Detect transformer dependency cycles in packages using barback transformers.

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

Index: sdk/lib/_internal/pub/test/serve/detects_a_transformer_cycle.dart
diff --git a/sdk/lib/_internal/pub/test/serve/runs_one_third_party_transformer_on_another_test.dart b/sdk/lib/_internal/pub/test/serve/detects_a_transformer_cycle.dart
similarity index 50%
copy from sdk/lib/_internal/pub/test/serve/runs_one_third_party_transformer_on_another_test.dart
copy to sdk/lib/_internal/pub/test/serve/detects_a_transformer_cycle.dart
index 96732e907b6a657145f7bad699b56dbdea01e380..1da308071637c3914901aebaf6785658effb2b56 100644
--- a/sdk/lib/_internal/pub/test/serve/runs_one_third_party_transformer_on_another_test.dart
+++ b/sdk/lib/_internal/pub/test/serve/detects_a_transformer_cycle.dart
@@ -4,51 +4,46 @@
 
 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("runs one third-party transformer on another", () {
+  integration("detects a transformer cycle", () {
     d.dir("foo", [
       d.pubspec({
         "name": "foo",
-        "version": "1.0.0"
-      }),
-      d.dir("lib", [
-        d.file("transformer.dart", dartTransformer('foo')),
-      ])
-    ]).create();
-
-    d.dir("bar", [
-      d.pubspec({
-        "name": "bar",
         "version": "1.0.0",
-        "transformers": ["foo/transformer"],
-        "dependencies": {"foo": {"path": "../foo"}}
+        "transformers": ["myapp/transformer"],
+        "dependencies": {'myapp': {'path': '../myapp'}}
       }),
       d.dir("lib", [
-        d.file("transformer.dart", dartTransformer('bar')),
+        d.file("transformer.dart", dartTransformer('foo')),
       ])
     ]).create();
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["bar/transformer"],
-        "dependencies": {'bar': {'path': '../bar'}}
+        "transformers": ["foo/transformer"],
+        "dependencies": {'foo': {'path': '../foo'}}
       }),
-      d.dir("web", [
-        d.file("main.dart", 'const TOKEN = "main.dart";')
+      d.dir("lib", [
+        d.file("transformer.dart", dartTransformer('myapp')),
       ])
     ]).create();
 
-    createLockFile('myapp', sandbox: ['foo', 'bar'], pkg: ['barback']);
+    createLockFile('myapp', sandbox: ['foo'], pkg: ['barback']);
 
-    startPubServe();
-    requestShouldSucceed("main.dart",
-        'const TOKEN = "(main.dart, (bar, foo))";');
-    endPubServe();
+    // 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"
+        "  foo is transformed by myapp/transformer\n"
+        "  myapp is transformed by foo/transformer")));
   });
 }