packages/flutter_tools/lib/src/dart/pub.dart - external/github.com/flutter/flutter - Git at Google

 // Copyright 2014 The Flutter 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 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 import 'package:process/process.dart';

 import '../base/bot_detector.dart';
 import '../base/common.dart';
 import '../base/context.dart';
 import '../base/file_system.dart';
 import '../base/io.dart' as io;
 import '../base/logger.dart';
 import '../base/platform.dart';
 import '../base/process.dart';
 import '../cache.dart';
 import '../dart/package_map.dart';
 import '../reporting/reporting.dart';

 /// The [Pub] instance.
 Pub get pub => context.get<Pub>();

 /// The console environment key used by the pub tool.
 const String _kPubEnvironmentKey = 'PUB_ENVIRONMENT';

 /// The console environment key used by the pub tool to find the cache directory.
 const String _kPubCacheEnvironmentKey = 'PUB_CACHE';

 typedef MessageFilter = String Function(String message);

 /// Represents Flutter-specific data that is added to the `PUB_ENVIRONMENT`
 /// environment variable and allows understanding the type of requests made to
 /// the package site on Flutter's behalf.
 // DO NOT update without contacting kevmoo.
 // We have server-side tooling that assumes the values are consistent.
 class PubContext {
   PubContext._(this._values) {
     for (final String item in _values) {
       if (!_validContext.hasMatch(item)) {
         throw ArgumentError.value(
           _values, 'value', 'Must match RegExp ${_validContext.pattern}');
       }
     }
   }

   static PubContext getVerifyContext(String commandName) =>
       PubContext._(<String>['verify', commandName.replaceAll('-', '_')]);

   static final PubContext create = PubContext._(<String>['create']);
   static final PubContext createPackage = PubContext._(<String>['create_pkg']);
   static final PubContext createPlugin = PubContext._(<String>['create_plugin']);
   static final PubContext interactive = PubContext._(<String>['interactive']);
   static final PubContext pubGet = PubContext._(<String>['get']);
   static final PubContext pubUpgrade = PubContext._(<String>['upgrade']);
   static final PubContext pubForward = PubContext._(<String>['forward']);
   static final PubContext runTest = PubContext._(<String>['run_test']);
   static final PubContext flutterTests = PubContext._(<String>['flutter_tests']);
   static final PubContext updatePackages = PubContext._(<String>['update_packages']);

   final List<String> _values;

   static final RegExp _validContext = RegExp('[a-z][a-z_]*[a-z]');

   @override
   String toString() => 'PubContext: ${_values.join(':')}';

   String toAnalyticsString()  {
     return _values.map((String s) => s.replaceAll('_', '-')).toList().join('-');
   }
 }

 /// A handle for interacting with the pub tool.
 abstract class Pub {
   /// Create a default [Pub] instance.
   factory Pub({
     @required FileSystem fileSystem,
     @required Logger logger,
     @required ProcessManager processManager,
     @required Platform platform,
     @required BotDetector botDetector,
     @required Usage usage,
     File Function() toolStampFile,
   }) = _DefaultPub;

   /// Runs `pub get`.
   ///
   /// [context] provides extra information to package server requests to
   /// understand usage.
   Future<void> get({
     @required PubContext context,
     String directory,
     bool skipIfAbsent = false,
     bool upgrade = false,
     bool offline = false,
     bool checkLastModified = true,
     bool skipPubspecYamlCheck = false,
     bool generateSyntheticPackage = false,
     String flutterRootOverride,
   });

   /// Runs pub in 'batch' mode.
   ///
   /// forwarding complete lines written by pub to its stdout/stderr streams to
   /// the corresponding stream of this process, optionally applying filtering.
   /// The pub process will not receive anything on its stdin stream.
   ///
   /// The `--trace` argument is passed to `pub` (by mutating the provided
   /// `arguments` list) when `showTraceForErrors` is true, and when `showTraceForErrors`
   /// is null/unset, and `isRunningOnBot` is true.
   ///
   /// [context] provides extra information to package server requests to
   /// understand usage.
   Future<void> batch(
     List<String> arguments, {
     @required PubContext context,
     String directory,
     MessageFilter filter,
     String failureMessage = 'pub failed',
     @required bool retry,
     bool showTraceForErrors,
   });


   /// Runs pub in 'interactive' mode.
   ///
   /// directly piping the stdin stream of this process to that of pub, and the
   /// stdout/stderr stream of pub to the corresponding streams of this process.
   Future<void> interactively(
     List<String> arguments, {
     String directory,
     @required io.Stdio stdio,
   });
 }

 class _DefaultPub implements Pub {
   _DefaultPub({
     @required FileSystem fileSystem,
     @required Logger logger,
     @required ProcessManager processManager,
     @required Platform platform,
     @required BotDetector botDetector,
     @required Usage usage,
    File Function() toolStampFile,
   }) : _toolStampFile = toolStampFile,
        _fileSystem = fileSystem,
        _logger = logger,
        _platform = platform,
        _botDetector = botDetector,
        _usage = usage,
        _processUtils = ProcessUtils(
          logger: logger,
          processManager: processManager,
        );

   final FileSystem _fileSystem;
   final Logger _logger;
   final ProcessUtils _processUtils;
   final Platform _platform;
   final BotDetector _botDetector;
   final Usage _usage;
   final File Function() _toolStampFile;

   @override
   Future<void> get({
     @required PubContext context,
     String directory,
     bool skipIfAbsent = false,
     bool upgrade = false,
     bool offline = false,
     bool checkLastModified = true,
     bool skipPubspecYamlCheck = false,
     bool generateSyntheticPackage = false,
     String flutterRootOverride,
   }) async {
     directory ??= _fileSystem.currentDirectory.path;

     final File pubSpecYaml = _fileSystem.file(
       _fileSystem.path.join(directory, 'pubspec.yaml'));
     final File packageConfigFile = _fileSystem.file(
       _fileSystem.path.join(directory, '.dart_tool', 'package_config.json'));
     final Directory generatedDirectory = _fileSystem.directory(
       _fileSystem.path.join(directory, '.dart_tool', 'flutter_gen'));

     if (!skipPubspecYamlCheck && !pubSpecYaml.existsSync()) {
       if (!skipIfAbsent) {
         throwToolExit('$directory: no pubspec.yaml found');
       }
       return;
     }

     final DateTime originalPubspecYamlModificationTime = pubSpecYaml.lastModifiedSync();

     if (!checkLastModified || _shouldRunPubGet(
       pubSpecYaml: pubSpecYaml,
       packageConfigFile: packageConfigFile,
     )) {
       final String command = upgrade ? 'upgrade' : 'get';
       final Status status = _logger.startProgress(
         'Running "flutter pub $command" in ${_fileSystem.path.basename(directory)}...',
       );
       final bool verbose = _logger.isVerbose;
       final List<String> args = <String>[
         if (verbose)
           '--verbose'
         else
           '--verbosity=warning',
         ...<String>[
           command,
           '--no-precompile',
         ],
         if (offline)
           '--offline',
       ];
       try {
         await batch(
           args,
           context: context,
           directory: directory,
           failureMessage: 'pub $command failed',
           retry: true,
           flutterRootOverride: flutterRootOverride,
         );
         status.stop();
       // The exception is rethrown, so don't catch only Exceptions.
       } catch (exception) { // ignore: avoid_catches_without_on_clauses
         status.cancel();
         rethrow;
       }
     }

     if (!packageConfigFile.existsSync()) {
       throwToolExit('$directory: pub did not create .dart_tools/package_config.json file.');
     }
     if (pubSpecYaml.lastModifiedSync() != originalPubspecYamlModificationTime) {
       throwToolExit(
         '$directory: unexpected concurrent modification of '
         'pubspec.yaml while running pub.');
     }
     // We don't check if dotPackages was actually modified, because as far as we can tell sometimes
     // pub will decide it does not need to actually modify it.
     final DateTime now = DateTime.now();
     if (now.isBefore(originalPubspecYamlModificationTime)) {
       _logger.printError(
         'Warning: File "${_fileSystem.path.absolute(pubSpecYaml.path)}" was created in the future. '
         'Optimizations that rely on comparing time stamps will be unreliable. Check your '
         'system clock for accuracy.\n'
         'The timestamp was: $originalPubspecYamlModificationTime\n'
         'The time now is: $now'
       );
     }
     await _updatePackageConfig(
       packageConfigFile,
       generatedDirectory,
       generateSyntheticPackage,
     );
   }

   @override
   Future<void> batch(
     List<String> arguments, {
     @required PubContext context,
     String directory,
     MessageFilter filter,
     String failureMessage = 'pub failed',
     @required bool retry,
     bool showTraceForErrors,
     String flutterRootOverride,
   }) async {
     showTraceForErrors ??= await _botDetector.isRunningOnBot;

     String lastPubMessage = 'no message';
     bool versionSolvingFailed = false;
     String filterWrapper(String line) {
       lastPubMessage = line;
       if (line.contains('version solving failed')) {
         versionSolvingFailed = true;
       }
       if (filter == null) {
         return line;
       }
       return filter(line);
     }

     if (showTraceForErrors) {
       arguments.insert(0, '--trace');
     }
     int attempts = 0;
     int duration = 1;
     int code;
     loop: while (true) {
       attempts += 1;
       code = await _processUtils.stream(
         _pubCommand(arguments),
         workingDirectory: directory,
         mapFunction: filterWrapper, // may set versionSolvingFailed, lastPubMessage
         environment: await _createPubEnvironment(context, flutterRootOverride),
       );
       String message;
       switch (code) {
         case 69: // UNAVAILABLE in https://github.com/dart-lang/pub/blob/master/lib/src/exit_codes.dart
           message = 'server unavailable';
           break;
         default:
           break loop;
       }
       assert(message != null);
       versionSolvingFailed = false;
       _logger.printStatus(
         '$failureMessage ($message) -- attempting retry $attempts in $duration '
         'second${ duration == 1 ? "" : "s"}...',
       );
       await Future<void>.delayed(Duration(seconds: duration));
       if (duration < 64) {
         duration *= 2;
       }
     }
     assert(code != null);

     String result = 'success';
     if (versionSolvingFailed) {
       result = 'version-solving-failed';
     } else if (code != 0) {
       result = 'failure';
     }
     PubResultEvent(
       context: context.toAnalyticsString(),
       result: result,
       usage: _usage,
     ).send();

     if (code != 0) {
       throwToolExit('$failureMessage ($code; $lastPubMessage)', exitCode: code);
     }
   }

   @override
   Future<void> interactively(
     List<String> arguments, {
     String directory,
     @required io.Stdio stdio,
   }) async {
     final io.Process process = await _processUtils.start(
       _pubCommand(arguments),
       workingDirectory: directory,
       environment: await _createPubEnvironment(PubContext.interactive),
     );

     // Pipe the Flutter tool stdin to the pub stdin.
     unawaited(process.stdin.addStream(stdio.stdin)
       // If pub exits unexpectedly with an error, that will be reported below
       // by the tool exit after the exit code check.
       .catchError((dynamic err, StackTrace stack) {
         _logger.printTrace('Echoing stdin to the pub subprocess failed:');
         _logger.printTrace('$err\n$stack');
       }
     ));

     // Pipe the pub stdout and stderr to the tool stdout and stderr.
     try {
       await Future.wait<dynamic>(<Future<dynamic>>[
         stdio.addStdoutStream(process.stdout),
         stdio.addStderrStream(process.stderr),
       ]);
     } on Exception catch (err, stack) {
       _logger.printTrace('Echoing stdout or stderr from the pub subprocess failed:');
       _logger.printTrace('$err\n$stack');
     }

     // Wait for pub to exit.
     final int code = await process.exitCode;
     if (code != 0) {
       throwToolExit('pub finished with exit code $code', exitCode: code);
     }
   }

   /// The command used for running pub.
   List<String> _pubCommand(List<String> arguments) {
     // TODO(jonahwilliams): refactor to use artifacts.
     final String sdkPath = _fileSystem.path.joinAll(<String>[
       Cache.flutterRoot,
       'bin',
       'cache',
       'dart-sdk',
       'bin',
       if (_platform.isWindows)
         'pub.bat'
       else
         'pub'
     ]);
     return <String>[sdkPath, ...arguments];
   }

   bool _shouldRunPubGet({ @required File pubSpecYaml, @required File packageConfigFile }) {
     if (!packageConfigFile.existsSync()) {
       return true;
     }
     final DateTime dotPackagesLastModified = packageConfigFile.lastModifiedSync();
     if (pubSpecYaml.lastModifiedSync().isAfter(dotPackagesLastModified)) {
       return true;
     }
     final File toolStampFile = _toolStampFile != null ? _toolStampFile() : null;
     if (toolStampFile != null &&
         toolStampFile.existsSync() &&
         toolStampFile.lastModifiedSync().isAfter(dotPackagesLastModified)) {
       return true;
     }
     return false;
   }

   // Returns the environment value that should be used when running pub.
   //
   // Includes any existing environment variable, if one exists.
   //
   // [context] provides extra information to package server requests to
   // understand usage.
   Future<String> _getPubEnvironmentValue(PubContext pubContext) async {
     // DO NOT update this function without contacting kevmoo.
     // We have server-side tooling that assumes the values are consistent.
     final String existing = _platform.environment[_kPubEnvironmentKey];
     final List<String> values = <String>[
       if (existing != null && existing.isNotEmpty) existing,
       if (await _botDetector.isRunningOnBot) 'flutter_bot',
       'flutter_cli',
       ...pubContext._values,
     ];
     return values.join(':');
   }

   String _getRootPubCacheIfAvailable() {
     if (_platform.environment.containsKey(_kPubCacheEnvironmentKey)) {
       return _platform.environment[_kPubCacheEnvironmentKey];
     }

     final String cachePath = _fileSystem.path.join(Cache.flutterRoot, '.pub-cache');
     if (_fileSystem.directory(cachePath).existsSync()) {
       _logger.printTrace('Using $cachePath for the pub cache.');
       return cachePath;
     }

     // Use pub's default location by returning null.
     return null;
   }

   /// The full environment used when running pub.
   ///
   /// [context] provides extra information to package server requests to
   /// understand usage.
   Future<Map<String, String>> _createPubEnvironment(PubContext context, [ String flutterRootOverride ]) async {
     final Map<String, String> environment = <String, String>{
       'FLUTTER_ROOT': flutterRootOverride ?? Cache.flutterRoot,
       _kPubEnvironmentKey: await _getPubEnvironmentValue(context),
     };
     final String pubCache = _getRootPubCacheIfAvailable();
     if (pubCache != null) {
       environment[_kPubCacheEnvironmentKey] = pubCache;
     }
     return environment;
   }

   /// Update the package configuration file.
   ///
   /// Creates a corresponding `package_config_subset` file that is used by the build
   /// system to avoid rebuilds caused by an updated pub timestamp.
   ///
   /// if [generateSyntheticPackage] is true then insert flutter_gen synthetic
   /// package into the package configuration. This is used by the l10n localization
   /// tooling to insert a new reference into the package_config file, allowing the import
   /// of a package URI that is not specified in the pubspec.yaml
   ///
   /// For more information, see:
   ///   * [generateLocalizations], `in lib/src/localizations/gen_l10n.dart`
   Future<void> _updatePackageConfig(
     File packageConfigFile,
     Directory generatedDirectory,
     bool generateSyntheticPackage,
   ) async {
     final PackageConfig packageConfig = await loadPackageConfigWithLogging(packageConfigFile, logger: _logger);

     packageConfigFile.parent
       .childFile('package_config_subset')
       .writeAsStringSync(_computePackageConfigSubset(
         packageConfig,
         _fileSystem,
       ));

     if (!generateSyntheticPackage) {
       return;
     }
     final Package flutterGen = Package('flutter_gen', generatedDirectory.uri, languageVersion: LanguageVersion(2, 8));
     if (packageConfig.packages.any((Package package) => package.name == 'flutter_gen')) {
       return;
     }
     final PackageConfig newPackageConfig = PackageConfig(
       <Package>[
         ...packageConfig.packages,
         flutterGen,
       ],
     );
     // There is no current API for saving a package_config without hitting the real filesystem.
     if (packageConfigFile.fileSystem is LocalFileSystem) {
       await savePackageConfig(newPackageConfig, packageConfigFile.parent.parent);
     }
   }

   // Subset the package config file to only the parts that are relevant for
   // rerunning the dart compiler.
   String _computePackageConfigSubset(PackageConfig packageConfig, FileSystem fileSystem) {
     final StringBuffer buffer = StringBuffer();
     for (final Package package in packageConfig.packages) {
       buffer.writeln(package.name);
       buffer.writeln(package.languageVersion);
       buffer.writeln(package.root);
       buffer.writeln(package.packageUriRoot);
     }
     buffer.writeln(packageConfig.version);
     return buffer.toString();
   }
 }
	// Copyright 2014 The Flutter 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 'package:meta/meta.dart';
	import 'package:package_config/package_config.dart';
	import 'package:process/process.dart';

	import '../base/bot_detector.dart';
	import '../base/common.dart';
	import '../base/context.dart';
	import '../base/file_system.dart';
	import '../base/io.dart' as io;
	import '../base/logger.dart';
	import '../base/platform.dart';
	import '../base/process.dart';
	import '../cache.dart';
	import '../dart/package_map.dart';
	import '../reporting/reporting.dart';

	/// The [Pub] instance.
	Pub get pub => context.get<Pub>();

	/// The console environment key used by the pub tool.
	const String _kPubEnvironmentKey = 'PUB_ENVIRONMENT';

	/// The console environment key used by the pub tool to find the cache directory.
	const String _kPubCacheEnvironmentKey = 'PUB_CACHE';

	typedef MessageFilter = String Function(String message);

	/// Represents Flutter-specific data that is added to the `PUB_ENVIRONMENT`
	/// environment variable and allows understanding the type of requests made to
	/// the package site on Flutter's behalf.
	// DO NOT update without contacting kevmoo.
	// We have server-side tooling that assumes the values are consistent.
	class PubContext {
	PubContext._(this._values) {
	for (final String item in _values) {
	if (!_validContext.hasMatch(item)) {
	throw ArgumentError.value(
	_values, 'value', 'Must match RegExp ${_validContext.pattern}');
	}
	}
	}

	static PubContext getVerifyContext(String commandName) =>
	PubContext._(<String>['verify', commandName.replaceAll('-', '_')]);

	static final PubContext create = PubContext._(<String>['create']);
	static final PubContext createPackage = PubContext._(<String>['create_pkg']);
	static final PubContext createPlugin = PubContext._(<String>['create_plugin']);
	static final PubContext interactive = PubContext._(<String>['interactive']);
	static final PubContext pubGet = PubContext._(<String>['get']);
	static final PubContext pubUpgrade = PubContext._(<String>['upgrade']);
	static final PubContext pubForward = PubContext._(<String>['forward']);
	static final PubContext runTest = PubContext._(<String>['run_test']);
	static final PubContext flutterTests = PubContext._(<String>['flutter_tests']);
	static final PubContext updatePackages = PubContext._(<String>['update_packages']);

	final List<String> _values;

	static final RegExp _validContext = RegExp('[a-z][a-z_]*[a-z]');

	@override
	String toString() => 'PubContext: ${_values.join(':')}';

	String toAnalyticsString() {
	return _values.map((String s) => s.replaceAll('_', '-')).toList().join('-');
	}
	}

	/// A handle for interacting with the pub tool.
	abstract class Pub {
	/// Create a default [Pub] instance.
	factory Pub({
	@required FileSystem fileSystem,
	@required Logger logger,
	@required ProcessManager processManager,
	@required Platform platform,
	@required BotDetector botDetector,
	@required Usage usage,
	File Function() toolStampFile,
	}) = _DefaultPub;

	/// Runs `pub get`.
	///
	/// [context] provides extra information to package server requests to
	/// understand usage.
	Future<void> get({
	@required PubContext context,
	String directory,
	bool skipIfAbsent = false,
	bool upgrade = false,
	bool offline = false,
	bool checkLastModified = true,
	bool skipPubspecYamlCheck = false,
	bool generateSyntheticPackage = false,
	String flutterRootOverride,
	});

	/// Runs pub in 'batch' mode.
	///
	/// forwarding complete lines written by pub to its stdout/stderr streams to
	/// the corresponding stream of this process, optionally applying filtering.
	/// The pub process will not receive anything on its stdin stream.
	///
	/// The `--trace` argument is passed to `pub` (by mutating the provided
	/// `arguments` list) when `showTraceForErrors` is true, and when `showTraceForErrors`
	/// is null/unset, and `isRunningOnBot` is true.
	///
	/// [context] provides extra information to package server requests to
	/// understand usage.
	Future<void> batch(
	List<String> arguments, {
	@required PubContext context,
	String directory,
	MessageFilter filter,
	String failureMessage = 'pub failed',
	@required bool retry,
	bool showTraceForErrors,
	});


	/// Runs pub in 'interactive' mode.
	///
	/// directly piping the stdin stream of this process to that of pub, and the
	/// stdout/stderr stream of pub to the corresponding streams of this process.
	Future<void> interactively(
	List<String> arguments, {
	String directory,
	@required io.Stdio stdio,
	});
	}

	class _DefaultPub implements Pub {
	_DefaultPub({
	@required FileSystem fileSystem,
	@required Logger logger,
	@required ProcessManager processManager,
	@required Platform platform,
	@required BotDetector botDetector,
	@required Usage usage,
	File Function() toolStampFile,
	}) : _toolStampFile = toolStampFile,
	_fileSystem = fileSystem,
	_logger = logger,
	_platform = platform,
	_botDetector = botDetector,
	_usage = usage,
	_processUtils = ProcessUtils(
	logger: logger,
	processManager: processManager,
	);

	final FileSystem _fileSystem;
	final Logger _logger;
	final ProcessUtils _processUtils;
	final Platform _platform;
	final BotDetector _botDetector;
	final Usage _usage;
	final File Function() _toolStampFile;

	@override
	Future<void> get({
	@required PubContext context,
	String directory,
	bool skipIfAbsent = false,
	bool upgrade = false,
	bool offline = false,
	bool checkLastModified = true,
	bool skipPubspecYamlCheck = false,
	bool generateSyntheticPackage = false,
	String flutterRootOverride,
	}) async {
	directory ??= _fileSystem.currentDirectory.path;

	final File pubSpecYaml = _fileSystem.file(
	_fileSystem.path.join(directory, 'pubspec.yaml'));
	final File packageConfigFile = _fileSystem.file(
	_fileSystem.path.join(directory, '.dart_tool', 'package_config.json'));
	final Directory generatedDirectory = _fileSystem.directory(
	_fileSystem.path.join(directory, '.dart_tool', 'flutter_gen'));

	if (!skipPubspecYamlCheck && !pubSpecYaml.existsSync()) {
	if (!skipIfAbsent) {
	throwToolExit('$directory: no pubspec.yaml found');
	}
	return;
	}

	final DateTime originalPubspecYamlModificationTime = pubSpecYaml.lastModifiedSync();

	if (!checkLastModified \|\| _shouldRunPubGet(
	pubSpecYaml: pubSpecYaml,
	packageConfigFile: packageConfigFile,
	)) {
	final String command = upgrade ? 'upgrade' : 'get';
	final Status status = _logger.startProgress(
	'Running "flutter pub $command" in ${_fileSystem.path.basename(directory)}...',
	);
	final bool verbose = _logger.isVerbose;
	final List<String> args = <String>[
	if (verbose)
	'--verbose'
	else
	'--verbosity=warning',
	...<String>[
	command,
	'--no-precompile',
	],
	if (offline)
	'--offline',
	];
	try {
	await batch(
	args,
	context: context,
	directory: directory,
	failureMessage: 'pub $command failed',
	retry: true,
	flutterRootOverride: flutterRootOverride,
	);
	status.stop();
	// The exception is rethrown, so don't catch only Exceptions.
	} catch (exception) { // ignore: avoid_catches_without_on_clauses
	status.cancel();
	rethrow;
	}
	}

	if (!packageConfigFile.existsSync()) {
	throwToolExit('$directory: pub did not create .dart_tools/package_config.json file.');
	}
	if (pubSpecYaml.lastModifiedSync() != originalPubspecYamlModificationTime) {
	throwToolExit(
	'$directory: unexpected concurrent modification of '
	'pubspec.yaml while running pub.');
	}
	// We don't check if dotPackages was actually modified, because as far as we can tell sometimes
	// pub will decide it does not need to actually modify it.
	final DateTime now = DateTime.now();
	if (now.isBefore(originalPubspecYamlModificationTime)) {
	_logger.printError(
	'Warning: File "${_fileSystem.path.absolute(pubSpecYaml.path)}" was created in the future. '
	'Optimizations that rely on comparing time stamps will be unreliable. Check your '
	'system clock for accuracy.\n'
	'The timestamp was: $originalPubspecYamlModificationTime\n'
	'The time now is: $now'
	);
	}
	await _updatePackageConfig(
	packageConfigFile,
	generatedDirectory,
	generateSyntheticPackage,
	);
	}

	@override
	Future<void> batch(
	List<String> arguments, {
	@required PubContext context,
	String directory,
	MessageFilter filter,
	String failureMessage = 'pub failed',
	@required bool retry,
	bool showTraceForErrors,
	String flutterRootOverride,
	}) async {
	showTraceForErrors ??= await _botDetector.isRunningOnBot;

	String lastPubMessage = 'no message';
	bool versionSolvingFailed = false;
	String filterWrapper(String line) {
	lastPubMessage = line;
	if (line.contains('version solving failed')) {
	versionSolvingFailed = true;
	}
	if (filter == null) {
	return line;
	}
	return filter(line);
	}

	if (showTraceForErrors) {
	arguments.insert(0, '--trace');
	}
	int attempts = 0;
	int duration = 1;
	int code;
	loop: while (true) {
	attempts += 1;
	code = await _processUtils.stream(
	_pubCommand(arguments),
	workingDirectory: directory,
	mapFunction: filterWrapper, // may set versionSolvingFailed, lastPubMessage
	environment: await _createPubEnvironment(context, flutterRootOverride),
	);
	String message;
	switch (code) {
	case 69: // UNAVAILABLE in https://github.com/dart-lang/pub/blob/master/lib/src/exit_codes.dart
	message = 'server unavailable';
	break;
	default:
	break loop;
	}
	assert(message != null);
	versionSolvingFailed = false;
	_logger.printStatus(
	'$failureMessage ($message) -- attempting retry $attempts in $duration '
	'second${ duration == 1 ? "" : "s"}...',
	);
	await Future<void>.delayed(Duration(seconds: duration));
	if (duration < 64) {
	duration *= 2;
	}
	}
	assert(code != null);

	String result = 'success';
	if (versionSolvingFailed) {
	result = 'version-solving-failed';
	} else if (code != 0) {
	result = 'failure';
	}
	PubResultEvent(
	context: context.toAnalyticsString(),
	result: result,
	usage: _usage,
	).send();

	if (code != 0) {
	throwToolExit('$failureMessage ($code; $lastPubMessage)', exitCode: code);
	}
	}

	@override
	Future<void> interactively(
	List<String> arguments, {
	String directory,
	@required io.Stdio stdio,
	}) async {
	final io.Process process = await _processUtils.start(
	_pubCommand(arguments),
	workingDirectory: directory,
	environment: await _createPubEnvironment(PubContext.interactive),
	);

	// Pipe the Flutter tool stdin to the pub stdin.
	unawaited(process.stdin.addStream(stdio.stdin)
	// If pub exits unexpectedly with an error, that will be reported below
	// by the tool exit after the exit code check.
	.catchError((dynamic err, StackTrace stack) {
	_logger.printTrace('Echoing stdin to the pub subprocess failed:');
	_logger.printTrace('$err\n$stack');
	}
	));

	// Pipe the pub stdout and stderr to the tool stdout and stderr.
	try {
	await Future.wait<dynamic>(<Future<dynamic>>[
	stdio.addStdoutStream(process.stdout),
	stdio.addStderrStream(process.stderr),
	]);
	} on Exception catch (err, stack) {
	_logger.printTrace('Echoing stdout or stderr from the pub subprocess failed:');
	_logger.printTrace('$err\n$stack');
	}

	// Wait for pub to exit.
	final int code = await process.exitCode;
	if (code != 0) {
	throwToolExit('pub finished with exit code $code', exitCode: code);
	}
	}

	/// The command used for running pub.
	List<String> _pubCommand(List<String> arguments) {
	// TODO(jonahwilliams): refactor to use artifacts.
	final String sdkPath = _fileSystem.path.joinAll(<String>[
	Cache.flutterRoot,
	'bin',
	'cache',
	'dart-sdk',
	'bin',
	if (_platform.isWindows)
	'pub.bat'
	else
	'pub'
	]);
	return <String>[sdkPath, ...arguments];
	}

	bool _shouldRunPubGet({ @required File pubSpecYaml, @required File packageConfigFile }) {
	if (!packageConfigFile.existsSync()) {
	return true;
	}
	final DateTime dotPackagesLastModified = packageConfigFile.lastModifiedSync();
	if (pubSpecYaml.lastModifiedSync().isAfter(dotPackagesLastModified)) {
	return true;
	}
	final File toolStampFile = _toolStampFile != null ? _toolStampFile() : null;
	if (toolStampFile != null &&
	toolStampFile.existsSync() &&
	toolStampFile.lastModifiedSync().isAfter(dotPackagesLastModified)) {
	return true;
	}
	return false;
	}

	// Returns the environment value that should be used when running pub.
	//
	// Includes any existing environment variable, if one exists.
	//
	// [context] provides extra information to package server requests to
	// understand usage.
	Future<String> _getPubEnvironmentValue(PubContext pubContext) async {
	// DO NOT update this function without contacting kevmoo.
	// We have server-side tooling that assumes the values are consistent.
	final String existing = _platform.environment[_kPubEnvironmentKey];
	final List<String> values = <String>[
	if (existing != null && existing.isNotEmpty) existing,
	if (await _botDetector.isRunningOnBot) 'flutter_bot',
	'flutter_cli',
	...pubContext._values,
	];
	return values.join(':');
	}

	String _getRootPubCacheIfAvailable() {
	if (_platform.environment.containsKey(_kPubCacheEnvironmentKey)) {
	return _platform.environment[_kPubCacheEnvironmentKey];
	}

	final String cachePath = _fileSystem.path.join(Cache.flutterRoot, '.pub-cache');
	if (_fileSystem.directory(cachePath).existsSync()) {
	_logger.printTrace('Using $cachePath for the pub cache.');
	return cachePath;
	}

	// Use pub's default location by returning null.
	return null;
	}

	/// The full environment used when running pub.
	///
	/// [context] provides extra information to package server requests to
	/// understand usage.
	Future<Map<String, String>> _createPubEnvironment(PubContext context, [ String flutterRootOverride ]) async {
	final Map<String, String> environment = <String, String>{
	'FLUTTER_ROOT': flutterRootOverride ?? Cache.flutterRoot,
	_kPubEnvironmentKey: await _getPubEnvironmentValue(context),
	};
	final String pubCache = _getRootPubCacheIfAvailable();
	if (pubCache != null) {
	environment[_kPubCacheEnvironmentKey] = pubCache;
	}
	return environment;
	}

	/// Update the package configuration file.
	///
	/// Creates a corresponding `package_config_subset` file that is used by the build
	/// system to avoid rebuilds caused by an updated pub timestamp.
	///
	/// if [generateSyntheticPackage] is true then insert flutter_gen synthetic
	/// package into the package configuration. This is used by the l10n localization
	/// tooling to insert a new reference into the package_config file, allowing the import
	/// of a package URI that is not specified in the pubspec.yaml
	///
	/// For more information, see:
	/// * [generateLocalizations], `in lib/src/localizations/gen_l10n.dart`
	Future<void> _updatePackageConfig(
	File packageConfigFile,
	Directory generatedDirectory,
	bool generateSyntheticPackage,
	) async {
	final PackageConfig packageConfig = await loadPackageConfigWithLogging(packageConfigFile, logger: _logger);

	packageConfigFile.parent
	.childFile('package_config_subset')
	.writeAsStringSync(_computePackageConfigSubset(
	packageConfig,
	_fileSystem,
	));

	if (!generateSyntheticPackage) {
	return;
	}
	final Package flutterGen = Package('flutter_gen', generatedDirectory.uri, languageVersion: LanguageVersion(2, 8));
	if (packageConfig.packages.any((Package package) => package.name == 'flutter_gen')) {
	return;
	}
	final PackageConfig newPackageConfig = PackageConfig(
	<Package>[
	...packageConfig.packages,
	flutterGen,
	],
	);
	// There is no current API for saving a package_config without hitting the real filesystem.
	if (packageConfigFile.fileSystem is LocalFileSystem) {
	await savePackageConfig(newPackageConfig, packageConfigFile.parent.parent);
	}
	}

	// Subset the package config file to only the parts that are relevant for
	// rerunning the dart compiler.
	String _computePackageConfigSubset(PackageConfig packageConfig, FileSystem fileSystem) {
	final StringBuffer buffer = StringBuffer();
	for (final Package package in packageConfig.packages) {
	buffer.writeln(package.name);
	buffer.writeln(package.languageVersion);
	buffer.writeln(package.root);
	buffer.writeln(package.packageUriRoot);
	}
	buffer.writeln(packageConfig.version);
	return buffer.toString();
	}
	}