utils/bazel/kernel_worker.dart - sdk.git - Git at Google

 // Copyright (c) 2017, 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.

 // @dart = 2.8

 /// A tool that invokes the CFE to compute kernel summary files.
 ///
 /// This script can be used as a command-line command or a persistent server.
 /// The server is implemented using the bazel worker protocol, so it can be used
 /// within bazel as is. Other tools (like pub-build and package-build) also
 /// use this persistent worker via the same protocol.

 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';

 import 'package:args/args.dart';
 import 'package:bazel_worker/bazel_worker.dart';
 import 'package:build_integration/file_system/multi_root.dart';
 import 'package:dev_compiler/src/kernel/target.dart';
 import 'package:front_end/src/api_unstable/bazel_worker.dart' as fe;
 import 'package:kernel/ast.dart' show Component, Library, Reference;
 import 'package:kernel/target/targets.dart';
 import 'package:vm/target/vm.dart';
 import 'package:vm/target/flutter.dart';
 import 'package:vm/target/flutter_runner.dart';
 import 'package:compiler/src/kernel/dart2js_target.dart';

 /// [sendPort] may be passed in when started in an isolate. If provided, it is
 /// used for bazel worker communication instead of stdin/stdout.
 main(List<String> args, SendPort sendPort) async {
   args = preprocessArgs(args);

   if (args.contains('--persistent_worker')) {
     if (args.length != 1) {
       throw new StateError(
           "unexpected args, expected only --persistent-worker but got: $args");
     }
     await new KernelWorker(sendPort: sendPort).run();
   } else {
     var result = await computeKernel(args);
     if (!result.succeeded) {
       exitCode = 15;
     }
   }
 }

 /// A bazel worker loop that can compute full or summary kernel files.
 class KernelWorker extends AsyncWorkerLoop {
   fe.InitializedCompilerState previousState;

   /// If [sendPort] is provided it is used for bazel worker communication
   /// instead of stdin/stdout.
   KernelWorker({SendPort sendPort})
       : super(
             connection: sendPort == null
                 ? null
                 : SendPortAsyncWorkerConnection(sendPort));

   Future<WorkResponse> performRequest(WorkRequest request) async {
     var outputBuffer = new StringBuffer();
     var response = new WorkResponse()..exitCode = 0;
     try {
       fe.InitializedCompilerState previousStateToPass;
       if (request.arguments.contains("--reuse-compiler-result")) {
         previousStateToPass = previousState;
       } else {
         previousState = null;
       }
       var result = await computeKernel(request.arguments,
           isWorker: true,
           outputBuffer: outputBuffer,
           inputs: request.inputs,
           previousState: previousStateToPass);
       previousState = result.previousState;
       if (!result.succeeded) {
         response.exitCode = 15;
       }
     } catch (e, s) {
       outputBuffer.writeln(e);
       outputBuffer.writeln(s);
       response.exitCode = 15;
     }
     response.output = outputBuffer.toString();
     return response;
   }
 }

 /// If the last arg starts with `@`, this reads the file it points to and treats
 /// each line as an additional arg.
 ///
 /// This is how individual work request args are differentiated from startup
 /// args in bazel (inidividual work request args go in that file).
 List<String> preprocessArgs(List<String> args) {
   args = new List.from(args);
   if (args.isEmpty) {
     return args;
   }
   String lastArg = args.last;
   if (lastArg.startsWith('@')) {
     File argsFile = new File(lastArg.substring(1));
     try {
       args.removeLast();
       args.addAll(argsFile.readAsLinesSync());
     } on FileSystemException catch (e) {
       throw new Exception('Failed to read file specified by $lastArg : $e');
     }
   }
   return args;
 }

 /// An [ArgParser] for generating kernel summaries.
 final summaryArgsParser = new ArgParser()
   ..addFlag('help', negatable: false, abbr: 'h')
   ..addFlag('exclude-non-sources',
       negatable: false,
       help: 'Whether source files loaded implicitly should be included as '
           'part of the summary.')
   ..addFlag('summary-only',
       defaultsTo: true,
       negatable: true,
       help: 'Whether to only build summary files.')
   ..addOption('target',
       allowed: const [
         'vm',
         'flutter',
         'flutter_runner',
         'dart2js',
         'ddc',
       ],
       help: 'Build kernel for the vm, flutter, flutter_runner, dart2js or ddc')
   ..addOption('dart-sdk-summary')
   ..addMultiOption('input-summary')
   ..addMultiOption('input-linked')
   ..addMultiOption('multi-root')
   ..addOption('multi-root-scheme', defaultsTo: 'org-dartlang-multi-root')
   ..addOption('libraries-file')
   ..addOption('packages-file')
   ..addMultiOption('source')
   ..addOption('output')
   ..addFlag('reuse-compiler-result', defaultsTo: false)
   ..addFlag('use-incremental-compiler', defaultsTo: false)
   ..addOption('used-inputs')
   ..addFlag('track-widget-creation', defaultsTo: false)
   ..addMultiOption('enable-experiment',
       help: 'Enable a language experiment when invoking the CFE.')
   ..addMultiOption('define', abbr: 'D')
   ..addFlag('verbose', defaultsTo: false)
   ..addFlag('sound-null-safety', defaultsTo: false)
   ..addOption('verbosity',
       defaultsTo: fe.Verbosity.defaultValue,
       help: 'Sets the verbosity level used for filtering messages during '
           'compilation.',
       allowed: fe.Verbosity.allowedValues,
       allowedHelp: fe.Verbosity.allowedValuesHelp);

 class ComputeKernelResult {
   final bool succeeded;
   final fe.InitializedCompilerState previousState;

   ComputeKernelResult(this.succeeded, this.previousState);
 }

 /// Computes a kernel file based on [args].
 ///
 /// If [isWorker] is true then exit codes will not be set on failure.
 ///
 /// If [outputBuffer] is provided then messages will be written to that buffer
 /// instead of printed to the console.
 ///
 /// Returns whether or not the summary was successfully output.
 Future<ComputeKernelResult> computeKernel(List<String> args,
     {bool isWorker: false,
     StringBuffer outputBuffer,
     Iterable<Input> inputs,
     fe.InitializedCompilerState previousState}) async {
   dynamic out = outputBuffer ?? stderr;
   bool succeeded = true;

   var parsedArgs = summaryArgsParser.parse(args);

   if (parsedArgs['help']) {
     out.writeln(summaryArgsParser.usage);
     if (!isWorker) exit(0);
     return new ComputeKernelResult(false, previousState);
   }

   // Bazel creates an overlay file system where some files may be located in the
   // source tree, some in a gendir, and some in a bindir. The multi-root file
   // system hides this from the front end.
   var multiRoots = parsedArgs['multi-root'].map(Uri.base.resolve).toList();
   if (multiRoots.isEmpty) multiRoots.add(Uri.base);
   var fileSystem = new MultiRootFileSystem(parsedArgs['multi-root-scheme'],
       multiRoots, fe.StandardFileSystem.instance);
   var sources = (parsedArgs['source'] as List<String>).map(_toUri).toList();
   var excludeNonSources = parsedArgs['exclude-non-sources'] as bool;

   var nnbdMode = parsedArgs['sound-null-safety'] as bool
       ? fe.NnbdMode.Strong
       : fe.NnbdMode.Weak;
   var summaryOnly = parsedArgs['summary-only'] as bool;
   var trackWidgetCreation = parsedArgs['track-widget-creation'] as bool;

   // TODO(sigmund,jakemac): make target mandatory. We allow null to be backwards
   // compatible while we migrate existing clients of this tool.
   var targetName =
       (parsedArgs['target'] as String) ?? (summaryOnly ? 'ddc' : 'vm');
   var targetFlags = new TargetFlags(
       trackWidgetCreation: trackWidgetCreation,
       enableNullSafety: nnbdMode == fe.NnbdMode.Strong);
   Target target;
   switch (targetName) {
     case 'vm':
       target = new VmTarget(targetFlags);
       if (summaryOnly) {
         out.writeln('error: --summary-only not supported for the vm target');
       }
       break;
     case 'flutter':
       target = new FlutterTarget(targetFlags);
       if (summaryOnly) {
         throw new ArgumentError(
             'error: --summary-only not supported for the flutter target');
       }
       break;
     case 'flutter_runner':
       target = new FlutterRunnerTarget(targetFlags);
       if (summaryOnly) {
         throw new ArgumentError('error: --summary-only not supported for the '
             'flutter_runner target');
       }
       break;
     case 'dart2js':
       target = new Dart2jsTarget('dart2js', targetFlags);
       if (summaryOnly) {
         out.writeln(
             'error: --summary-only not supported for the dart2js target');
       }
       break;
     case 'ddc':
       // TODO(jakemac):If `generateKernel` changes to return a summary
       // component, process the component instead.
       target =
           new DevCompilerSummaryTarget(sources, excludeNonSources, targetFlags);
       if (!summaryOnly) {
         out.writeln('error: --no-summary-only not supported for the '
             'ddc target');
       }
       break;
     default:
       out.writeln('error: unsupported target: $targetName');
   }

   List<Uri> linkedInputs =
       (parsedArgs['input-linked'] as List<String>).map(_toUri).toList();

   List<Uri> summaryInputs =
       (parsedArgs['input-summary'] as List<String>).map(_toUri).toList();

   fe.InitializedCompilerState state;
   bool usingIncrementalCompiler = false;
   bool recordUsedInputs = parsedArgs["used-inputs"] != null;
   var environmentDefines = _parseEnvironmentDefines(parsedArgs['define']);
   var verbose = parsedArgs['verbose'] as bool;
   var verbosity = fe.Verbosity.parseArgument(parsedArgs['verbosity']);

   if (parsedArgs['use-incremental-compiler']) {
     usingIncrementalCompiler = true;

     /// Build a map of uris to digests.
     final inputDigests = <Uri, List<int>>{};
     if (inputs != null) {
       for (var input in inputs) {
         inputDigests[_toUri(input.path)] = input.digest;
       }
     }

     // If digests weren't given and if not in worker mode, create fake data and
     // ensure we don't have a previous state (as that wouldn't be safe with
     // fake input digests).
     if (!isWorker && inputDigests.isEmpty) {
       previousState = null;
       inputDigests[_toUri(parsedArgs['dart-sdk-summary'])] = const [0];
       for (Uri uri in summaryInputs) {
         inputDigests[uri] = const [0];
       }
       for (Uri uri in linkedInputs) {
         inputDigests[uri] = const [0];
       }
     }

     state = await fe.initializeIncrementalCompiler(
         previousState,
         {
           "target=$targetName",
           "trackWidgetCreation=$trackWidgetCreation",
           "multiRootScheme=${fileSystem.markerScheme}",
           "multiRootRoots=${fileSystem.roots}",
         },
         _toUri(parsedArgs['dart-sdk-summary']),
         _toUri(parsedArgs['packages-file']),
         _toUri(parsedArgs['libraries-file']),
         [...summaryInputs, ...linkedInputs],
         inputDigests,
         target,
         fileSystem,
         (parsedArgs['enable-experiment'] as List<String>),
         summaryOnly,
         environmentDefines,
         trackNeededDillLibraries: recordUsedInputs,
         verbose: verbose,
         nnbdMode: nnbdMode);
   } else {
     state = await fe.initializeCompiler(
         // TODO(sigmund): pass an old state once we can make use of it.
         null,
         _toUri(parsedArgs['dart-sdk-summary']),
         _toUri(parsedArgs['libraries-file']),
         _toUri(parsedArgs['packages-file']),
         [...summaryInputs, ...linkedInputs],
         target,
         fileSystem,
         parsedArgs['enable-experiment'] as List<String>,
         environmentDefines,
         verbose: verbose,
         nnbdMode: nnbdMode);
   }

   void onDiagnostic(fe.DiagnosticMessage message) {
     if (fe.Verbosity.shouldPrint(verbosity, message)) {
       fe.printDiagnosticMessage(message, out.writeln);
     }
     if (message.severity == fe.Severity.error) {
       succeeded = false;
     }
   }

   List<int> kernel;
   bool wroteUsedDills = false;
   if (usingIncrementalCompiler) {
     state.options.onDiagnostic = onDiagnostic;
     Component incrementalComponent = await state.incrementalCompiler
         .computeDelta(entryPoints: sources, fullComponent: true);

     if (recordUsedInputs) {
       Set<Uri> usedOutlines = {};
       for (Library lib in state.incrementalCompiler.neededDillLibraries) {
         if (lib.importUri.scheme == "dart") continue;
         Uri uri = state.libraryToInputDill[lib.importUri];
         if (uri == null) {
           throw new StateError("Library ${lib.importUri} was recorded as used, "
               "but was not in the list of known libraries.");
         }
         usedOutlines.add(uri);
       }
       var outputUsedFile = new File(parsedArgs["used-inputs"]);
       outputUsedFile.createSync(recursive: true);
       outputUsedFile.writeAsStringSync(usedOutlines.join("\n"));
       wroteUsedDills = true;
     }

     kernel = await state.incrementalCompiler.context.runInContext((_) {
       if (summaryOnly) {
         incrementalComponent.uriToSource.clear();
         incrementalComponent.problemsAsJson = null;
         incrementalComponent.setMainMethodAndMode(
             null, true, incrementalComponent.mode);
         target.performOutlineTransformations(incrementalComponent);
         makeStable(incrementalComponent);
         return Future.value(fe.serializeComponent(incrementalComponent,
             includeSources: false, includeOffsets: false));
       }

       makeStable(incrementalComponent);

       return Future.value(fe.serializeComponent(incrementalComponent,
           filter: excludeNonSources
               ? (library) => sources.contains(library.importUri)
               : null,
           includeOffsets: true));
     });
   } else if (summaryOnly) {
     kernel = await fe.compileSummary(state, sources, onDiagnostic,
         includeOffsets: false);
   } else {
     Component component =
         await fe.compileComponent(state, sources, onDiagnostic);
     kernel = fe.serializeComponent(component,
         filter: excludeNonSources
             ? (library) => sources.contains(library.importUri)
             : null,
         includeOffsets: true);
   }
   state.options.onDiagnostic = null; // See http://dartbug.com/36983.

   if (!wroteUsedDills && recordUsedInputs) {
     // The path taken didn't record inputs used: Say we used everything.
     var outputUsedFile = new File(parsedArgs["used-inputs"]);
     outputUsedFile.createSync(recursive: true);
     Set<Uri> allFiles = {...summaryInputs, ...linkedInputs};
     outputUsedFile.writeAsStringSync(allFiles.join("\n"));
     wroteUsedDills = true;
   }

   if (kernel != null) {
     var outputFile = new File(parsedArgs['output']);
     outputFile.createSync(recursive: true);
     outputFile.writeAsBytesSync(kernel);
   } else {
     assert(!succeeded);
   }

   return new ComputeKernelResult(succeeded, state);
 }

 /// Make sure the output is stable by sorting libraries and additional exports.
 void makeStable(Component c) {
   // Make sure the output is stable.
   c.libraries.sort((l1, l2) {
     return "${l1.fileUri}".compareTo("${l2.fileUri}");
   });
   c.problemsAsJson?.sort();
   c.computeCanonicalNames();
   for (Library library in c.libraries) {
     library.additionalExports.sort((Reference r1, Reference r2) {
       return "${r1.canonicalName}".compareTo("${r2.canonicalName}");
     });
     library.problemsAsJson?.sort();
   }
 }

 /// Extends the DevCompilerTarget to transform outlines to meet the requirements
 /// of summaries in bazel and package-build.
 ///
 /// Build systems like package-build may provide the same input file twice to
 /// the summary worker, but only intends to have it in one output summary.  The
 /// convention is that if it is listed as a source, it is intended to be part of
 /// the output, if the source file was loaded as a dependency, then it was
 /// already included in a different summary.  The transformation below ensures
 /// that the output summary doesn't include those implicit inputs.
 ///
 /// Note: this transformation is destructive and is only intended to be used
 /// when generating summaries.
 class DevCompilerSummaryTarget extends DevCompilerTarget {
   final List<Uri> sources;
   final bool excludeNonSources;

   DevCompilerSummaryTarget(
       this.sources, this.excludeNonSources, TargetFlags targetFlags)
       : super(targetFlags);

   @override
   void performOutlineTransformations(Component component) {
     super.performOutlineTransformations(component);
     if (!excludeNonSources) return;

     List<Library> libraries = new List.from(component.libraries);
     component.libraries.clear();
     Set<Uri> include = sources.toSet();
     for (var lib in libraries) {
       if (include.contains(lib.importUri)) {
         component.libraries.add(lib);
       } else {
         // Excluding the library also means that their canonical names will not
         // be computed as part of serialization, so we need to do that
         // preemtively here to avoid errors when serializing references to
         // elements of these libraries.
         component.root.getChildFromUri(lib.importUri).bindTo(lib.reference);
         lib.computeCanonicalNames();
       }
     }
   }
 }

 Uri _toUri(String uriString) {
   if (uriString == null) return null;
   // Windows-style paths use '\', so convert them to '/' in case they've been
   // concatenated with Unix-style paths.
   return Uri.base.resolve(uriString.replaceAll("\\", "/"));
 }

 Map<String, String> _parseEnvironmentDefines(List<String> args) {
   var environment = <String, String>{};

   for (var arg in args) {
     var eq = arg.indexOf('=');
     if (eq <= 0) {
       var kind = eq == 0 ? 'name' : 'value';
       throw FormatException('no $kind given to -D option `$arg`');
     }
     var name = arg.substring(0, eq);
     var value = arg.substring(eq + 1);
     environment[name] = value;
   }

   return environment;
 }
	// Copyright (c) 2017, 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.

	// @dart = 2.8

	/// A tool that invokes the CFE to compute kernel summary files.
	///
	/// This script can be used as a command-line command or a persistent server.
	/// The server is implemented using the bazel worker protocol, so it can be used
	/// within bazel as is. Other tools (like pub-build and package-build) also
	/// use this persistent worker via the same protocol.

	import 'dart:async';
	import 'dart:io';
	import 'dart:isolate';

	import 'package:args/args.dart';
	import 'package:bazel_worker/bazel_worker.dart';
	import 'package:build_integration/file_system/multi_root.dart';
	import 'package:dev_compiler/src/kernel/target.dart';
	import 'package:front_end/src/api_unstable/bazel_worker.dart' as fe;
	import 'package:kernel/ast.dart' show Component, Library, Reference;
	import 'package:kernel/target/targets.dart';
	import 'package:vm/target/vm.dart';
	import 'package:vm/target/flutter.dart';
	import 'package:vm/target/flutter_runner.dart';
	import 'package:compiler/src/kernel/dart2js_target.dart';

	/// [sendPort] may be passed in when started in an isolate. If provided, it is
	/// used for bazel worker communication instead of stdin/stdout.
	main(List<String> args, SendPort sendPort) async {
	args = preprocessArgs(args);

	if (args.contains('--persistent_worker')) {
	if (args.length != 1) {
	throw new StateError(
	"unexpected args, expected only --persistent-worker but got: $args");
	}
	await new KernelWorker(sendPort: sendPort).run();
	} else {
	var result = await computeKernel(args);
	if (!result.succeeded) {
	exitCode = 15;
	}
	}
	}

	/// A bazel worker loop that can compute full or summary kernel files.
	class KernelWorker extends AsyncWorkerLoop {
	fe.InitializedCompilerState previousState;

	/// If [sendPort] is provided it is used for bazel worker communication
	/// instead of stdin/stdout.
	KernelWorker({SendPort sendPort})
	: super(
	connection: sendPort == null
	? null
	: SendPortAsyncWorkerConnection(sendPort));

	Future<WorkResponse> performRequest(WorkRequest request) async {
	var outputBuffer = new StringBuffer();
	var response = new WorkResponse()..exitCode = 0;
	try {
	fe.InitializedCompilerState previousStateToPass;
	if (request.arguments.contains("--reuse-compiler-result")) {
	previousStateToPass = previousState;
	} else {
	previousState = null;
	}
	var result = await computeKernel(request.arguments,
	isWorker: true,
	outputBuffer: outputBuffer,
	inputs: request.inputs,
	previousState: previousStateToPass);
	previousState = result.previousState;
	if (!result.succeeded) {
	response.exitCode = 15;
	}
	} catch (e, s) {
	outputBuffer.writeln(e);
	outputBuffer.writeln(s);
	response.exitCode = 15;
	}
	response.output = outputBuffer.toString();
	return response;
	}
	}

	/// If the last arg starts with `@`, this reads the file it points to and treats
	/// each line as an additional arg.
	///
	/// This is how individual work request args are differentiated from startup
	/// args in bazel (inidividual work request args go in that file).
	List<String> preprocessArgs(List<String> args) {
	args = new List.from(args);
	if (args.isEmpty) {
	return args;
	}
	String lastArg = args.last;
	if (lastArg.startsWith('@')) {
	File argsFile = new File(lastArg.substring(1));
	try {
	args.removeLast();
	args.addAll(argsFile.readAsLinesSync());
	} on FileSystemException catch (e) {
	throw new Exception('Failed to read file specified by $lastArg : $e');
	}
	}
	return args;
	}

	/// An [ArgParser] for generating kernel summaries.
	final summaryArgsParser = new ArgParser()
	..addFlag('help', negatable: false, abbr: 'h')
	..addFlag('exclude-non-sources',
	negatable: false,
	help: 'Whether source files loaded implicitly should be included as '
	'part of the summary.')
	..addFlag('summary-only',
	defaultsTo: true,
	negatable: true,
	help: 'Whether to only build summary files.')
	..addOption('target',
	allowed: const [
	'vm',
	'flutter',
	'flutter_runner',
	'dart2js',
	'ddc',
	],
	help: 'Build kernel for the vm, flutter, flutter_runner, dart2js or ddc')
	..addOption('dart-sdk-summary')
	..addMultiOption('input-summary')
	..addMultiOption('input-linked')
	..addMultiOption('multi-root')
	..addOption('multi-root-scheme', defaultsTo: 'org-dartlang-multi-root')
	..addOption('libraries-file')
	..addOption('packages-file')
	..addMultiOption('source')
	..addOption('output')
	..addFlag('reuse-compiler-result', defaultsTo: false)
	..addFlag('use-incremental-compiler', defaultsTo: false)
	..addOption('used-inputs')
	..addFlag('track-widget-creation', defaultsTo: false)
	..addMultiOption('enable-experiment',
	help: 'Enable a language experiment when invoking the CFE.')
	..addMultiOption('define', abbr: 'D')
	..addFlag('verbose', defaultsTo: false)
	..addFlag('sound-null-safety', defaultsTo: false)
	..addOption('verbosity',
	defaultsTo: fe.Verbosity.defaultValue,
	help: 'Sets the verbosity level used for filtering messages during '
	'compilation.',
	allowed: fe.Verbosity.allowedValues,
	allowedHelp: fe.Verbosity.allowedValuesHelp);

	class ComputeKernelResult {
	final bool succeeded;
	final fe.InitializedCompilerState previousState;

	ComputeKernelResult(this.succeeded, this.previousState);
	}

	/// Computes a kernel file based on [args].
	///
	/// If [isWorker] is true then exit codes will not be set on failure.
	///
	/// If [outputBuffer] is provided then messages will be written to that buffer
	/// instead of printed to the console.
	///
	/// Returns whether or not the summary was successfully output.
	Future<ComputeKernelResult> computeKernel(List<String> args,
	{bool isWorker: false,
	StringBuffer outputBuffer,
	Iterable<Input> inputs,
	fe.InitializedCompilerState previousState}) async {
	dynamic out = outputBuffer ?? stderr;
	bool succeeded = true;

	var parsedArgs = summaryArgsParser.parse(args);

	if (parsedArgs['help']) {
	out.writeln(summaryArgsParser.usage);
	if (!isWorker) exit(0);
	return new ComputeKernelResult(false, previousState);
	}

	// Bazel creates an overlay file system where some files may be located in the
	// source tree, some in a gendir, and some in a bindir. The multi-root file
	// system hides this from the front end.
	var multiRoots = parsedArgs['multi-root'].map(Uri.base.resolve).toList();
	if (multiRoots.isEmpty) multiRoots.add(Uri.base);
	var fileSystem = new MultiRootFileSystem(parsedArgs['multi-root-scheme'],
	multiRoots, fe.StandardFileSystem.instance);
	var sources = (parsedArgs['source'] as List<String>).map(_toUri).toList();
	var excludeNonSources = parsedArgs['exclude-non-sources'] as bool;

	var nnbdMode = parsedArgs['sound-null-safety'] as bool
	? fe.NnbdMode.Strong
	: fe.NnbdMode.Weak;
	var summaryOnly = parsedArgs['summary-only'] as bool;
	var trackWidgetCreation = parsedArgs['track-widget-creation'] as bool;

	// TODO(sigmund,jakemac): make target mandatory. We allow null to be backwards
	// compatible while we migrate existing clients of this tool.
	var targetName =
	(parsedArgs['target'] as String) ?? (summaryOnly ? 'ddc' : 'vm');
	var targetFlags = new TargetFlags(
	trackWidgetCreation: trackWidgetCreation,
	enableNullSafety: nnbdMode == fe.NnbdMode.Strong);
	Target target;
	switch (targetName) {
	case 'vm':
	target = new VmTarget(targetFlags);
	if (summaryOnly) {
	out.writeln('error: --summary-only not supported for the vm target');
	}
	break;
	case 'flutter':
	target = new FlutterTarget(targetFlags);
	if (summaryOnly) {
	throw new ArgumentError(
	'error: --summary-only not supported for the flutter target');
	}
	break;
	case 'flutter_runner':
	target = new FlutterRunnerTarget(targetFlags);
	if (summaryOnly) {
	throw new ArgumentError('error: --summary-only not supported for the '
	'flutter_runner target');
	}
	break;
	case 'dart2js':
	target = new Dart2jsTarget('dart2js', targetFlags);
	if (summaryOnly) {
	out.writeln(
	'error: --summary-only not supported for the dart2js target');
	}
	break;
	case 'ddc':
	// TODO(jakemac):If `generateKernel` changes to return a summary
	// component, process the component instead.
	target =
	new DevCompilerSummaryTarget(sources, excludeNonSources, targetFlags);
	if (!summaryOnly) {
	out.writeln('error: --no-summary-only not supported for the '
	'ddc target');
	}
	break;
	default:
	out.writeln('error: unsupported target: $targetName');
	}

	List<Uri> linkedInputs =
	(parsedArgs['input-linked'] as List<String>).map(_toUri).toList();

	List<Uri> summaryInputs =
	(parsedArgs['input-summary'] as List<String>).map(_toUri).toList();

	fe.InitializedCompilerState state;
	bool usingIncrementalCompiler = false;
	bool recordUsedInputs = parsedArgs["used-inputs"] != null;
	var environmentDefines = _parseEnvironmentDefines(parsedArgs['define']);
	var verbose = parsedArgs['verbose'] as bool;
	var verbosity = fe.Verbosity.parseArgument(parsedArgs['verbosity']);

	if (parsedArgs['use-incremental-compiler']) {
	usingIncrementalCompiler = true;

	/// Build a map of uris to digests.
	final inputDigests = <Uri, List<int>>{};
	if (inputs != null) {
	for (var input in inputs) {
	inputDigests[_toUri(input.path)] = input.digest;
	}
	}

	// If digests weren't given and if not in worker mode, create fake data and
	// ensure we don't have a previous state (as that wouldn't be safe with
	// fake input digests).
	if (!isWorker && inputDigests.isEmpty) {
	previousState = null;
	inputDigests[_toUri(parsedArgs['dart-sdk-summary'])] = const [0];
	for (Uri uri in summaryInputs) {
	inputDigests[uri] = const [0];
	}
	for (Uri uri in linkedInputs) {
	inputDigests[uri] = const [0];
	}
	}

	state = await fe.initializeIncrementalCompiler(
	previousState,
	{
	"target=$targetName",
	"trackWidgetCreation=$trackWidgetCreation",
	"multiRootScheme=${fileSystem.markerScheme}",
	"multiRootRoots=${fileSystem.roots}",
	},
	_toUri(parsedArgs['dart-sdk-summary']),
	_toUri(parsedArgs['packages-file']),
	_toUri(parsedArgs['libraries-file']),
	[...summaryInputs, ...linkedInputs],
	inputDigests,
	target,
	fileSystem,
	(parsedArgs['enable-experiment'] as List<String>),
	summaryOnly,
	environmentDefines,
	trackNeededDillLibraries: recordUsedInputs,
	verbose: verbose,
	nnbdMode: nnbdMode);
	} else {
	state = await fe.initializeCompiler(
	// TODO(sigmund): pass an old state once we can make use of it.
	null,
	_toUri(parsedArgs['dart-sdk-summary']),
	_toUri(parsedArgs['libraries-file']),
	_toUri(parsedArgs['packages-file']),
	[...summaryInputs, ...linkedInputs],
	target,
	fileSystem,
	parsedArgs['enable-experiment'] as List<String>,
	environmentDefines,
	verbose: verbose,
	nnbdMode: nnbdMode);
	}

	void onDiagnostic(fe.DiagnosticMessage message) {
	if (fe.Verbosity.shouldPrint(verbosity, message)) {
	fe.printDiagnosticMessage(message, out.writeln);
	}
	if (message.severity == fe.Severity.error) {
	succeeded = false;
	}
	}

	List<int> kernel;
	bool wroteUsedDills = false;
	if (usingIncrementalCompiler) {
	state.options.onDiagnostic = onDiagnostic;
	Component incrementalComponent = await state.incrementalCompiler
	.computeDelta(entryPoints: sources, fullComponent: true);

	if (recordUsedInputs) {
	Set<Uri> usedOutlines = {};
	for (Library lib in state.incrementalCompiler.neededDillLibraries) {
	if (lib.importUri.scheme == "dart") continue;
	Uri uri = state.libraryToInputDill[lib.importUri];
	if (uri == null) {
	throw new StateError("Library ${lib.importUri} was recorded as used, "
	"but was not in the list of known libraries.");
	}
	usedOutlines.add(uri);
	}
	var outputUsedFile = new File(parsedArgs["used-inputs"]);
	outputUsedFile.createSync(recursive: true);
	outputUsedFile.writeAsStringSync(usedOutlines.join("\n"));
	wroteUsedDills = true;
	}

	kernel = await state.incrementalCompiler.context.runInContext((_) {
	if (summaryOnly) {
	incrementalComponent.uriToSource.clear();
	incrementalComponent.problemsAsJson = null;
	incrementalComponent.setMainMethodAndMode(
	null, true, incrementalComponent.mode);
	target.performOutlineTransformations(incrementalComponent);
	makeStable(incrementalComponent);
	return Future.value(fe.serializeComponent(incrementalComponent,
	includeSources: false, includeOffsets: false));
	}

	makeStable(incrementalComponent);

	return Future.value(fe.serializeComponent(incrementalComponent,
	filter: excludeNonSources
	? (library) => sources.contains(library.importUri)
	: null,
	includeOffsets: true));
	});
	} else if (summaryOnly) {
	kernel = await fe.compileSummary(state, sources, onDiagnostic,
	includeOffsets: false);
	} else {
	Component component =
	await fe.compileComponent(state, sources, onDiagnostic);
	kernel = fe.serializeComponent(component,
	filter: excludeNonSources
	? (library) => sources.contains(library.importUri)
	: null,
	includeOffsets: true);
	}
	state.options.onDiagnostic = null; // See http://dartbug.com/36983.

	if (!wroteUsedDills && recordUsedInputs) {
	// The path taken didn't record inputs used: Say we used everything.
	var outputUsedFile = new File(parsedArgs["used-inputs"]);
	outputUsedFile.createSync(recursive: true);
	Set<Uri> allFiles = {...summaryInputs, ...linkedInputs};
	outputUsedFile.writeAsStringSync(allFiles.join("\n"));
	wroteUsedDills = true;
	}

	if (kernel != null) {
	var outputFile = new File(parsedArgs['output']);
	outputFile.createSync(recursive: true);
	outputFile.writeAsBytesSync(kernel);
	} else {
	assert(!succeeded);
	}

	return new ComputeKernelResult(succeeded, state);
	}

	/// Make sure the output is stable by sorting libraries and additional exports.
	void makeStable(Component c) {
	// Make sure the output is stable.
	c.libraries.sort((l1, l2) {
	return "${l1.fileUri}".compareTo("${l2.fileUri}");
	});
	c.problemsAsJson?.sort();
	c.computeCanonicalNames();
	for (Library library in c.libraries) {
	library.additionalExports.sort((Reference r1, Reference r2) {
	return "${r1.canonicalName}".compareTo("${r2.canonicalName}");
	});
	library.problemsAsJson?.sort();
	}
	}

	/// Extends the DevCompilerTarget to transform outlines to meet the requirements
	/// of summaries in bazel and package-build.
	///
	/// Build systems like package-build may provide the same input file twice to
	/// the summary worker, but only intends to have it in one output summary. The
	/// convention is that if it is listed as a source, it is intended to be part of
	/// the output, if the source file was loaded as a dependency, then it was
	/// already included in a different summary. The transformation below ensures
	/// that the output summary doesn't include those implicit inputs.
	///
	/// Note: this transformation is destructive and is only intended to be used
	/// when generating summaries.
	class DevCompilerSummaryTarget extends DevCompilerTarget {
	final List<Uri> sources;
	final bool excludeNonSources;

	DevCompilerSummaryTarget(
	this.sources, this.excludeNonSources, TargetFlags targetFlags)
	: super(targetFlags);

	@override
	void performOutlineTransformations(Component component) {
	super.performOutlineTransformations(component);
	if (!excludeNonSources) return;

	List<Library> libraries = new List.from(component.libraries);
	component.libraries.clear();
	Set<Uri> include = sources.toSet();
	for (var lib in libraries) {
	if (include.contains(lib.importUri)) {
	component.libraries.add(lib);
	} else {
	// Excluding the library also means that their canonical names will not
	// be computed as part of serialization, so we need to do that
	// preemtively here to avoid errors when serializing references to
	// elements of these libraries.
	component.root.getChildFromUri(lib.importUri).bindTo(lib.reference);
	lib.computeCanonicalNames();
	}
	}
	}
	}

	Uri _toUri(String uriString) {
	if (uriString == null) return null;
	// Windows-style paths use '\', so convert them to '/' in case they've been
	// concatenated with Unix-style paths.
	return Uri.base.resolve(uriString.replaceAll("\\", "/"));
	}

	Map<String, String> _parseEnvironmentDefines(List<String> args) {
	var environment = <String, String>{};

	for (var arg in args) {
	var eq = arg.indexOf('=');
	if (eq <= 0) {
	var kind = eq == 0 ? 'name' : 'value';
	throw FormatException('no $kind given to -D option `$arg`');
	}
	var name = arg.substring(0, eq);
	var value = arg.substring(eq + 1);
	environment[name] = value;
	}

	return environment;
	}