Move barback to a more event-based model.

pkg/barback/test/package_graph/errors_test.dart

 // Copyright (c) 2013, 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.source_test;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../utils.dart';
 
 main() {
   initConfig();
 
   test("errors if two transformers output the same file", () {
     initGraph(["app|foo.a"], {"app": [
       [
         new RewriteTransformer("a", "b"),
         new RewriteTransformer("a", "b")
       ]
     ]});
     updateSources(["app|foo.a"]);
 
     buildShouldFail([isAssetCollisionException("app|foo.b")]);
   });
 
+  test("errors if a new transformer outputs the same file as an old "
+      "transformer", () {
+    initGraph(["app|foo.a", "app|foo.b"], {"app": [
+      [
+        new RewriteTransformer("a", "c"),
+        new RewriteTransformer("b", "c")
+      ]
+    ]});
+    updateSources(["app|foo.a"]);
+    expectAsset("app|foo.c", "foo.c");
+    buildShouldSucceed();
+
+    schedule(() => updateSources(["app|foo.b"]));
+    buildShouldFail([isAssetCollisionException("app|foo.c")]);
+  });
+
   test("does not report asset not found errors in results", () {
     initGraph(["app|bar.txt"]);
 
     // Trigger a build.
     updateSources(["app|bar.txt"]);
 
     expectNoAsset("app|foo.txt");
     buildShouldSucceed();
   });
 
@@ skipping 61 matching lines @@
 
     schedule(() {
       updateSources(["app|foo.txt"]);
     });
 
     expectNoAsset("app|foo.out");
 
     buildShouldFail([equals(BadTransformer.ERROR)]);
   });
 
-  // TODO(rnystrom): Is this the behavior we expect? If a transformer fails
-  // to transform a file, should we just skip past it to the source?
-  test("yields a source if a transform fails on it", () {
+  test("doesn't yield a source if a transform fails on it", () {
     initGraph(["app|foo.txt"], {"app": [
       [new BadTransformer(["app|foo.txt"])]
     ]});
 
     schedule(() {
       updateSources(["app|foo.txt"]);
     });
 
-    expectAsset("app|foo.txt");
+    expectNoAsset("app|foo.txt");
   });
 
   test("catches errors even if nothing is waiting for process results", () {
     initGraph(["app|foo.txt"], {"app": [[new BadTransformer([])]]});
 
     schedule(() {
       updateSources(["app|foo.txt"]);
     });
 
     // Note: No asset requests here.
@@ skipping 33 matching lines @@
 
     schedule(() {
       updateSources(["pkg1|foo.txt", "pkg2|foo.txt"]);
     });
 
     buildShouldFail([
       equals(BadTransformer.ERROR),
       equals(BadTransformer.ERROR)
     ]);
   });
+
+  test("an error loading an asset removes the asset from the graph", () {
+    initGraph(["app|foo.txt"]);
+
+    setAssetError("app|foo.txt");
+    schedule(() => updateSources(["app|foo.txt"]));
+    expectNoAsset("app|foo.txt");
+    buildShouldFail([isMockLoadException("app|foo.txt")]);
+  });
 }