Revert commits r33138, r33135, and r33134.

pkg/barback/test/package_graph/transform_test.dart

Index: pkg/barback/test/package_graph/transform_test.dart
diff --git a/pkg/barback/test/package_graph/transform_test.dart b/pkg/barback/test/package_graph/transform_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..ae097a6f4f6e789b8a9aea0b0237080417e63fb2
--- /dev/null
+++ b/pkg/barback/test/package_graph/transform_test.dart
@@ -0,0 +1,1179 @@
+// 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 'package:barback/src/utils.dart';
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../utils.dart';
+
+main() {
+  initConfig();
+  test("gets a transformed asset with a different path", () {
+    initGraph(["app|foo.blub"], {"app": [
+      [new RewriteTransformer("blub", "blab")]
+    ]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+  });
+
+  test("gets a transformed asset with the same path", () {
+    initGraph(["app|foo.blub"], {"app": [
+      [new RewriteTransformer("blub", "blub")]
+    ]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blub", "foo.blub");
+    buildShouldSucceed();
+  });
+
+  test("doesn't find an output from a later phase", () {
+    initGraph(["app|foo.a"], {"app": [
+      [new RewriteTransformer("b", "c")],
+      [new RewriteTransformer("a", "b")]
+    ]});
+    updateSources(["app|foo.a"]);
+    expectNoAsset("app|foo.c");
+    buildShouldSucceed();
+  });
+
+  test("doesn't find an output from the same phase", () {
+    initGraph(["app|foo.a"], {"app": [
+      [
+        new RewriteTransformer("a", "b"),
+        new RewriteTransformer("b", "c")
+      ]
+    ]});
+    updateSources(["app|foo.a"]);
+    expectAsset("app|foo.b", "foo.b");
+    expectNoAsset("app|foo.c");
+    buildShouldSucceed();
+  });
+
+  test("finds the latest output before the transformer's phase", () {
+    initGraph(["app|foo.blub"], {"app": [
+      [new RewriteTransformer("blub", "blub")],
+      [
+        new RewriteTransformer("blub", "blub"),
+        new RewriteTransformer("blub", "done")
+      ],
+      [new RewriteTransformer("blub", "blub")]
+    ]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.done", "foo.blub.done");
+    buildShouldSucceed();
+  });
+
+  test("applies multiple transformations to an asset", () {
+    initGraph(["app|foo.a"], {"app": [
+      [new RewriteTransformer("a", "b")],
+      [new RewriteTransformer("b", "c")],
+      [new RewriteTransformer("c", "d")],
+      [new RewriteTransformer("d", "e")],
+      [new RewriteTransformer("e", "f")],
+      [new RewriteTransformer("f", "g")],
+      [new RewriteTransformer("g", "h")],
+      [new RewriteTransformer("h", "i")],
+      [new RewriteTransformer("i", "j")],
+      [new RewriteTransformer("j", "k")],
+    ]});
+    updateSources(["app|foo.a"]);
+    expectAsset("app|foo.k", "foo.b.c.d.e.f.g.h.i.j.k");
+    buildShouldSucceed();
+  });
+
+  test("only runs a transform once for all of its outputs", () {
+    var transformer = new RewriteTransformer("blub", "a b c");
+    initGraph(["app|foo.blub"], {"app": [[transformer]]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.a", "foo.a");
+    expectAsset("app|foo.b", "foo.b");
+    expectAsset("app|foo.c", "foo.c");
+    buildShouldSucceed();
+    expect(transformer.numRuns, completion(equals(1)));
+  });
+
+  test("runs transforms in the same phase in parallel", () {
+    var transformerA = new RewriteTransformer("txt", "a");
+    var transformerB = new RewriteTransformer("txt", "b");
+    initGraph(["app|foo.txt"], {"app": [[transformerA, transformerB]]});
+
+    transformerA.pauseApply();
+    transformerB.pauseApply();
+
+    updateSources(["app|foo.txt"]);
+
+    transformerA.waitUntilStarted();
+    transformerB.waitUntilStarted();
+
+    // They should both still be running.
+    expect(transformerA.isRunning, completion(isTrue));
+    expect(transformerB.isRunning, completion(isTrue));
+
+    transformerA.resumeApply();
+    transformerB.resumeApply();
+
+    expectAsset("app|foo.a", "foo.a");
+    expectAsset("app|foo.b", "foo.b");
+    buildShouldSucceed();
+  });
+
+  test("outputs are inaccessible once used", () {
+    initGraph(["app|foo.a"], {"app": [
+      [new RewriteTransformer("a", "b")],
+      [new RewriteTransformer("a", "c")]
+    ]});
+    updateSources(["app|foo.a"]);
+    expectAsset("app|foo.b", "foo.b");
+    expectNoAsset("app|foo.a");
+    expectNoAsset("app|foo.c");
+    buildShouldSucceed();
+  });
+
+  test("does not reapply transform when inputs are not modified", () {
+    var transformer = new RewriteTransformer("blub", "blab");
+    initGraph(["app|foo.blub"], {"app": [[transformer]]});
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    expectAsset("app|foo.blab", "foo.blab");
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(equals(1)));
+  });
+
+  test("reapplies a transform when its input is modified", () {
+    var transformer = new RewriteTransformer("blub", "blab");
+    initGraph(["app|foo.blub"], {"app": [[transformer]]});
+
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+
+    updateSources(["app|foo.blub"]);
+    expectAsset("app|foo.blab", "foo.blab");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(equals(3)));
+  });
+
+  test("does not reapply transform when a removed input is modified", () {
+    var transformer = new ManyToOneTransformer("txt");
+    initGraph({
+      "app|a.txt": "a.inc,b.inc",
+      "app|a.inc": "a",
+      "app|b.inc": "b"
+    }, {"app": [[transformer]]});
+
+    updateSources(["app|a.txt", "app|a.inc", "app|b.inc"]);
+
+    expectAsset("app|a.out", "ab");
+    buildShouldSucceed();
+
+    // Remove the dependency on the non-primary input.
+    modifyAsset("app|a.txt", "a.inc");
+    updateSources(["app|a.txt"]);
+
+    // Process it again.
+    expectAsset("app|a.out", "a");
+    buildShouldSucceed();
+
+    // Now touch the removed input. It should not trigger another build.
+    updateSources(["app|b.inc"]);
+    expectAsset("app|a.out", "a");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(equals(2)));
+  });
+
+  test("allows a transform to generate multiple outputs", () {
+    initGraph({"app|foo.txt": "a.out,b.out"}, {"app": [
+      [new OneToManyTransformer("txt")]
+    ]});
+
+    updateSources(["app|foo.txt"]);
+
+    expectAsset("app|a.out", "spread txt");
+    expectAsset("app|b.out", "spread txt");
+    buildShouldSucceed();
+  });
+
+  test("does not rebuild transforms that don't use modified source", () {
+    var a = new RewriteTransformer("a", "aa");
+    var aa = new RewriteTransformer("aa", "aaa");
+    var b = new RewriteTransformer("b", "bb");
+    var bb = new RewriteTransformer("bb", "bbb");
+    initGraph(["app|foo.a", "app|foo.b"], {"app": [
+      [a, b],
+      [aa, bb],
+    ]});
+
+    updateSources(["app|foo.a"]);
+    updateSources(["app|foo.b"]);
+
+    expectAsset("app|foo.aaa", "foo.aa.aaa");
+    expectAsset("app|foo.bbb", "foo.bb.bbb");
+    buildShouldSucceed();
+
+    updateSources(["app|foo.a"]);
+    expectAsset("app|foo.aaa", "foo.aa.aaa");
+    expectAsset("app|foo.bbb", "foo.bb.bbb");
+    buildShouldSucceed();
+
+    expect(aa.numRuns, completion(equals(2)));
+    expect(bb.numRuns, completion(equals(1)));
+  });
+
+  test("doesn't get an output from a transform whose primary input is removed",
+      () {
+    initGraph(["app|foo.txt"], {"app": [
+      [new RewriteTransformer("txt", "out")]
+    ]});
+
+    updateSources(["app|foo.txt"]);
+    expectAsset("app|foo.out", "foo.out");
+    buildShouldSucceed();
+
+    removeSources(["app|foo.txt"]);
+    expectNoAsset("app|foo.out");
+    buildShouldSucceed();
+  });
+
+  test("discards outputs from a transform whose primary input is removed "
+      "during processing", () {
+    var rewrite = new RewriteTransformer("txt", "out");
+    initGraph(["app|foo.txt"], {"app": [[rewrite]]});
+
+    rewrite.pauseApply();
+    updateSources(["app|foo.txt"]);
+    rewrite.waitUntilStarted();
+
+    removeSources(["app|foo.txt"]);
+    rewrite.resumeApply();
+    expectNoAsset("app|foo.out");
+    buildShouldSucceed();
+  });
+
+  test("reapplies a transform when a non-primary input changes", () {
+    initGraph({
+      "app|a.txt": "a.inc",
+      "app|a.inc": "a"
+    }, {"app": [[new ManyToOneTransformer("txt")]]});
+
+    updateSources(["app|a.txt", "app|a.inc"]);
+    expectAsset("app|a.out", "a");
+    buildShouldSucceed();
+
+    modifyAsset("app|a.inc", "after");
+    updateSources(["app|a.inc"]);
+
+    expectAsset("app|a.out", "after");
+    buildShouldSucceed();
+  });
+
+  test("applies a transform when it becomes newly primary", () {
+    initGraph({
+      "app|foo.txt": "this",
+    }, {"app": [[new CheckContentTransformer("that", " and the other")]]});
+
+    updateSources(["app|foo.txt"]);
+    expectAsset("app|foo.txt", "this");
+    buildShouldSucceed();
+
+    modifyAsset("app|foo.txt", "that");
+    updateSources(["app|foo.txt"]);
+
+    expectAsset("app|foo.txt", "that and the other");
+    buildShouldSucceed();
+  });
+
+  test("applies the correct transform if an asset is modified during isPrimary",
+      () {
+    var check1 = new CheckContentTransformer("first", "#1");
+    var check2 = new CheckContentTransformer("second", "#2");
+    initGraph({
+      "app|foo.txt": "first",
+    }, {"app": [[check1, check2]]});
+
+    check1.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    // Ensure that we're waiting on check1's isPrimary.
+    schedule(pumpEventQueue);
+
+    modifyAsset("app|foo.txt", "second");
+    updateSources(["app|foo.txt"]);
+    check1.resumeIsPrimary("app|foo.txt");
+
+    expectAsset("app|foo.txt", "second#2");
+    buildShouldSucceed();
+  });
+
+  test("applies the correct transform if an asset is removed and added during "
+      "isPrimary", () {
+    var check1 = new CheckContentTransformer("first", "#1");
+    var check2 = new CheckContentTransformer("second", "#2");
+    initGraph({
+      "app|foo.txt": "first",
+    }, {"app": [[check1, check2]]});
+
+    check1.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    // Ensure that we're waiting on check1's isPrimary.
+    schedule(pumpEventQueue);
+
+    removeSources(["app|foo.txt"]);
+    modifyAsset("app|foo.txt", "second");
+    updateSources(["app|foo.txt"]);
+    check1.resumeIsPrimary("app|foo.txt");
+
+    expectAsset("app|foo.txt", "second#2");
+    buildShouldSucceed();
+  });
+
+  test("restarts processing if a change occurs during processing", () {
+    var transformer = new RewriteTransformer("txt", "out");
+    initGraph(["app|foo.txt"], {"app": [[transformer]]});
+
+    transformer.pauseApply();
+
+    updateSources(["app|foo.txt"]);
+    transformer.waitUntilStarted();
+
+    // Now update the graph during it.
+    updateSources(["app|foo.txt"]);
+    transformer.resumeApply();
+
+    expectAsset("app|foo.out", "foo.out");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(equals(2)));
+  });
+
+  test("aborts processing if the primary input is removed during processing",
+      () {
+    var transformer = new RewriteTransformer("txt", "out");
+    initGraph(["app|foo.txt"], {"app": [[transformer]]});
+
+    transformer.pauseApply();
+
+    updateSources(["app|foo.txt"]);
+    transformer.waitUntilStarted();
+
+    // Now remove its primary input while it's running.
+    removeSources(["app|foo.txt"]);
+    transformer.resumeApply();
+
+    expectNoAsset("app|foo.out");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(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"]);
+    transformer.waitUntilStarted();
+
+    // 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");
+    updateSources(["app|bar.inc"]);
+    // Give bar.inc enough time to be loaded and marked available before the
+    // transformer completes.
+    schedule(pumpEventQueue);
+
+    transformer.resumeApply();
+
+    expectAsset("app|foo.out", "baz");
+    buildShouldSucceed();
+
+    expect(transformer.numRuns, completion(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();
+
+    transformer.pauseApply();
+    modifyAsset("app|foo.txt", "baz.inc");
+    updateSources(["app|foo.txt"]);
+    transformer.waitUntilStarted();
+
+    // Now update the old secondary input before the transform finishes.
+    modifyAsset("app|bar.inc", "new bar");
+    updateSources(["app|bar.inc"]);
+    // Give bar.inc enough time to be loaded and marked available before the
+    // transformer completes.
+    schedule(pumpEventQueue);
+
+    transformer.resumeApply();
+    expectAsset("app|foo.out", "baz");
+    buildShouldSucceed();
+
+    // 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, completion(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"]);
+
+    expectAsset("app|a.out", "spread a");
+    expectAsset("app|b.out", "spread b");
+    expectAsset("app|shared.out", "spread a");
+    buildShouldSucceed();
+
+    // Now switch their contents so that "shared.out" will be output by "b.b"'s
+    // transformer.
+    modifyAsset("app|a.a", "a.out");
+    modifyAsset("app|b.b", "b.out,shared.out");
+    updateSources(["app|a.a", "app|b.b"]);
+
+    expectAsset("app|a.out", "spread a");
+    expectAsset("app|b.out", "spread b");
+    expectAsset("app|shared.out", "spread b");
+    buildShouldSucceed();
+  });
+
+  test("restarts before finishing later phases when a change occurs", () {
+    var txtToInt = new RewriteTransformer("txt", "int");
+    var intToOut = new RewriteTransformer("int", "out");
+    initGraph(["app|foo.txt", "app|bar.txt"],
+        {"app": [[txtToInt], [intToOut]]});
+
+    txtToInt.pauseApply();
+
+    updateSources(["app|foo.txt"]);
+    txtToInt.waitUntilStarted();
+
+    // Now update the graph during it.
+    updateSources(["app|bar.txt"]);
+    txtToInt.resumeApply();
+
+    expectAsset("app|foo.out", "foo.int.out");
+    expectAsset("app|bar.out", "bar.int.out");
+    buildShouldSucceed();
+
+    // Should only have run each transform once for each primary.
+    expect(txtToInt.numRuns, completion(equals(2)));
+    expect(intToOut.numRuns, completion(equals(2)));
+  });
+
+  test("applies transforms to the correct packages", () {
+    var rewrite1 = new RewriteTransformer("txt", "out1");
+    var rewrite2 = new RewriteTransformer("txt", "out2");
+    initGraph([
+      "pkg1|foo.txt",
+      "pkg2|foo.txt"
+    ], {"pkg1": [[rewrite1]], "pkg2": [[rewrite2]]});
+
+    updateSources(["pkg1|foo.txt", "pkg2|foo.txt"]);
+    expectAsset("pkg1|foo.out1", "foo.out1");
+    expectAsset("pkg2|foo.out2", "foo.out2");
+    buildShouldSucceed();
+  });
+
+  test("transforms don't see generated assets in other packages", () {
+    var fooToBar = new RewriteTransformer("foo", "bar");
+    var barToBaz = new RewriteTransformer("bar", "baz");
+    initGraph(["pkg1|file.foo"], {"pkg1": [[fooToBar]], "pkg2": [[barToBaz]]});
+
+    updateSources(["pkg1|file.foo"]);
+    expectAsset("pkg1|file.bar", "file.bar");
+    expectNoAsset("pkg2|file.baz");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return an asset until it's finished rebuilding", () {
+    initGraph(["app|foo.in"], {"app": [
+      [new RewriteTransformer("in", "mid")],
+      [new RewriteTransformer("mid", "out")]
+    ]});
+
+    updateSources(["app|foo.in"]);
+    expectAsset("app|foo.out", "foo.mid.out");
+    buildShouldSucceed();
+
+    pauseProvider();
+    modifyAsset("app|foo.in", "new");
+    updateSources(["app|foo.in"]);
+    expectAssetDoesNotComplete("app|foo.out");
+    buildShouldNotBeDone();
+
+    resumeProvider();
+    expectAsset("app|foo.out", "new.mid.out");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return an asset until its in-place transform is done", () {
+    var rewrite = new RewriteTransformer("txt", "txt");
+    initGraph(["app|foo.txt"], {"app": [[rewrite]]});
+
+    rewrite.pauseApply();
+    updateSources(["app|foo.txt"]);
+    expectAssetDoesNotComplete("app|foo.txt");
+
+    rewrite.resumeApply();
+    expectAsset("app|foo.txt", "foo.txt");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return an asset until we know it won't be transformed",
+      () {
+    var rewrite = new RewriteTransformer("txt", "txt");
+    initGraph(["app|foo.a"], {"app": [[rewrite]]});
+
+    rewrite.pauseIsPrimary("app|foo.a");
+    updateSources(["app|foo.a"]);
+    expectAssetDoesNotComplete("app|foo.a");
+
+    rewrite.resumeIsPrimary("app|foo.a");
+    expectAsset("app|foo.a", "foo");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return a modified asset until we know it will still be "
+      "transformed", () {
+    var rewrite = new RewriteTransformer("txt", "txt");
+    initGraph(["app|foo.txt"], {"app": [[rewrite]]});
+
+    updateSources(["app|foo.txt"]);
+    expectAsset("app|foo.txt", "foo.txt");
+    buildShouldSucceed();
+
+    rewrite.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    expectAssetDoesNotComplete("app|foo.txt");
+
+    rewrite.resumeIsPrimary("app|foo.txt");
+    expectAsset("app|foo.txt", "foo.txt");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return an asset that's removed during isPrimary", () {
+    var rewrite = new RewriteTransformer("txt", "txt");
+    initGraph(["app|foo.txt"], {"app": [[rewrite]]});
+
+    rewrite.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    // Make sure we're waiting on isPrimary.
+    schedule(pumpEventQueue);
+
+    removeSources(["app|foo.txt"]);
+    rewrite.resumeIsPrimary("app|foo.txt");
+    expectNoAsset("app|foo.txt");
+    buildShouldSucceed();
+  });
+
+  test("doesn't transform an asset that goes from primary to non-primary "
+      "during isPrimary", () {
+    var check = new CheckContentTransformer(new RegExp(r"^do$"), "ne");
+    initGraph({
+      "app|foo.txt": "do"
+    }, {"app": [[check]]});
+
+    check.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    // Make sure we're waiting on isPrimary.
+    schedule(pumpEventQueue);
+
+    modifyAsset("app|foo.txt", "don't");
+    updateSources(["app|foo.txt"]);
+    check.resumeIsPrimary("app|foo.txt");
+
+    expectAsset("app|foo.txt", "don't");
+    buildShouldSucceed();
+  });
+
+  test("transforms an asset that goes from non-primary to primary "
+      "during isPrimary", () {
+    var check = new CheckContentTransformer("do", "ne");
+    initGraph({
+      "app|foo.txt": "don't"
+    }, {"app": [[check]]});
+
+    check.pauseIsPrimary("app|foo.txt");
+    updateSources(["app|foo.txt"]);
+    // Make sure we're waiting on isPrimary.
+    schedule(pumpEventQueue);
+
+    modifyAsset("app|foo.txt", "do");
+    updateSources(["app|foo.txt"]);
+    check.resumeIsPrimary("app|foo.txt");
+
+    expectAsset("app|foo.txt", "done");
+    buildShouldSucceed();
+  });
+
+  test("doesn't return an asset that's removed during another transformer's "
+      "isPrimary", () {
+    var rewrite1 = new RewriteTransformer("txt", "txt");
+    var rewrite2 = new RewriteTransformer("md", "md");
+    initGraph(["app|foo.txt", "app|foo.md"], {"app": [[rewrite1, rewrite2]]});
+
+    rewrite2.pauseIsPrimary("app|foo.md");
+    updateSources(["app|foo.txt", "app|foo.md"]);
+    // Make sure we're waiting on the correct isPrimary.
+    schedule(pumpEventQueue);
+
+    removeSources(["app|foo.txt"]);
+    rewrite2.resumeIsPrimary("app|foo.md");
+    expectNoAsset("app|foo.txt");
+    expectAsset("app|foo.md", "foo.md");
+    buildShouldSucceed();
+  });
+
+  test("doesn't transform an asset that goes from primary to non-primary "
+      "during another transformer's isPrimary", () {
+    var rewrite = new RewriteTransformer("md", "md");
+    var check = new CheckContentTransformer(new RegExp(r"^do$"), "ne");
+    initGraph({
+      "app|foo.txt": "do",
+      "app|foo.md": "foo"
+    }, {"app": [[rewrite, check]]});
+
+    rewrite.pauseIsPrimary("app|foo.md");
+    updateSources(["app|foo.txt", "app|foo.md"]);
+    // Make sure we're waiting on the correct isPrimary.
+    schedule(pumpEventQueue);
+
+    modifyAsset("app|foo.txt", "don't");
+    updateSources(["app|foo.txt"]);
+    rewrite.resumeIsPrimary("app|foo.md");
+
+    expectAsset("app|foo.txt", "don't");
+    expectAsset("app|foo.md", "foo.md");
+    buildShouldSucceed();
+  });
+
+  test("transforms an asset that goes from non-primary to primary "
+      "during another transformer's isPrimary", () {
+    var rewrite = new RewriteTransformer("md", "md");
+    var check = new CheckContentTransformer("do", "ne");
+    initGraph({
+      "app|foo.txt": "don't",
+      "app|foo.md": "foo"
+    }, {"app": [[rewrite, check]]});
+
+    rewrite.pauseIsPrimary("app|foo.md");
+    updateSources(["app|foo.txt", "app|foo.md"]);
+    // Make sure we're waiting on the correct isPrimary.
+    schedule(pumpEventQueue);
+
+    modifyAsset("app|foo.txt", "do");
+    updateSources(["app|foo.txt"]);
+    rewrite.resumeIsPrimary("app|foo.md");
+
+    expectAsset("app|foo.txt", "done");
+    expectAsset("app|foo.md", "foo.md");
+    buildShouldSucceed();
+  });
+
+  test("removes pipelined transforms when the root primary input is removed",
+      () {
+    initGraph(["app|foo.txt"], {"app": [
+      [new RewriteTransformer("txt", "mid")],
+      [new RewriteTransformer("mid", "out")]
+    ]});
+
+    updateSources(["app|foo.txt"]);
+    expectAsset("app|foo.out", "foo.mid.out");
+    buildShouldSucceed();
+
+    removeSources(["app|foo.txt"]);
+    expectNoAsset("app|foo.out");
+    buildShouldSucceed();
+  });
+
+  test("removes pipelined transforms when the parent ceases to generate the "
+      "primary input", () {
+    initGraph({"app|foo.txt": "foo.mid"}, {'app': [
+      [new OneToManyTransformer('txt')],
+      [new RewriteTransformer('mid', 'out')]
+    ]});
+
+    updateSources(['app|foo.txt']);
+    expectAsset('app|foo.out', 'spread txt.out');
+    buildShouldSucceed();
+
+    modifyAsset("app|foo.txt", "bar.mid");
+    updateSources(["app|foo.txt"]);
+    expectNoAsset('app|foo.out');
+    expectAsset('app|bar.out', 'spread txt.out');
+    buildShouldSucceed();
+  });
+
+  test("returns an asset even if an unrelated build is running", () {
+    initGraph([
+      "app|foo.in",
+      "app|bar.in",
+    ], {"app": [[new RewriteTransformer("in", "out")]]});
+
+    updateSources(["app|foo.in", "app|bar.in"]);
+    expectAsset("app|foo.out", "foo.out");
+    expectAsset("app|bar.out", "bar.out");
+    buildShouldSucceed();
+
+    pauseProvider();
+    modifyAsset("app|foo.in", "new");
+    updateSources(["app|foo.in"]);
+    expectAssetDoesNotComplete("app|foo.out");
+    expectAsset("app|bar.out", "bar.out");
+    buildShouldNotBeDone();
+
+    resumeProvider();
+    expectAsset("app|foo.out", "new.out");
+    buildShouldSucceed();
+  });
+
+  test("doesn't report AssetNotFound until all builds are finished", () {
+    initGraph([
+      "app|foo.in",
+    ], {"app": [[new RewriteTransformer("in", "out")]]});
+
+    updateSources(["app|foo.in"]);
+    expectAsset("app|foo.out", "foo.out");
+    buildShouldSucceed();
+
+    pauseProvider();
+    updateSources(["app|foo.in"]);
+    expectAssetDoesNotComplete("app|foo.out");
+    expectAssetDoesNotComplete("app|non-existent.out");
+    buildShouldNotBeDone();
+
+    resumeProvider();
+    expectAsset("app|foo.out", "foo.out");
+    expectNoAsset("app|non-existent.out");
+    buildShouldSucceed();
+  });
+
+  test("doesn't emit a result until all builds are finished", () {
+    var rewrite = new RewriteTransformer("txt", "out");
+    initGraph([
+      "pkg1|foo.txt",
+      "pkg2|foo.txt"
+    ], {"pkg1": [[rewrite]], "pkg2": [[rewrite]]});
+
+    // First, run both packages' transformers so both packages are successful.
+    updateSources(["pkg1|foo.txt", "pkg2|foo.txt"]);
+    expectAsset("pkg1|foo.out", "foo.out");
+    expectAsset("pkg2|foo.out", "foo.out");
+    buildShouldSucceed();
+
+    // pkg1 is still successful, but pkg2 is waiting on the provider, so the
+    // overall build shouldn't finish.
+    pauseProvider();
+    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();
+  });
+
+  test("one transformer takes a long time while the other finishes, then "
+      "the input is removed", () {
+    var rewrite1 = new RewriteTransformer("txt", "out1");
+    var rewrite2 = new RewriteTransformer("txt", "out2");
+    initGraph(["app|foo.txt"], {"app": [[rewrite1, rewrite2]]});
+
+    rewrite1.pauseApply();
+
+    updateSources(["app|foo.txt"]);
+
+    // Wait for rewrite1 to pause and rewrite2 to finish.
+    schedule(pumpEventQueue);
+
+    removeSources(["app|foo.txt"]);
+
+    // Make sure the removal is processed completely before we restart rewrite2.
+    schedule(pumpEventQueue);
+    rewrite1.resumeApply();
+
+    buildShouldSucceed();
+    expectNoAsset("app|foo.out1");
+    expectNoAsset("app|foo.out2");
+  });
+
+  group("pass-through", () {
+    test("passes an asset through a phase in which no transforms apply", () {
+      initGraph([
+        "app|foo.in",
+        "app|bar.zip",
+      ], {"app": [
+        [new RewriteTransformer("in", "mid")],
+        [new RewriteTransformer("zip", "zap")],
+        [new RewriteTransformer("mid", "out")],
+      ]});
+
+      updateSources(["app|foo.in", "app|bar.zip"]);
+      expectAsset("app|foo.out", "foo.mid.out");
+      expectAsset("app|bar.zap", "bar.zap");
+      buildShouldSucceed();
+    });
+
+    test("doesn't pass an asset through a phase in which a transform consumes "
+        "it", () {
+      initGraph([
+        "app|foo.in",
+      ], {"app": [
+        [new RewriteTransformer("in", "mid")],
+        [new RewriteTransformer("mid", "phase2")],
+        [new RewriteTransformer("mid", "phase3")],
+      ]});
+
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.phase2", "foo.mid.phase2");
+      expectNoAsset("app|foo.phase3");
+      buildShouldSucceed();
+    });
+
+    test("removes a pass-through asset when the source is removed", () {
+      initGraph([
+        "app|foo.in",
+        "app|bar.zip",
+      ], {"app": [
+        [new RewriteTransformer("zip", "zap")],
+        [new RewriteTransformer("in", "out")],
+      ]});
+
+      updateSources(["app|foo.in", "app|bar.zip"]);
+      expectAsset("app|foo.out", "foo.out");
+      buildShouldSucceed();
+
+      removeSources(["app|foo.in"]);
+      expectNoAsset("app|foo.in");
+      expectNoAsset("app|foo.out");
+      buildShouldSucceed();
+    });
+
+    test("updates a pass-through asset when the source is updated", () {
+      initGraph([
+        "app|foo.in",
+        "app|bar.zip",
+      ], {"app": [
+        [new RewriteTransformer("zip", "zap")],
+        [new RewriteTransformer("in", "out")],
+      ]});
+
+      updateSources(["app|foo.in", "app|bar.zip"]);
+      expectAsset("app|foo.out", "foo.out");
+      buildShouldSucceed();
+
+      modifyAsset("app|foo.in", "boo");
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.out", "boo.out");
+      buildShouldSucceed();
+    });
+
+    test("passes an asset through a phase in which transforms have ceased to "
+        "apply", () {
+      initGraph([
+        "app|foo.in",
+      ], {"app": [
+        [new RewriteTransformer("in", "mid")],
+        [new CheckContentTransformer("foo.mid", ".phase2")],
+        [new CheckContentTransformer(new RegExp(r"\.mid$"), ".phase3")],
+      ]});
+
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.mid", "foo.mid.phase2");
+      buildShouldSucceed();
+
+      modifyAsset("app|foo.in", "bar");
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.mid", "bar.mid.phase3");
+      buildShouldSucceed();
+    });
+
+    test("doesn't pass an asset through a phase in which transforms have "
+        "started to apply", () {
+      initGraph([
+        "app|foo.in",
+      ], {"app": [
+        [new RewriteTransformer("in", "mid")],
+        [new CheckContentTransformer("bar.mid", ".phase2")],
+        [new CheckContentTransformer(new RegExp(r"\.mid$"), ".phase3")],
+      ]});
+
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.mid", "foo.mid.phase3");
+      buildShouldSucceed();
+
+      modifyAsset("app|foo.in", "bar");
+      updateSources(["app|foo.in"]);
+      expectAsset("app|foo.mid", "bar.mid.phase2");
+      buildShouldSucceed();
+    });
+
+    test("doesn't pass an asset through if it's removed during isPrimary", () {
+      var check = new CheckContentTransformer("bar", " modified");
+      initGraph(["app|foo.txt"], {"app": [[check]]});
+
+      updateSources(["app|foo.txt"]);
+      expectAsset("app|foo.txt", "foo");
+      buildShouldSucceed();
+
+      check.pauseIsPrimary("app|foo.txt");
+      modifyAsset("app|foo.txt", "bar");
+      updateSources(["app|foo.txt"]);
+      // Ensure we're waiting on [check.isPrimary]
+      schedule(pumpEventQueue);
+
+      removeSources(["app|foo.txt"]);
+      check.resumeIsPrimary("app|foo.txt");
+      expectNoAsset("app|foo.txt");
+      buildShouldSucceed();
+    });
+  });
+
+  group('cross-package transforms', () {
+    test("can access other packages' source assets", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {"pkg1": [[new ManyToOneTransformer("txt")]]});
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a");
+      buildShouldSucceed();
+    });
+
+    test("can access other packages' transformed assets", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.txt": "a"
+      }, {
+        "pkg1": [[new ManyToOneTransformer("txt")]],
+        "pkg2": [[new RewriteTransformer("txt", "inc")]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.txt"]);
+      expectAsset("pkg1|a.out", "a.inc");
+      buildShouldSucceed();
+    });
+
+    test("re-runs a transform when an input from another package changes", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {
+        "pkg1": [[new ManyToOneTransformer("txt")]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.inc", "new a");
+      updateSources(["pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "new a");
+      buildShouldSucceed();
+    });
+
+    test("re-runs a transform when a transformed input from another package "
+        "changes", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.txt": "a"
+      }, {
+        "pkg1": [[new ManyToOneTransformer("txt")]],
+        "pkg2": [[new RewriteTransformer("txt", "inc")]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.txt"]);
+      expectAsset("pkg1|a.out", "a.inc");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.txt", "new a");
+      updateSources(["pkg2|a.txt"]);
+      expectAsset("pkg1|a.out", "new a.inc");
+      buildShouldSucceed();
+    });
+
+    test("doesn't complete the build until all packages' transforms are "
+        "finished running", () {
+      var transformer = new ManyToOneTransformer("txt");
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {
+        "pkg1": [[transformer]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a");
+      buildShouldSucceed();
+
+      transformer.pauseApply();
+      modifyAsset("pkg2|a.inc", "new a");
+      updateSources(["pkg2|a.inc"]);
+      buildShouldNotBeDone();
+
+      transformer.resumeApply();
+      buildShouldSucceed();
+    });
+
+    test("runs a transform that's added because of a change in another package",
+        () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "b"
+      }, {
+        "pkg1": [
+          [new ManyToOneTransformer("txt")],
+          [new OneToManyTransformer("out")],
+          [new RewriteTransformer("md", "done")]
+        ],
+      });
+
+      // pkg1|a.txt generates outputs based on the contents of pkg2|a.inc. At
+      // first pkg2|a.inc only includes "b", which is not transformed. Then
+      // pkg2|a.inc is updated to include "b,c.md". pkg1|c.md triggers the
+      // md->done rewrite transformer, producing pkg1|c.done.
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|b", "spread out");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.inc", "b,c.md");
+      updateSources(["pkg2|a.inc"]);
+      expectAsset("pkg1|b", "spread out");
+      expectAsset("pkg1|c.done", "spread out.done");
+      buildShouldSucceed();
+    });
+
+    test("doesn't run a transform that's removed because of a change in "
+        "another package", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "b,c.md"
+      }, {
+        "pkg1": [
+          [new ManyToOneTransformer("txt")],
+          [new OneToManyTransformer("out")],
+          [new RewriteTransformer("md", "done")]
+        ],
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|b", "spread out");
+      expectAsset("pkg1|c.done", "spread out.done");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.inc", "b");
+      updateSources(["pkg2|a.inc"]);
+      expectAsset("pkg1|b", "spread out");
+      expectNoAsset("pkg1|c.done");
+      buildShouldSucceed();
+    });
+
+    test("sees a transformer that's newly applied to a cross-package "
+        "dependency", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {
+        "pkg1": [[new ManyToOneTransformer("txt")]],
+        "pkg2": [[new CheckContentTransformer("b", " transformed")]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.inc", "b");
+      updateSources(["pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "b transformed");
+      buildShouldSucceed();
+    });
+
+    test("doesn't see a transformer that's newly not applied to a "
+        "cross-package dependency", () {
+      initGraph({
+        "pkg1|a.txt": "pkg2|a.inc",
+        "pkg2|a.inc": "a"
+      }, {
+        "pkg1": [[new ManyToOneTransformer("txt")]],
+        "pkg2": [[new CheckContentTransformer("a", " transformed")]]
+      });
+
+      updateSources(["pkg1|a.txt", "pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "a transformed");
+      buildShouldSucceed();
+
+      modifyAsset("pkg2|a.inc", "b");
+      updateSources(["pkg2|a.inc"]);
+      expectAsset("pkg1|a.out", "b");
+      buildShouldSucceed();
+    });
+
+    test("re-runs if the primary input is invalidated before accessing", () {
+      var transformer1 = new RewriteTransformer("txt", "mid");
+      var transformer2 = new RewriteTransformer("mid", "out");
+
+      initGraph([
+        "app|foo.txt"
+      ], {"app": [
+        [transformer1],
+        [transformer2]
+      ]});
+
+      transformer2.pausePrimaryInput();
+      updateSources(["app|foo.txt"]);
+
+      // Wait long enough to ensure that transformer1 has completed and
+      // transformer2 has started.
+      schedule(pumpEventQueue);
+
+      // Update the source again so that transformer1 invalidates the primary
+      // input of transformer2.
+      transformer1.pauseApply();
+      updateSources(["app|foo.txt"]);
+
+      transformer2.resumePrimaryInput();
+      transformer1.resumeApply();
+
+      expectAsset("app|foo.out", "foo.mid.out");
+      buildShouldSucceed();
+
+      expect(transformer1.numRuns, completion(equals(2)));
+      expect(transformer2.numRuns, completion(equals(2)));
+    });
+  });
+}