Improve parallelism when loading transformer plugins.

sdk/lib/_internal/pub/test/transformers_needed_by_transformers/cycle_test.dart

Index: sdk/lib/_internal/pub/test/transformers_needed_by_transformers/cycle_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/cycle_test.dart b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/cycle_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a8458c1499b8380f657a3965f7bfcfc402dc3a39
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/cycle_test.dart
@@ -0,0 +1,212 @@
+// 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.
+
+library pub_tests;
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+void main() {
+  initConfig();
+
+  integration("allows a package dependency cycle that's unrelated to "
+      "transformers", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp/first", "myapp/second"]
+      }),
+      d.dir('lib', [
+        d.file("first.dart", transformer()),
+        d.file("second.dart", transformer())
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0", deps: {"bar": {"path": "../bar"}})
+    ]).create();
+
+    d.dir("bar", [
+      d.libPubspec("bar", "1.0.0", deps: {"baz": {"path": "../baz"}})
+    ]).create();
+
+    d.dir("baz", [
+      d.libPubspec("baz", "1.0.0", deps: {"foo": {"path": "../foo"}})
+    ]).create();
+
+    expectDependencies({'myapp/first': [], 'myapp/second': ['myapp/first']});
+  });
+
+  integration("disallows a package dependency cycle that may be related to "
+      "transformers", () {
+    // Two layers of myapp transformers are necessary here because otherwise pub
+    // will figure out that the transformer doesn't import "foo" and thus
+    // doesn't transitively import itself. Import loops are tested below.
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp/first", "myapp/second"]
+      }),
+      d.dir('lib', [
+        d.file("first.dart", transformer()),
+        d.file("second.dart", transformer())
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0", deps: {"bar": {"path": "../bar"}})
+    ]).create();
+
+    d.dir("bar", [
+      d.libPubspec("bar", "1.0.0", deps: {"myapp": {"path": "../myapp"}})
+    ]).create();
+
+    expectCycleException([
+      "myapp is transformed by myapp/second",
+      "myapp depends on foo",
+      "foo depends on bar",
+      "bar depends on myapp",
+      "myapp is transformed by myapp/first"
+    ]);
+  });
+
+  integration("disallows a transformation dependency cycle", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["foo"]
+      }),
+      d.dir('lib', [d.file("myapp.dart", transformer())])
+    ]).create();
+
+    d.dir("foo", [
+      d.pubspec({
+        "name": "foo",
+        "dependencies": {"bar": {"path": "../bar"}},
+        "transformers": ["bar"]
+      }),
+      d.dir('lib', [d.file("foo.dart", transformer())])
+    ]).create();
+
+    d.dir("bar", [
+      d.pubspec({
+        "name": "bar",
+        "dependencies": {"myapp": {"path": "../myapp"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir('lib', [d.file("bar.dart", transformer())])
+    ]).create();
+
+    expectCycleException([
+      "bar is transformed by myapp",
+      "myapp is transformed by foo",
+      "foo is transformed by bar"
+    ]);
+  });
+
+  integration("allows a cross-package import cycle that's unrelated to "
+      "transformers", () {
+     d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir('lib', [
+        d.file("myapp.dart", transformer(['package:foo/foo.dart']))
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0", deps: {"bar": {"path": "../bar"}}),
+      d.dir('lib', [d.file("foo.dart", "import 'package:bar/bar.dart';")])
+    ]).create();
+
+    d.dir("bar", [
+      d.libPubspec("bar", "1.0.0", deps: {"baz": {"path": "../baz"}}),
+      d.dir('lib', [d.file("bar.dart", "import 'package:baz/baz.dart';")])
+    ]).create();
+
+    d.dir("baz", [
+      d.libPubspec("baz", "1.0.0", deps: {"foo": {"path": "../foo"}}),
+      d.dir('lib', [d.file("baz.dart", "import 'package:foo/foo.dart';")])
+    ]).create();
+
+    expectDependencies({'myapp': []});
+  });
+
+  integration("disallows a cross-package import cycle that's related to "
+      "transformers", () {
+     d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir('lib', [
+        d.file("myapp.dart", transformer(['package:foo/foo.dart']))
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0", deps: {"bar": {"path": "../bar"}}),
+      d.dir('lib', [d.file("foo.dart", "import 'package:bar/bar.dart';")])
+    ]).create();
+
+    d.dir("bar", [
+      d.libPubspec("bar", "1.0.0", deps: {"myapp": {"path": "../myapp"}}),
+      d.dir('lib', [d.file("bar.dart", "import 'package:myapp/myapp.dart';")])
+    ]).create();
+
+    expectCycleException([
+      "myapp is transformed by myapp",
+      "myapp depends on foo",
+      "foo depends on bar",
+      "bar depends on myapp"
+    ]);
+  });
+
+  integration("allows a single-package import cycle that's unrelated to "
+      "transformers", () {
+     d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir('lib', [
+        d.file("myapp.dart", transformer(['foo.dart'])),
+        d.file("foo.dart", "import 'bar.dart';"),
+        d.file("bar.dart", "import 'baz.dart';"),
+        d.file("baz.dart", "import 'foo.dart';")
+      ])
+    ]).create();
+
+    expectDependencies({'myapp': []});
+  });
+
+  integration("allows a single-package import cycle that's related to "
+      "transformers", () {
+     d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir('lib', [
+        d.file("myapp.dart", transformer(['foo.dart'])),
+        d.file("foo.dart", "import 'bar.dart';"),
+        d.file("bar.dart", "import 'myapp.dart';"),
+      ])
+    ]).create();
+
+    expectDependencies({'myapp': []});
+  });
+}