Support deploying an npm package exporting a formatCode method.

bin/node_format_service.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file

[Bob Nystrom, 2016/01/27 20:37:13]

bin/ isn't the right place for this since it's not a Dart executable end users
should be able to run.

How about tool/?

[Jacob, 2016/01/27 20:56:32]

Done.

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+import 'dart:js';
+import 'package:js/js.dart';
+
+import 'package:dart_style/dart_style.dart';
+
+int width = 80;

[Bob Nystrom, 2016/01/27 20:37:13]

Is this part of the public API, or just a constant? If it's a constant, you can
just delete it and rely on the default pageWidth in new DartFormatter().

[Jacob, 2016/01/27 20:56:32]

Done.
Was going to make it part of the api but it doesn't really matter as my dream of
120 character line dart strings isn't going to happen.

+
+@JS()
+@anonymous
+class FormatResult {
+  external factory FormatResult({String code, String error});
+  external String get code;
+  external String get error;
+}
+
+@JS('exports.formatCode')
+external set formatCode(Function formatter);
+
+void main() {
+  formatCode = allowInterop((String source) {
+    try {
+      return new FormatResult(
+          code: new DartFormatter(pageWidth: width).format(source));

[Bob Nystrom, 2016/01/27 20:37:13]

My little web script isn't a good example. How about getting rid of some of the
redundancy between the two cases by only constructing a single DartFormatter?

[Jacob, 2016/01/27 20:56:32]

Done.

+    } on FormatterException {
+      // Do nothing.
+    }
+
+    // Maybe it's a statement.
+    try {
+      return new FormatResult(
+          code: new DartFormatter(pageWidth: width).formatStatement(source));
+    } on FormatterException catch (err) {
+      return new FormatResult(code: source, error: "$err");
+    }
+  });
+}