Detect transformer dependency cycles in packages using barback transformers.

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

Index: sdk/lib/_internal/pub/test/serve/detects_an_ordering_dependency_cycle.dart
diff --git a/sdk/lib/_internal/pub/test/serve/detects_an_ordering_dependency_cycle.dart b/sdk/lib/_internal/pub/test/serve/detects_an_ordering_dependency_cycle.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3316e8d884f54e5c7896eb60aa53d8b23442ae62
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+++ b/sdk/lib/_internal/pub/test/serve/detects_an_ordering_dependency_cycle.dart
@@ -0,0 +1,67 @@
+// 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';
+import 'utils.dart';
+
+main() {
+  initConfig();
+  integration("detects an ordering dependency cycle", () {
+    d.dir("foo", [
+      d.pubspec({
+        "name": "foo",
+        "version": "1.0.0",
+        "transformers": ["myapp/transformer"],
+        "dependencies": {'myapp': {'path': '../myapp'}}
+      })
+    ]).create();
+
+    d.dir("bar", [
+      d.pubspec({
+        "name": "bar",
+        "version": "1.0.0",
+        "dependencies": {'foo': {'path': '../foo'}}
+      }),
+      d.dir("lib", [
+        d.file("transformer.dart", dartTransformer('bar')),
+      ])
+    ]).create();
+
+    d.dir("baz", [
+      d.pubspec({
+        "name": "baz",
+        "version": "1.0.0",
+        "transformers": ["bar/transformer"],
+        "dependencies": {'bar': {'path': '../bar'}}
+      })
+    ]).create();
+
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {'baz': {'path': '../baz'}}
+      }),
+      d.dir("lib", [
+        d.file("transformer.dart", dartTransformer('myapp')),
+      ])
+    ]).create();
+
+    createLockFile('myapp', sandbox: ['foo', 'bar', 'baz'], pkg: ['barback']);
+
+    // Use port 0 to get an ephemeral port.
+    var process = startPub(args: ["serve", "--port=0"]);
+    process.shouldExit(1);
+    expect(process.remainingStderr(), completion(equals(
+        "Transformer cycle detected:\n"
+        "  bar depends on foo\n"
+        "  foo is transformed by myapp/transformer\n"
+        "  myapp depends on baz\n"
+        "  baz is transformed by bar/transformer")));
+  });
+}