Add a Flutter command that builds an APK using a local build of the engine

Example:
   cd flutter/examples/stocks
   flutter --engine-src-path /path/to/engine/src apk -o Stocks.apk -m apk/AndroidManifest.xml

packages/flutter_tools/lib/executable.dart

@@ -10,6 +10,7 @@ import 'package:logging/logging.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 import 'src/commands/analyze.dart';
+import 'src/commands/apk.dart';
 import 'src/commands/build.dart';
 import 'src/commands/cache.dart';
 import 'src/commands/daemon.dart';
@@ -48,6 +49,7 @@ Future main(List<String> args) async {
 
   FlutterCommandRunner runner = new FlutterCommandRunner()
     ..addCommand(new AnalyzeCommand())
+    ..addCommand(new ApkCommand())
     ..addCommand(new BuildCommand())
     ..addCommand(new CacheCommand())
     ..addCommand(new DaemonCommand())

packages/flutter_tools/lib/src/commands/apk.dart

+// Copyright 2015 The Chromium Authors. 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:io';
+
+import 'package:logging/logging.dart';
+import 'package:path/path.dart' as path;
+
+import '../build_configuration.dart';
+import 'build.dart';
+import 'flutter_command.dart';
+import 'start.dart';
+
+const String _kDefaultAndroidManifestPath = 'apk/AndroidManifest.xml';
+const String _kDefaultOutputPath = 'build/app.apk';
+const String _kKeystoreKeyName = "chromiumdebugkey";
+const String _kKeystorePassword = "chromium";
+
+final Logger _logging = new Logger('flutter_tools.apk');
+
+/// Create the ancestor directories of a file path if they do not already exist.
+void _ensureDirectoryExists(String filePath) {
+  Directory dir = new Directory(path.dirname(filePath));
+  if (!dir.existsSync())
+    dir.createSync(recursive: true);
+}
+
+/// Copies files into a new directory structure.
+class _AssetBuilder {
+  final Directory outDir;
+
+  Directory _assetDir;
+
+  _AssetBuilder(this.outDir, String assetDirName) {
+    _assetDir = new Directory('${outDir.path}/$assetDirName');
+    _assetDir.createSync(recursive:  true);
+  }
+
+  void add(File asset, String relativePath) {
+    String destPath = path.join(_assetDir.path, relativePath);
+    _ensureDirectoryExists(destPath);
+    asset.copySync(destPath);
+  }
+
+  Directory get directory => _assetDir;
+}
+
+/// Builds an APK package using Android SDK tools.
+class _ApkBuilder {
+  static const String _kAndroidPlatformVersion = '22';
+  static const String _kBuildToolsVersion = '22.0.1';
+
+  final String androidSdk;
+
+  File _androidJar;
+  File _aapt;
+  File _zipalign;
+  String _jarsigner;
+
+  _ApkBuilder(this.androidSdk) {
+    _androidJar = new File('$androidSdk/platforms/android-$_kAndroidPlatformVersion/android.jar');
+
+    String buildTools = '$androidSdk/build-tools/$_kBuildToolsVersion';
+    _aapt = new File('$buildTools/aapt');
+    _zipalign = new File('$buildTools/zipalign');
+    _jarsigner = 'jarsigner';
+  }
+
+  void package(File outputApk, File androidManifest, Directory assets, Directory artifacts) {
+    _run(_aapt.path, [
+      'package',
+      '-M', androidManifest.path,
+      '-A', assets.path,
+      '-I', _androidJar.path,
+      '-F', outputApk.path,
+      artifacts.path
+    ]);
+  }
+
+  void sign(File keystore, String keystorePassword, String keyName, File outputApk) {
+    _run(_jarsigner, [
+      '-keystore', keystore.path,
+      '-storepass', keystorePassword,
+      outputApk.path,
+      keyName,
+    ]);
+  }
+
+  void align(File unalignedApk, File outputApk) {
+    _run(_zipalign.path, ['-f', '4', unalignedApk.path, outputApk.path]);
+  }
+
+  void _run(String command, List<String> args, { String workingDirectory }) {
+    ProcessResult result = Process.runSync(
+        command, args, workingDirectory: workingDirectory
+    );
+    if (result.exitCode == 0)
+      return;
+    stdout.write(result.stdout);
+    stderr.write(result.stderr);
+  }
+}
+
+class ApkCommand extends FlutterCommand {
+  final String name = 'apk';
+  final String description = 'Build an Android APK package.';
+
+  ApkCommand() {
+    argParser.addOption('manifest',
+        abbr: 'm',
+        defaultsTo: _kDefaultAndroidManifestPath,
+        help: 'Android manifest XML file.');
+    argParser.addOption('output-file',
+        abbr: 'o',
+        defaultsTo: _kDefaultOutputPath,
+        help: 'Output APK file.');
+    argParser.addOption('target',
+        abbr: 't',
+        defaultsTo: '',
+        help: 'Target app path or filename used to build the FLX.');
+    argParser.addOption('flx',
+        abbr: 'f',
+        defaultsTo: '',
+        help: 'Path to the FLX file. If this is not provided, an FLX will be built.');
+  }
+
+  int _buildApk(BuildConfiguration config, String flxPath) {
+    File androidManifest = new File(argResults['manifest']);
+    File icuData = new File('${runner.enginePath}/third_party/icu/android/icudtl.dat');
+    File classesDex = new File('${config.buildDir}/gen/sky/shell/shell/classes.dex');
+    File libSkyShell = new File('${config.buildDir}/gen/sky/shell/shell/shell/libs/armeabi-v7a/libsky_shell.so');
+    File keystore = new File('${runner.enginePath}/build/android/ant/chromium-debug.keystore');
+
+    for (File f in [androidManifest, icuData, classesDex, libSkyShell, keystore]) {
+      if (!f.existsSync()) {
+        _logging.severe('Can not locate file: ${f.path}');
+        return 1;
+      }
+    }
+
+    Directory androidSdk = new Directory('${runner.enginePath}/third_party/android_tools/sdk');
+    if (!androidSdk.existsSync()) {
+      _logging.severe('Can not locate Android SDK: ${androidSdk.path}');
+      return 1;
+    }
+
+    Directory tempDir = Directory.systemTemp.createTempSync('flutter_tools');
+    try {      
+      _AssetBuilder assetBuilder = new _AssetBuilder(tempDir, 'assets');
+      assetBuilder.add(icuData, 'icudtl.dat');
+      assetBuilder.add(new File(flxPath), 'app.flx');
+
+      _AssetBuilder artifactBuilder = new _AssetBuilder(tempDir, 'artifacts');
+      artifactBuilder.add(classesDex, 'classes.dex');
+      artifactBuilder.add(libSkyShell, 'lib/armeabi-v7a/libsky_shell.so');
+
+      _ApkBuilder builder = new _ApkBuilder(androidSdk.path);
+      File unalignedApk = new File('${tempDir.path}/app.apk.unaligned');
+      builder.package(unalignedApk, androidManifest, assetBuilder.directory,
+                      artifactBuilder.directory);
+      builder.sign(keystore, _kKeystorePassword, _kKeystoreKeyName, unalignedApk);
+
+      File finalApk = new File(argResults['output-file']);
+      _ensureDirectoryExists(finalApk.path);
+      builder.align(unalignedApk, finalApk);
+
+      return 0;
+    } finally {
+      tempDir.deleteSync(recursive: true);
+    }
+  }
+
+  @override
+  Future<int> runInProject() async {
+    if (runner.enginePath == null) {
+      _logging.severe('Unable to locate the Flutter engine.  Use the --engine-src-path option.');
+      return 1;
+    }
+
+    BuildConfiguration config = buildConfigurations.firstWhere(
+        (BuildConfiguration bc) => bc.targetPlatform == TargetPlatform.android
+    );
+
+    String flxPath = argResults['flx'];
+
+    if (!flxPath.isEmpty) {
+      if (!FileSystemEntity.isFileSync(flxPath)) {
+        _logging.severe('FLX does not exist: $flxPath');
+        _logging.severe('(Omit the --flx option to build the FLX automatically)');
+        return 1;
+      }
+      return _buildApk(config, flxPath);
+    } else {
+      await downloadToolchain();
+
+      // Find the path to the main Dart file.
+      String mainPath = StartCommand.findMainDartFile(argResults['target']);
+
+      // Build the FLX.
+      BuildCommand builder = new BuildCommand();
+      builder.inheritFromParent(this);
+      int result;
+      await builder.buildInTempDir(
+          mainPath: mainPath,
+          onBundleAvailable: (String localBundlePath) {
+        result = _buildApk(config, localBundlePath);
+      }
+      );
+
+      return result;
+    }
+  }
+}

packages/flutter_tools/lib/src/commands/flutter_command_runner.dart

@@ -113,6 +113,16 @@ class FlutterCommandRunner extends CommandRunner {
   }
   List<BuildConfiguration> _buildConfigurations;
 
+  String get enginePath {
+    if (!_enginePathSet) {
+      _enginePath = _findEnginePath(_globalResults);
+      _enginePathSet = true;
+    }
+    return _enginePath;
+  }
+  String _enginePath;
+  bool _enginePathSet = false;
+
   ArgResults _globalResults;
 
   String get defaultFlutterRoot {
@@ -141,33 +151,31 @@ class FlutterCommandRunner extends CommandRunner {
     return super.runCommand(globalResults);
   }
 
-  List<BuildConfiguration> _createBuildConfigurations(ArgResults globalResults) {
-    String enginePath = globalResults['engine-src-path'] ?? Platform.environment[kFlutterEngineEnvironmentVariableName];
+  String _findEnginePath(ArgResults globalResults) {
+    String engineSourcePath = globalResults['engine-src-path'] ?? Platform.environment[kFlutterEngineEnvironmentVariableName];
     bool isDebug = globalResults['debug'];
     bool isRelease = globalResults['release'];
-    HostPlatform hostPlatform = getCurrentHostPlatform();
-    TargetPlatform hostPlatformAsTarget = getCurrentHostPlatformAsTarget();
 
-    if (enginePath == null && (isDebug || isRelease)) {
+    if (engineSourcePath == null && (isDebug || isRelease)) {
       if (ArtifactStore.isPackageRootValid) {
         Directory engineDir = new Directory(path.join(ArtifactStore.packageRoot, kFlutterEnginePackageName));
         try {
           String realEnginePath = engineDir.resolveSymbolicLinksSync();
-          enginePath = path.dirname(path.dirname(path.dirname(path.dirname(realEnginePath))));
-          bool dirExists = FileSystemEntity.isDirectorySync(path.join(enginePath, 'out'));
-          if (enginePath == '/' || enginePath.isEmpty || !dirExists)
-            enginePath = null;
+          engineSourcePath = path.dirname(path.dirname(path.dirname(path.dirname(realEnginePath))));
+          bool dirExists = FileSystemEntity.isDirectorySync(path.join(engineSourcePath, 'out'));
+          if (engineSourcePath == '/' || engineSourcePath.isEmpty || !dirExists)
+            engineSourcePath = null;
         } on FileSystemException { }
       }
-      if (enginePath == null) {
+      if (engineSourcePath == null) {
         String tryEnginePath(String enginePath) {
           if (FileSystemEntity.isDirectorySync(path.join(enginePath, 'out')))
             return enginePath;
           return null;
         }
-        enginePath = tryEnginePath(path.join(ArtifactStore.flutterRoot, '../engine/src'));
+        engineSourcePath = tryEnginePath(path.join(ArtifactStore.flutterRoot, '../engine/src'));
       }
-      if (enginePath == null) {
+      if (engineSourcePath == null) {
         stderr.writeln('Unable to detect local Flutter engine build directory.\n'
             'Either specify a dependency_override for the $kFlutterEnginePackageName package in your pubspec.yaml and\n'
             'ensure --package-root is set if necessary, or set the \$$kFlutterEngineEnvironmentVariableName environment variable, or\n'
@@ -176,6 +184,15 @@ class FlutterCommandRunner extends CommandRunner {
       }
     }
 
+    return engineSourcePath;
+  }
+
+  List<BuildConfiguration> _createBuildConfigurations(ArgResults globalResults) {
+    bool isDebug = globalResults['debug'];
+    bool isRelease = globalResults['release'];
+    HostPlatform hostPlatform = getCurrentHostPlatform();
+    TargetPlatform hostPlatformAsTarget = getCurrentHostPlatformAsTarget();
+
     List<BuildConfiguration> configs = <BuildConfiguration>[];
 
     if (enginePath == null) {

packages/flutter_tools/lib/src/commands/start.dart

@@ -37,6 +37,17 @@ class StartCommand extends FlutterCommand {
         help: 'Boot the iOS Simulator if it isn\'t already running.');
   }
 
+  /// Given the value of the --target option, return the path of the Dart file
+  /// where the app's main function should be.
+  static String findMainDartFile(String target) {
+    String targetPath = path.absolute(target);
+    if (FileSystemEntity.isDirectorySync(targetPath)) {
+      return path.join(targetPath, 'lib', 'main.dart');
+    } else {
+      return targetPath;
+    }
+  }
+
   @override
   Future<int> runInProject() async {
     await Future.wait([
@@ -63,10 +74,7 @@ class StartCommand extends FlutterCommand {
       if (package == null || !device.isConnected())
         continue;
       if (device is AndroidDevice) {
-        String target = path.absolute(argResults['target']);
-        String mainPath = target;
-        if (FileSystemEntity.isDirectorySync(target))
-          mainPath = path.join(target, 'lib', 'main.dart');
+        String mainPath = findMainDartFile(argResults['target']);
         if (!FileSystemEntity.isFileSync(mainPath)) {
           String message = 'Tried to run $mainPath, but that file does not exist.';
           if (!argResults.wasParsed('target'))