Support empty lines in header comments

Fixes #2657

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/DocumentationRules/FileHeaderCodeFixProvider.cs

@@ -7,6 +7,7 @@ namespace StyleCop.Analyzers.DocumentationRules
     using System.Collections.Generic;
     using System.Collections.Immutable;
     using System.Composition;
+    using System.Linq;
     using System.Text;
     using System.Threading;
     using System.Threading.Tasks;
@@ -139,8 +140,7 @@ private static SyntaxNode ReplaceWellFormedMultiLineCommentHeader(Document docum
             triviaStringParts[0] = commentIndentation + interlinePadding + " " + triviaStringParts[0];
             StringBuilder sb = StringBuilderPool.Allocate();
             string fileName = Path.GetFileName(document.FilePath);
-            var copyrightText = commentIndentation + interlinePadding + " " +
-                GetCopyrightText(commentIndentation + interlinePadding, settings.DocumentationRules.GetCopyrightText(fileName), newLineText);
+            var copyrightText = GetCopyrightText(commentIndentation + interlinePadding, settings.DocumentationRules.GetCopyrightText(fileName), newLineText);
             var newHeader = WrapInXmlComment(commentIndentation + interlinePadding, copyrightText, document.Name, settings, newLineText);
 
             sb.Append(commentIndentation);
@@ -385,7 +385,7 @@ private static SyntaxNode AddHeader(Document document, SyntaxNode root, string n
 
         private static SyntaxTriviaList CreateNewHeader(string prefixWithLeadingSpaces, string fileName, StyleCopSettings settings, string newLineText)
         {
-            var copyrightText = prefixWithLeadingSpaces + " " + GetCopyrightText(prefixWithLeadingSpaces, settings.DocumentationRules.GetCopyrightText(fileName), newLineText);
+            var copyrightText = GetCopyrightText(prefixWithLeadingSpaces, settings.DocumentationRules.GetCopyrightText(fileName), newLineText);
             var newHeader = settings.DocumentationRules.XmlHeader
                 ? WrapInXmlComment(prefixWithLeadingSpaces, copyrightText, fileName, settings, newLineText)
                 : copyrightText;
@@ -417,7 +417,18 @@ private static string WrapInXmlComment(string prefixWithLeadingSpaces, string co
         private static string GetCopyrightText(string prefixWithLeadingSpaces, string copyrightText, string newLineText)
         {
             copyrightText = copyrightText.Replace("\r\n", "\n");
-            return string.Join(newLineText + prefixWithLeadingSpaces + " ", copyrightText.Split('\n')).Replace(prefixWithLeadingSpaces + " " + newLineText, prefixWithLeadingSpaces + newLineText);
+            var lines = copyrightText.Split('\n');
+            return string.Join(newLineText, lines.Select(line =>
+            {
+                if (string.IsNullOrEmpty(line))
+                {
+                    return prefixWithLeadingSpaces;
+                }
+                else
+                {
+                    return prefixWithLeadingSpaces + " " + line;
+                }
+            }));
         }
 
         private static SyntaxTriviaList RemoveHeaderDecorationLines(SyntaxTriviaList trivia, StyleCopSettings settings)

StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/NoXmlFileHeaderUnitTests.cs

@@ -31,6 +31,22 @@ public class NoXmlFileHeaderUnitTests : CodeFixVerifier
     }
   }
 }
+";
+
+        private const string TestSettingsWithEmptyLines = @"
+{
+  ""settings"": {
+    ""documentationRules"": {
+      ""companyName"": ""FooCorp"",
+      ""copyrightText"": ""\nCopyright (c) {companyName}. All rights reserved.\n\nLicensed under the {licenseName} license. See {licenseFile} file in the project root for full license information.\n"",
+      ""variables"": {
+        ""licenseName"": ""???"",
+        ""licenseFile"": ""LICENSE""
+      },
+      ""xmlHeader"": false
+    }
+  }
+}
 ";
 
         private string currentTestSettings = TestSettings;
@@ -368,6 +384,35 @@ namespace Bar
             await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
         }
 
+        [Fact]
+        [WorkItem(2657, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2657")]
+        public async Task TestHeaderMissingRequiredNewLinesAsync()
+        {
+            var testCode = @"// Copyright (c) FooCorp. All rights reserved.
+// Licensed under the ??? license. See LICENSE file in the project root for full license information.
+
+namespace Bar
+{
+}
+";
+            var fixedCode = @"//
+// Copyright (c) FooCorp. All rights reserved.
+//
+// Licensed under the ??? license. See LICENSE file in the project root for full license information.
+//
+
+namespace Bar
+{
+}
+";
+
+            this.currentTestSettings = TestSettingsWithEmptyLines;
+            var expected = this.CSharpDiagnostic(FileHeaderAnalyzers.SA1636Descriptor).WithLocation(1, 1);
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
+        }
+
         /// <inheritdoc/>
         protected override string GetSettings()
         {