[flutter_tool] partial null safety migration of tool source code (#105798)

dev/bots/test.dart

@@ -339,6 +339,7 @@ Future<void> _runGeneralToolTests() async {
     _toolsPath,
     testPaths: <String>[path.join('test', 'general.shard')],
     enableFlutterToolAsserts: false,
+
     // Detect unit test time regressions (poor time delay handling, etc).
     // This overrides the 15 minute default for tools tests.
     // See the README.md and dart_test.yaml files in the flutter_tools package.

packages/flutter_tools/lib/executable.dart

@@ -2,10 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
-import 'package:meta/meta.dart';
-
 import 'runner.dart' as runner;
 import 'src/artifacts.dart';
 import 'src/base/context.dart';
@@ -110,7 +106,7 @@ Future<void> main(List<String> args) async {
       // devtools source code.
       DevtoolsLauncher: () => DevtoolsServerLauncher(
         processManager: globals.processManager,
-        dartExecutable: globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
+        dartExecutable: globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path,
         logger: globals.logger,
         botDetector: globals.botDetector,
       ),
@@ -134,8 +130,8 @@ Future<void> main(List<String> args) async {
 }
 
 List<FlutterCommand> generateCommands({
-  @required bool verboseHelp,
-  @required bool verbose,
+  required bool verboseHelp,
+  required bool verbose,
 }) => <FlutterCommand>[
   AnalyzeCommand(
     verboseHelp: verboseHelp,
@@ -144,7 +140,7 @@ List<FlutterCommand> generateCommands({
     processManager: globals.processManager,
     logger: globals.logger,
     terminal: globals.terminal,
-    artifacts: globals.artifacts,
+    artifacts: globals.artifacts!,
   ),
   AssembleCommand(verboseHelp: verboseHelp, buildSystem: globals.buildSystem),
   AttachCommand(verboseHelp: verboseHelp),
@@ -210,9 +206,9 @@ List<FlutterCommand> generateCommands({
 /// Our logger class hierarchy and runtime requirements are overly complicated.
 class LoggerFactory {
   LoggerFactory({
-    @required Terminal terminal,
-    @required Stdio stdio,
-    @required OutputPreferences outputPreferences,
+    required Terminal terminal,
+    required Stdio stdio,
+    required OutputPreferences outputPreferences,
     StopwatchFactory stopwatchFactory = const StopwatchFactory(),
   }) : _terminal = terminal,
        _stdio = stdio,
@@ -226,11 +222,11 @@ class LoggerFactory {
 
   /// Create the appropriate logger for the current platform and configuration.
   Logger createLogger({
-    @required bool verbose,
-    @required bool prefixedErrors,
-    @required bool machine,
-    @required bool daemon,
-    @required bool windows,
+    required bool verbose,
+    required bool prefixedErrors,
+    required bool machine,
+    required bool daemon,
+    required bool windows,
   }) {
     Logger logger;
     if (windows) {

packages/flutter_tools/lib/runner.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:async';
 
@@ -31,9 +31,9 @@ Future<int> run(
     bool muteCommandLogging = false,
     bool verbose = false,
     bool verboseHelp = false,
-    bool reportCrashes,
-    String flutterVersion,
-    Map<Type, Generator> overrides,
+    bool? reportCrashes,
+    String? flutterVersion,
+    Map<Type, Generator>? overrides,
   }) async {
   if (muteCommandLogging) {
     // Remove the verbose option; for help and doctor, users don't need to see
@@ -55,8 +55,8 @@ Future<int> run(
     );
 
     String getVersion() => flutterVersion ?? globals.flutterVersion.getVersionString(redactUnknownBranches: true);
-    Object firstError;
-    StackTrace firstStackTrace;
+    Object? firstError;
+    StackTrace? firstStackTrace;
     return runZoned<Future<int>>(() async {
       try {
         await runner.run(args);
@@ -74,7 +74,7 @@ Future<int> run(
         // This catches all exceptions to send to crash logging, etc.
         firstError = error;
         firstStackTrace = stackTrace;
-        return _handleToolError(error, stackTrace, verbose, args, reportCrashes, getVersion);
+        return _handleToolError(error, stackTrace, verbose, args, reportCrashes!, getVersion);
       }
     }, onError: (Object error, StackTrace stackTrace) async { // ignore: deprecated_member_use
       // If sending a crash report throws an error into the zone, we don't want
@@ -82,14 +82,14 @@ Future<int> run(
       // to send the original error that triggered the crash report.
       firstError ??= error;
       firstStackTrace ??= stackTrace;
-      await _handleToolError(firstError, firstStackTrace, verbose, args, reportCrashes, getVersion);
+      await _handleToolError(firstError!, firstStackTrace, verbose, args, reportCrashes!, getVersion);
     });
   }, overrides: overrides);
 }
 
 Future<int> _handleToolError(
-  dynamic error,
-  StackTrace stackTrace,
+  Object error,
+  StackTrace? stackTrace,
   bool verbose,
   List<String> args,
   bool reportCrashes,
@@ -102,7 +102,7 @@ Future<int> _handleToolError(
     return _exit(64);
   } else if (error is ToolExit) {
     if (error.message != null) {
-      globals.printError(error.message);
+      globals.printError(error.message!);
     }
     if (verbose) {
       globals.printError('\n$stackTrace\n');
@@ -138,7 +138,7 @@ Future<int> _handleToolError(
       );
       await crashReportSender.sendReport(
         error: error,
-        stackTrace: stackTrace,
+        stackTrace: stackTrace!,
         getFlutterVersion: getFlutterVersion,
         command: args.join(' '),
       );
@@ -159,17 +159,17 @@ Future<int> _handleToolError(
       final CrashDetails details = CrashDetails(
         command: _crashCommand(args),
         error: error,
-        stackTrace: stackTrace,
+        stackTrace: stackTrace!,
         doctorText: doctorText,
       );
       final File file = await _createLocalCrashReport(details);
-      await globals.crashReporter.informUser(details, file);
+      await globals.crashReporter!.informUser(details, file);
 
       return _exit(1);
     // This catch catches all exceptions to ensure the message below is printed.
-    } catch (error) { // ignore: avoid_catches_without_on_clauses
+    } catch (error, st) { // ignore: avoid_catches_without_on_clauses
       globals.stdio.stderrWrite(
-        'Unable to generate crash report due to secondary error: $error\n'
+        'Unable to generate crash report due to secondary error: $error\n$st\n'
         '${globals.userMessages.flutterToolBugInstructions}\n',
       );
       // Any exception thrown here (including one thrown by `_exit()`) will
@@ -241,7 +241,7 @@ Future<int> _exit(int code) async {
   }
 
   // Run shutdown hooks before flushing logs
-  await globals.shutdownHooks.runShutdownHooks();
+  await globals.shutdownHooks!.runShutdownHooks();
 
   final Completer<void> completer = Completer<void>();
 

packages/flutter_tools/lib/src/android/android_workflow.dart

@@ -271,7 +271,7 @@ class AndroidValidator extends DoctorValidator {
 /// SDK have been accepted.
 class AndroidLicenseValidator extends DoctorValidator {
   AndroidLicenseValidator({
-    required AndroidSdk androidSdk,
+    required AndroidSdk? androidSdk,
     required Platform platform,
     required OperatingSystemUtils operatingSystemUtils,
     required FileSystem fileSystem,
@@ -291,7 +291,7 @@ class AndroidLicenseValidator extends DoctorValidator {
        _userMessages = userMessages,
        super('Android license subvalidator');
 
-  final AndroidSdk _androidSdk;
+  final AndroidSdk? _androidSdk;
   final AndroidStudio? _androidStudio;
   final Stdio _stdio;
   final OperatingSystemUtils _operatingSystemUtils;
@@ -309,13 +309,13 @@ class AndroidLicenseValidator extends DoctorValidator {
     final List<ValidationMessage> messages = <ValidationMessage>[];
 
     // Match pre-existing early termination behavior
-    if (_androidSdk == null || _androidSdk.latestVersion == null ||
-        _androidSdk.validateSdkWellFormed().isNotEmpty ||
+    if (_androidSdk == null || _androidSdk?.latestVersion == null ||
+        _androidSdk!.validateSdkWellFormed().isNotEmpty ||
         ! await _checkJavaVersionNoOutput()) {
       return ValidationResult(ValidationType.missing, messages);
     }
 
-    final String sdkVersionText = _userMessages.androidStatusInfo(_androidSdk.latestVersion!.buildToolsVersionName);
+    final String sdkVersionText = _userMessages.androidStatusInfo(_androidSdk!.latestVersion!.buildToolsVersionName);
 
     // Check for licenses.
     switch (await licensesAccepted) {
@@ -392,8 +392,8 @@ class AndroidLicenseValidator extends DoctorValidator {
 
     try {
       final Process process = await _processManager.start(
-        <String>[_androidSdk.sdkManagerPath!, '--licenses'],
-        environment: _androidSdk.sdkManagerEnv,
+        <String>[_androidSdk!.sdkManagerPath!, '--licenses'],
+        environment: _androidSdk!.sdkManagerEnv,
       );
       process.stdin.write('n\n');
       // We expect logcat streams to occasionally contain invalid utf-8,
@@ -432,8 +432,8 @@ class AndroidLicenseValidator extends DoctorValidator {
 
     try {
       final Process process = await _processManager.start(
-        <String>[_androidSdk.sdkManagerPath!, '--licenses'],
-        environment: _androidSdk.sdkManagerEnv,
+        <String>[_androidSdk!.sdkManagerPath!, '--licenses'],
+        environment: _androidSdk!.sdkManagerEnv,
       );
 
       // The real stdin will never finish streaming. Pipe until the child process
@@ -463,7 +463,7 @@ class AndroidLicenseValidator extends DoctorValidator {
       return exitCode == 0;
     } on ProcessException catch (e) {
       throwToolExit(_userMessages.androidCannotRunSdkManager(
-        _androidSdk.sdkManagerPath ?? '',
+        _androidSdk?.sdkManagerPath ?? '',
         e.toString(),
         _platform,
       ));
@@ -471,7 +471,7 @@ class AndroidLicenseValidator extends DoctorValidator {
   }
 
   bool _canRunSdkManager() {
-    final String? sdkManagerPath = _androidSdk.sdkManagerPath;
+    final String? sdkManagerPath = _androidSdk?.sdkManagerPath;
     if (sdkManagerPath == null) {
       return false;
     }

packages/flutter_tools/lib/src/android/application_package.dart

@@ -97,7 +97,7 @@ class AndroidApk extends ApplicationPackage implements PrebuiltApplicationPackag
   /// Creates a new AndroidApk based on the information in the Android manifest.
   static Future<AndroidApk?> fromAndroidProject(
     AndroidProject androidProject, {
-    required AndroidSdk androidSdk,
+    required AndroidSdk? androidSdk,
     required ProcessManager processManager,
     required UserMessages userMessages,
     required ProcessUtils processUtils,
@@ -113,7 +113,7 @@ class AndroidApk extends ApplicationPackage implements PrebuiltApplicationPackag
         // the application Id, so we need to look at what was actually built.
         return AndroidApk.fromApk(
           apkFile,
-          androidSdk: androidSdk,
+          androidSdk: androidSdk!,
           processManager: processManager,
           logger: logger,
           userMessages: userMessages,

packages/flutter_tools/lib/src/base/utils.dart

@@ -157,9 +157,9 @@ class SettingsFile {
 
 /// Given a data structure which is a Map of String to dynamic values, return
 /// the same structure (`Map<String, dynamic>`) with the correct runtime types.
-Map<String, dynamic>? castStringKeyedMap(dynamic untyped) {
+Map<String, Object?>? castStringKeyedMap(Object? untyped) {
   final Map<dynamic, dynamic>? map = untyped as Map<dynamic, dynamic>?;
-  return map?.cast<String, dynamic>();
+  return map?.cast<String, Object?>();
 }
 
 /// Smallest column that will be used for text wrapping. If the requested column

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

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:async';
 
@@ -49,10 +49,10 @@ import 'run.dart';
 class DriveCommand extends RunCommandBase {
   DriveCommand({
     bool verboseHelp = false,
-    @visibleForTesting FlutterDriverFactory flutterDriverFactory,
-    @required FileSystem fileSystem,
-    @required Logger logger,
-    @required Platform platform,
+    @visibleForTesting FlutterDriverFactory? flutterDriverFactory,
+    required FileSystem fileSystem,
+    required Logger? logger,
+    required Platform platform,
   }) : _flutterDriverFactory = flutterDriverFactory,
        _fileSystem = fileSystem,
        _logger = logger,
@@ -156,15 +156,15 @@ class DriveCommand extends RunCommandBase {
   // specified not to.
   @override
   bool get shouldRunPub {
-    if (argResults.wasParsed('pub') && !boolArgDeprecated('pub')) {
+    if (argResults!.wasParsed('pub') && !boolArgDeprecated('pub')) {
       return false;
     }
     return true;
   }
 
-  FlutterDriverFactory _flutterDriverFactory;
+  FlutterDriverFactory? _flutterDriverFactory;
   final FileSystem _fileSystem;
-  final Logger _logger;
+  final Logger? _logger;
   final FileSystemUtils _fsUtils;
 
   @override
@@ -179,9 +179,9 @@ class DriveCommand extends RunCommandBase {
   @override
   final List<String> aliases = <String>['driver'];
 
-  String get userIdentifier => stringArgDeprecated(FlutterOptions.kDeviceUser);
+  String? get userIdentifier => stringArgDeprecated(FlutterOptions.kDeviceUser);
 
-  String get screenshot => stringArgDeprecated('screenshot');
+  String? get screenshot => stringArgDeprecated('screenshot');
 
   @override
   bool get startPausedDefault => true;
@@ -192,7 +192,7 @@ class DriveCommand extends RunCommandBase {
   @override
   Future<void> validateCommand() async {
     if (userIdentifier != null) {
-      final Device device = await findTargetDevice();
+      final Device? device = await findTargetDevice();
       if (device is! AndroidDevice) {
         throwToolExit('--${FlutterOptions.kDeviceUser} is only supported for Android');
       }
@@ -202,39 +202,39 @@ class DriveCommand extends RunCommandBase {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    final String testFile = _getTestFile();
+    final String testFile = _getTestFile()!;
     if (testFile == null) {
       throwToolExit(null);
     }
     if (await _fileSystem.type(testFile) != FileSystemEntityType.file) {
       throwToolExit('Test file not found: $testFile');
     }
-    final String applicationBinaryPath = stringArgDeprecated(FlutterOptions.kUseApplicationBinary);
-    final Device device = await findTargetDevice(includeUnsupportedDevices: applicationBinaryPath == null);
+    final String? applicationBinaryPath = stringArgDeprecated(FlutterOptions.kUseApplicationBinary);
+    final Device? device = await findTargetDevice(includeUnsupportedDevices: applicationBinaryPath == null);
     if (device == null) {
       throwToolExit(null);
     }
     if (screenshot != null && !device.supportsScreenshot) {
-      _logger.printError('Screenshot not supported for ${device.name}.');
+      _logger!.printError('Screenshot not supported for ${device.name}.');
     }
 
     final bool web = device is WebServerDevice || device is ChromiumDevice;
     _flutterDriverFactory ??= FlutterDriverFactory(
-      applicationPackageFactory: ApplicationPackageFactory.instance,
-      logger: _logger,
+      applicationPackageFactory: ApplicationPackageFactory.instance!,
+      logger: _logger!,
       processUtils: globals.processUtils,
-      dartSdkPath: globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
-      devtoolsLauncher: DevtoolsLauncher.instance,
+      dartSdkPath: globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path,
+      devtoolsLauncher: DevtoolsLauncher.instance!,
     );
     final PackageConfig packageConfig = await loadPackageConfigWithLogging(
       _fileSystem.file('.packages'),
-      logger: _logger,
+      logger: _logger!,
       throwOnError: false,
-    ) ?? PackageConfig.empty;
-    final DriverService driverService = _flutterDriverFactory.createDriverService(web);
+    );
+    final DriverService driverService = _flutterDriverFactory!.createDriverService(web);
     final BuildInfo buildInfo = await getBuildInfo();
     final DebuggingOptions debuggingOptions = await createDebuggingOptions(web);
-    final File applicationBinary = applicationBinaryPath == null
+    final File? applicationBinary = applicationBinaryPath == null
       ? null
       : _fileSystem.file(applicationBinaryPath);
 
@@ -245,7 +245,7 @@ class DriveCommand extends RunCommandBase {
           buildInfo,
           device,
           debuggingOptions,
-          ipv6,
+          ipv6 ?? false,
           applicationBinary: applicationBinary,
           route: route,
           userIdentifier: userIdentifier,
@@ -260,7 +260,7 @@ class DriveCommand extends RunCommandBase {
           }
         );
       } else {
-        final Uri uri = Uri.tryParse(stringArgDeprecated('use-existing-app'));
+        final Uri? uri = Uri.tryParse(stringArgDeprecated('use-existing-app')!);
         if (uri == null) {
           throwToolExit('Invalid VM Service URI: ${stringArgDeprecated('use-existing-app')}');
         }
@@ -268,7 +268,7 @@ class DriveCommand extends RunCommandBase {
           uri,
           device,
           debuggingOptions,
-          ipv6,
+          ipv6 ?? false,
         );
       }
 
@@ -279,10 +279,10 @@ class DriveCommand extends RunCommandBase {
         packageConfig,
         chromeBinary: stringArgDeprecated('chrome-binary'),
         headless: boolArgDeprecated('headless'),
-        browserDimension: stringArgDeprecated('browser-dimension').split(','),
+        browserDimension: stringArgDeprecated('browser-dimension')!.split(','),
         browserName: stringArgDeprecated('browser-name'),
         driverPort: stringArgDeprecated('driver-port') != null
-          ? int.tryParse(stringArgDeprecated('driver-port'))
+          ? int.tryParse(stringArgDeprecated('driver-port')!)
           : null,
         androidEmulator: boolArgDeprecated('android-emulator'),
         profileMemory: stringArgDeprecated('profile-memory'),
@@ -293,10 +293,10 @@ class DriveCommand extends RunCommandBase {
         screenshotTaken = true;
       }
 
-      if (boolArgDeprecated('keep-app-running') ?? (argResults['use-existing-app'] != null)) {
-        _logger.printStatus('Leaving the application running.');
+      if (boolArgDeprecated('keep-app-running')) {
+        _logger!.printStatus('Leaving the application running.');
       } else {
-        final File skslFile = stringArgDeprecated('write-sksl-on-exit') != null
+        final File? skslFile = stringArgDeprecated('write-sksl-on-exit') != null
           ? _fileSystem.file(stringArgDeprecated('write-sksl-on-exit'))
           : null;
         await driverService.stop(userIdentifier: userIdentifier, writeSkslOnExit: skslFile);
@@ -316,8 +316,8 @@ class DriveCommand extends RunCommandBase {
     return FlutterCommandResult.success();
   }
 
-  String _getTestFile() {
-    if (argResults['driver'] != null) {
+  String? _getTestFile() {
+    if (argResults!['driver'] != null) {
       return stringArgDeprecated('driver');
     }
 
@@ -332,7 +332,7 @@ class DriveCommand extends RunCommandBase {
     // for the corresponding test file relative to it.
     if (!_fileSystem.path.isRelative(appFile)) {
       if (!_fileSystem.path.isWithin(packageDir, appFile)) {
-        _logger.printError(
+        _logger!.printError(
           'Application file $appFile is outside the package directory $packageDir'
         );
         return null;
@@ -344,7 +344,7 @@ class DriveCommand extends RunCommandBase {
     final List<String> parts = _fileSystem.path.split(appFile);
 
     if (parts.length < 2) {
-      _logger.printError(
+      _logger!.printError(
         'Application file $appFile must reside in one of the sub-directories '
         'of the package structure, not in the root directory.'
       );
@@ -372,9 +372,9 @@ class DriveCommand extends RunCommandBase {
         'png',
       );
       await device.takeScreenshot(outputFile);
-      _logger.printStatus('Screenshot written to ${outputFile.path}');
+      _logger!.printStatus('Screenshot written to ${outputFile.path}');
     } on Exception catch (error) {
-      _logger.printError('Error taking screenshot: $error');
+      _logger!.printError('Error taking screenshot: $error');
     }
   }
 }

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

@@ -2,10 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
-import 'package:meta/meta.dart';
-
 import '../base/common.dart';
 import '../base/logger.dart';
 import '../base/platform.dart';
@@ -18,10 +14,10 @@ import '../runner/flutter_command.dart';
 class PrecacheCommand extends FlutterCommand {
   PrecacheCommand({
     bool verboseHelp = false,
-    @required Cache cache,
-    @required Platform platform,
-    @required Logger logger,
-    @required FeatureFlags featureFlags,
+    required Cache? cache,
+    required Platform platform,
+    required Logger logger,
+    required FeatureFlags featureFlags,
   }) : _cache = cache,
        _platform = platform,
        _logger = logger,
@@ -30,39 +26,39 @@ class PrecacheCommand extends FlutterCommand {
         help: 'Precache artifacts for all host platforms.');
     argParser.addFlag('force', abbr: 'f', negatable: false,
         help: 'Force re-downloading of artifacts.');
-    argParser.addFlag('android', negatable: true, defaultsTo: false,
+    argParser.addFlag('android',
         help: 'Precache artifacts for Android development.',
         hide: !verboseHelp);
-    argParser.addFlag('android_gen_snapshot', negatable: true, defaultsTo: false,
+    argParser.addFlag('android_gen_snapshot',
         help: 'Precache gen_snapshot for Android development.',
         hide: !verboseHelp);
-    argParser.addFlag('android_maven', negatable: true, defaultsTo: false,
+    argParser.addFlag('android_maven',
         help: 'Precache Gradle dependencies for Android development.',
         hide: !verboseHelp);
-    argParser.addFlag('android_internal_build', negatable: true, defaultsTo: false,
+    argParser.addFlag('android_internal_build',
         help: 'Precache dependencies for internal Android development.',
         hide: !verboseHelp);
-    argParser.addFlag('ios', negatable: true, defaultsTo: false,
+    argParser.addFlag('ios',
         help: 'Precache artifacts for iOS development.');
-    argParser.addFlag('web', negatable: true, defaultsTo: false,
+    argParser.addFlag('web',
         help: 'Precache artifacts for web development.');
-    argParser.addFlag('linux', negatable: true, defaultsTo: false,
+    argParser.addFlag('linux',
         help: 'Precache artifacts for Linux desktop development.');
-    argParser.addFlag('windows', negatable: true, defaultsTo: false,
+    argParser.addFlag('windows',
         help: 'Precache artifacts for Windows desktop development.');
-    argParser.addFlag('macos', negatable: true, defaultsTo: false,
+    argParser.addFlag('macos',
         help: 'Precache artifacts for macOS desktop development.');
-    argParser.addFlag('fuchsia', negatable: true, defaultsTo: false,
+    argParser.addFlag('fuchsia',
         help: 'Precache artifacts for Fuchsia development.');
-    argParser.addFlag('universal', negatable: true, defaultsTo: true,
+    argParser.addFlag('universal', defaultsTo: true,
         help: 'Precache artifacts required for any development platform.');
-    argParser.addFlag('flutter_runner', negatable: true, defaultsTo: false,
+    argParser.addFlag('flutter_runner',
         help: 'Precache the flutter runner artifacts.', hide: !verboseHelp);
-    argParser.addFlag('use-unsigned-mac-binaries', negatable: true, defaultsTo: false,
+    argParser.addFlag('use-unsigned-mac-binaries',
         help: 'Precache the unsigned macOS binaries when available.', hide: !verboseHelp);
   }
 
-  final Cache _cache;
+  final Cache? _cache;
   final Logger _logger;
   final Platform _platform;
   final FeatureFlags _featureFlags;
@@ -106,9 +102,9 @@ class PrecacheCommand extends FlutterCommand {
   Set<String> _explicitArtifactSelections() {
     final Map<String, String> umbrellaForArtifact = _umbrellaForArtifactMap();
     final Set<String> selections = <String>{};
-    bool explicitlySelected(String name) => boolArgDeprecated(name) && argResults.wasParsed(name);
+    bool explicitlySelected(String name) => boolArgDeprecated(name) && argResults!.wasParsed(name);
     for (final DevelopmentArtifact artifact in DevelopmentArtifact.values) {
-      final String umbrellaName = umbrellaForArtifact[artifact.name];
+      final String? umbrellaName = umbrellaForArtifact[artifact.name];
       if (explicitlySelected(artifact.name) ||
           (umbrellaName != null && explicitlySelected(umbrellaName))) {
         selections.add(artifact.name);
@@ -120,11 +116,11 @@ class PrecacheCommand extends FlutterCommand {
   @override
   Future<void> validateCommand() {
     _expandedArtifacts.forEach((String umbrellaName, List<String> childArtifactNames) {
-      if (!argResults.arguments.contains('--no-$umbrellaName')) {
+      if (!argResults!.arguments.contains('--no-$umbrellaName')) {
         return;
       }
       for (final String childArtifactName in childArtifactNames) {
-        if (argResults.arguments.contains('--$childArtifactName')) {
+        if (argResults!.arguments.contains('--$childArtifactName')) {
           throwToolExit('--$childArtifactName requires --$umbrellaName');
         }
       }
@@ -137,21 +133,21 @@ class PrecacheCommand extends FlutterCommand {
   Future<FlutterCommandResult> runCommand() async {
     // Re-lock the cache.
     if (_platform.environment['FLUTTER_ALREADY_LOCKED'] != 'true') {
-      await _cache.lock();
+      await _cache!.lock();
     }
     if (boolArgDeprecated('force')) {
-      _cache.clearStampFiles();
+      _cache!.clearStampFiles();
     }
 
     final bool includeAllPlatforms = boolArgDeprecated('all-platforms');
     if (includeAllPlatforms) {
-      _cache.includeAllPlatforms = true;
+      _cache!.includeAllPlatforms = true;
     }
     if (boolArgDeprecated('use-unsigned-mac-binaries')) {
-      _cache.useUnsignedMacBinaries = true;
+      _cache!.useUnsignedMacBinaries = true;
     }
     final Set<String> explicitlyEnabled = _explicitArtifactSelections();
-    _cache.platformOverrideArtifacts = explicitlyEnabled;
+    _cache!.platformOverrideArtifacts = explicitlyEnabled;
 
     // If the user did not provide any artifact flags, then download
     // all artifacts that correspond to an enabled platform.
@@ -159,7 +155,7 @@ class PrecacheCommand extends FlutterCommand {
     final Map<String, String> umbrellaForArtifact = _umbrellaForArtifactMap();
     final Set<DevelopmentArtifact> requiredArtifacts = <DevelopmentArtifact>{};
     for (final DevelopmentArtifact artifact in DevelopmentArtifact.values) {
-      if (artifact.feature != null && !_featureFlags.isEnabled(artifact.feature)) {
+      if (artifact.feature != null && !_featureFlags.isEnabled(artifact.feature!)) {
         continue;
       }
 
@@ -168,8 +164,8 @@ class PrecacheCommand extends FlutterCommand {
         requiredArtifacts.add(artifact);
       }
     }
-    if (!await _cache.isUpToDate()) {
-      await _cache.updateAll(requiredArtifacts);
+    if (!await _cache!.isUpToDate()) {
+      await _cache!.updateAll(requiredArtifacts);
     } else {
       _logger.printStatus('Already up-to-date.');
     }

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

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:math' as math;
 
@@ -95,7 +95,6 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
         help: 'Run only tests that do not have the specified tags. See: https://pub.dev/packages/test#tagging-tests',
       )
       ..addFlag('start-paused',
-        defaultsTo: false,
         negatable: false,
         help: 'Start in a paused mode and wait for a debugger to connect.\n'
               'You must specify a single test file to run, explicitly.\n'
@@ -103,23 +102,19 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
               'console once the test has started.',
       )
       ..addFlag('run-skipped',
-        defaultsTo: false,
         help: 'Run skipped tests instead of skipping them.',
       )
       ..addFlag('disable-service-auth-codes',
-        defaultsTo: false,
         negatable: false,
         hide: !verboseHelp,
         help: '(deprecated) Allow connections to the VM service without using authentication codes. '
               '(Not recommended! This can open your device to remote code execution attacks!)'
       )
       ..addFlag('coverage',
-        defaultsTo: false,
         negatable: false,
         help: 'Whether to collect coverage information.',
       )
       ..addFlag('merge-coverage',
-        defaultsTo: false,
         negatable: false,
         help: 'Whether to merge coverage data with "coverage/lcov.base.info".\n'
               'Implies collecting coverage data. (Requires lcov.)',
@@ -153,7 +148,6 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       )
       ..addFlag('test-assets',
         defaultsTo: true,
-        negatable: true,
         help: 'Whether to build the assets bundle for testing. '
               'This takes additional time before running the tests. '
               'Consider using "--no-test-assets" if assets are not required.',
@@ -191,7 +185,6 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
               'them separately.'
       )
       ..addFlag('enable-vmservice',
-        defaultsTo: false,
         hide: !verboseHelp,
         help: 'Enables the VM service without "--start-paused". This flag is '
               'intended for use with tests that will use "dart:developer" to '
@@ -255,8 +248,8 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
   String get category => FlutterCommandCategory.project;
 
   @override
-  Future<FlutterCommandResult> verifyThenRunCommand(String commandPath) {
-    _testFiles = argResults.rest.map<String>(globals.fs.path.absolute).toList();
+  Future<FlutterCommandResult> verifyThenRunCommand(String? commandPath) {
+    _testFiles = argResults!.rest.map<String>(globals.fs.path.absolute).toList();
     if (_testFiles.isEmpty) {
       // We don't scan the entire package, only the test/ subdirectory, so that
       // files with names like "hit_test.dart" don't get run.
@@ -305,8 +298,8 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
     final bool buildTestAssets = boolArgDeprecated('test-assets');
     final List<String> names = stringsArg('name');
     final List<String> plainNames = stringsArg('plain-name');
-    final String tags = stringArgDeprecated('tags');
-    final String excludeTags = stringArgDeprecated('exclude-tags');
+    final String? tags = stringArgDeprecated('tags');
+    final String? excludeTags = stringArgDeprecated('exclude-tags');
     final BuildInfo buildInfo = await getBuildInfo(forcedBuildMode: BuildMode.debug);
 
     if (buildInfo.packageConfig['test_api'] == null) {
@@ -320,11 +313,11 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       );
     }
 
-    String testAssetDirectory;
+    String? testAssetDirectory;
     if (buildTestAssets) {
       await _buildTestAsset();
       testAssetDirectory = globals.fs.path.
-        join(flutterProject?.directory?.path ?? '', 'build', 'unit_test_assets');
+        join(flutterProject.directory.path, 'build', 'unit_test_assets');
     }
 
     final bool startPaused = boolArgDeprecated('start-paused');
@@ -335,14 +328,14 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       );
     }
 
-    int jobs = int.tryParse(stringArgDeprecated('concurrency'));
+    int? jobs = int.tryParse(stringArgDeprecated('concurrency')!);
     if (jobs == null || jobs <= 0 || !jobs.isFinite) {
       throwToolExit(
         'Could not parse -j/--concurrency argument. It must be an integer greater than zero.'
       );
     }
     if (_isIntegrationTest) {
-      if (argResults.wasParsed('concurrency')) {
+      if (argResults!.wasParsed('concurrency')) {
         globals.printStatus(
           '-j/--concurrency was parsed but will be ignored, this option is not '
           'supported when running Integration Tests.',
@@ -353,13 +346,13 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       jobs = 1;
     }
 
-    final int shardIndex = int.tryParse(stringArgDeprecated('shard-index') ?? '');
+    final int? shardIndex = int.tryParse(stringArgDeprecated('shard-index') ?? '');
     if (shardIndex != null && (shardIndex < 0 || !shardIndex.isFinite)) {
       throwToolExit(
           'Could not parse --shard-index=$shardIndex argument. It must be an integer greater than -1.');
     }
 
-    final int totalShards = int.tryParse(stringArgDeprecated('total-shards') ?? '');
+    final int? totalShards = int.tryParse(stringArgDeprecated('total-shards') ?? '');
     if (totalShards != null && (totalShards <= 0 || !totalShards.isFinite)) {
       throwToolExit(
           'Could not parse --total-shards=$totalShards argument. It must be an integer greater than zero.');
@@ -375,7 +368,7 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
     }
 
     final bool machine = boolArgDeprecated('machine');
-    CoverageCollector collector;
+    CoverageCollector? collector;
     if (boolArgDeprecated('coverage') || boolArgDeprecated('merge-coverage')) {
       final String projectName = flutterProject.manifest.appName;
       collector = CoverageCollector(
@@ -385,7 +378,7 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       );
     }
 
-    TestWatcher watcher;
+    TestWatcher? watcher;
     if (machine) {
       watcher = EventPrinter(parent: collector, out: globals.stdio.stdout);
     } else if (collector != null) {
@@ -402,7 +395,7 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
       nullAssertions: boolArgDeprecated(FlutterOptions.kNullAssertions),
     );
 
-    Device integrationTestDevice;
+    Device? integrationTestDevice;
     if (_isIntegrationTest) {
       integrationTestDevice = await findTargetDevice();
 

packages/flutter_tools/lib/src/context_runner.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:async';
 
@@ -70,12 +70,12 @@ import 'windows/windows_workflow.dart';
 
 Future<T> runInContext<T>(
   FutureOr<T> Function() runner, {
-  Map<Type, Generator> overrides,
+  Map<Type, Generator>? overrides,
 }) async {
 
   // Wrap runner with any asynchronous initialization that should run with the
   // overrides and callbacks.
-  bool runningOnBot;
+  late bool runningOnBot;
   FutureOr<T> runnerWrapper() async {
     runningOnBot = await globals.isRunningOnBot;
     return runner();
@@ -90,9 +90,9 @@ Future<T> runInContext<T>(
         logger: globals.logger,
         processManager: globals.processManager,
         fileSystem: globals.fs,
-        artifacts: globals.artifacts,
+        artifacts: globals.artifacts!,
         usage: globals.flutterUsage,
-        gradleUtils: globals.gradleUtils,
+        gradleUtils: globals.gradleUtils!,
         platform: globals.platform,
       ),
       AndroidLicenseValidator: () => AndroidLicenseValidator(
@@ -158,11 +158,11 @@ Future<T> runInContext<T>(
         processManager: globals.processManager,
         logger: globals.logger,
         platform: globals.platform,
-        xcodeProjectInterpreter: globals.xcodeProjectInterpreter,
+        xcodeProjectInterpreter: globals.xcodeProjectInterpreter!,
         usage: globals.flutterUsage,
       ),
       CocoaPodsValidator: () => CocoaPodsValidator(
-        globals.cocoaPods,
+        globals.cocoaPods!,
         globals.userMessages,
       ),
       Config: () => Config(
@@ -187,29 +187,29 @@ Future<T> runInContext<T>(
         processManager: globals.processManager,
         platform: globals.platform,
         androidSdk: globals.androidSdk,
-        iosSimulatorUtils: globals.iosSimulatorUtils,
+        iosSimulatorUtils: globals.iosSimulatorUtils!,
         featureFlags: featureFlags,
         fileSystem: globals.fs,
-        iosWorkflow: globals.iosWorkflow,
-        artifacts: globals.artifacts,
+        iosWorkflow: globals.iosWorkflow!,
+        artifacts: globals.artifacts!,
         flutterVersion: globals.flutterVersion,
-        androidWorkflow: androidWorkflow,
-        fuchsiaWorkflow: fuchsiaWorkflow,
-        xcDevice: globals.xcdevice,
+        androidWorkflow: androidWorkflow!,
+        fuchsiaWorkflow: fuchsiaWorkflow!,
+        xcDevice: globals.xcdevice!,
         userMessages: globals.userMessages,
-        windowsWorkflow: windowsWorkflow,
+        windowsWorkflow: windowsWorkflow!,
         macOSWorkflow: MacOSWorkflow(
           platform: globals.platform,
           featureFlags: featureFlags,
         ),
-        fuchsiaSdk: globals.fuchsiaSdk,
+        fuchsiaSdk: globals.fuchsiaSdk!,
         operatingSystemUtils: globals.os,
         terminal: globals.terminal,
         customDevicesConfig: globals.customDevicesConfig,
       ),
       DevtoolsLauncher: () => DevtoolsServerLauncher(
         processManager: globals.processManager,
-        dartExecutable: globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
+        dartExecutable: globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path,
         logger: globals.logger,
         botDetector: globals.botDetector,
       ),
@@ -220,7 +220,7 @@ Future<T> runInContext<T>(
         processManager: globals.processManager,
         logger: globals.logger,
         fileSystem: globals.fs,
-        androidWorkflow: androidWorkflow,
+        androidWorkflow: androidWorkflow!,
       ),
       FeatureFlags: () => FlutterFeatureFlags(
         flutterVersion: globals.flutterVersion,
@@ -234,7 +234,7 @@ Future<T> runInContext<T>(
       FuchsiaWorkflow: () => FuchsiaWorkflow(
         featureFlags: featureFlags,
         platform: globals.platform,
-        fuchsiaArtifacts: globals.fuchsiaArtifacts,
+        fuchsiaArtifacts: globals.fuchsiaArtifacts!,
       ),
       GradleUtils: () => GradleUtils(
         fileSystem: globals.fs,
@@ -247,11 +247,11 @@ Future<T> runInContext<T>(
       IOSSimulatorUtils: () => IOSSimulatorUtils(
         logger: globals.logger,
         processManager: globals.processManager,
-        xcode: globals.xcode,
+        xcode: globals.xcode!,
       ),
       IOSWorkflow: () => IOSWorkflow(
         featureFlags: featureFlags,
-        xcode: globals.xcode,
+        xcode: globals.xcode!,
         platform: globals.platform,
       ),
       LocalEngineLocator: () => LocalEngineLocator(
@@ -259,7 +259,7 @@ Future<T> runInContext<T>(
         logger: globals.logger,
         platform: globals.platform,
         fileSystem: globals.fs,
-        flutterRoot: Cache.flutterRoot,
+        flutterRoot: Cache.flutterRoot!,
       ),
       Logger: () => globals.platform.isWindows
         ? WindowsStdoutLogger(
@@ -287,7 +287,7 @@ Future<T> runInContext<T>(
         processManager: globals.processManager,
       ),
       OutputPreferences: () => OutputPreferences(
-        wrapText: globals.stdio.hasTerminal ?? false,
+        wrapText: globals.stdio.hasTerminal,
         showColor:  globals.platform.stdoutSupportsAnsi,
         stdio: globals.stdio,
       ),
@@ -318,7 +318,7 @@ Future<T> runInContext<T>(
       SystemClock: () => const SystemClock(),
       Usage: () => Usage(
         runningOnBot: runningOnBot,
-        firstRunMessenger: FirstRunMessenger(persistentToolState: globals.persistentToolState),
+        firstRunMessenger: FirstRunMessenger(persistentToolState: globals.persistentToolState!),
       ),
       UserMessages: () => UserMessages(),
       VisualStudioValidator: () => VisualStudioValidator(
@@ -343,17 +343,17 @@ Future<T> runInContext<T>(
         processManager: globals.processManager,
         platform: globals.platform,
         fileSystem: globals.fs,
-        xcodeProjectInterpreter: globals.xcodeProjectInterpreter,
+        xcodeProjectInterpreter: globals.xcodeProjectInterpreter!,
       ),
       XCDevice: () => XCDevice(
         processManager: globals.processManager,
         logger: globals.logger,
-        artifacts: globals.artifacts,
+        artifacts: globals.artifacts!,
         cache: globals.cache,
         platform: globals.platform,
-        xcode: globals.xcode,
+        xcode: globals.xcode!,
         iproxy: IProxy(
-          iproxyPath: globals.artifacts.getHostArtifact(
+          iproxyPath: globals.artifacts!.getHostArtifact(
             HostArtifact.iproxy,
           ).path,
           logger: globals.logger,

packages/flutter_tools/lib/src/daemon.dart

@@ -301,7 +301,7 @@ class DaemonConnection {
   }
 
   /// Sends an error response to the other end of the connection.
-  void sendErrorResponse(Object id, Object error, StackTrace trace) {
+  void sendErrorResponse(Object id, Object? error, StackTrace trace) {
     _daemonStreams.send(<String, Object?>{
       'id': id,
       'error': error,

packages/flutter_tools/lib/src/desktop_device.dart

@@ -44,7 +44,7 @@ abstract class DesktopDevice extends Device {
   final DesktopLogReader _deviceLogReader = DesktopLogReader();
 
   @override
-  DevFSWriter createDevFSWriter(covariant ApplicationPackage app, String userIdentifier) {
+  DevFSWriter createDevFSWriter(covariant ApplicationPackage? app, String? userIdentifier) {
     return LocalDevFSWriter(fileSystem: _fileSystem);
   }
 

packages/flutter_tools/lib/src/devfs.dart

@@ -477,7 +477,7 @@ class DevFS {
   final StopwatchFactory _stopwatchFactory;
 
   final String fsName;
-  final Directory rootDirectory;
+  final Directory? rootDirectory;
   final Set<String> assetPathsToEvict = <String>{};
 
   // A flag to indicate whether we have called `setAssetDirectory` on the target device.
@@ -497,7 +497,7 @@ class DevFS {
     final String baseUriString = baseUri.toString();
     if (deviceUriString.startsWith(baseUriString)) {
       final String deviceUriSuffix = deviceUriString.substring(baseUriString.length);
-      return rootDirectory.uri.resolve(deviceUriSuffix);
+      return rootDirectory!.uri.resolve(deviceUriSuffix);
     }
     return deviceUri;
   }

packages/flutter_tools/lib/src/device.dart

@@ -557,8 +557,8 @@ abstract class Device {
   /// For example, the desktop device classes can use a writer which
   /// copies the files across the local file system.
   DevFSWriter? createDevFSWriter(
-    covariant ApplicationPackage app,
-    String userIdentifier,
+    covariant ApplicationPackage? app,
+    String? userIdentifier,
   ) {
     return null;
   }
@@ -593,7 +593,7 @@ abstract class Device {
   /// [platformArgs] allows callers to pass platform-specific arguments to the
   /// start call. The build mode is not used by all platforms.
   Future<LaunchResult> startApp(
-    covariant ApplicationPackage package, {
+    covariant ApplicationPackage? package, {
     String? mainPath,
     String? route,
     required DebuggingOptions debuggingOptions,
@@ -624,7 +624,7 @@ abstract class Device {
   ///
   /// Specify [userIdentifier] to stop app installed to a profile (Android only).
   Future<bool> stopApp(
-    covariant ApplicationPackage app, {
+    covariant ApplicationPackage? app, {
     String? userIdentifier,
   });
 

packages/flutter_tools/lib/src/devtools_launcher.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:async';
 
@@ -20,10 +20,10 @@ import 'resident_runner.dart';
 /// start a server instance.
 class DevtoolsServerLauncher extends DevtoolsLauncher {
   DevtoolsServerLauncher({
-    @required ProcessManager processManager,
-    @required String dartExecutable,
-    @required Logger logger,
-    @required BotDetector botDetector,
+    required ProcessManager processManager,
+    required String dartExecutable,
+    required Logger? logger,
+    required BotDetector botDetector,
   })  : _processManager = processManager,
         _dartExecutable = dartExecutable,
         _logger = logger,
@@ -31,14 +31,14 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
 
   final ProcessManager _processManager;
   final String _dartExecutable;
-  final Logger _logger;
+  final Logger? _logger;
   final BotDetector _botDetector;
   final Completer<void> _processStartCompleter = Completer<void>();
 
-  io.Process _devToolsProcess;
+  io.Process? _devToolsProcess;
   bool _devToolsProcessKilled = false;
   @visibleForTesting
-  Future<void> devToolsProcessExit;
+  Future<void>? devToolsProcessExit;
 
   static final RegExp _serveDevToolsPattern =
       RegExp(r'Serving DevTools at ((http|//)[a-zA-Z0-9:/=_\-\.\[\]]+?)\.?$');
@@ -47,7 +47,7 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
   Future<void> get processStart => _processStartCompleter.future;
 
   @override
-  Future<void> launch(Uri vmServiceUri, {List<String> additionalArguments}) async {
+  Future<void> launch(Uri? vmServiceUri, {List<String>? additionalArguments}) async {
     // Place this entire method in a try/catch that swallows exceptions because
     // this method is guaranteed not to return a Future that throws.
     try {
@@ -60,23 +60,23 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
       ]);
       _processStartCompleter.complete();
       final Completer<Uri> completer = Completer<Uri>();
-      _devToolsProcess.stdout
+      _devToolsProcess!.stdout
           .transform(utf8.decoder)
           .transform(const LineSplitter())
           .listen((String line) {
-            final Match match = _serveDevToolsPattern.firstMatch(line);
+            final Match? match = _serveDevToolsPattern.firstMatch(line);
             if (match != null) {
-              final String url = match[1];
+              final String url = match[1]!;
               completer.complete(Uri.parse(url));
             }
          });
-      _devToolsProcess.stderr
+      _devToolsProcess!.stderr
           .transform(utf8.decoder)
           .transform(const LineSplitter())
-          .listen(_logger.printError);
+          .listen(_logger!.printError);
 
       final bool runningOnBot = await _botDetector.isRunningOnBot;
-      devToolsProcessExit = _devToolsProcess.exitCode.then(
+      devToolsProcessExit = _devToolsProcess!.exitCode.then(
         (int exitCode) {
           if (!_devToolsProcessKilled && runningOnBot) {
             throwToolExit('DevTools process failed: exitCode=$exitCode');
@@ -86,12 +86,12 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
 
       devToolsUrl = await completer.future;
     } on Exception catch (e, st) {
-      _logger.printError('Failed to launch DevTools: $e', stackTrace: st);
+      _logger!.printError('Failed to launch DevTools: $e', stackTrace: st);
     }
   }
 
   @override
-  Future<DevToolsServerAddress> serve() async {
+  Future<DevToolsServerAddress?> serve() async {
     if (activeDevToolsServer == null) {
       await launch(null);
     }
@@ -105,7 +105,7 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
     }
     if (_devToolsProcess != null) {
       _devToolsProcessKilled = true;
-      _devToolsProcess.kill();
+      _devToolsProcess!.kill();
     }
   }
 }

packages/flutter_tools/lib/src/drive/drive_service.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:dds/dds.dart' as dds;
@@ -25,11 +23,11 @@ import 'web_driver_service.dart';
 
 class FlutterDriverFactory {
   FlutterDriverFactory({
-    @required ApplicationPackageFactory applicationPackageFactory,
-    @required Logger logger,
-    @required ProcessUtils processUtils,
-    @required String dartSdkPath,
-    @required DevtoolsLauncher devtoolsLauncher,
+    required ApplicationPackageFactory applicationPackageFactory,
+    required Logger logger,
+    required ProcessUtils processUtils,
+    required String dartSdkPath,
+    required DevtoolsLauncher devtoolsLauncher,
   }) : _applicationPackageFactory = applicationPackageFactory,
        _logger = logger,
        _processUtils = processUtils,
@@ -69,10 +67,10 @@ abstract class DriverService {
     Device device,
     DebuggingOptions debuggingOptions,
     bool ipv6, {
-    File applicationBinary,
-    String route,
-    String userIdentifier,
-    String mainPath,
+    File? applicationBinary,
+    String? route,
+    String? userIdentifier,
+    String? mainPath,
     Map<String, Object> platformArgs = const <String, Object>{},
   });
 
@@ -94,13 +92,13 @@ abstract class DriverService {
     List<String> arguments,
     Map<String, String> environment,
     PackageConfig packageConfig, {
-    bool headless,
-    String chromeBinary,
-    String browserName,
-    bool androidEmulator,
-    int driverPort,
-    List<String> browserDimension,
-    String profileMemory,
+    bool? headless,
+    String? chromeBinary,
+    String? browserName,
+    bool? androidEmulator,
+    int? driverPort,
+    List<String>? browserDimension,
+    String? profileMemory,
   });
 
   /// Stop the running application and uninstall it from the device.
@@ -109,8 +107,8 @@ abstract class DriverService {
   /// and write SkSL to the file. This is only supported on mobile and
   /// desktop devices.
   Future<void> stop({
-    File writeSkslOnExit,
-    String userIdentifier,
+    File? writeSkslOnExit,
+    String? userIdentifier,
   });
 }
 
@@ -118,11 +116,11 @@ abstract class DriverService {
 /// applications.
 class FlutterDriverService extends DriverService {
   FlutterDriverService({
-    @required ApplicationPackageFactory applicationPackageFactory,
-    @required Logger logger,
-    @required ProcessUtils processUtils,
-    @required String dartSdkPath,
-    @required DevtoolsLauncher devtoolsLauncher,
+    required ApplicationPackageFactory applicationPackageFactory,
+    required Logger logger,
+    required ProcessUtils processUtils,
+    required String dartSdkPath,
+    required DevtoolsLauncher devtoolsLauncher,
     @visibleForTesting VMServiceConnector vmServiceConnector = connectToVmService,
   }) : _applicationPackageFactory = applicationPackageFactory,
        _logger = logger,
@@ -140,10 +138,10 @@ class FlutterDriverService extends DriverService {
   final VMServiceConnector _vmServiceConnector;
   final DevtoolsLauncher _devtoolsLauncher;
 
-  Device _device;
-  ApplicationPackage _applicationPackage;
-  String _vmServiceUri;
-  FlutterVmService _vmService;
+  Device? _device;
+  ApplicationPackage? _applicationPackage;
+  late String _vmServiceUri;
+  late FlutterVmService _vmService;
 
   @override
   Future<void> start(
@@ -151,11 +149,11 @@ class FlutterDriverService extends DriverService {
     Device device,
     DebuggingOptions debuggingOptions,
     bool ipv6, {
-    File applicationBinary,
-    String route,
-    String userIdentifier,
+    File? applicationBinary,
+    String? route,
+    String? userIdentifier,
     Map<String, Object> platformArgs = const <String, Object>{},
-    String mainPath,
+    String? mainPath,
   }) async {
     if (buildInfo.isRelease) {
       throwToolExit(
@@ -173,7 +171,7 @@ class FlutterDriverService extends DriverService {
       applicationBinary: applicationBinary,
     );
     int attempt = 0;
-    LaunchResult result;
+    LaunchResult? result;
     bool prebuiltApplication = applicationBinary != null;
     while (attempt < _kLaunchAttempts) {
       result = await device.startApp(
@@ -197,7 +195,7 @@ class FlutterDriverService extends DriverService {
       throwToolExit('Application failed to start. Will not run test. Quitting.', exitCode: 1);
     }
     return reuseApplication(
-      result.observatoryUri,
+      result.observatoryUri!,
       device,
       debuggingOptions,
       ipv6,
@@ -251,13 +249,13 @@ class FlutterDriverService extends DriverService {
     List<String> arguments,
     Map<String, String> environment,
     PackageConfig packageConfig, {
-    bool headless,
-    String chromeBinary,
-    String browserName,
-    bool androidEmulator,
-    int driverPort,
-    List<String> browserDimension,
-    String profileMemory,
+    bool? headless,
+    String? chromeBinary,
+    String? browserName,
+    bool? androidEmulator,
+    int? driverPort,
+    List<String>? browserDimension,
+    String? profileMemory,
   }) async {
     if (profileMemory != null) {
       unawaited(_devtoolsLauncher.launch(
@@ -285,35 +283,35 @@ class FlutterDriverService extends DriverService {
 
   @override
   Future<void> stop({
-    File writeSkslOnExit,
-    String userIdentifier,
+    File? writeSkslOnExit,
+    String? userIdentifier,
   }) async {
     if (writeSkslOnExit != null) {
       final FlutterView flutterView = (await _vmService.getFlutterViews()).first;
-      final Map<String, Object> result = await _vmService.getSkSLs(
+      final Map<String, Object> result = await (_vmService.getSkSLs(
         viewId: flutterView.id
-      );
-      await sharedSkSlWriter(_device, result, outputFile: writeSkslOnExit, logger: _logger);
+      ) as FutureOr<Map<String, Object>>);
+      await sharedSkSlWriter(_device!, result, outputFile: writeSkslOnExit, logger: _logger);
     }
     // If the application package is available, stop and uninstall.
     if (_applicationPackage != null) {
-      if (!await _device.stopApp(_applicationPackage, userIdentifier: userIdentifier)) {
+      if (!await _device!.stopApp(_applicationPackage, userIdentifier: userIdentifier)) {
         _logger.printError('Failed to stop app');
       }
-      if (!await _device.uninstallApp(_applicationPackage, userIdentifier: userIdentifier)) {
+      if (!await _device!.uninstallApp(_applicationPackage!, userIdentifier: userIdentifier)) {
         _logger.printError('Failed to uninstall app');
       }
-    } else if (_device.supportsFlutterExit) {
+    } else if (_device!.supportsFlutterExit) {
       // Otherwise use the VM Service URI to stop the app as a best effort approach.
       final vm_service.VM vm = await _vmService.service.getVM();
-      final vm_service.IsolateRef isolateRef = vm.isolates
+      final vm_service.IsolateRef isolateRef = vm.isolates!
         .firstWhere((vm_service.IsolateRef element) {
-          return !element.isSystemIsolate;
-        }, orElse: () => null);
-      unawaited(_vmService.flutterExit(isolateId: isolateRef.id));
+          return !element.isSystemIsolate!;
+        });
+      unawaited(_vmService.flutterExit(isolateId: isolateRef.id!));
     } else {
       _logger.printTrace('No application package for $_device, leaving app running');
     }
-    await _device.dispose();
+    await _device!.dispose();
   }
 }

packages/flutter_tools/lib/src/drive/web_driver_service.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'dart:async';
 import 'dart:math' as math;
@@ -28,9 +28,9 @@ import 'drive_service.dart';
 /// An implementation of the driver service for web debug and release applications.
 class WebDriverService extends DriverService {
   WebDriverService({
-    @required ProcessUtils processUtils,
-    @required String dartSdkPath,
-    @required Logger logger,
+    required ProcessUtils processUtils,
+    required String dartSdkPath,
+    required Logger logger,
   }) : _processUtils = processUtils,
        _dartSdkPath = dartSdkPath,
        _logger = logger;
@@ -39,15 +39,15 @@ class WebDriverService extends DriverService {
   final String _dartSdkPath;
   final Logger _logger;
 
-  ResidentRunner _residentRunner;
-  Uri _webUri;
+  late ResidentRunner _residentRunner;
+  Uri? _webUri;
 
   /// The result of [ResidentRunner.run].
   ///
   /// This is expected to stay `null` throughout the test, as the application
   /// must be running until [stop] is called. If it becomes non-null, it likely
   /// indicates a bug.
-  int _runResult;
+  int? _runResult;
 
   @override
   Future<void> start(
@@ -55,10 +55,10 @@ class WebDriverService extends DriverService {
     Device device,
     DebuggingOptions debuggingOptions,
     bool ipv6, {
-    File applicationBinary,
-    String route,
-    String userIdentifier,
-    String mainPath,
+    File? applicationBinary,
+    String? route,
+    String? userIdentifier,
+    String? mainPath,
     Map<String, Object> platformArgs = const <String, Object>{},
   }) async {
     final FlutterDevice flutterDevice = await FlutterDevice.create(
@@ -67,7 +67,7 @@ class WebDriverService extends DriverService {
       buildInfo: buildInfo,
       platform: globals.platform,
     );
-    _residentRunner = webRunnerFactory.createWebRunner(
+    _residentRunner = webRunnerFactory!.createWebRunner(
       flutterDevice,
       target: mainPath,
       ipv6: ipv6,
@@ -90,21 +90,21 @@ class WebDriverService extends DriverService {
       systemClock: globals.systemClock,
     );
     final Completer<void> appStartedCompleter = Completer<void>.sync();
-    final Future<int> runFuture = _residentRunner.run(
+    final Future<int?> runFuture = _residentRunner.run(
       appStartedCompleter: appStartedCompleter,
       route: route,
     );
 
     bool isAppStarted = false;
     await Future.any<Object>(<Future<Object>>[
-      runFuture.then((int result) {
+      runFuture.then((int? result) {
         _runResult = result;
         return null;
-      }),
+      } as FutureOr<Object> Function(int?)),
       appStartedCompleter.future.then((_) {
         isAppStarted = true;
         return null;
-      }),
+      } as FutureOr<Object> Function(void)),
     ]);
 
     if (_runResult != null) {
@@ -126,22 +126,25 @@ class WebDriverService extends DriverService {
   }
 
   @override
-  Future<int> startTest(String testFile, List<String> arguments, Map<String, String> environment, PackageConfig packageConfig, {
-    @required bool headless,
-    String chromeBinary,
-    @required String browserName,
-    bool androidEmulator,
-    int driverPort,
-    List<String> browserDimension,
-    String profileMemory,
+  Future<int> startTest(
+    String testFile,
+    List<String> arguments,
+    Map<String, String> environment,
+    PackageConfig packageConfig, {
+    bool? headless,
+    String? chromeBinary,
+    String? browserName,
+    bool? androidEmulator,
+    int? driverPort,
+    List<String>? browserDimension,
+    String? profileMemory,
   }) async {
-    async_io.WebDriver webDriver;
+    late async_io.WebDriver webDriver;
     final Browser browser = _browserNameToEnum(browserName);
     try {
       webDriver = await async_io.createDriver(
         uri: Uri.parse('http://localhost:$driverPort/'),
         desired: getDesiredCapabilities(browser, headless, chromeBinary),
-        spec: async_io.WebDriverSpec.Auto
       );
     } on SocketException catch (error) {
       _logger.printTrace('$error');
@@ -156,11 +159,11 @@ class WebDriverService extends DriverService {
     final bool isAndroidChrome = browser == Browser.androidChrome;
     // Do not set the window size for android chrome browser.
     if (!isAndroidChrome) {
-      assert(browserDimension.length == 2);
-      int x;
-      int y;
+      assert(browserDimension!.length == 2);
+      late int x;
+      late int y;
       try {
-        x = int.parse(browserDimension[0]);
+        x = int.parse(browserDimension![0]);
         y = int.parse(browserDimension[1]);
       } on FormatException catch (ex) {
         throwToolExit('Dimension provided to --browser-dimension is invalid: $ex');
@@ -184,7 +187,7 @@ class WebDriverService extends DriverService {
   }
 
   @override
-  Future<void> stop({File writeSkslOnExit, String userIdentifier}) async {
+  Future<void> stop({File? writeSkslOnExit, String? userIdentifier}) async {
     final bool appDidFinishPrematurely = _runResult != null;
     await _residentRunner.exitApp();
     await _residentRunner.cleanupAtFinish();
@@ -197,7 +200,7 @@ class WebDriverService extends DriverService {
     }
   }
 
-  Map<String, String> _additionalDriverEnvironment(async_io.WebDriver webDriver, String browserName, bool androidEmulator) {
+  Map<String, String> _additionalDriverEnvironment(async_io.WebDriver webDriver, String? browserName, bool? androidEmulator) {
     return <String, String>{
       'DRIVER_SESSION_ID': webDriver.id,
       'DRIVER_SESSION_URI': webDriver.uri.toString(),
@@ -205,7 +208,7 @@ class WebDriverService extends DriverService {
       'DRIVER_SESSION_CAPABILITIES': json.encode(webDriver.capabilities),
       'SUPPORT_TIMELINE_ACTION': (_browserNameToEnum(browserName) == Browser.chrome).toString(),
       'FLUTTER_WEB_TEST': 'true',
-      'ANDROID_CHROME_ON_EMULATOR': (_browserNameToEnum(browserName) == Browser.androidChrome && androidEmulator).toString(),
+      'ANDROID_CHROME_ON_EMULATOR': (_browserNameToEnum(browserName) == Browser.androidChrome && androidEmulator!).toString(),
     };
   }
 
@@ -234,7 +237,7 @@ enum Browser {
 /// Returns desired capabilities for given [browser], [headless] and
 /// [chromeBinary].
 @visibleForTesting
-Map<String, dynamic> getDesiredCapabilities(Browser browser, bool headless, [String chromeBinary]) {
+Map<String, dynamic> getDesiredCapabilities(Browser browser, bool? headless, [String? chromeBinary]) {
   switch (browser) {
     case Browser.chrome:
       return <String, dynamic>{
@@ -258,7 +261,7 @@ Map<String, dynamic> getDesiredCapabilities(Browser browser, bool headless, [Str
             '--no-default-browser-check',
             '--no-sandbox',
             '--no-first-run',
-            if (headless) '--headless',
+            if (headless!) '--headless',
           ],
           'perfLoggingPrefs': <String, String>{
             'traceCategories':
@@ -268,14 +271,13 @@ Map<String, dynamic> getDesiredCapabilities(Browser browser, bool headless, [Str
           },
         },
       };
-      break;
     case Browser.firefox:
       return <String, dynamic>{
         'acceptInsecureCerts': true,
         'browserName': 'firefox',
         'moz:firefoxOptions' : <String, dynamic>{
           'args': <String>[
-            if (headless) '-headless',
+            if (headless!) '-headless',
           ],
           'prefs': <String, dynamic>{
             'dom.file.createInChild': true,
@@ -290,18 +292,15 @@ Map<String, dynamic> getDesiredCapabilities(Browser browser, bool headless, [Str
           'log': <String, String>{'level': 'trace'},
         },
       };
-      break;
     case Browser.edge:
       return <String, dynamic>{
         'acceptInsecureCerts': true,
         'browserName': 'edge',
       };
-      break;
     case Browser.safari:
       return <String, dynamic>{
         'browserName': 'safari',
       };
-      break;
     case Browser.iosSafari:
       return <String, dynamic>{
         'platformName': 'ios',
@@ -318,11 +317,10 @@ Map<String, dynamic> getDesiredCapabilities(Browser browser, bool headless, [Str
         },
       };
   }
-  throw UnsupportedError('Browser $browser not supported.'); // dead code; remove with null safety migration
 }
 
 /// Converts [browserName] string to [Browser]
-Browser _browserNameToEnum(String browserName) {
+Browser _browserNameToEnum(String? browserName) {
   switch (browserName) {
     case 'android-chrome': return Browser.androidChrome;
     case 'chrome': return Browser.chrome;

packages/flutter_tools/lib/src/flutter_application_package.dart

@@ -25,7 +25,7 @@ import 'windows/application_package.dart';
 /// A package factory that supports all Flutter target platforms.
 class FlutterApplicationPackageFactory extends ApplicationPackageFactory {
   FlutterApplicationPackageFactory({
-    required AndroidSdk androidSdk,
+    required AndroidSdk? androidSdk,
     required ProcessManager processManager,
     required Logger logger,
     required UserMessages userMessages,
@@ -38,7 +38,7 @@ class FlutterApplicationPackageFactory extends ApplicationPackageFactory {
        _processUtils = ProcessUtils(logger: logger, processManager: processManager);
 
 
-  final AndroidSdk _androidSdk;
+  final AndroidSdk? _androidSdk;
   final ProcessManager _processManager;
   final Logger _logger;
   final ProcessUtils _processUtils;
@@ -72,7 +72,7 @@ class FlutterApplicationPackageFactory extends ApplicationPackageFactory {
           applicationBinary,
           processManager: _processManager,
           logger: _logger,
-          androidSdk: _androidSdk,
+          androidSdk: _androidSdk!,
           userMessages: _userMessages,
           processUtils: _processUtils,
         );

packages/flutter_tools/lib/src/flutter_device_manager.dart

@@ -40,7 +40,7 @@ class FlutterDeviceManager extends DeviceManager {
     required Platform platform,
     required ProcessManager processManager,
     required FileSystem fileSystem,
-    required AndroidSdk androidSdk,
+    required AndroidSdk? androidSdk,
     required FeatureFlags featureFlags,
     required IOSSimulatorUtils iosSimulatorUtils,
     required XCDevice xcDevice,

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -338,7 +338,7 @@ class IOSSimulator extends Device {
   final SimControl _simControl;
 
   @override
-  DevFSWriter createDevFSWriter(covariant ApplicationPackage app, String userIdentifier) {
+  DevFSWriter createDevFSWriter(covariant ApplicationPackage? app, String? userIdentifier) {
     return LocalDevFSWriter(fileSystem: globals.fs);
   }
 

packages/flutter_tools/lib/src/isolated/sdk_web_configuration.dart

@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
+// ignore: import_of_legacy_library_into_null_safe
 import 'package:dwds/dwds.dart';
 
 import '../artifacts.dart';
@@ -17,12 +16,12 @@ class SdkWebConfigurationProvider extends SdkConfigurationProvider {
   SdkWebConfigurationProvider(this._artifacts);
 
   final Artifacts _artifacts;
-  SdkConfiguration _configuration;
+  SdkConfiguration? _configuration;
 
   /// Create and validate configuration matching the default SDK layout.
   /// Create configuration matching the default SDK layout.
   @override
-  Future<SdkConfiguration> get configuration async {
+  Future<SdkConfiguration?> get configuration async {
     if (_configuration == null) {
       final String sdkDir = _artifacts.getHostArtifact(HostArtifact.flutterWebSdk).path;
       final String unsoundSdkSummaryPath = _artifacts.getHostArtifact(HostArtifact.webPlatformKernelDill).path;
@@ -40,7 +39,7 @@ class SdkWebConfigurationProvider extends SdkConfigurationProvider {
   }
 
   /// Validate that SDK configuration exists on disk.
-  static void validate(SdkConfiguration configuration, { FileSystem fileSystem }) {
+  static void validate(SdkConfiguration configuration, { required FileSystem fileSystem }) {
     configuration.validateSdkDir(fileSystem: fileSystem);
     configuration.validateSummaries(fileSystem: fileSystem);
     configuration.validateLibrariesSpec(fileSystem: fileSystem);

packages/flutter_tools/lib/src/preview_device.dart

@@ -181,7 +181,7 @@ class PreviewDevice extends Device {
   }
 
   @override
-  DevFSWriter createDevFSWriter(covariant ApplicationPackage app, String userIdentifier) {
+  DevFSWriter createDevFSWriter(covariant ApplicationPackage? app, String? userIdentifier) {
     return LocalDevFSWriter(fileSystem: _fileSystem);
   }
 }

packages/flutter_tools/lib/src/run_cold.dart

@@ -2,18 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
-import 'package:meta/meta.dart';
-
 import 'base/file_system.dart';
 import 'base/logger.dart';
 import 'build_info.dart';
-import 'device.dart';
 import 'globals.dart' as globals;
-import 'resident_devtools_handler.dart';
 import 'resident_runner.dart';
 import 'tracing.dart';
 import 'vmservice.dart';
@@ -21,31 +15,24 @@ import 'vmservice.dart';
 const String kFlutterTestOutputsDirEnvName = 'FLUTTER_TEST_OUTPUTS_DIR';
 class ColdRunner extends ResidentRunner {
   ColdRunner(
-    List<FlutterDevice> devices, {
-    @required String target,
-    @required DebuggingOptions debuggingOptions,
+    super.devices, {
+    required super.target,
+    required super.debuggingOptions,
     this.traceStartup = false,
     this.awaitFirstFrameWhenTracing = true,
     this.applicationBinary,
     this.multidexEnabled = false,
-    bool ipv6 = false,
-    bool stayResident = true,
-    bool machine = false,
-    ResidentDevtoolsHandlerFactory devtoolsHandler = createDefaultHandler,
+    bool super.ipv6 = false,
+    super.stayResident,
+    super.machine,
+    super.devtoolsHandler,
   }) : super(
-          devices,
-          target: target,
-          debuggingOptions: debuggingOptions,
           hotMode: false,
-          stayResident: stayResident,
-          ipv6: ipv6,
-          machine: machine,
-          devtoolsHandler: devtoolsHandler,
         );
 
   final bool traceStartup;
   final bool awaitFirstFrameWhenTracing;
-  final File applicationBinary;
+  final File? applicationBinary;
   final bool multidexEnabled;
   bool _didAttach = false;
 
@@ -60,14 +47,14 @@ class ColdRunner extends ResidentRunner {
 
   @override
   Future<int> run({
-    Completer<DebugConnectionInfo> connectionInfoCompleter,
-    Completer<void> appStartedCompleter,
+    Completer<DebugConnectionInfo>? connectionInfoCompleter,
+    Completer<void>? appStartedCompleter,
     bool enableDevTools = false,
-    String route,
+    String? route,
   }) async {
     try {
-      for (final FlutterDevice device in flutterDevices) {
-        final int result = await device.runCold(
+      for (final FlutterDevice? device in flutterDevices) {
+        final int result = await device!.runCold(
           coldRunner: this,
           route: route,
         );
@@ -95,38 +82,38 @@ class ColdRunner extends ResidentRunner {
 
     if (enableDevTools && debuggingEnabled) {
       // The method below is guaranteed never to return a failing future.
-      unawaited(residentDevtoolsHandler.serveAndAnnounceDevTools(
+      unawaited(residentDevtoolsHandler!.serveAndAnnounceDevTools(
         devToolsServerAddress: debuggingOptions.devToolsServerAddress,
         flutterDevices: flutterDevices,
       ));
     }
 
-    if (flutterDevices.first.observatoryUris != null) {
+    if (flutterDevices.first!.observatoryUris != null) {
       // For now, only support one debugger connection.
       connectionInfoCompleter?.complete(DebugConnectionInfo(
-        httpUri: flutterDevices.first.vmService.httpAddress,
-        wsUri: flutterDevices.first.vmService.wsAddress,
+        httpUri: flutterDevices.first!.vmService!.httpAddress,
+        wsUri: flutterDevices.first!.vmService!.wsAddress,
       ));
     }
 
     globals.printTrace('Application running.');
 
-    for (final FlutterDevice device in flutterDevices) {
-      if (device.vmService == null) {
+    for (final FlutterDevice? device in flutterDevices) {
+      if (device!.vmService == null) {
         continue;
       }
       await device.initLogReader();
-      globals.printTrace('Connected to ${device.device.name}');
+      globals.printTrace('Connected to ${device.device!.name}');
     }
 
     if (traceStartup) {
       // Only trace startup for the first device.
-      final FlutterDevice device = flutterDevices.first;
+      final FlutterDevice device = flutterDevices.first!;
       if (device.vmService != null) {
-        globals.printStatus('Tracing startup on ${device.device.name}.');
+        globals.printStatus('Tracing startup on ${device.device!.name}.');
         final String outputPath = globals.platform.environment[kFlutterTestOutputsDirEnvName] ?? getBuildDirectory();
         await downloadStartupTrace(
-          device.vmService,
+          device.vmService!,
           awaitFirstFrame: awaitFirstFrameWhenTracing,
           logger: globals.logger,
           output: globals.fs.directory(outputPath),
@@ -148,8 +135,8 @@ class ColdRunner extends ResidentRunner {
 
   @override
   Future<int> attach({
-    Completer<DebugConnectionInfo> connectionInfoCompleter,
-    Completer<void> appStartedCompleter,
+    Completer<DebugConnectionInfo>? connectionInfoCompleter,
+    Completer<void>? appStartedCompleter,
     bool allowExistingDdsInstance = false,
     bool enableDevTools = false,
     bool needsFullRestart = true,
@@ -165,11 +152,11 @@ class ColdRunner extends ResidentRunner {
       return 2;
     }
 
-    for (final FlutterDevice device in flutterDevices) {
-      await device.initLogReader();
+    for (final FlutterDevice? device in flutterDevices) {
+      await device!.initLogReader();
     }
-    for (final FlutterDevice device in flutterDevices) {
-      final List<FlutterView> views = await device.vmService.getFlutterViews();
+    for (final FlutterDevice? device in flutterDevices) {
+      final List<FlutterView> views = await device!.vmService!.getFlutterViews();
       for (final FlutterView view in views) {
         globals.printTrace('Connected to $view.');
       }
@@ -177,7 +164,7 @@ class ColdRunner extends ResidentRunner {
 
     if (enableDevTools && debuggingEnabled) {
       // The method below is guaranteed never to return a failing future.
-      unawaited(residentDevtoolsHandler.serveAndAnnounceDevTools(
+      unawaited(residentDevtoolsHandler!.serveAndAnnounceDevTools(
         devToolsServerAddress: debuggingOptions.devToolsServerAddress,
         flutterDevices: flutterDevices,
       ));
@@ -202,16 +189,16 @@ class ColdRunner extends ResidentRunner {
 
   @override
   Future<void> cleanupAtFinish() async {
-    for (final FlutterDevice flutterDevice in flutterDevices) {
-      await flutterDevice.device.dispose();
+    for (final FlutterDevice? flutterDevice in flutterDevices) {
+      await flutterDevice!.device!.dispose();
     }
 
-    await residentDevtoolsHandler.shutdown();
+    await residentDevtoolsHandler!.shutdown();
     await stopEchoingDeviceLog();
   }
 
   @override
-  void printHelp({ @required bool details }) {
+  void printHelp({ required bool details }) {
     globals.printStatus('Flutter run key commands.');
     if (details) {
       printHelpDetails();
@@ -229,10 +216,10 @@ class ColdRunner extends ResidentRunner {
 
   @override
   Future<void> preExit() async {
-    for (final FlutterDevice device in flutterDevices) {
+    for (final FlutterDevice? device in flutterDevices) {
       // If we're running in release mode, stop the app using the device logic.
-      if (device.vmService == null) {
-        await device.device.stopApp(device.package, userIdentifier: device.userIdentifier);
+      if (device!.vmService == null) {
+        await device.device!.stopApp(device.package, userIdentifier: device.userIdentifier);
       }
     }
     await super.preExit();

packages/flutter_tools/test/general.shard/web/devfs_web_test.dart

@@ -4,6 +4,8 @@
 
 // @dart = 2.8
 
+// ignore_for_file: avoid_redundant_argument_values
+
 import 'dart:io' hide Directory, File;
 
 import 'package:flutter_tools/src/artifacts.dart';