Support loading transformer plugins from pub.

sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart

Index: sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart b/sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart
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index 0000000000000000000000000000000000000000..38f96c122731c7d0bae7944fb1701572325f1f07
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+++ b/sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart
@@ -0,0 +1,36 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+main() {
+  initConfig();
+
+  // A syntax error will cause the analyzer to fail to parse the transformer
+  // when attempting to rewrite its imports.
+  integration("fails to load a transform with a syntax error", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": ["myapp/src/transformer"]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", "syntax error")
+      ])])
+    ]).create();
+
+    createLockFile('myapp', {}, pkg: ['barback']);
+
+    var pub = startPub(args: ['serve', '--port=0']);
+    expect(pub.nextErrLine(), completion(startsWith('Error on line')));
+    pub.shouldExit(1);
+    expect(pub.remainingStderr(),
+        completion(isNot(contains('This is an unexpected error'))));
+  });
+}