Add option to do custom code formatting

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.5.8
+
+* Add `formatOutput` optional parameter to the `GeneratorBuilder` constructor.
+  This is a lamda of the form `String formatOutput(String originalCode)` which
+  allows you do do custom formatting.
+
 ## 0.5.7
 
 * Support for package:analyzer 0.30.0

lib/src/builder.dart

@@ -11,13 +11,19 @@ import 'generated_output.dart';
 import 'generator.dart';
 import 'utils.dart';
 
+typedef String OutputFormatter(String generatedCode);
+
 class GeneratorBuilder extends Builder {
+  final OutputFormatter formatOutput;
   final List<Generator> generators;
   final String generatedExtension;
   final bool isStandalone;
 
   GeneratorBuilder(this.generators,
-      {this.generatedExtension: '.g.dart', this.isStandalone: false}) {
+      {OutputFormatter formatOutput,
+      this.generatedExtension: '.g.dart',
+      this.isStandalone: false})
+      : formatOutput = formatOutput ?? _formatter.format {
     // TODO: validate that generatedExtension starts with a `.'
     //       not null, empty, etc
     if (this.isStandalone && this.generators.length > 1) {
@@ -72,9 +78,8 @@ class GeneratorBuilder extends Builder {
 
     var genPartContent = contentBuffer.toString();
 
-    var formatter = new DartFormatter();
     try {
-      genPartContent = formatter.format(genPartContent);
+      genPartContent = formatOutput(genPartContent);
     } catch (e, stack) {
       log.severe(
           'Error formatting generated source code for ${library.identifier}'
@@ -124,6 +129,8 @@ Stream<GeneratedOutput> _processUnitMember(
   }
 }
 
+final _formatter = new DartFormatter();
+
 const _topHeader = '''// GENERATED CODE - DO NOT MODIFY BY HAND
 
 ''';

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 0.5.7
+version: 0.5.8
 author: Dart Team <[email protected]>
 description: Automatic sourcecode generation for Dart
 homepage: https://github.com/dart-lang/source_gen

test/builder_test.dart

@@ -11,6 +11,7 @@ import 'package:source_gen/source_gen.dart';
 import 'package:test/test.dart';
 
 import 'src/comment_generator.dart';
+import 'src/unformatted_code_generator.dart';
 
 void main() {
   test('Simple Generator test', _simpleTest);
@@ -93,6 +94,41 @@ void main() {
           '$pkgName|lib/test_lib.g.dart': _testGenPartContentError,
         });
   });
+
+  test('defaults to formatting generated code with the DartFormatter',
+      () async {
+    await testBuilder(new GeneratorBuilder([new UnformattedCodeGenerator()]),
+        {'$pkgName|lib/a.dart': 'library a; part "a.part.dart";'},
+        generateFor: new Set.from(['$pkgName|lib/a.dart']),
+        outputs: {
+          '$pkgName|lib/a.g.dart':
+              contains(UnformattedCodeGenerator.formattedCode),
+        });
+  });
+
+  test('can skip formatting with a trivial lambda', () async {
+    await testBuilder(
+        new GeneratorBuilder([new UnformattedCodeGenerator()],
+            formatOutput: (s) => s),
+        {'$pkgName|lib/a.dart': 'library a; part "a.part.dart";'},
+        generateFor: new Set.from(['$pkgName|lib/a.dart']),
+        outputs: {
+          '$pkgName|lib/a.g.dart':
+              contains(UnformattedCodeGenerator.unformattedCode),
+        });
+  });
+
+  test('can pass a custom formatter with formatOutput', () async {
+    var customOutput = 'final String hello = "hello";';
+    await testBuilder(
+        new GeneratorBuilder([new UnformattedCodeGenerator()],
+            formatOutput: (_) => customOutput),
+        {'$pkgName|lib/a.dart': 'library a; part "a.part.dart";'},
+        generateFor: new Set.from(['$pkgName|lib/a.dart']),
+        outputs: {
+          '$pkgName|lib/a.g.dart': contains(customOutput),
+        });
+  });
 }
 
 Future _simpleTest() => _generateTest(

test/src/unformatted_code_generator.dart

@@ -0,0 +1,26 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// 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:async';
+
+import 'package:analyzer/dart/element/element.dart';
+import 'package:source_gen/source_gen.dart';
+
+/// Generates a single-line of unformatted code.
+class UnformattedCodeGenerator extends Generator {
+  const UnformattedCodeGenerator();
+
+  @override
+  Future<String> generate(Element element, _) async {
+    return unformattedCode;
+  }
+
+  static const formattedCode = '''
+void hello() => print('hello');
+''';
+
+  static const unformattedCode = '''
+void hello ()=>  print('hello');
+''';
+}