Lazy transformers followed by non-lazy ones shouldn't always be forced.

pkg/barback/test/package_graph/lazy_transformer_test.dart

 // 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 barback.test.package_graph.lazy_asset_test;
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/utils.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
@@ skipping 118 matching lines @@
       [new LazyRewriteTransformer("one", "two")],
       [new DeclaringRewriteTransformer("two", "three")],
       [new DeclaringRewriteTransformer("three", "four")],
       [new DeclaringRewriteTransformer("four", "five")]
     ]});
     updateSources(["app|foo.one"]);
     expectAsset("app|foo.five", "foo.two.three.four.five");
     buildShouldSucceed();
   });
 
+  test("a lazy asset piped into a non-lazy transformer that doesn't use its "
+      "outputs isn't eagerly compiled", () {
+    var transformer = new LazyRewriteTransformer("blub", "blab");
+    initGraph(["app|foo.blub"], {"app": [
+      [transformer],
+      [new RewriteTransformer("txt", "out")]
+    ]});
+    updateSources(["app|foo.blub"]);
+    buildShouldSucceed();
+    expect(transformer.numRuns, completion(equals(0)));
+  });
+
+  test("a lazy asset piped into a non-lazy transformer that doesn't use its "
+      "outputs is compiled on-demand", () {
+    initGraph(["app|foo.blub"], {"app": [
+      [new LazyRewriteTransformer("blub", "blab")],
+      [new RewriteTransformer("txt", "out")]
+    ]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+  });
+
   test("a lazy transformer followed by a non-lazy transformer is re-run "
       "eagerly", () {
     var rewrite = new LazyRewriteTransformer("one", "two");
     initGraph(["app|foo.one"], {"app": [
       [rewrite],
       [new RewriteTransformer("two", "three")]
     ]});
 
     updateSources(["app|foo.one"]);
     expectAsset("app|foo.three", "foo.two.three");
@@ skipping 198 matching lines @@
     resumeProvider();
     expectAsset("app|foo.txt", "foo");
     buildShouldSucceed();
 
     modifyAsset("app|foo.txt", "bar");
     updateSources(["app|foo.txt"]);
     expectAsset("app|foo.txt", "bar");
     buildShouldSucceed();
   });
 }