packages/flutter_tools/lib/src/base/build.dart - mirrors/flutter - Git at Google

 // Copyright 2017 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 'package:meta/meta.dart';

 import '../artifacts.dart';
 import '../build_info.dart';
 import '../bundle.dart';
 import '../compile.dart';
 import '../dart/package_map.dart';
 import '../globals.dart';
 import '../macos/xcode.dart';
 import '../project.dart';
 import '../reporting/reporting.dart';

 import 'context.dart';
 import 'file_system.dart';
 import 'process.dart';

 GenSnapshot get genSnapshot => context.get<GenSnapshot>();

 /// A snapshot build configuration.
 class SnapshotType {
   SnapshotType(this.platform, this.mode)
     : assert(mode != null);

   final TargetPlatform platform;
   final BuildMode mode;

   @override
   String toString() => '$platform $mode';
 }

 /// Interface to the gen_snapshot command-line tool.
 class GenSnapshot {
   const GenSnapshot();

   static String getSnapshotterPath(SnapshotType snapshotType) {
     return artifacts.getArtifactPath(
         Artifact.genSnapshot, platform: snapshotType.platform, mode: snapshotType.mode);
   }

   Future<int> run({
     @required SnapshotType snapshotType,
     DarwinArch darwinArch,
     Iterable<String> additionalArgs = const <String>[],
   }) {
     final List<String> args = <String>[
       '--causal_async_stacks',
       ...additionalArgs,
     ];

     String snapshotterPath = getSnapshotterPath(snapshotType);

     // iOS has a separate gen_snapshot for armv7 and arm64 in the same,
     // directory. So we need to select the right one.
     if (snapshotType.platform == TargetPlatform.ios) {
       snapshotterPath += '_' + getNameForDarwinArch(darwinArch);
     }

     StringConverter outputFilter;
     if (additionalArgs.contains('--strip')) {
       // Filter out gen_snapshot's warning message about stripping debug symbols
       // from ELF library snapshots.
       const String kStripWarning = 'Warning: Generating ELF library without DWARF debugging information.';
       outputFilter = (String line) => line != kStripWarning ? line : null;
     }

     return runCommandAndStreamOutput(<String>[snapshotterPath, ...args], mapFunction: outputFilter);
   }
 }

 class AOTSnapshotter {
   AOTSnapshotter({this.reportTimings = false});

   /// If true then AOTSnapshotter would report timings for individual building
   /// steps (Dart front-end parsing and snapshot generation) in a stable
   /// machine readable form. See [AOTSnapshotter._timedStep].
   final bool reportTimings;

   /// Builds an architecture-specific ahead-of-time compiled snapshot of the specified script.
   Future<int> build({
     @required TargetPlatform platform,
     @required BuildMode buildMode,
     @required String mainPath,
     @required String packagesPath,
     @required String outputPath,
     DarwinArch darwinArch,
     List<String> extraGenSnapshotOptions = const <String>[],
     @required bool bitcode,
   }) async {
     if (bitcode && platform != TargetPlatform.ios) {
       printError('Bitcode is only supported for iOS.');
       return 1;
     }

     if (!_isValidAotPlatform(platform, buildMode)) {
       printError('${getNameForTargetPlatform(platform)} does not support AOT compilation.');
       return 1;
     }
     // TODO(cbracken): replace IOSArch with TargetPlatform.ios_{armv7,arm64}.
     assert(platform != TargetPlatform.ios || darwinArch != null);

     final PackageMap packageMap = PackageMap(packagesPath);
     final String packageMapError = packageMap.checkValid();
     if (packageMapError != null) {
       printError(packageMapError);
       return 1;
     }

     final Directory outputDir = fs.directory(outputPath);
     outputDir.createSync(recursive: true);

     final String skyEnginePkg = _getPackagePath(packageMap, 'sky_engine');
     final String uiPath = fs.path.join(skyEnginePkg, 'lib', 'ui', 'ui.dart');
     final String vmServicePath = fs.path.join(skyEnginePkg, 'sdk_ext', 'vmservice_io.dart');

     final List<String> inputPaths = <String>[uiPath, vmServicePath, mainPath];
     final Set<String> outputPaths = <String>{};
     final List<String> genSnapshotArgs = <String>[
       '--deterministic',
     ];
     if (extraGenSnapshotOptions != null && extraGenSnapshotOptions.isNotEmpty) {
       printTrace('Extra gen_snapshot options: $extraGenSnapshotOptions');
       genSnapshotArgs.addAll(extraGenSnapshotOptions);
     }

     final String assembly = fs.path.join(outputDir.path, 'snapshot_assembly.S');
     if (platform == TargetPlatform.ios || platform == TargetPlatform.darwin_x64) {
       // Assembly AOT snapshot.
       outputPaths.add(assembly);
       genSnapshotArgs.add('--snapshot_kind=app-aot-assembly');
       genSnapshotArgs.add('--assembly=$assembly');
     } else {
       final String aotSharedLibrary = fs.path.join(outputDir.path, 'app.so');
       outputPaths.add(aotSharedLibrary);
       genSnapshotArgs.add('--snapshot_kind=app-aot-elf');
       genSnapshotArgs.add('--elf=$aotSharedLibrary');
       genSnapshotArgs.add('--strip');
     }

     if (platform == TargetPlatform.android_arm || darwinArch == DarwinArch.armv7) {
       // Use softfp for Android armv7 devices.
       // This is the default for armv7 iOS builds, but harmless to set.
       // TODO(cbracken): eliminate this when we fix https://github.com/flutter/flutter/issues/17489
       genSnapshotArgs.add('--no-sim-use-hardfp');

       // Not supported by the Pixel in 32-bit mode.
       genSnapshotArgs.add('--no-use-integer-division');
     }

     genSnapshotArgs.add(mainPath);

     // Verify that all required inputs exist.
     final Iterable<String> missingInputs = inputPaths.where((String p) => !fs.isFileSync(p));
     if (missingInputs.isNotEmpty) {
       printError('Missing input files: $missingInputs from $inputPaths');
       return 1;
     }

     final SnapshotType snapshotType = SnapshotType(platform, buildMode);
     final int genSnapshotExitCode =
       await _timedStep('snapshot(CompileTime)', 'aot-snapshot',
         () => genSnapshot.run(
       snapshotType: snapshotType,
       additionalArgs: genSnapshotArgs,
       darwinArch: darwinArch,
     ));
     if (genSnapshotExitCode != 0) {
       printError('Dart snapshot generator failed with exit code $genSnapshotExitCode');
       return genSnapshotExitCode;
     }

     // TODO(dnfield): This should be removed when https://github.com/dart-lang/sdk/issues/37560
     // is resolved.
     // The DWARF section confuses Xcode tooling, so this strips it. Ideally,
     // gen_snapshot would provide an argument to do this automatically.
     if (platform == TargetPlatform.ios && bitcode) {
       final IOSink sink = fs.file('$assembly.bitcode').openWrite();
       for (String line in await fs.file(assembly).readAsLines()) {
         if (line.startsWith('.section __DWARF')) {
           break;
         }
         sink.writeln(line);
       }
       await sink.close();
     }

     // Write path to gen_snapshot, since snapshots have to be re-generated when we roll
     // the Dart SDK.
     final String genSnapshotPath = GenSnapshot.getSnapshotterPath(snapshotType);
     await outputDir.childFile('gen_snapshot.d').writeAsString('gen_snapshot.d: $genSnapshotPath\n');

     // On iOS, we use Xcode to compile the snapshot into a dynamic library that the
     // end-developer can link into their app.
     if (platform == TargetPlatform.ios || platform == TargetPlatform.darwin_x64) {
       final RunResult result = await _buildFramework(
         appleArch: darwinArch,
         assemblyPath: bitcode ? '$assembly.bitcode' : assembly,
         outputPath: outputDir.path,
         bitcode: bitcode,
       );
       if (result.exitCode != 0)
         return result.exitCode;
     }
     return 0;
   }

   /// Builds an iOS or macOS framework at [outputPath]/App.framework from the assembly
   /// source at [assemblyPath].
   Future<RunResult> _buildFramework({
     @required DarwinArch appleArch,
     @required String assemblyPath,
     @required String outputPath,
     @required bool bitcode,
   }) async {
     final String targetArch = getNameForDarwinArch(appleArch);
     printStatus('Building App.framework for $targetArch...');
     final List<String> commonBuildOptions = <String>[
       '-arch', targetArch,
       if (appleArch == DarwinArch.arm64 || appleArch == DarwinArch.armv7)
         '-miphoneos-version-min=8.0',
     ];

     final String assemblyO = fs.path.join(outputPath, 'snapshot_assembly.o');
     final RunResult compileResult = await xcode.cc(<String>[
       ...commonBuildOptions,
       '-c',
       assemblyPath,
       '-o',
       assemblyO,
       if (bitcode) '-fembed-bitcode',
     ]);
     if (compileResult.exitCode != 0) {
       printError('Failed to compile AOT snapshot. Compiler terminated with exit code ${compileResult.exitCode}');
       return compileResult;
     }

     final String frameworkDir = fs.path.join(outputPath, 'App.framework');
     fs.directory(frameworkDir).createSync(recursive: true);
     final String appLib = fs.path.join(frameworkDir, 'App');
     final List<String> linkArgs = <String>[
       ...commonBuildOptions,
       '-dynamiclib',
       '-Xlinker', '-rpath', '-Xlinker', '@executable_path/Frameworks',
       '-Xlinker', '-rpath', '-Xlinker', '@loader_path/Frameworks',
       '-install_name', '@rpath/App.framework/App',
       if (bitcode) '-fembed-bitcode',
       '-o', appLib,
       assemblyO,
     ];
     final RunResult linkResult = await xcode.clang(linkArgs);
     if (linkResult.exitCode != 0) {
       printError('Failed to link AOT snapshot. Linker terminated with exit code ${compileResult.exitCode}');
       return linkResult;
     }
     // See https://github.com/flutter/flutter/issues/22560
     // These have to be placed in a .noindex folder to prevent Xcode from
     // using Spotlight to find them and potentially attach the wrong ones.
     final RunResult dsymResult = await xcode.dsymutil(<String>[
       appLib,
       '-o', fs.path.join(outputPath, 'App.framework.dSYM.noindex'),
     ]);
     if (dsymResult.exitCode != 0) {
       printError('Failed to extract dSYM out of dynamic lib');
     }
     return dsymResult;
   }

   /// Compiles a Dart file to kernel.
   ///
   /// Returns the output kernel file path, or null on failure.
   Future<String> compileKernel({
     @required TargetPlatform platform,
     @required BuildMode buildMode,
     @required String mainPath,
     @required String packagesPath,
     @required String outputPath,
     @required bool trackWidgetCreation,
     List<String> extraFrontEndOptions = const <String>[],
   }) async {
     final FlutterProject flutterProject = FlutterProject.current();
     final Directory outputDir = fs.directory(outputPath);
     outputDir.createSync(recursive: true);

     printTrace('Compiling Dart to kernel: $mainPath');

     if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
       printTrace('Extra front-end options: $extraFrontEndOptions');

     final String depfilePath = fs.path.join(outputPath, 'kernel_compile.d');
     final KernelCompiler kernelCompiler = await kernelCompilerFactory.create(flutterProject);
     final CompilerOutput compilerOutput =
       await _timedStep('frontend(CompileTime)', 'aot-kernel',
         () => kernelCompiler.compile(
       sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath, mode: buildMode),
       mainPath: mainPath,
       packagesPath: packagesPath,
       outputFilePath: getKernelPathForTransformerOptions(
         fs.path.join(outputPath, 'app.dill'),
         trackWidgetCreation: trackWidgetCreation,
       ),
       depFilePath: depfilePath,
       extraFrontEndOptions: extraFrontEndOptions,
       linkPlatformKernelIn: true,
       aot: true,
       trackWidgetCreation: trackWidgetCreation,
       targetProductVm: buildMode == BuildMode.release,
     ));

     // Write path to frontend_server, since things need to be re-generated when that changes.
     final String frontendPath = artifacts.getArtifactPath(Artifact.frontendServerSnapshotForEngineDartSdk);
     await fs.directory(outputPath).childFile('frontend_server.d').writeAsString('frontend_server.d: $frontendPath\n');

     return compilerOutput?.outputFilename;
   }

   bool _isValidAotPlatform(TargetPlatform platform, BuildMode buildMode) {
     if (buildMode == BuildMode.debug)
       return false;
     return const <TargetPlatform>[
       TargetPlatform.android_arm,
       TargetPlatform.android_arm64,
       TargetPlatform.ios,
       TargetPlatform.darwin_x64,
     ].contains(platform);
   }

   String _getPackagePath(PackageMap packageMap, String package) {
     return fs.path.dirname(fs.path.fromUri(packageMap.map[package]));
   }

   /// This method is used to measure duration of an action and emit it into
   /// verbose output from flutter_tool for other tools (e.g. benchmark runner)
   /// to find.
   /// Important: external performance tracking tools expect format of this
   /// output to be stable.
   Future<T> _timedStep<T>(String marker, String analyticsVar, FutureOr<T> Function() action) async {
     final Stopwatch sw = Stopwatch()..start();
     final T value = await action();
     if (reportTimings) {
       printStatus('$marker: ${sw.elapsedMilliseconds} ms.');
     }
     flutterUsage.sendTiming('build', analyticsVar, Duration(milliseconds: sw.elapsedMilliseconds));
     return value;
   }
 }
	// Copyright 2017 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 'package:meta/meta.dart';

	import '../artifacts.dart';
	import '../build_info.dart';
	import '../bundle.dart';
	import '../compile.dart';
	import '../dart/package_map.dart';
	import '../globals.dart';
	import '../macos/xcode.dart';
	import '../project.dart';
	import '../reporting/reporting.dart';

	import 'context.dart';
	import 'file_system.dart';
	import 'process.dart';

	GenSnapshot get genSnapshot => context.get<GenSnapshot>();

	/// A snapshot build configuration.
	class SnapshotType {
	SnapshotType(this.platform, this.mode)
	: assert(mode != null);

	final TargetPlatform platform;
	final BuildMode mode;

	@override
	String toString() => '$platform $mode';
	}

	/// Interface to the gen_snapshot command-line tool.
	class GenSnapshot {
	const GenSnapshot();

	static String getSnapshotterPath(SnapshotType snapshotType) {
	return artifacts.getArtifactPath(
	Artifact.genSnapshot, platform: snapshotType.platform, mode: snapshotType.mode);
	}

	Future<int> run({
	@required SnapshotType snapshotType,
	DarwinArch darwinArch,
	Iterable<String> additionalArgs = const <String>[],
	}) {
	final List<String> args = <String>[
	'--causal_async_stacks',
	...additionalArgs,
	];

	String snapshotterPath = getSnapshotterPath(snapshotType);

	// iOS has a separate gen_snapshot for armv7 and arm64 in the same,
	// directory. So we need to select the right one.
	if (snapshotType.platform == TargetPlatform.ios) {
	snapshotterPath += '_' + getNameForDarwinArch(darwinArch);
	}

	StringConverter outputFilter;
	if (additionalArgs.contains('--strip')) {
	// Filter out gen_snapshot's warning message about stripping debug symbols
	// from ELF library snapshots.
	const String kStripWarning = 'Warning: Generating ELF library without DWARF debugging information.';
	outputFilter = (String line) => line != kStripWarning ? line : null;
	}

	return runCommandAndStreamOutput(<String>[snapshotterPath, ...args], mapFunction: outputFilter);
	}
	}

	class AOTSnapshotter {
	AOTSnapshotter({this.reportTimings = false});

	/// If true then AOTSnapshotter would report timings for individual building
	/// steps (Dart front-end parsing and snapshot generation) in a stable
	/// machine readable form. See [AOTSnapshotter._timedStep].
	final bool reportTimings;

	/// Builds an architecture-specific ahead-of-time compiled snapshot of the specified script.
	Future<int> build({
	@required TargetPlatform platform,
	@required BuildMode buildMode,
	@required String mainPath,
	@required String packagesPath,
	@required String outputPath,
	DarwinArch darwinArch,
	List<String> extraGenSnapshotOptions = const <String>[],
	@required bool bitcode,
	}) async {
	if (bitcode && platform != TargetPlatform.ios) {
	printError('Bitcode is only supported for iOS.');
	return 1;
	}

	if (!_isValidAotPlatform(platform, buildMode)) {
	printError('${getNameForTargetPlatform(platform)} does not support AOT compilation.');
	return 1;
	}
	// TODO(cbracken): replace IOSArch with TargetPlatform.ios_{armv7,arm64}.
	assert(platform != TargetPlatform.ios \|\| darwinArch != null);

	final PackageMap packageMap = PackageMap(packagesPath);
	final String packageMapError = packageMap.checkValid();
	if (packageMapError != null) {
	printError(packageMapError);
	return 1;
	}

	final Directory outputDir = fs.directory(outputPath);
	outputDir.createSync(recursive: true);

	final String skyEnginePkg = _getPackagePath(packageMap, 'sky_engine');
	final String uiPath = fs.path.join(skyEnginePkg, 'lib', 'ui', 'ui.dart');
	final String vmServicePath = fs.path.join(skyEnginePkg, 'sdk_ext', 'vmservice_io.dart');

	final List<String> inputPaths = <String>[uiPath, vmServicePath, mainPath];
	final Set<String> outputPaths = <String>{};
	final List<String> genSnapshotArgs = <String>[
	'--deterministic',
	];
	if (extraGenSnapshotOptions != null && extraGenSnapshotOptions.isNotEmpty) {
	printTrace('Extra gen_snapshot options: $extraGenSnapshotOptions');
	genSnapshotArgs.addAll(extraGenSnapshotOptions);
	}

	final String assembly = fs.path.join(outputDir.path, 'snapshot_assembly.S');
	if (platform == TargetPlatform.ios \|\| platform == TargetPlatform.darwin_x64) {
	// Assembly AOT snapshot.
	outputPaths.add(assembly);
	genSnapshotArgs.add('--snapshot_kind=app-aot-assembly');
	genSnapshotArgs.add('--assembly=$assembly');
	} else {
	final String aotSharedLibrary = fs.path.join(outputDir.path, 'app.so');
	outputPaths.add(aotSharedLibrary);
	genSnapshotArgs.add('--snapshot_kind=app-aot-elf');
	genSnapshotArgs.add('--elf=$aotSharedLibrary');
	genSnapshotArgs.add('--strip');
	}

	if (platform == TargetPlatform.android_arm \|\| darwinArch == DarwinArch.armv7) {
	// Use softfp for Android armv7 devices.
	// This is the default for armv7 iOS builds, but harmless to set.
	// TODO(cbracken): eliminate this when we fix https://github.com/flutter/flutter/issues/17489
	genSnapshotArgs.add('--no-sim-use-hardfp');

	// Not supported by the Pixel in 32-bit mode.
	genSnapshotArgs.add('--no-use-integer-division');
	}

	genSnapshotArgs.add(mainPath);

	// Verify that all required inputs exist.
	final Iterable<String> missingInputs = inputPaths.where((String p) => !fs.isFileSync(p));
	if (missingInputs.isNotEmpty) {
	printError('Missing input files: $missingInputs from $inputPaths');
	return 1;
	}

	final SnapshotType snapshotType = SnapshotType(platform, buildMode);
	final int genSnapshotExitCode =
	await _timedStep('snapshot(CompileTime)', 'aot-snapshot',
	() => genSnapshot.run(
	snapshotType: snapshotType,
	additionalArgs: genSnapshotArgs,
	darwinArch: darwinArch,
	));
	if (genSnapshotExitCode != 0) {
	printError('Dart snapshot generator failed with exit code $genSnapshotExitCode');
	return genSnapshotExitCode;
	}

	// TODO(dnfield): This should be removed when https://github.com/dart-lang/sdk/issues/37560
	// is resolved.
	// The DWARF section confuses Xcode tooling, so this strips it. Ideally,
	// gen_snapshot would provide an argument to do this automatically.
	if (platform == TargetPlatform.ios && bitcode) {
	final IOSink sink = fs.file('$assembly.bitcode').openWrite();
	for (String line in await fs.file(assembly).readAsLines()) {
	if (line.startsWith('.section __DWARF')) {
	break;
	}
	sink.writeln(line);
	}
	await sink.close();
	}

	// Write path to gen_snapshot, since snapshots have to be re-generated when we roll
	// the Dart SDK.
	final String genSnapshotPath = GenSnapshot.getSnapshotterPath(snapshotType);
	await outputDir.childFile('gen_snapshot.d').writeAsString('gen_snapshot.d: $genSnapshotPath\n');

	// On iOS, we use Xcode to compile the snapshot into a dynamic library that the
	// end-developer can link into their app.
	if (platform == TargetPlatform.ios \|\| platform == TargetPlatform.darwin_x64) {
	final RunResult result = await _buildFramework(
	appleArch: darwinArch,
	assemblyPath: bitcode ? '$assembly.bitcode' : assembly,
	outputPath: outputDir.path,
	bitcode: bitcode,
	);
	if (result.exitCode != 0)
	return result.exitCode;
	}
	return 0;
	}

	/// Builds an iOS or macOS framework at [outputPath]/App.framework from the assembly
	/// source at [assemblyPath].
	Future<RunResult> _buildFramework({
	@required DarwinArch appleArch,
	@required String assemblyPath,
	@required String outputPath,
	@required bool bitcode,
	}) async {
	final String targetArch = getNameForDarwinArch(appleArch);
	printStatus('Building App.framework for $targetArch...');
	final List<String> commonBuildOptions = <String>[
	'-arch', targetArch,
	if (appleArch == DarwinArch.arm64 \|\| appleArch == DarwinArch.armv7)
	'-miphoneos-version-min=8.0',
	];

	final String assemblyO = fs.path.join(outputPath, 'snapshot_assembly.o');
	final RunResult compileResult = await xcode.cc(<String>[
	...commonBuildOptions,
	'-c',
	assemblyPath,
	'-o',
	assemblyO,
	if (bitcode) '-fembed-bitcode',
	]);
	if (compileResult.exitCode != 0) {
	printError('Failed to compile AOT snapshot. Compiler terminated with exit code ${compileResult.exitCode}');
	return compileResult;
	}

	final String frameworkDir = fs.path.join(outputPath, 'App.framework');
	fs.directory(frameworkDir).createSync(recursive: true);
	final String appLib = fs.path.join(frameworkDir, 'App');
	final List<String> linkArgs = <String>[
	...commonBuildOptions,
	'-dynamiclib',
	'-Xlinker', '-rpath', '-Xlinker', '@executable_path/Frameworks',
	'-Xlinker', '-rpath', '-Xlinker', '@loader_path/Frameworks',
	'-install_name', '@rpath/App.framework/App',
	if (bitcode) '-fembed-bitcode',
	'-o', appLib,
	assemblyO,
	];
	final RunResult linkResult = await xcode.clang(linkArgs);
	if (linkResult.exitCode != 0) {
	printError('Failed to link AOT snapshot. Linker terminated with exit code ${compileResult.exitCode}');
	return linkResult;
	}
	// See https://github.com/flutter/flutter/issues/22560
	// These have to be placed in a .noindex folder to prevent Xcode from
	// using Spotlight to find them and potentially attach the wrong ones.
	final RunResult dsymResult = await xcode.dsymutil(<String>[
	appLib,
	'-o', fs.path.join(outputPath, 'App.framework.dSYM.noindex'),
	]);
	if (dsymResult.exitCode != 0) {
	printError('Failed to extract dSYM out of dynamic lib');
	}
	return dsymResult;
	}

	/// Compiles a Dart file to kernel.
	///
	/// Returns the output kernel file path, or null on failure.
	Future<String> compileKernel({
	@required TargetPlatform platform,
	@required BuildMode buildMode,
	@required String mainPath,
	@required String packagesPath,
	@required String outputPath,
	@required bool trackWidgetCreation,
	List<String> extraFrontEndOptions = const <String>[],
	}) async {
	final FlutterProject flutterProject = FlutterProject.current();
	final Directory outputDir = fs.directory(outputPath);
	outputDir.createSync(recursive: true);

	printTrace('Compiling Dart to kernel: $mainPath');

	if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
	printTrace('Extra front-end options: $extraFrontEndOptions');

	final String depfilePath = fs.path.join(outputPath, 'kernel_compile.d');
	final KernelCompiler kernelCompiler = await kernelCompilerFactory.create(flutterProject);
	final CompilerOutput compilerOutput =
	await _timedStep('frontend(CompileTime)', 'aot-kernel',
	() => kernelCompiler.compile(
	sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath, mode: buildMode),
	mainPath: mainPath,
	packagesPath: packagesPath,
	outputFilePath: getKernelPathForTransformerOptions(
	fs.path.join(outputPath, 'app.dill'),
	trackWidgetCreation: trackWidgetCreation,
	),
	depFilePath: depfilePath,
	extraFrontEndOptions: extraFrontEndOptions,
	linkPlatformKernelIn: true,
	aot: true,
	trackWidgetCreation: trackWidgetCreation,
	targetProductVm: buildMode == BuildMode.release,
	));

	// Write path to frontend_server, since things need to be re-generated when that changes.
	final String frontendPath = artifacts.getArtifactPath(Artifact.frontendServerSnapshotForEngineDartSdk);
	await fs.directory(outputPath).childFile('frontend_server.d').writeAsString('frontend_server.d: $frontendPath\n');

	return compilerOutput?.outputFilename;
	}

	bool _isValidAotPlatform(TargetPlatform platform, BuildMode buildMode) {
	if (buildMode == BuildMode.debug)
	return false;
	return const <TargetPlatform>[
	TargetPlatform.android_arm,
	TargetPlatform.android_arm64,
	TargetPlatform.ios,
	TargetPlatform.darwin_x64,
	].contains(platform);
	}

	String _getPackagePath(PackageMap packageMap, String package) {
	return fs.path.dirname(fs.path.fromUri(packageMap.map[package]));
	}

	/// This method is used to measure duration of an action and emit it into
	/// verbose output from flutter_tool for other tools (e.g. benchmark runner)
	/// to find.
	/// Important: external performance tracking tools expect format of this
	/// output to be stable.
	Future<T> _timedStep<T>(String marker, String analyticsVar, FutureOr<T> Function() action) async {
	final Stopwatch sw = Stopwatch()..start();
	final T value = await action();
	if (reportTimings) {
	printStatus('$marker: ${sw.elapsedMilliseconds} ms.');
	}
	flutterUsage.sendTiming('build', analyticsVar, Duration(milliseconds: sw.elapsedMilliseconds));
	return value;
	}
	}