Adding some asset-related utilities to code_transformers

pkg/code_transformers/test/entry_point_test.dart

Index: pkg/code_transformers/test/entry_point_test.dart
diff --git a/pkg/code_transformers/test/entry_point_test.dart b/pkg/code_transformers/test/entry_point_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1000aceca62ec2c97e528938efd082f72c5060af
--- /dev/null
+++ b/pkg/code_transformers/test/entry_point_test.dart
@@ -0,0 +1,92 @@
+// Copyright (c) 2014, 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.
+
+library code_transformers.test.assets_test;
+
+import 'dart:async';
+import 'dart:io' show File, Platform;
+
+import 'package:barback/barback.dart';
+import 'package:code_transformers/resolver.dart';
+import 'package:code_transformers/tests.dart';
+import 'package:path/path.dart' as path;
+import 'package:unittest/compact_vm_config.dart';
+import 'package:unittest/unittest.dart';
+
+main() {
+  useCompactVMConfiguration();
+
+  Future checkDartEntry({Map<String, String> inputs, bool expectation}) {
+    var transformer = new Validator((transform) {
+      return isPossibleDartEntry(transform.primaryInput).then((value) {
+        expect(value, expectation);
+      });
+    });
+    return applyTransformers(
+          [[transformer]],
+          inputs: inputs);
+  }
+
+  group('isPossibleDartEntry', () {
+    test('should handle empty files', () {
+      return checkDartEntry(
+          inputs: {
+            'a|web/main.dart': '',
+          },
+          expectation: false);
+    });
+
+    test('should detect main methods', () {
+      return checkDartEntry(
+          inputs: {
+            'a|web/main.dart': 'main() {}',
+          },
+          expectation: true);
+    });
+
+    test('should exclude dart mains in lib folder', () {
+      return checkDartEntry(
+          inputs: {
+            'a|lib/main.dart': 'main() {}',
+          },
+          expectation: false);
+    });
+
+    test('should validate file extension', () {
+      return checkDartEntry(
+          inputs: {
+            'a|web/main.not_dart': 'main() {}',
+          },
+          expectation: false);
+    });
+
+    test('should count exports as main', () {
+      return checkDartEntry(
+          inputs: {
+            'a|web/main.dart': 'export "foo.dart";',
+          },
+          expectation: true);
+    });
+
+    test('should count parts as main', () {
+      return checkDartEntry(
+          inputs: {
+            'a|web/main.dart': 'part "foo.dart";',
+          },
+          expectation: true);
+    });
+  });
+}
+
+class Validator extends Transformer {
+  final Function validation;
+
+  Validator(this.validation);
+
+  Future<bool> isPrimary(Asset input) => new Future.value(true);
+
+  Future apply(Transform transform) {
+    return new Future.value(validation(transform));
+  }
+}