Always ignore non-public transformers.

This was happening for the most part, but the dependency computer could
get tripped up when a package used a transformer from a dev dependency
on only private files.

R=rnystrom@google.com
BUG= http://dartbug.com/23480

Review URL: https://codereview.chromium.org//1143453006

sdk/lib/_internal/pub/lib/src/barback/dependency_computer.dart

@@ -254,6 +254,9 @@ class _PackageDependencyComputer {
           String packageName)
       : _dependencyComputer = dependencyComputer,
         _package = dependencyComputer._graph.packages[packageName] {
+    var isRootPackage =
+        packageName == _dependencyComputer._graph.entrypoint.root.name;
+
     // If [_package] uses its own transformers, there will be fewer transformers
     // running on [_package] while its own transformers are loading than there
     // will be once all its transformers are finished loading. To handle this,
@@ -262,6 +265,9 @@ class _PackageDependencyComputer {
     // smaller.
     for (var phase in _package.pubspec.transformers) {
       for (var config in phase) {
+        // Ignore non-root transformers on non-public files.
+        if (!isRootPackage && !config.canTransformPublicFiles) continue;
+
         var id = config.id;
         try {
           if (id.package != _package.name) {

sdk/lib/_internal/pub/test/transformer/ignores_a_transformer_on_test_files_in_a_dependency_test.dart

@@ -0,0 +1,57 @@
+// Copyright (c) 2015, 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.
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import '../serve/utils.dart';
+
+main() {
+  initConfig();
+  // Regression test for issue 23480
+  integration("ignores a transformer on test files in a dependency", () {
+    servePackages((builder) {
+      builder.serveRepoPackage('barback');
+
+      builder.serve("bar", "1.2.3", contents: [
+        d.dir("lib", [
+          // Make this invalid so that if it does get loaded, pub will
+          // definitely throw an error.
+          d.file("bar.dart", "{invalid Dart code)")
+        ])
+      ]);
+
+      builder.serve("foo", "1.2.3",
+        pubspec: {
+        "name": "foo",
+        "version": "1.0.0",
+        "dev_dependencies": {
+          "bar": "any"
+        },
+        "transformers": [{
+          "bar": {"\$include": "test/**"}
+        }]
+      }, contents: [
+        d.dir("test", [
+          d.file("my_test.dart", "void main() {}")
+        ])
+      ]);
+    });
+
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "dependencies": {"foo": "any"}
+      }),
+      d.dir("web", [
+        d.file("foo.txt", "foo")
+      ])
+    ]).create();
+
+    pubGet();
+
+    pubServe();
+    requestShouldSucceed("foo.txt", "foo");
+    endPubServe();
+  });
+}