Improve parallelism when loading transformer plugins.

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

Index: sdk/lib/_internal/pub/test/transformers_needed_by_transformers/utils.dart
diff --git a/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/utils.dart b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/utils.dart
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index 0000000000000000000000000000000000000000..47e1cf7894ed4af132ea576318a8b48a0b7f7603
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+++ b/sdk/lib/_internal/pub/test/transformers_needed_by_transformers/utils.dart
@@ -0,0 +1,112 @@
+// Copyright (c) 2014, 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:path/path.dart' as p;
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../../lib/src/barback/cycle_exception.dart';
+import '../../lib/src/barback/transformers_needed_by_transformers.dart';
+import '../../lib/src/entrypoint.dart';
+import '../../lib/src/io.dart';
+import '../../lib/src/package.dart';
+import '../../lib/src/package_graph.dart';
+import '../../lib/src/source/path.dart';
+import '../../lib/src/system_cache.dart';
+import '../../lib/src/utils.dart';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+/// Expects that [computeTransformersNeededByTransformers] will return a graph
+/// matching [expected] when run on the package graph defined by packages in
+/// the sandbox.
+void expectDependencies(Map<String, Iterable<String>> expected) {
+  expected = mapMap(expected, value: (_, ids) => ids.toSet());
+
+  schedule(() {
+    var result = mapMap(
+        computeTransformersNeededByTransformers(_loadPackageGraph()),
+        key: (id, _) => id.toString(),
+        value: (_, ids) => ids.map((id) => id.toString()).toSet());
+    expect(result, equals(expected));
+  }, "expect dependencies to match $expected");
+}
+
+/// Expects that [computeTransformersNeededByTransformers] will throw an
+/// exception matching [matcher] when run on the package graph defiend by
+/// packages in the sandbox.
+void expectException(matcher) {
+  schedule(() {
+    expect(() => computeTransformersNeededByTransformers(_loadPackageGraph()),
+        throwsA(matcher));
+  }, "expect an exception: $matcher");
+}
+
+/// Expects that [computeTransformersNeededByTransformers] will throw a
+/// [CycleException] with the given [steps] when run on the package graph
+/// defiend by packages in the sandbox.
+void expectCycleException(Iterable<String> steps) {
+  expectException(predicate((error) {
+    expect(error, new isInstanceOf<CycleException>());
+    expect(error.steps, equals(steps));
+    return true;
+  }, "cycle exception:\n${steps.map((step) => "  $step").join("\n")}"));
+}
+
+/// Loads a [PackageGraph] from the packages in the sandbox.
+///
+/// This graph will also include barback and its transitive dependencies from
+/// the repo.
+PackageGraph _loadPackageGraph() {
+  // Load the sandbox packages.
+  var packages = {};
+
+  var systemCache = new SystemCache(p.join(sandboxDir, cachePath));
+  systemCache.sources
+      ..register(new PathSource())
+      ..setDefault('path');
+  var entrypoint = new Entrypoint(p.join(sandboxDir, appPath), systemCache);
+
+  for (var package in listDir(sandboxDir)) {
+    if (!fileExists(p.join(package, 'pubspec.yaml'))) continue;
+    var packageName = p.basename(package);
+    packages[packageName] = new Package.load(
+        packageName, package, systemCache.sources);
+  }
+
+  loadPackage(packageName) {
+    if (packages.containsKey(packageName)) return;
+    packages[packageName] = new Package.load(
+        packageName, p.join(pkgPath, packageName), systemCache.sources);
+    for (var dep in packages[packageName].dependencies) {
+      loadPackage(dep.name);
+    }
+  }
+
+  loadPackage('barback');
+
+  return new PackageGraph(entrypoint, null, packages);
+}
+
+/// Returns the contents of a no-op transformer that imports each URL in
+/// [imports].
+String transformer([Iterable<String> imports]) {
+  if (imports == null) imports = [];
+
+  var buffer = new StringBuffer()
+      ..writeln('import "package:barback/barback.dart";');
+  for (var import in imports) {
+    buffer.writeln('import "$import";');
+  }
+
+  buffer.writeln("""
+NoOpTransformer extends Transformer {
+  bool isPrimary(AssetId id) => true;
+  void apply(Transform transform) {}
+}
+""");
+
+  return buffer.toString();
+}