Allow transformers to exclude and include assets.

sdk/lib/_internal/pub/test/transformer/exclusion/exclude_asset_string_test.dart

Index: sdk/lib/_internal/pub/test/transformer/exclusion/exclude_asset_string_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/exclusion/exclude_asset_string_test.dart b/sdk/lib/_internal/pub/test/transformer/exclusion/exclude_asset_string_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..b5bf7141556a243b92c9b46553e63e83348ba594
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/transformer/exclusion/exclude_asset_string_test.dart
@@ -0,0 +1,45 @@
+// 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 '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+import '../../serve/utils.dart';
+
+main() {
+  initConfig();
+  integration("allows a single string as the asset to exclude", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": [
+          {
+            "myapp/src/transformer": {
+              "\$exclude": "web/foo.txt"
+            }
+          }
+        ]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", REWRITE_TRANSFORMER)
+      ])]),
+      d.dir("web", [
+        d.file("foo.txt", "foo"),
+        d.file("bar.txt", "bar"),
+        d.dir("sub", [
+          d.file("foo.txt", "foo"),
+        ])
+      ])
+    ]).create();
+
+    createLockFile('myapp', pkg: ['barback']);
+
+    pubServe();
+    requestShould404("foo.out");
+    requestShouldSucceed("sub/foo.out", "foo.out");
+    requestShouldSucceed("bar.out", "bar.out");
+    endPubServe();
+  });
+}