
+                {
+                    Id = "CS1035",
+                    Message = "End-of-file found, '*/' expected",
+                    Severity = DiagnosticSeverity.Error,
+                    Locations = new[] { new DiagnosticResultLocation("Test0.cs", 4, 1) }
+                },
+                this.CSharpDiagnostic().WithLocation(4, 1),
+            };
+
+            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);
+        }
+
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {
             yield return new SA1120CommentsMustContainText();

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/SA1120CommentsMustContainText.cs

@@ -74,7 +74,7 @@ private static void HandleMultiLineComment(SyntaxTreeAnalysisContext context, Sy
             var nodeText = multiLineComment.ToString();
 
             // We remove the /* and the */ and determine if the comment has any content.
-            var commentText = nodeText.Substring(2, nodeText.Length - 4);
+            var commentText = nodeText.Substring(2, Math.Max(0, nodeText.Length - 4));
 
             if (string.IsNullOrWhiteSpace(commentText))
             {