Improve parallelism when loading transformer plugins.

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

Index: sdk/lib/_internal/pub/test/transformers_needed_by_transformers/no_dependencies_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/no_dependencies_test.dart b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/no_dependencies_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c28e4a0ae694329fd29a26a292f5303ee30cbb85
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/no_dependencies_test.dart
@@ -0,0 +1,161 @@
+// 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("reports no dependencies if no transformers are used", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}}
+      })
+    ]).create();
+
+    d.dir("foo", [d.libPubspec("foo", "1.0.0")]).create();
+
+    expectDependencies({});
+  });
+
+  integration("reports no dependencies if a transformer is used in a "
+      "package that doesn't expose a transformer", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["foo"]
+      })
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0"),
+      d.dir("lib", [d.file("foo.dart", transformer())])
+    ]).create();
+
+    expectDependencies({"foo": []});
+  });
+
+  integration("reports no dependencies for non-file/package imports", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir("lib", [
+        d.file("myapp.dart", transformer([
+          "dart:async",
+          "http://dartlang.org/nonexistent.dart"
+        ]))
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0"),
+      d.dir("lib", [d.file("foo.dart", transformer())])
+    ]).create();
+
+    expectDependencies({"myapp": []});
+  });
+
+  integration("reports no dependencies for a single self transformer", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": ["myapp"]
+      }),
+      d.dir("lib", [d.file("myapp.dart", transformer())])
+    ]).create();
+
+    expectDependencies({"myapp": []});
+  });
+
+  integration("reports no dependencies if a transformer applies to files that "
+      "aren't used by the exposed transformer", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": [
+          {"foo": {"\$include": "lib/myapp.dart"}},
+          {"foo": {"\$exclude": "lib/transformer.dart"}},
+          "myapp"
+        ]
+      }),
+      d.dir("lib", [
+        d.file("myapp.dart", ""),
+        d.file("transformer.dart", transformer())
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0"),
+      d.dir("lib", [d.file("foo.dart", transformer())])
+    ]).create();
+
+    expectDependencies({"myapp": [], "foo": []});
+  });
+
+  integration("reports no dependencies if a transformer applies to a "
+      "dependency's files that aren't used by the exposed transformer", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": {"path": "../foo"}},
+        "transformers": ["myapp"]
+      }),
+      d.dir("lib", [
+        d.file("myapp.dart", ""),
+        d.file("transformer.dart", transformer(["package:foo/foo.dart"]))
+      ])
+    ]).create();
+
+    d.dir("foo", [
+      d.pubspec({
+        "name": "foo",
+        "version": "1.0.0",
+        "transformers": [{"foo": {"\$exclude": "lib/foo.dart"}}]
+      }),
+      d.dir("lib", [
+        d.file("foo.dart", ""),
+        d.file("transformer.dart", transformer())
+      ])
+    ]).create();
+
+    expectDependencies({'myapp': [], 'foo': []});
+  });
+
+  test("reports no dependencies on transformers in future phases", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": [
+          {"myapp/first": {"\$include": "lib/myapp.dart"}},
+          {"myapp/second": {"\$include": "lib/first.dart"}},
+          {"myapp/third": {"\$include": "lib/second.dart"}}
+        ]
+      }),
+      d.dir("lib", [
+        d.file("myapp.dart", ""),
+        d.file("first.dart", transformer()),
+        d.file("second.dart", transformer()),
+        d.file("third.dart", transformer())
+      ])
+    ]).create();
+
+    expectDependencies({
+      'myapp/first': [],
+      'myapp/second': [],
+      'myapp/third': []
+    });
+  });
+}