Migrate emulators, packages, upgrade, and downgrade to null safety (#95712)

packages/flutter_tools/lib/src/commands/downgrade.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 'package:process/process.dart';
 
 import '../base/common.dart';
@@ -31,13 +29,13 @@ import '../version.dart';
 class DowngradeCommand extends FlutterCommand {
   DowngradeCommand({
     bool verboseHelp = false,
-    PersistentToolState persistentToolState,
-    Logger logger,
-    ProcessManager processManager,
-    FlutterVersion flutterVersion,
-    Terminal terminal,
-    Stdio stdio,
-    FileSystem fileSystem,
+    PersistentToolState? persistentToolState,
+    Logger? logger,
+    ProcessManager? processManager,
+    FlutterVersion? flutterVersion,
+    Terminal? terminal,
+    Stdio? stdio,
+    FileSystem? fileSystem,
   }) : _terminal = terminal,
        _flutterVersion = flutterVersion,
        _persistentToolState = persistentToolState,
@@ -61,14 +59,14 @@ class DowngradeCommand extends FlutterCommand {
     );
   }
 
-  Terminal _terminal;
-  FlutterVersion _flutterVersion;
-  PersistentToolState _persistentToolState;
-  ProcessUtils _processUtils;
-  ProcessManager _processManager;
-  Logger _logger;
-  Stdio _stdio;
-  FileSystem _fileSystem;
+  Terminal? _terminal;
+  FlutterVersion? _flutterVersion;
+  PersistentToolState? _persistentToolState;
+  ProcessUtils? _processUtils;
+  ProcessManager? _processManager;
+  Logger? _logger;
+  Stdio? _stdio;
+  FileSystem? _fileSystem;
 
   @override
   String get description => 'Downgrade Flutter to the last active version for the current channel.';
@@ -89,25 +87,26 @@ class DowngradeCommand extends FlutterCommand {
     _flutterVersion ??= globals.flutterVersion;
     _persistentToolState ??= globals.persistentToolState;
     _processManager ??= globals.processManager;
-    _processUtils ??= ProcessUtils(processManager: _processManager, logger: _logger);
+    _processUtils ??= ProcessUtils(processManager: _processManager!, logger: _logger!);
     _stdio ??= globals.stdio;
     _fileSystem ??= globals.fs;
-    String workingDirectory = Cache.flutterRoot;
-    if (argResults.wasParsed('working-directory')) {
-      workingDirectory = stringArg('working-directory');
+    String workingDirectory = Cache.flutterRoot!;
+    if (argResults!.wasParsed('working-directory')) {
+      workingDirectory = stringArg('working-directory')!;
       _flutterVersion = FlutterVersion(workingDirectory: workingDirectory);
     }
 
-    final String currentChannel = _flutterVersion.channel;
-    final Channel channel = getChannelForName(currentChannel);
+    final String currentChannel = _flutterVersion!.channel;
+    final Channel? channel = getChannelForName(currentChannel);
     if (channel == null) {
       throwToolExit(
         'Flutter is not currently on a known channel. Use "flutter channel <name>" '
         'to switch to an official channel.',
       );
     }
-    final String lastFlutterVersion = _persistentToolState.lastActiveVersion(channel);
-    final String currentFlutterVersion = _flutterVersion.frameworkRevision;
+    final PersistentToolState persistentToolState = _persistentToolState!;
+    final String? lastFlutterVersion = persistentToolState.lastActiveVersion(channel);
+    final String? currentFlutterVersion = _flutterVersion?.frameworkRevision;
     if (lastFlutterVersion == null || currentFlutterVersion == lastFlutterVersion) {
       final String trailing = await _createErrorMessage(workingDirectory, channel);
       throwToolExit(
@@ -117,7 +116,8 @@ class DowngradeCommand extends FlutterCommand {
     }
 
     // Detect unknown versions.
-    final RunResult parseResult = await _processUtils.run(<String>[
+    final ProcessUtils processUtils = _processUtils!;
+    final RunResult parseResult = await processUtils.run(<String>[
       'git', 'describe', '--tags', lastFlutterVersion,
     ], workingDirectory: workingDirectory);
     if (parseResult.exitCode != 0) {
@@ -126,25 +126,28 @@ class DowngradeCommand extends FlutterCommand {
     final String humanReadableVersion = parseResult.stdout;
 
     // If there is a terminal attached, prompt the user to confirm the downgrade.
-    if (_stdio.hasTerminal && boolArg('prompt')) {
-      _terminal.usesTerminalUi = true;
-      final String result = await _terminal.promptForCharInput(
+    final Stdio stdio = _stdio!;
+    final Terminal terminal = _terminal!;
+    final Logger logger = _logger!;
+    if (stdio.hasTerminal && boolArg('prompt')) {
+      terminal.usesTerminalUi = true;
+      final String result = await terminal.promptForCharInput(
         const <String>['y', 'n'],
         prompt: 'Downgrade flutter to version $humanReadableVersion?',
-        logger: _logger,
+        logger: logger,
       );
       if (result == 'n') {
         return FlutterCommandResult.success();
       }
     } else {
-      _logger.printStatus('Downgrading Flutter to version $humanReadableVersion');
+      logger.printStatus('Downgrading Flutter to version $humanReadableVersion');
     }
 
     // To downgrade the tool, we perform a git checkout --hard, and then
     // switch channels. The version recorded must have existed on that branch
     // so this operation is safe.
     try {
-      await _processUtils.run(
+      await processUtils.run(
         <String>['git', 'reset', '--hard', lastFlutterVersion],
         throwOnError: true,
         workingDirectory: workingDirectory,
@@ -158,7 +161,7 @@ class DowngradeCommand extends FlutterCommand {
       );
     }
     try {
-      await _processUtils.run(
+      await processUtils.run(
         <String>['git', 'checkout', currentChannel, '--'],
         throwOnError: true,
         workingDirectory: workingDirectory,
@@ -172,7 +175,7 @@ class DowngradeCommand extends FlutterCommand {
       );
     }
     await FlutterVersion.resetFlutterVersionFreshnessCheck();
-    _logger.printStatus('Success');
+    logger.printStatus('Success');
     return FlutterCommandResult.success();
   }
 
@@ -183,11 +186,11 @@ class DowngradeCommand extends FlutterCommand {
       if (channel == currentChannel) {
         continue;
       }
-      final String sha = _persistentToolState.lastActiveVersion(channel);
+      final String? sha = _persistentToolState?.lastActiveVersion(channel);
       if (sha == null) {
         continue;
       }
-      final RunResult parseResult = await _processUtils.run(<String>[
+      final RunResult parseResult = await _processUtils!.run(<String>[
         'git', 'describe', '--tags', sha,
       ], workingDirectory: workingDirectory);
       if (parseResult.exitCode == 0) {

packages/flutter_tools/lib/src/commands/emulators.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 'package:args/args.dart';
 
 import '../base/common.dart';
 import '../base/utils.dart';
@@ -39,22 +39,22 @@ class EmulatorsCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    if (globals.doctor.workflows.every((Workflow w) => !w.canListEmulators)) {
+    if (globals.doctor!.workflows.every((Workflow w) => !w.canListEmulators)) {
       throwToolExit(
           'Unable to find any emulator sources. Please ensure you have some\n'
           'Android AVD images ${globals.platform.isMacOS ? 'or an iOS Simulator ' : ''}available.',
           exitCode: 1);
     }
-
-    if (argResults.wasParsed('launch')) {
-      final bool coldBoot = argResults.wasParsed('cold');
-      await _launchEmulator(stringArg('launch'), coldBoot: coldBoot);
-    } else if (argResults.wasParsed('create')) {
+    final ArgResults argumentResults = argResults!;
+    if (argumentResults.wasParsed('launch')) {
+      final bool coldBoot = argumentResults.wasParsed('cold');
+      await _launchEmulator(stringArg('launch')!, coldBoot: coldBoot);
+    } else if (argumentResults.wasParsed('create')) {
       await _createEmulator(name: stringArg('name'));
     } else {
-      final String searchText =
-          argResults.rest != null && argResults.rest.isNotEmpty
-              ? argResults.rest.first
+      final String? searchText =
+          argumentResults.rest != null && argumentResults.rest.isNotEmpty
+              ? argumentResults.rest.first
               : null;
       await _listEmulators(searchText);
     }
@@ -62,9 +62,9 @@ class EmulatorsCommand extends FlutterCommand {
     return FlutterCommandResult.success();
   }
 
-  Future<void> _launchEmulator(String id, {bool coldBoot}) async {
+  Future<void> _launchEmulator(String id, { required bool coldBoot }) async {
     final List<Emulator> emulators =
-        await emulatorManager.getEmulatorsMatching(id);
+        await emulatorManager!.getEmulatorsMatching(id);
 
     if (emulators.isEmpty) {
       globals.printStatus("No emulator found that matches '$id'.");
@@ -78,23 +78,26 @@ class EmulatorsCommand extends FlutterCommand {
     }
   }
 
-  Future<void> _createEmulator({ String name }) async {
+  Future<void> _createEmulator({ String? name }) async {
     final CreateEmulatorResult createResult =
-        await emulatorManager.createEmulator(name: name);
+        await emulatorManager!.createEmulator(name: name);
 
     if (createResult.success) {
       globals.printStatus("Emulator '${createResult.emulatorName}' created successfully.");
     } else {
       globals.printStatus("Failed to create emulator '${createResult.emulatorName}'.\n");
-      globals.printStatus(createResult.error.trim());
+      final String? error = createResult.error;
+      if (error != null) {
+        globals.printStatus(error.trim());
+      }
       _printAdditionalInfo();
     }
   }
 
-  Future<void> _listEmulators(String searchText) async {
+  Future<void> _listEmulators(String? searchText) async {
     final List<Emulator> emulators = searchText == null
-        ? await emulatorManager.getAllAvailableEmulators()
-        : await emulatorManager.getEmulatorsMatching(searchText);
+        ? await emulatorManager!.getAllAvailableEmulators()
+        : await emulatorManager!.getEmulatorsMatching(searchText);
 
     if (emulators.isEmpty) {
       globals.printStatus('No emulators available.');

packages/flutter_tools/lib/src/commands/packages.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 'package:args/args.dart';
 
 import '../base/common.dart';
@@ -55,7 +53,7 @@ class PackagesCommand extends FlutterCommand {
   String get category => FlutterCommandCategory.project;
 
   @override
-  Future<FlutterCommandResult> runCommand() async => null;
+  Future<FlutterCommandResult> runCommand() async => FlutterCommandResult.fail();
 }
 
 class PackagesGetCommand extends FlutterCommand {
@@ -79,15 +77,16 @@ class PackagesGetCommand extends FlutterCommand {
 
   @override
   String get invocation {
-    return '${runner.executableName} pub $name [<target directory>]';
+    return '${runner!.executableName} pub $name [<target directory>]';
   }
 
   /// The pub packages usage values are incorrect since these are calculated/sent
   /// before pub get completes. This needs to be performed after dependency resolution.
   @override
   Future<CustomDimensions> get usageValues async {
-    final String workingDirectory = argResults.rest.length == 1 ? argResults.rest[0] : null;
-    final String target = findProjectRoot(globals.fs, workingDirectory);
+    final ArgResults argumentResults = argResults!;
+    final String? workingDirectory = argumentResults.rest.length == 1 ? argumentResults.rest[0] : null;
+    final String? target = findProjectRoot(globals.fs, workingDirectory);
     if (target == null) {
       return const CustomDimensions();
     }
@@ -118,7 +117,7 @@ class PackagesGetCommand extends FlutterCommand {
   Future<void> _runPubGet(String directory, FlutterProject flutterProject) async {
     if (flutterProject.manifest.generateSyntheticPackage) {
       final Environment environment = Environment(
-        artifacts: globals.artifacts,
+        artifacts: globals.artifacts!,
         logger: globals.logger,
         cacheDir: globals.cache.getRoot(),
         engineVersion: globals.flutterVersion.engineRevision,
@@ -159,12 +158,13 @@ class PackagesGetCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    if (argResults.rest.length > 1) {
+    final ArgResults argumentResults = argResults!;
+    if (argumentResults.rest.length > 1) {
       throwToolExit('Too many arguments.\n$usage');
     }
 
-    final String workingDirectory = argResults.rest.length == 1 ? argResults.rest[0] : null;
-    final String target = findProjectRoot(globals.fs, workingDirectory);
+    final String? workingDirectory = argumentResults.rest.length == 1 ? argumentResults.rest[0] : null;
+    final String? target = findProjectRoot(globals.fs, workingDirectory);
     if (target == null) {
       throwToolExit(
         'Expected to find project root in '
@@ -207,12 +207,12 @@ class PackagesTestCommand extends FlutterCommand {
 
   @override
   String get invocation {
-    return '${runner.executableName} pub test [<tests...>]';
+    return '${runner!.executableName} pub test [<tests...>]';
   }
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    await pub.batch(<String>['run', 'test', ...argResults.rest], context: PubContext.runTest, retry: false);
+    await pub.batch(<String>['run', 'test', ...argResults!.rest], context: PubContext.runTest, retry: false);
     return FlutterCommandResult.success();
   }
 }
@@ -241,12 +241,12 @@ class PackagesForwardCommand extends FlutterCommand {
 
   @override
   String get invocation {
-    return '${runner.executableName} pub $_commandName [<arguments...>]';
+    return '${runner!.executableName} pub $_commandName [<arguments...>]';
   }
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    final List<String> subArgs = argResults.rest.toList()
+    final List<String> subArgs = argResults!.rest.toList()
       ..removeWhere((String arg) => arg == '--');
     await pub.interactively(<String>[_commandName, ...subArgs], stdio: globals.stdio);
     return FlutterCommandResult.success();
@@ -268,12 +268,12 @@ class PackagesPassthroughCommand extends FlutterCommand {
 
   @override
   String get invocation {
-    return '${runner.executableName} packages pub [<arguments...>]';
+    return '${runner!.executableName} packages pub [<arguments...>]';
   }
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    await pub.interactively(argResults.rest, stdio: globals.stdio);
+    await pub.interactively(argResults!.rest, stdio: globals.stdio);
     return FlutterCommandResult.success();
   }
 }
@@ -298,14 +298,14 @@ class PackagesInteractiveGetCommand extends FlutterCommand {
 
   @override
   String get invocation {
-    return '${runner.executableName} pub $_commandName [<arguments...>]';
+    return '${runner!.executableName} pub $_commandName [<arguments...>]';
   }
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    List<String> rest = argResults.rest;
+    List<String> rest = argResults!.rest;
     final bool isHelp = rest.contains('-h') || rest.contains('--help');
-    String target;
+    String? target;
     if (rest.length == 1 && (rest.single.contains('/') || rest.single.contains(r'\'))) {
       // For historical reasons, if there is one argument to the command and it contains
       // a multiple-component path (i.e. contains a slash) then we use that to determine
@@ -316,7 +316,7 @@ class PackagesInteractiveGetCommand extends FlutterCommand {
       target = findProjectRoot(globals.fs);
     }
 
-    FlutterProject flutterProject;
+    FlutterProject? flutterProject;
     if (!isHelp) {
       if (target == null) {
         throwToolExit('Expected to find project root in current working directory.');
@@ -325,7 +325,7 @@ class PackagesInteractiveGetCommand extends FlutterCommand {
 
       if (flutterProject.manifest.generateSyntheticPackage) {
         final Environment environment = Environment(
-          artifacts: globals.artifacts,
+          artifacts: globals.artifacts!,
           logger: globals.logger,
           cacheDir: globals.cache.getRoot(),
           engineVersion: globals.flutterVersion.engineRevision,
@@ -351,7 +351,7 @@ class PackagesInteractiveGetCommand extends FlutterCommand {
       directory: target,
       stdio: globals.stdio,
       touchesPackageConfig: !isHelp,
-      generateSyntheticPackage: flutterProject?.manifest?.generateSyntheticPackage ?? false,
+      generateSyntheticPackage: flutterProject?.manifest.generateSyntheticPackage ?? false,
     );
 
     await flutterProject?.regeneratePlatformSpecificTooling();

packages/flutter_tools/lib/src/commands/upgrade.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 'package:meta/meta.dart';
 
 import '../base/common.dart';
@@ -13,6 +11,7 @@ import '../base/process.dart';
 import '../cache.dart';
 import '../dart/pub.dart';
 import '../globals.dart' as globals;
+import '../persistent_tool_state.dart';
 import '../runner/flutter_command.dart';
 import '../version.dart';
 
@@ -21,8 +20,8 @@ const String _flutterInstallDocs = 'https://flutter.dev/docs/get-started/install
 
 class UpgradeCommand extends FlutterCommand {
   UpgradeCommand({
-    @required bool verboseHelp,
-    UpgradeCommandRunner commandRunner,
+    required bool verboseHelp,
+    UpgradeCommandRunner? commandRunner,
   })
     : _commandRunner = commandRunner ?? UpgradeCommandRunner() {
     argParser
@@ -70,7 +69,7 @@ class UpgradeCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() {
-    _commandRunner.workingDirectory = stringArg('working-directory') ?? Cache.flutterRoot;
+    _commandRunner.workingDirectory = stringArg('working-directory') ?? Cache.flutterRoot!;
     return _commandRunner.runCommand(
       force: boolArg('force'),
       continueFlow: boolArg('continue'),
@@ -87,15 +86,15 @@ class UpgradeCommand extends FlutterCommand {
 @visibleForTesting
 class UpgradeCommandRunner {
 
-  String workingDirectory;
+  String? workingDirectory;
 
   Future<FlutterCommandResult> runCommand({
-    @required bool force,
-    @required bool continueFlow,
-    @required bool testFlow,
-    @required GitTagVersion gitTagVersion,
-    @required FlutterVersion flutterVersion,
-    @required bool verifyOnly,
+    required bool force,
+    required bool continueFlow,
+    required bool testFlow,
+    required GitTagVersion gitTagVersion,
+    required FlutterVersion flutterVersion,
+    required bool verifyOnly,
   }) async {
     if (!continueFlow) {
       await runCommandFirstHalf(
@@ -112,11 +111,11 @@ class UpgradeCommandRunner {
   }
 
   Future<void> runCommandFirstHalf({
-    @required bool force,
-    @required GitTagVersion gitTagVersion,
-    @required FlutterVersion flutterVersion,
-    @required bool testFlow,
-    @required bool verifyOnly,
+    required bool force,
+    required GitTagVersion gitTagVersion,
+    required FlutterVersion flutterVersion,
+    required bool testFlow,
+    required bool verifyOnly,
   }) async {
     final FlutterVersion upstreamVersion = await fetchLatestVersion(localVersion: flutterVersion);
     if (flutterVersion.frameworkRevision == upstreamVersion.frameworkRevision) {
@@ -172,11 +171,11 @@ class UpgradeCommandRunner {
   }
 
   void recordState(FlutterVersion flutterVersion) {
-    final Channel channel = getChannelForName(flutterVersion.channel);
+    final Channel? channel = getChannelForName(flutterVersion.channel);
     if (channel == null) {
       return;
     }
-    globals.persistentToolState.updateLastActiveVersion(flutterVersion.frameworkRevision, channel);
+    globals.persistentToolState!.updateLastActiveVersion(flutterVersion.frameworkRevision, channel);
   }
 
   Future<void> flutterUpgradeContinue() async {
@@ -200,12 +199,13 @@ class UpgradeCommandRunner {
   // re-entrantly with the `--continue` flag
   Future<void> runCommandSecondHalf(FlutterVersion flutterVersion) async {
     // Make sure the welcome message re-display is delayed until the end.
-    globals.persistentToolState.setShouldRedisplayWelcomeMessage(false);
+    final PersistentToolState persistentToolState = globals.persistentToolState!;
+    persistentToolState.setShouldRedisplayWelcomeMessage(false);
     await precacheArtifacts();
     await updatePackages(flutterVersion);
     await runDoctor();
     // Force the welcome message to re-display following the upgrade.
-    globals.persistentToolState.setShouldRedisplayWelcomeMessage(true);
+    persistentToolState.setShouldRedisplayWelcomeMessage(true);
   }
 
   Future<bool> hasUncommittedChanges() async {
@@ -235,7 +235,8 @@ class UpgradeCommandRunner {
   /// Exits tool if the tracking remote is not standard.
   void verifyStandardRemote(FlutterVersion localVersion) {
     // If repositoryUrl of the local version is null, exit
-    if (localVersion.repositoryUrl == null) {
+    final String? repositoryUrl = localVersion.repositoryUrl;
+    if (repositoryUrl == null) {
       throwToolExit(
         'Unable to upgrade Flutter: The tool could not determine the remote '
         'upstream which is being tracked by the SDK.\n'
@@ -244,7 +245,7 @@ class UpgradeCommandRunner {
     }
 
     // Strip `.git` suffix before comparing the remotes
-    final String trackingUrl = stripDotGit(localVersion.repositoryUrl);
+    final String trackingUrl = stripDotGit(repositoryUrl);
     final String flutterGitUrl = stripDotGit(globals.flutterGit);
 
     // Exempt the official flutter git SSH remote from this check
@@ -287,18 +288,18 @@ class UpgradeCommandRunner {
   // URLs without ".git" suffix will remain unaffected.
   String stripDotGit(String url) {
     final RegExp pattern = RegExp(r'(.*)(\.git)$');
-    final RegExpMatch match = pattern.firstMatch(url);
+    final RegExpMatch? match = pattern.firstMatch(url);
     if (match == null) {
       return url;
     }
-    return match.group(1);
+    return match.group(1)!;
   }
 
   /// Returns the remote HEAD flutter version.
   ///
   /// Exits tool if HEAD isn't pointing to a branch, or there is no upstream.
   Future<FlutterVersion> fetchLatestVersion({
-    @required FlutterVersion localVersion,
+    required FlutterVersion localVersion,
   }) async {
     String revision;
     try {
@@ -380,14 +381,13 @@ class UpgradeCommandRunner {
   Future<void> updatePackages(FlutterVersion flutterVersion) async {
     globals.printStatus('');
     globals.printStatus(flutterVersion.toString());
-    final String projectRoot = findProjectRoot(globals.fs);
+    final String? projectRoot = findProjectRoot(globals.fs);
     if (projectRoot != null) {
       globals.printStatus('');
       await pub.get(
         context: PubContext.pubUpgrade,
         directory: projectRoot,
         upgrade: true,
-        generateSyntheticPackage: false,
       );
     }
   }

packages/flutter_tools/lib/src/dart/pub.dart

@@ -101,7 +101,7 @@ abstract class Pub {
     bool upgrade = false,
     bool offline = false,
     bool generateSyntheticPackage = false,
-    String flutterRootOverride,
+    String? flutterRootOverride,
     bool checkUpToDate = false,
     bool shouldSkipThirdPartyGenerator = true,
     bool printProgress = true,
@@ -135,7 +135,7 @@ abstract class Pub {
   /// stdout/stderr stream of pub to the corresponding streams of this process.
   Future<void> interactively(
     List<String> arguments, {
-    String directory,
+    String? directory,
     required io.Stdio stdio,
     bool touchesPackageConfig = false,
     bool generateSyntheticPackage = false,