Allow transformers to exclude and include assets.

sdk/lib/_internal/pub/test/pubspec_test.dart

Index: sdk/lib/_internal/pub/test/pubspec_test.dart
diff --git a/sdk/lib/_internal/pub/test/pubspec_test.dart b/sdk/lib/_internal/pub/test/pubspec_test.dart
index f451f1fb1edfe9c315c91999a8f876bd7f351828..344e6b7975b839948b61674c5fc0f8bea667de11 100644
--- a/sdk/lib/_internal/pub/test/pubspec_test.dart
+++ b/sdk/lib/_internal/pub/test/pubspec_test.dart
@@ -241,13 +241,13 @@ dependencies:
           '"transformers.pkg" field must be a map');
     });
 
-    test("throws if a transformer's configuration contains a top-level key "
-        "beginning with a dollar sign", () {
+    test("throws if a transformer's configuration contains an unknown "
+        "reserved key at the top level", () {
       expectPubspecException('''
 name: pkg
 transformers: [{pkg: {\$key: "value"}}]''',
           (pubspec) => pubspec.transformers,
-          '"transformers.pkg" field cannot contain reserved field "\$key"');
+          'Unknown reserved field "\$key"');

[nweiz, 2014/02/24 21:42:46]

This is a much worse error message than before. It's very valuable to include
the path to the key.

The errors below also don't contain the path.

[Bob Nystrom, 2014/02/26 01:09:41]

Done. The paths were always in the error message, the tests just didn't validate
it. Now they do.

     });
 
     test("doesn't throw if a transformer's configuration contains a "
@@ -262,6 +262,44 @@ transformers:
       expect(pkg.configuration["outer"]["\$inner"], equals("value"));
     });
 
+    test("throws if the \$include value is not a string or list", () {
+      expectPubspecException('''
+name: pkg
+transformers:
+- pkg: {\$include: 123}''',
+          (pubspec) => pubspec.transformers,
+          '"\$include" field must be a string or list, but was "123"');
+    });
+
+    test("throws if the \$include list contains a non-string", () {
+      expectPubspecException('''
+name: pkg
+transformers:
+- pkg: {\$include: ["ok", 123, "alright", null]}''',
+        (pubspec) => pubspec.transformers,
+        '"\$include" list field may only contain strings, but contained '
+        '"123" and "null"');
+    });
+
+    test("throws if the \$exclude value is not a string or list", () {
+      expectPubspecException('''
+name: pkg
+transformers:
+- pkg: {\$exclude: 123}''',
+        (pubspec) => pubspec.transformers,
+        '"\$exclude" field must be a string or list, but was "123"');
+    });
+
+    test("throws if the \$exclude list contains a non-string", () {
+      expectPubspecException('''
+name: pkg
+transformers:
+- pkg: {\$exclude: ["ok", 123, "alright", null]}''',
+        (pubspec) => pubspec.transformers,
+        '"\$exclude" list field may only contain strings, but contained '
+        '"123" and "null"');
+    });
+
     test("throws if a transformer is not from a dependency", () {
       expectPubspecException('''
 name: pkg