Support passing configuration data to a transformer plugin.

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

Index: sdk/lib/_internal/pub/test/serve/with_configuration_only_instantiates_configurable_transformers_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/with_configuration_only_instantiates_configurable_transformers_test.dart b/sdk/lib/_internal/pub/test/serve/with_configuration_only_instantiates_configurable_transformers_test.dart
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+// 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 'dart:convert';
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+final transformer = """
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:barback/barback.dart';
+
+class ConfigTransformer extends Transformer {
+  final Map configuration;
+
+  ConfigTransformer.asPlugin(this.configuration);
+
+  String get allowedExtensions => '.txt';
+
+  Future apply(Transform transform) {
+    return transform.primaryInput.readAsString().then((contents) {
+      var id = transform.primaryInput.id.changeExtension(".json");
+      transform.addOutput(new Asset.fromString(id, JSON.encode(configuration)));
+    });
+  }
+}
+
+class RewriteTransformer extends Transformer {
+  RewriteTransformer.asPlugin();
+
+  String get allowedExtensions => '.txt';
+
+  Future apply(Transform transform) {
+    return transform.primaryInput.readAsString().then((contents) {
+      var id = transform.primaryInput.id.changeExtension(".out");
+      transform.addOutput(new Asset.fromString(id, "\$contents.out"));
+    });
+  }
+}
+""";
+
+main() {
+  initConfig();
+  integration("with configuration, only instantiates configurable transformers",
+      () {
+    var configuration = {"param": ["list", "of", "values"]};
+
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": [{"myapp/src/transformer": configuration}]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", transformer)
+      ])]),
+      d.dir("web", [
+        d.file("foo.txt", "foo")
+      ])
+    ]).create();
+
+    createLockFile('myapp', pkg: ['barback']);
+
+    var server = startPubServe();
+    requestShouldSucceed("foo.json", JSON.encode(configuration));
+    requestShould404("foo.out");
+    endPubServe();
+  });
+}