track build outputs in a file for subsequent builds

.gitignore

@@ -4,6 +4,9 @@ build/
 .pub/
 pubspec.lock
 
+# Files generated by build runs
+.build
+
 # Generated by tool/create_all_test.dart
 tool/test_all.dart
 

lib/src/asset/cache.dart

@@ -97,4 +97,10 @@ class CachedAssetWriter extends AssetWriter {
     _cache.put(asset);
     return _writer.writeAsString(asset, encoding: encoding);
   }
+
+  @override
+  Future delete(AssetId id) {
+    _cache.remove(id);
+    return _writer.delete(id);
+  }
 }

lib/src/asset/file_based.dart

@@ -56,10 +56,8 @@ class FileBasedAssetReader implements AssetReader {
       var packageNode = packageGraph[inputSet.package];
       var packagePath = packageNode.location.toFilePath();
       for (var glob in inputSet.globs) {
-        var fileStream = glob
-            .list(followLinks: false, root: packagePath)
-            .where((e) =>
-                e is File && !ignoredDirs.contains(path.split(e.path)[1]));
+        var fileStream = glob.list(followLinks: false, root: packagePath).where(
+            (e) => e is File && !ignoredDirs.contains(path.split(e.path)[1]));
         await for (var entity in fileStream) {
           var id = _fileToAssetId(entity, packageNode);
           if (!seenAssets.add(id)) continue;
@@ -98,6 +96,16 @@ class FileBasedAssetWriter implements AssetWriter {
     await file.create(recursive: true);
     await file.writeAsString(asset.stringContents, encoding: encoding);
   }
+
+  @override
+  delete(AssetId id) async {
+    assert(id.package == packageGraph.root.name);
+
+    var file = _fileFor(id, packageGraph);
+    if (await file.exists()) {
+      await file.delete();
+    }
+  }
 }
 
 /// Returns a [File] for [id] given [packageGraph].

lib/src/asset/writer.dart

@@ -5,7 +5,10 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'asset.dart';
+import 'id.dart';
 
 abstract class AssetWriter {
   Future writeAsString(Asset asset, {Encoding encoding: UTF8});
+
+  Future delete(AssetId id);
 }

lib/src/generate/build.dart

@@ -2,6 +2,7 @@
 // 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.
 import 'dart:async';
+import 'dart:convert';
 
 import 'package:logging/logging.dart';
 import 'package:path/path.dart' as path;
@@ -49,17 +50,43 @@ Future<BuildResult> build(List<List<Phase>> phaseGroups,
       new CachedAssetReader(cache, new FileBasedAssetReader(packageGraph));
   writer ??=
       new CachedAssetWriter(cache, new FileBasedAssetWriter(packageGraph));
-  var result = runZoned(() {
-    return _runPhases(phaseGroups);
-  }, onError: (e, s) {
-    return new BuildResult(BuildStatus.Failure, BuildType.Full, [],
-        exception: e, stackTrace: s);
+
+  /// Asset containing previous build outputs.
+  var buildOuputsId =
+      new AssetId(packageGraph.root.name, '.build/build_outputs.json');
+
+  /// Run the build in a zone.
+  var result = await runZoned(() async {
+    try {
+      /// Read in previous build_outputs file, and delete them all.
+      if (await _reader.hasInput(buildOuputsId)) {
+        var previousOutputs =
+            JSON.decode(await _reader.readAsString(buildOuputsId));
+        await writer.delete(buildOuputsId);
+        await Future.wait(previousOutputs.map((output) {
+          return writer.delete(new AssetId.deserialize(output));
+        }));
+      }
+
+      /// Run a fresh build.
+      return _runPhases(phaseGroups);
+    } catch(e, s) {
+      return new BuildResult(BuildStatus.Failure, BuildType.Full, [],
+          exception: e, stackTrace: s);
+    }
   }, zoneValues: {
     _assetReaderKey: reader,
     _assetWriterKey: writer,
     _packageGraphKey: packageGraph,
   });
+
   await logListener.cancel();
+
+  // Write out the new build_outputs file.
+  var buildOutputsAsset = new Asset(buildOuputsId,
+      JSON.encode(result.outputs.map((output) => output.id.serialize()).toList()));
+  await writer.writeAsString(buildOutputsAsset);
+
   return result;
 }
 
@@ -91,6 +118,7 @@ Future<BuildResult> _runPhases(List<List<Phase>> phaseGroups) async {
         }
       }
     }
+
     /// Once the group is done, add all outputs so they can be used in the next
     /// phase.
     for (var output in groupOutputs) {

lib/src/transformer/transformer.dart

@@ -99,6 +99,7 @@ class _TransformAssetReader implements AssetReader {
       transform.readInputAsString(toBarbackAssetId(id), encoding: encoding);
 
   @override
+
   /// No way to implement this, but luckily its not necessary.
   Stream<build.AssetId> listAssetIds(_) => throw new UnimplementedError();
 }
@@ -114,6 +115,10 @@ class _TransformAssetWriter implements AssetWriter {
     transform.addOutput(toBarbackAsset(asset));
     return new Future.value(null);
   }
+
+  @override
+  Future delete(build.AssetId id) =>
+      throw new UnsupportedError('_TransformAssetWriter can\'t delete files.');
 }
 
 /// All the expected outputs for [id] given [builders].

test/asset/cache_test.dart

@@ -170,5 +170,12 @@ main() {
       await writer.writeAsString(a);
       expect(() => writer.writeAsString(a), throwsArgumentError);
     });
+
+    test('delete deletes from cache and writer', () async {
+      await writer.writeAsString(a);
+      await writer.delete(a.id);
+      expect(cache.get(a.id), isNull);
+      expect(childWriterAssets[a.id], isNull);
+    });
   });
 }

test/asset/file_based_test.dart

@@ -69,15 +69,15 @@ main() {
 
     test('can list files based on simple InputSets', () async {
       var inputSets = [
-        new InputSet('basic_pkg'),
-        new InputSet('a'),
+        new InputSet('basic_pkg', filePatterns: ['{lib,web}/**']),
+        new InputSet('a', filePatterns: ['lib/**']),
       ];
       expect(await reader.listAssetIds(inputSets).toList(), unorderedEquals([
         makeAssetId('basic_pkg|lib/hello.txt'),
         makeAssetId('basic_pkg|web/hello.txt'),
         makeAssetId('a|lib/a.txt'),
       ]));
-    }, skip: 'Fails for multiple reasons.');
+    });
 
     test('can list files based on InputSets with globs', () async {
       var inputSets = [
@@ -94,14 +94,16 @@ main() {
   group('FileBasedAssetWriter', () {
     final writer = new FileBasedAssetWriter(packageGraph);
 
-    test('can output files in the application package', () async {
+    test('can output and delete files in the application package', () async {
       var asset = makeAsset('basic_pkg|test_file.txt', 'test');
       await writer.writeAsString(asset);
       var id = asset.id;
       var file = new File('test/fixtures/${id.package}/${id.path}');
       expect(await file.exists(), isTrue);
       expect(await file.readAsString(), 'test');
-      await file.delete();
+
+      await writer.delete(asset.id);
+      expect(await file.exists(), isFalse);
     });
 
     test('can\'t output files in package dependencies', () async {
@@ -113,5 +115,15 @@ main() {
       var asset = makeAsset('foo|bar.txt');
       expect(writer.writeAsString(asset), throwsA(invalidOutputException));
     });
+
+    test('can\'t delete files in package dependencies', () async {
+      var id = makeAssetId('a|test.txt');
+      expect(writer.delete(id), throws);
+    });
+
+    test('can\'t delete files in arbitrary dependencies', () async {
+      var id = makeAssetId('foo|test.txt');
+      expect(writer.delete(id), throws);
+    });
   });
 }

test/common/in_memory_writer.dart

@@ -14,4 +14,8 @@ class InMemoryAssetWriter implements AssetWriter {
   Future writeAsString(Asset asset, {Encoding encoding: UTF8}) async {
     assets[asset.id] = asset.stringContents;
   }
+
+  Future delete(AssetId id) async {
+    assets.remove(id);
+  }
 }

test/common/stub_writer.dart

@@ -9,4 +9,6 @@ import 'package:build/build.dart';
 class StubAssetWriter implements AssetWriter {
   Future writeAsString(Asset asset, {Encoding encoding: UTF8}) =>
       new Future.value(null);
+
+  Future delete(AssetId id) => new Future.value(null);
 }

test/generate/build_test.dart

@@ -1,6 +1,8 @@
 // Copyright (c) 2016, 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.
+import 'dart:convert';
+
 import 'package:test/test.dart';
 
 import 'package:build/build.dart';
@@ -172,17 +174,52 @@ main() {
             'the BuildStep level.');
   });
 
+  test('tracks previous outputs in a build_outputs.json file', () async {
+    var phases = [
+      [
+        new Phase([new CopyBuilder()], [new InputSet('a')]),
+      ]
+    ];
+    final writer = new InMemoryAssetWriter();
+    await testPhases(phases, {'a|web/a.txt': 'a', 'a|lib/b.txt': 'b'},
+        outputs: {'a|web/a.txt.copy': 'a', 'a|lib/b.txt.copy': 'b'},
+        writer: writer);
+
+    var outputId = makeAssetId('a|.build/build_outputs.json');
+    expect(writer.assets, contains(outputId));
+    var outputs = JSON.decode(writer.assets[outputId]);
+    expect(
+        outputs,
+        unorderedEquals([
+          ['a', 'web/a.txt.copy'],
+          ['a', 'lib/b.txt.copy'],
+        ]));
+  });
+
   test('outputs from previous full builds shouldn\'t be inputs to later ones',
-      () {},
-      skip: 'Unimplemented: https://github.com/dart-lang/build/issues/34');
+      () async {
+    var phases = [
+      [
+        new Phase([new CopyBuilder()], [new InputSet('a')]),
+      ]
+    ];
+    final writer = new InMemoryAssetWriter();
+    var inputs = {'a|web/a.txt': 'a', 'a|lib/b.txt': 'b'};
+    var outputs = {'a|web/a.txt.copy': 'a', 'a|lib/b.txt.copy': 'b'};
+    // First run, nothing special.
+    await testPhases(phases, inputs, outputs: outputs, writer: writer);
+    // Second run, should have no extra outputs.
+    await testPhases(phases, inputs, outputs: outputs, writer: writer);
+  });
 }
 
 testPhases(List<List<Phase>> phases, Map<String, String> inputs,
     {Map<String, String> outputs,
     PackageGraph packageGraph,
     BuildStatus status: BuildStatus.Success,
-    exceptionMatcher}) async {
-  final writer = new InMemoryAssetWriter();
+    exceptionMatcher,
+    InMemoryAssetWriter writer}) async {
+  writer ??= new InMemoryAssetWriter();
   final actualAssets = writer.assets;
   final reader = new InMemoryAssetReader(actualAssets);
   inputs.forEach((serializedId, contents) {