First pass at build dependency graph for barback.

pkg/barback/test/asset_graph/source_test.dart

Index: pkg/barback/test/asset_graph/source_test.dart
diff --git a/pkg/barback/test/asset_graph/source_test.dart b/pkg/barback/test/asset_graph/source_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..32d7f3d0f0f3696f68e0c092639b1b3f1b39ebb9
--- /dev/null
+++ b/pkg/barback/test/asset_graph/source_test.dart
@@ -0,0 +1,170 @@
+// 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.asset_graph.source_test;
+
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+import 'package:barback/src/asset_graph.dart';
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../utils.dart';
+
+main() {
+  initConfig();
+  test("gets a source asset", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, []);
+    graph.updateSources([new AssetId.parse("app|foo.txt")]);
+
+    expectAsset(graph, "app|foo.txt");
+  });
+
+  test("doesn't get an unknown source", () {
+    var provider = new MockProvider([]);
+    var graph = new AssetGraph(provider, []);
+
+    expectNoAsset(graph, "app|unknown.txt");
+  });
+
+  test("doesn't get an unprovided source", () {
+    var provider = new MockProvider([]);
+    var graph = new AssetGraph(provider, []);
+
+    graph.updateSources([new AssetId.parse("app|unknown.txt")]);
+    expectNoAsset(graph, "app|unknown.txt");
+  });
+
+  test("doesn't get an asset that isn't an updated source", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, []);
+
+    // Sources must be explicitly made visible to barback by calling
+    // updateSources() on them. It isn't enough for the provider to be able
+    // to provide it.
+    //
+    // This lets you distinguish between sources that you want to be primaries
+    // and the larger set of inputs that those primaries are allowed to pull in.
+    expectNoAsset(graph, "app|foo.txt");
+  });
+
+  test("gets a source asset if not transformed", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, [
+      [new RewriteTransformer("nottxt", "whatever")]
+    ]);
+    graph.updateSources([new AssetId.parse("app|foo.txt")]);
+
+    expectAsset(graph, "app|foo.txt");
+  });
+
+  test("doesn't get a removed source", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, [[]]);
+    graph.updateSources([new AssetId.parse("app|foo.txt")]);
+
+    expectAsset(graph, "app|foo.txt");
+
+    schedule(() {
+      graph.removeSources([new AssetId.parse("app|foo.txt")]);
+    });
+
+    expectNoAsset(graph, "app|foo.txt");
+  });
+
+  test("collapses redundant updates", () {
+    var provider = new MockProvider(["app|foo.blub"]);
+    var transformer = new RewriteTransformer("blub", "blab");
+    var graph = new AssetGraph(provider, [[transformer]]);
+
+    schedule(() {
+      // Make a bunch of synchronous update calls.
+      graph.updateSources([new AssetId.parse("app|foo.blub")]);
+      graph.updateSources([new AssetId.parse("app|foo.blub")]);
+      graph.updateSources([new AssetId.parse("app|foo.blub")]);
+      graph.updateSources([new AssetId.parse("app|foo.blub")]);
+    });
+
+    expectAsset(graph, "app|foo.blab", "foo.blab");
+
+    schedule(() {
+      expect(transformer.numRuns, equals(1));
+    });
+  });
+
+  test("a removal cancels out an update", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, [[]]);
+
+    schedule(() {
+      graph.updateSources([new AssetId.parse("app|foo.txt")]);
+      graph.removeSources([new AssetId.parse("app|foo.txt")]);
+    });
+
+    expectNoAsset(graph, "app|foo.txt");
+  });
+
+  test("an update cancels out a removal", () {
+    var provider = new MockProvider(["app|foo.txt"]);
+    var graph = new AssetGraph(provider, [[]]);
+
+    schedule(() {
+      graph.removeSources([new AssetId.parse("app|foo.txt")]);
+      graph.updateSources([new AssetId.parse("app|foo.txt")]);
+    });
+
+    expectAsset(graph, "app|foo.txt");
+  });
+
+  test("restarts a build if a source is updated while sources are loading", () {
+    var provider = new MockProvider(["app|foo.txt", "app|other.bar"]);
+    var transformer = new RewriteTransformer("txt", "out");
+    var graph = new AssetGraph(provider, [[transformer]]);
+
+    var numBuilds = 0;
+    var buildCompleter = new Completer();
+    graph.results.listen(wrapAsync((result) {
+      expect(result.error, isNull);
+      numBuilds++;
+
+      // There should be two builds, one for each update call.
+      if (numBuilds == 2) buildCompleter.complete();
+    }));
+
+    // Run the whole graph so all nodes are clean.
+    graph.updateSources([
+      new AssetId.parse("app|foo.txt"),
+      new AssetId.parse("app|other.bar")
+    ]);
+    expectAsset(graph, "app|foo.out", "foo.out");
+    expectAsset(graph, "app|other.bar");
+
+    schedule(() {
+      // Make the provider slow to load a source.
+      provider.wait();
+
+      // Update an asset that doesn't trigger any transformers.
+      graph.updateSources([new AssetId.parse("app|other.bar")]);
+    });
+
+    schedule(() {
+      // Now update an asset that does trigger a transformer.
+      graph.updateSources([new AssetId.parse("app|foo.txt")]);
+    });
+
+    schedule(() {
+      provider.complete();
+    });
+
+    schedule(() {
+      // Wait until the build has completed.
+      return buildCompleter.future;
+    });
+
+    schedule(() {
+      expect(transformer.numRuns, equals(2));
+    });
+  });
+}