Fixed encoding issue

The encoding for a Document can be null after modification.  In that
case just grab the encoding from the original document.

This seems like a bug.  The code is not explicitly changing the encoding
hence it shouldn't be changing.  Will followup with Roslyn.

Author: jaredpar

src/Microsoft.DotNet.CodeFormatting/FormattingEngineImplementation.cs

@@ -67,7 +67,15 @@ private async Task FormatAsync(Workspace workspace, IReadOnlyList<DocumentId> do
             solution = await RunSyntaxPass(solution, documentIds, cancellationToken);
             solution = await RunLocalSemanticPass(solution, documentIds, cancellationToken);
             solution = await RunGlobalSemanticPass(solution, documentIds, cancellationToken);
-            
+
+            await SaveChanges(solution, originalSolution, cancellationToken);
+
+            watch.Stop();
+            Console.WriteLine("Total time {0}", watch.Elapsed);
+        }
+
+        private async Task SaveChanges(Solution solution, Solution originalSolution, CancellationToken cancellationToken)
+        {
             foreach (var projectChange in solution.GetChanges(originalSolution).GetProjectChanges())
             {
                 foreach (var documentId in projectChange.GetChangedDocuments())
@@ -76,6 +84,17 @@ private async Task FormatAsync(Workspace workspace, IReadOnlyList<DocumentId> do
                     var sourceText = await document.GetTextAsync(cancellationToken);
                     using (var file = File.Open(document.FilePath, FileMode.Truncate, FileAccess.Write))
                     {
+                        var encoding = sourceText.Encoding;
+
+                        // TODO: It seems like a bug that Encoding could change but it is definitely
+                        // happening.  Ex: ArrayBuilder.Enumerator.cs
+                        if (encoding == null)
+                        {
+                            var originalDocument = originalSolution.GetDocument(documentId);
+                            var originalSourceText = await originalDocument.GetTextAsync(cancellationToken);
+                            encoding = originalSourceText.Encoding;
+                        }
+
                         using (var writer = new StreamWriter(file, sourceText.Encoding))
                         {
                             sourceText.Write(writer, cancellationToken);
@@ -84,8 +103,6 @@ private async Task FormatAsync(Workspace workspace, IReadOnlyList<DocumentId> do
                 }
             }
 
-            watch.Stop();
-            Console.WriteLine("Total time {0}", watch.Elapsed);
         }
 
         private async Task<bool> ShouldBeProcessedAsync(Document document)

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

@@ -38,7 +38,6 @@ public override SyntaxNode VisitMemberAccessExpression(MemberAccessExpressionSyn
                 var name = node.Name.Identifier.ValueText;
                 if (node.Expression != null &&
                     node.Expression.CSharpKind() == SyntaxKind.ThisExpression &&
-                    name.StartsWith("_", StringComparison.Ordinal) &&
                     IsPrivateField(node))
                 {
                     _addedAnnotations = true;

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

@@ -24,10 +24,13 @@ internal sealed class HasCopyrightHeaderFormattingRule : ISyntaxFormattingRule
 
         public SyntaxNode Process(SyntaxNode syntaxNode)
         {
+            /*
             if (HasCopyrightHeader(syntaxNode))
                 return syntaxNode;
 
             return AddCopyrightHeader(syntaxNode);
+            */
+            return syntaxNode;
         }
 
         private static bool HasCopyrightHeader(SyntaxNode syntaxNode)

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

@@ -181,13 +181,6 @@ private static async Task<Solution> RenameFields(Solution solution, DocumentId d
             Solution oldSolution = null;
             for (int i = 0; i < count; i++)
             {
-                // If this is not the first field then clean up the Rename annotations left
-                // in the tree.
-                if (i > 0)
-                {
-                    solution = await CleanSolutionAsync(solution, oldSolution, cancellationToken);
-                }
-
                 oldSolution = solution;
 
                 var semanticModel = await solution.GetDocument(documentId).GetSemanticModelAsync(cancellationToken);
@@ -203,6 +196,7 @@ private static async Task<Solution> RenameFields(Solution solution, DocumentId d
                 }
 
                 solution = await Renamer.RenameSymbolAsync(solution, fieldSymbol, newName, solution.Workspace.Options, cancellationToken).ConfigureAwait(false);
+                solution = await CleanSolutionAsync(solution, oldSolution, cancellationToken);
             }
 
             return solution;