Teach Linux to use local engine (#31631)

packages/flutter_tools/bin/tool_backend.dart

+// Copyright 2019 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:io'; // ignore: dart_io_import.
+import 'package:path/path.dart' as path; // ignore: package_path_import.
+
+/// Executes the required flutter tasks for a linux build.
+Future<void> main(List<String> arguments) async {
+  final String targetPlatform = arguments[0];
+  final String buildMode = arguments[1];
+
+  final String projectDirectory = Platform.environment['PROJECT_DIR'];
+  final bool verbose = Platform.environment['VERBOSE_SCRIPT_LOGGING'] != null;
+  final bool trackWidgetCreation = Platform.environment['TRACK_WIDGET_CREATION'] != null;
+  final String flutterTarget = Platform.environment['FLUTTER_TARGET'] ?? 'lib/main.dart';
+  final String flutterEngine = Platform.environment['FLUTTER_ENGINE'];
+  final String localEngine = Platform.environment['LOCAL_ENGINE'];
+  final String flutterRoot = Platform.environment['FLUTTER_ROOT'];
+
+  Directory.current = projectDirectory;
+
+  if (localEngine != null && !localEngine.contains(buildMode)) {
+    stderr.write('''
+ERROR: Requested build with Flutter local engine at '$localEngine'
+This engine is not compatible with FLUTTER_BUILD_MODE: '$buildMode'.
+You can fix this by updating the LOCAL_ENGINE environment variable, or
+by running:
+  flutter build linux --local-engine=host_$buildMode
+or
+  flutter build linux --local-engine=host_${buildMode}_unopt
+========================================================================
+''');
+    exit(1);
+  }
+
+  String cacheDirectory;
+  switch (targetPlatform) {
+    case 'linux-x64':
+      cacheDirectory = 'linux/flutter';
+      break;
+    default:
+      stderr.write('Unsupported target platform $targetPlatform');
+      exit(1);
+  }
+
+  final String flutterExecutable = path.join(
+      flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');
+  final ProcessResult unpackResult = await Process.run(
+    flutterExecutable,
+    <String>[
+      '--suppress-analytics',
+      if (verbose) '--verbose',
+      'unpack',
+      '--target-platform=$targetPlatform',
+      '--cache-dir=$cacheDirectory',
+      if (flutterEngine != null) '--local-engine-src-path=$flutterEngine',
+      if (localEngine != null) '--local-engine=$localEngine',
+    ]);
+  if (unpackResult.exitCode != 0) {
+    stderr.write(unpackResult.stderr);
+    exit(1);
+  }
+  final ProcessResult buildResult = await Process.run(
+    flutterExecutable,
+    <String>[
+      '--suppress-analytics',
+      if (verbose) '--verbose',
+      'build',
+      'bundle',
+      '--target=$flutterTarget',
+      '--target-platform=$targetPlatform',
+      if (trackWidgetCreation) '--track-widget-creation',
+      if (flutterEngine != null) '--local-engine-src-path=$flutterEngine',
+      if (localEngine != null) '--local-engine=$localEngine',
+    ]);
+  if (buildResult.exitCode != 0) {
+    stderr.write(buildResult.stderr);
+    exit(1);
+  }
+  exit(0);
+}

packages/flutter_tools/bin/tool_backend.sh

+#!/usr/bin/env bash
+# Copyright 2018 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.
+
+readonly flutter_bin_dir="${FLUTTER_ROOT}/bin"
+readonly dart_bin_dir="${flutter_bin_dir}/cache/dart-sdk/bin"
+
+exec "${dart_bin_dir}/dart" "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.dart" "${@:1}"

packages/flutter_tools/lib/executable.dart

@@ -37,6 +37,7 @@ import 'src/commands/screenshot.dart';
 import 'src/commands/shell_completion.dart';
 import 'src/commands/test.dart';
 import 'src/commands/train.dart';
+import 'src/commands/unpack.dart';
 import 'src/commands/update_packages.dart';
 import 'src/commands/upgrade.dart';
 import 'src/commands/version.dart';
@@ -82,6 +83,7 @@ Future<void> main(List<String> args) async {
     ShellCompletionCommand(),
     TestCommand(verboseHelp: verboseHelp),
     TrainingCommand(),
+    UnpackCommand(),
     UpdatePackagesCommand(hidden: !verboseHelp),
     UpgradeCommand(),
     VersionCommand(),

packages/flutter_tools/lib/src/linux/build_linux.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import '../artifacts.dart';
 import '../base/common.dart';
+import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/logger.dart';
 import '../base/process_manager.dart';
@@ -13,21 +15,32 @@ import '../globals.dart';
 import '../project.dart';
 
 /// Builds the Linux project through the Makefile.
-Future<void> buildLinux(LinuxProject linuxProject, BuildInfo buildInfo) async {
-  /// Cache flutter root in linux directory.
-  linuxProject.editableHostAppDirectory.childFile('.generated_flutter_root')
+Future<void> buildLinux(LinuxProject linuxProject, BuildInfo buildInfo, {String target = 'lib/main.dart'}) async {
+  final String buildFlag = buildInfo?.isDebug == true ? 'debug' : 'release';
+  final StringBuffer buffer = StringBuffer('''
+# Generated code do not commit.
+export FLUTTER_ROOT=${Cache.flutterRoot}
+export BUILD=$buildFlag
+export TRACK_WIDGET_CREATION=${buildInfo?.trackWidgetCreation == true}
+export FLUTTER_TARGET=$target
+export PROJECT_DIR=${linuxProject.project.directory.path}
+''');
+  if (artifacts is LocalEngineArtifacts) {
+    final LocalEngineArtifacts localEngineArtifacts = artifacts;
+    final String engineOutPath = localEngineArtifacts.engineOutPath;
+    buffer.writeln('export FLUTTER_ENGINE=${fs.path.dirname(fs.path.dirname(engineOutPath))}');
+    buffer.writeln('export LOCAL_ENGINE=${fs.path.basename(engineOutPath)}');
+  }
+
+  /// Cache flutter configuration files in the linux directory.
+  linuxProject.cacheDirectory.childFile('generated_config')
     ..createSync(recursive: true)
-    ..writeAsStringSync(Cache.flutterRoot);
+    ..writeAsStringSync(buffer.toString());
 
-  final String buildFlag = buildInfo?.isDebug == true ? 'debug' : 'release';
-  final String bundleFlags = buildInfo?.trackWidgetCreation == true ? '--track-widget-creation' : '';
   final Process process = await processManager.start(<String>[
     'make',
     '-C',
     linuxProject.editableHostAppDirectory.path,
-    'BUILD=$buildFlag',
-    'FLUTTER_ROOT=${Cache.flutterRoot}',
-    'FLUTTER_BUNDLE_FLAGS=$bundleFlags',
   ], runInShell: true);
   final Status status = logger.startProgress(
     'Building Linux application...',

packages/flutter_tools/lib/src/project.dart

@@ -599,6 +599,8 @@ class LinuxProject {
 
   Directory get editableHostAppDirectory => project.directory.childDirectory('linux');
 
+  Directory get cacheDirectory => editableHostAppDirectory.childDirectory('flutter');
+
   bool existsSync() => editableHostAppDirectory.existsSync();
 
   /// The Linux project makefile.

packages/flutter_tools/pubspec.yaml

@@ -5,7 +5,7 @@ author: Flutter Authors <flutter-dev@googlegroups.com>
 
 environment:
   # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
-  sdk: ">=2.2.0 <3.0.0"
+  sdk: ">=2.2.2 <3.0.0"
 
 dependencies:
   # To update these, use "flutter update-packages --force-upgrade".

packages/flutter_tools/test/commands/build_linux_test.dart

@@ -21,7 +21,6 @@ import '../src/mocks.dart';
 void main() {
   Cache.disableLocking();
   final MockProcessManager mockProcessManager = MockProcessManager();
-  final MemoryFileSystem memoryFilesystem = MemoryFileSystem();
   final MockProcess mockProcess = MockProcess();
   final MockPlatform linuxPlatform = MockPlatform();
   final MockPlatform notLinuxPlatform = MockPlatform();
@@ -46,7 +45,7 @@ void main() {
     ), throwsA(isInstanceOf<ToolExit>()));
   }, overrides: <Type, Generator>{
     Platform: () => linuxPlatform,
-    FileSystem: () => memoryFilesystem,
+    FileSystem: () => MemoryFileSystem(),
   });
 
   testUsingContext('Linux build fails on non-linux platform', () async {
@@ -61,22 +60,20 @@ void main() {
     ), throwsA(isInstanceOf<ToolExit>()));
   }, overrides: <Type, Generator>{
     Platform: () => notLinuxPlatform,
-    FileSystem: () => memoryFilesystem,
+    FileSystem: () => MemoryFileSystem(),
   });
 
-  testUsingContext('Linux build invokes make', () async {
+  testUsingContext('Linux build invokes make and writes temporary files', () async {
     final BuildCommand command = BuildCommand();
     applyMocksToCommand(command);
     fs.file('linux/build.sh').createSync(recursive: true);
     fs.file('pubspec.yaml').createSync();
     fs.file('.packages').createSync();
+
     when(mockProcessManager.start(<String>[
       'make',
       '-C',
       '/linux',
-      'BUILD=release',
-      'FLUTTER_ROOT=/',
-      'FLUTTER_BUNDLE_FLAGS=',
     ], runInShell: true)).thenAnswer((Invocation invocation) async {
       return mockProcess;
     });
@@ -84,8 +81,9 @@ void main() {
     await createTestCommandRunner(command).run(
       const <String>['build', 'linux']
     );
+    expect(fs.file('linux/flutter/generated_config').existsSync(), true);
   }, overrides: <Type, Generator>{
-    FileSystem: () => memoryFilesystem,
+    FileSystem: () => MemoryFileSystem(),
     ProcessManager: () => mockProcessManager,
     Platform: () => linuxPlatform,
   });