Add rule 'HasNewLinesAtStartOfDocument'

Author: Lakshmi Priya Sekar

src/Microsoft.DotNet.CodeFormatting/Rules/HasNewLinesAtStartOfDocumentFormattingRule.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under MIT. See LICENSE in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace Microsoft.DotNet.CodeFormatting.Rules
+{
+    [Export(typeof(IFormattingRule))]
+    internal sealed class HasNewLinesAtStartOfDocumentFormattingRule : IFormattingRule
+    {
+        public async Task<Document> ProcessAsync(Document document, CancellationToken cancellationToken)
+        {
+            var syntaxRoot = await document.GetSyntaxRootAsync(cancellationToken) as CSharpSyntaxNode;
+            if (syntaxRoot == null)
+                return document;
+            Document newDocument;
+            // NewLine between copyright and using directives.
+            var firstUsing = syntaxRoot.DescendantNodesAndSelf().OfType<UsingDirectiveSyntax>().First();
+            var hasEndOfLineTrivia = firstUsing.GetLeadingTrivia().First().CSharpKind() == SyntaxKind.EndOfLineTrivia;
+            if (!hasEndOfLineTrivia)
+            {
+                var newTriviaList = firstUsing.GetLeadingTrivia().Insert(0, SyntaxFactory.EndOfLine("\n"));
+                newDocument =  document.WithSyntaxRoot(syntaxRoot.ReplaceNode(firstUsing, firstUsing.WithLeadingTrivia(newTriviaList)));
+            }
+
+            return document;
+        }
+    }
+}