Support an additional edge case in barback.

pkg/barback/test/package_graph/transform_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.transform_test;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/utils.dart';
@@ skipping 414 matching lines @@
     });
 
     expectNoAsset("app|foo.out");
     buildShouldSucceed();
 
     schedule(() {
       expect(transformer.numRuns, equals(1));
     });
   });
 
+  test("restarts processing if a change to a new secondary input occurs during "
+      "processing", () {
+    var transformer = new ManyToOneTransformer("txt");
+    initGraph({
+      "app|foo.txt": "bar.inc",
+      "app|bar.inc": "bar"
+    }, {"app": [[transformer]]});
+
+    transformer.pauseApply();
+
+    updateSources(["app|foo.txt", "app|bar.inc"]);
+    // Wait for the transform to start.
+    schedule(() => transformer.started);
+
+    // Give the transform time to load bar.inc the first time.
+    schedule(pumpEventQueue);
+
+    // Now update the secondary input before the transform finishes.
+    modifyAsset("app|bar.inc", "baz");
+    schedule(() => updateSources(["app|bar.inc"]));
+    // Give bar.inc enough time to be loaded and marked available before the
+    // transformer completes.
+    schedule(pumpEventQueue);
+
+    schedule(transformer.resumeApply);
+
+    expectAsset("app|foo.out", "baz");
+    buildShouldSucceed();
+
+    schedule(() {
+      expect(transformer.numRuns, equals(2));
+    });
+  });
+
+  test("doesn't restart processing if a change to an old secondary input "
+      "occurs during processing", () {
+    var transformer = new ManyToOneTransformer("txt");
+    initGraph({
+      "app|foo.txt": "bar.inc",
+      "app|bar.inc": "bar",
+      "app|baz.inc": "baz"
+    }, {"app": [[transformer]]});
+
+    updateSources(["app|foo.txt", "app|bar.inc", "app|baz.inc"]);
+    expectAsset("app|foo.out", "bar");
+    buildShouldSucceed();
+
+    schedule(transformer.pauseApply);
+    modifyAsset("app|foo.txt", "baz.inc");
+    schedule(() {
+      updateSources(["app|foo.txt"]);
+      // Wait for the transform to start.
+      return transformer.started;
+    });
+
+    // Now update the old secondary input before the transform finishes.
+    modifyAsset("app|bar.inc", "new bar");
+    schedule(() => updateSources(["app|bar.inc"]));
+    // Give bar.inc enough time to be loaded and marked available before the
+    // transformer completes.
+    schedule(pumpEventQueue);
+
+    schedule(transformer.resumeApply);
+
+    expectAsset("app|foo.out", "baz");
+    buildShouldSucceed();
+
+    schedule(() {
+      // Should have run once the first time, then again when switching to
+      // baz.inc. Should not run a third time because of bar.inc being modified.
+      expect(transformer.numRuns, equals(2));
+    });
+  });
+
   test("handles an output moving from one transformer to another", () {
     // In the first run, "shared.out" is created by the "a.a" transformer.
     initGraph({
       "app|a.a": "a.out,shared.out",
       "app|b.b": "b.out"
     }, {"app": [
       [new OneToManyTransformer("a"), new OneToManyTransformer("b")]
     ]});
 
     updateSources(["app|a.a", "app|b.b"]);
@@ skipping 369 matching lines @@
     schedule(() => updateSources(["pkg2|foo.txt"]));
     expectAsset("pkg1|foo.out", "foo.out");
     buildShouldNotBeDone();
 
     // Now that the provider is unpaused, pkg2's transforms finish and the
     // overall build succeeds.
     resumeProvider();
     buildShouldSucceed();
   });
 }