Support defining environment constants for dart2js via the command-line.

sdk/lib/_internal/pub/test/dart2js/environment_constant_test.dart

Index: sdk/lib/_internal/pub/test/dart2js/environment_constant_test.dart
diff --git a/sdk/lib/_internal/pub/test/dart2js/environment_constant_test.dart b/sdk/lib/_internal/pub/test/dart2js/environment_constant_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..dab1260f1abca74a83a6c0d0786caf98a5c46b0c
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/dart2js/environment_constant_test.dart
@@ -0,0 +1,65 @@
+// 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.
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../serve/utils.dart';
+import '../test_pub.dart';
+
+main() {
+  initConfig();
+  group("passes environment constants to dart2js", () {
+    setUp(() {
+      // Dart2js can take a long time to compile dart code, so we increase the
+      // timeout to cope with that.
+      currentSchedule.timeout *= 3;
+
+      d.dir(appPath, [
+        d.appPubspec(),
+        d.dir('web', [
+          d.file('file.dart',
+              'void main() => print(const String.fromEnvironment("name"));')
+        ])
+      ]).create();
+    });
+
+    integration('from "pub build"', () {
+      schedulePub(args: ["build", "--define", "name=fblthp"],

[kevmoo, 2015/04/24 00:23:14]

Can I define many variables this way?

[nweiz, 2015/04/24 00:26:48]

Yes, it passes allowMultiple to ArgParser.addOption.

+          output: new RegExp(r'Built 1 file to "build".'));
+
+      d.dir(appPath, [
+        d.dir('build', [
+          d.dir('web', [
+            d.matcherFile('file.dart.js', contains('fblthp')),
+          ])
+        ])
+      ]).validate();
+    });
+
+    integration('from "pub serve"', () {
+      pubServe(args: ["--define", "name=fblthp"]);
+      requestShouldSucceed("file.dart.js", contains("fblthp"));
+      endPubServe();
+    });
+
+    integration('which takes precedence over the pubspec', () {
+      d.dir(appPath, [
+        d.pubspec({
+          "name": "myapp",
+          "transformers": [
+            {"\$dart2js": {"environment": {"name": "slartibartfast"}}}
+          ]
+        })
+      ]).create();
+
+      pubServe(args: ["--define", "name=fblthp"]);
+      requestShouldSucceed("file.dart.js", allOf([
+        contains("fblthp"),
+        isNot(contains("slartibartfast"))
+      ]));
+      endPubServe();
+    });
+  });
+}