[flutter_tools] migrate more unit tests to null safety (#106153)

packages/flutter_tools/lib/src/build_system/targets/assets.dart

@@ -210,10 +210,10 @@ DevFSContent? processSkSLBundle(String? bundlePath, {
   }
 
   // Step 2: validate top level bundle structure.
-  Map<String, Object>? bundle;
+  Map<String, Object?>? bundle;
   try {
     final Object? rawBundle = json.decode(skSLBundleFile.readAsStringSync());
-    if (rawBundle is Map<String, Object>) {
+    if (rawBundle is Map<String, Object?>) {
       bundle = rawBundle;
     } else {
       logger.printError('"$bundle" was not a JSON object: $rawBundle');

packages/flutter_tools/lib/src/cache.dart

@@ -389,10 +389,10 @@ class Cache {
         throw Exception('Could not find file at $versionFilePath');
       }
       final dynamic data = jsonDecode(versionFile.readAsStringSync());
-      if (data is! Map<String, Object>) {
-        throw Exception("Expected object of type 'Map<String, Object>' but got one of type '${data.runtimeType}'");
+      if (data is! Map<String, Object?>) {
+        throw Exception("Expected object of type 'Map<String, Object?>' but got one of type '${data.runtimeType}'");
       }
-      final dynamic version = data['version'];
+      final Object? version = data['version'];
       if (version == null) {
         throw Exception('Could not parse DevTools version from $version');
       }

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

@@ -668,11 +668,11 @@ abstract class CreateBase extends FlutterCommand {
       'templates',
       'template_manifest.json',
     );
-    final Map<String, Object> manifest = json.decode(
+    final Map<String, Object?> manifest = json.decode(
       globals.fs.file(manifestPath).readAsStringSync(),
-    ) as Map<String, Object>;
+    ) as Map<String, Object?>;
     return Set<Uri>.from(
-      (manifest['files']! as List<Object>).cast<String>().map<Uri>(
+      (manifest['files']! as List<Object?>).cast<String>().map<Uri>(
           (String path) =>
               Uri.file(globals.fs.path.join(flutterToolsAbsolutePath, path))),
     );

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

@@ -86,8 +86,8 @@ abstract class MacOSApp extends ApplicationPackage {
       return null;
     }
     final Map<String, dynamic> propertyValues = globals.plistParser.parseFile(plistPath);
-    final String id = propertyValues[PlistParser.kCFBundleIdentifierKey] as String;
-    final String executableName = propertyValues[PlistParser.kCFBundleExecutable] as String;
+    final String? id = propertyValues[PlistParser.kCFBundleIdentifierKey] as String?;
+    final String? executableName = propertyValues[PlistParser.kCFBundleExecutable] as String?;
     if (id == null) {
       globals.printError('Invalid prebuilt macOS app. Info.plist does not contain bundle identifier');
       return null;

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -1534,7 +1534,7 @@ abstract class FlutterCommand extends Command<void> {
     if (!argParser.options.containsKey(name)) {
       return null;
     }
-    return argResults![name] as String;
+    return argResults![name] as String?;
   }
 
   /// Gets the parsed command-line option named [name] as an `int`.

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

@@ -117,7 +117,7 @@ class CoverageCollector extends TestWatcher {
     );
 
     final Future<void> collectionComplete = testDevice.observatoryUri
-      .then((Uri observatoryUri) {
+      .then((Uri? observatoryUri) {
         _logMessage('collecting coverage data from $testDevice at $observatoryUri...');
         return collect(observatoryUri, libraryNames)
           .then<void>((Map<String, dynamic> result) {

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

@@ -494,7 +494,7 @@ class FlutterPlatform extends PlatformPlugin {
       await Future.any<void>(<Future<void>>[
         testDevice.finished,
         () async {
-          final Uri processObservatoryUri = await testDevice.observatoryUri;
+          final Uri? processObservatoryUri = await testDevice.observatoryUri;
           if (processObservatoryUri != null) {
             globals.printTrace('test $ourTestCount: Observatory uri is available at $processObservatoryUri');
           } else {

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

@@ -47,8 +47,7 @@ class FlutterTesterTestDevice extends TestDevice {
   })  : assert(shellPath != null), // Please provide the path to the shell in the SKY_SHELL environment variable.
         assert(!debuggingOptions.startPaused || enableObservatory),
         _gotProcessObservatoryUri = enableObservatory
-            // ignore: null_argument_to_non_null_type
-            ? Completer<Uri>() : (Completer<Uri>()..complete()),
+            ? Completer<Uri?>() : (Completer<Uri?>()..complete()),
         _operatingSystemUtils = OperatingSystemUtils(
           fileSystem: fileSystem,
           logger: logger,
@@ -73,7 +72,7 @@ class FlutterTesterTestDevice extends TestDevice {
   final CompileExpression? compileExpression;
   final FontConfigManager fontConfigManager;
 
-  final Completer<Uri> _gotProcessObservatoryUri;
+  final Completer<Uri?> _gotProcessObservatoryUri;
   final Completer<int> _exitCode = Completer<int>();
 
   Process? _process;
@@ -209,7 +208,7 @@ class FlutterTesterTestDevice extends TestDevice {
   }
 
   @override
-  Future<Uri> get observatoryUri {
+  Future<Uri?> get observatoryUri {
     assert(_gotProcessObservatoryUri != null);
     return _gotProcessObservatoryUri.future;
   }

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

@@ -79,7 +79,7 @@ class TestCompiler {
   late File outputDill;
 
   Future<String?> compile(Uri mainDart) {
-    final Completer<String> completer = Completer<String>();
+    final Completer<String?> completer = Completer<String?>();
     if (compilerController.isClosed) {
       return Future<String?>.value();
     }
@@ -175,7 +175,7 @@ class TestCompiler {
       // compiler to avoid reusing compiler that might have gotten into
       // a weird state.
       if (outputPath == null || compilerOutput!.errorCount > 0) {
-        request.result.complete(null);
+        request.result.complete();
         await _shutdown();
       } else {
         if (shouldCopyDillFile) {

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

@@ -22,7 +22,7 @@ abstract class TestDevice {
   Future<StreamChannel<String>> start(String entrypointPath);
 
   /// Should complete with null if the observatory is not enabled.
-  Future<Uri> get observatoryUri;
+  Future<Uri?> get observatoryUri;
 
   /// Terminates the test device.
   Future<void> kill();

packages/flutter_tools/test/general.shard/analytics_test.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/command_runner.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/android_workflow.dart';
@@ -37,8 +35,8 @@ void main() {
   });
 
   group('analytics', () {
-    Directory tempDir;
-    Config testConfig;
+    late Directory tempDir;
+    late Config testConfig;
 
     setUp(() {
       Cache.flutterRoot = '../..';
@@ -108,7 +106,7 @@ void main() {
     });
 
     testUsingContext('Usage records one feature in experiment setting', () async {
-      testConfig.setValue(flutterWebFeature.configSetting, true);
+      testConfig.setValue(flutterWebFeature.configSetting!, true);
       final Usage usage = Usage(runningOnBot: true);
       usage.sendCommand('test');
 
@@ -126,9 +124,9 @@ void main() {
     });
 
     testUsingContext('Usage records multiple features in experiment setting', () async {
-      testConfig.setValue(flutterWebFeature.configSetting, true);
-      testConfig.setValue(flutterLinuxDesktopFeature.configSetting, true);
-      testConfig.setValue(flutterMacOSDesktopFeature.configSetting, true);
+      testConfig.setValue(flutterWebFeature.configSetting!, true);
+      testConfig.setValue(flutterLinuxDesktopFeature.configSetting!, true);
+      testConfig.setValue(flutterMacOSDesktopFeature.configSetting!, true);
       final Usage usage = Usage(runningOnBot: true);
       usage.sendCommand('test');
 
@@ -150,11 +148,11 @@ void main() {
   });
 
   group('analytics with fakes', () {
-    MemoryFileSystem memoryFileSystem;
-    FakeStdio fakeStdio;
-    TestUsage testUsage;
-    FakeClock fakeClock;
-    FakeDoctor doctor;
+    late MemoryFileSystem memoryFileSystem;
+    late FakeStdio fakeStdio;
+    late TestUsage testUsage;
+    late FakeClock fakeClock;
+    late FakeDoctor doctor;
 
     setUp(() {
       memoryFileSystem = MemoryFileSystem.test();
@@ -211,7 +209,7 @@ void main() {
 
     testUsingContext('compound command usage path', () async {
       final BuildCommand buildCommand = BuildCommand();
-      final FlutterCommand buildApkCommand = buildCommand.subcommands['apk'] as FlutterCommand;
+      final FlutterCommand buildApkCommand = buildCommand.subcommands['apk']! as FlutterCommand;
 
       expect(await buildApkCommand.usagePath, 'build/apk');
     }, overrides: <Type, Generator>{
@@ -280,7 +278,7 @@ void main() {
   });
 
   group('analytics bots', () {
-    Directory tempDir;
+    late Directory tempDir;
 
     setUp(() {
       tempDir = globals.fs.systemTempDirectory.createTempSync('flutter_tools_analytics_bots_test.');
@@ -341,8 +339,8 @@ Analytics throwingAnalyticsIOFactory(
   String trackingId,
   String applicationName,
   String applicationVersion, {
-  String analyticsUrl,
-  Directory documentDirectory,
+  String? analyticsUrl,
+  Directory? documentDirectory,
 }) {
   throw const FileSystemException('Could not create file');
 }
@@ -368,9 +366,9 @@ class FakeDoctor extends Fake implements Doctor {
     bool androidLicenses = false,
     bool verbose = true,
     bool showColor = true,
-    AndroidLicenseValidator androidLicenseValidator,
+    AndroidLicenseValidator? androidLicenseValidator,
     bool showPii = true,
-    List<ValidatorTask> startedValidatorTasks,
+    List<ValidatorTask>? startedValidatorTasks,
     bool sendEvent = true,
   }) async {
     return diagnoseSucceeds;

packages/flutter_tools/test/general.shard/android/android_gradle_builder_test.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:archive/archive.dart';
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
@@ -27,10 +25,10 @@ import '../../src/fake_process_manager.dart';
 
 void main() {
   group('gradle build', () {
-    BufferLogger logger;
-    TestUsage testUsage;
-    FileSystem fileSystem;
-    FakeProcessManager processManager;
+    late BufferLogger logger;
+    late TestUsage testUsage;
+    late FileSystem fileSystem;
+    late FakeProcessManager processManager;
 
     setUp(() {
       processManager = FakeProcessManager.empty();
@@ -99,10 +97,10 @@ void main() {
                 return line.contains('Some gradle message');
               },
               handler: ({
-                String line,
-                FlutterProject project,
-                bool usesAndroidX,
-                bool multidexEnabled
+                String? line,
+                FlutterProject? project,
+                bool? usesAndroidX,
+                bool? multidexEnabled
               }) async {
                 handlerCalled = true;
                 return GradleBuildStatus.exit;
@@ -263,10 +261,10 @@ void main() {
                 return false;
               },
               handler: ({
-                String line,
-                FlutterProject project,
-                bool usesAndroidX,
-                bool multidexEnabled
+                String? line,
+                FlutterProject? project,
+                bool? usesAndroidX,
+                bool? multidexEnabled
               }) async {
                 return GradleBuildStatus.retry;
               },
@@ -351,10 +349,10 @@ void main() {
                 return line.contains('Some gradle message');
               },
               handler: ({
-                String line,
-                FlutterProject project,
-                bool usesAndroidX,
-                bool multidexEnabled
+                String? line,
+                FlutterProject? project,
+                bool? usesAndroidX,
+                bool? multidexEnabled
               }) async {
                 handlerCalled = true;
                 return GradleBuildStatus.exit;
@@ -517,10 +515,10 @@ void main() {
               return line.contains('Some gradle message');
             },
             handler: ({
-              String line,
-              FlutterProject project,
-              bool usesAndroidX,
-                bool multidexEnabled
+              String? line,
+              FlutterProject? project,
+              bool? usesAndroidX,
+                bool? multidexEnabled
             }) async {
               return GradleBuildStatus.retry;
             },
@@ -595,7 +593,7 @@ void main() {
         .childDirectory('flutter-apk')
         .childFile('app-release.apk')
         ..createSync(recursive: true)
-        ..writeAsBytesSync(ZipEncoder().encode(archive));
+        ..writeAsBytesSync(ZipEncoder().encode(archive)!);
 
       fileSystem.file('foo/snapshot.arm64-v8a.json')
         ..createSync(recursive: true)

packages/flutter_tools/test/general.shard/android/android_studio_validator_test.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:file/memory.dart';
 import 'package:flutter_tools/src/android/android_studio_validator.dart';
 import 'package:flutter_tools/src/base/config.dart';
@@ -24,8 +22,8 @@ final Platform linuxPlatform = FakePlatform(
 );
 
 void main() {
-  FileSystem fileSystem;
-  FakeProcessManager fakeProcessManager;
+  late FileSystem fileSystem;
+  late FakeProcessManager fakeProcessManager;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();

packages/flutter_tools/test/general.shard/android/deferred_components_prebuild_validator_test.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:file/memory.dart';
 import 'package:flutter_tools/src/android/deferred_components_prebuild_validator.dart';
 import 'package:flutter_tools/src/android/deferred_components_validator.dart';
@@ -16,11 +14,11 @@ import '../../src/common.dart';
 import '../../src/context.dart';
 
 void main() {
-  FileSystem fileSystem;
-  BufferLogger logger;
-  Directory projectDir;
-  Platform platform;
-  Directory flutterRootDir;
+  late FileSystem fileSystem;
+  late BufferLogger logger;
+  late Directory projectDir;
+  late Platform platform;
+  late Directory flutterRootDir;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();

packages/flutter_tools/test/general.shard/android/gradle_test.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:file/memory.dart';
 import 'package:flutter_tools/src/android/android_sdk.dart';
 import 'package:flutter_tools/src/android/gradle.dart';
@@ -33,7 +31,7 @@ void main() {
   Cache.flutterRoot = getFlutterRoot();
 
   group('build artifacts', () {
-    FileSystem fileSystem;
+    late FileSystem fileSystem;
 
     setUp(() {
       fileSystem = MemoryFileSystem.test();
@@ -194,8 +192,8 @@ void main() {
   });
 
   group('Gradle local.properties', () {
-    Artifacts localEngineArtifacts;
-    FileSystem fs;
+    late Artifacts localEngineArtifacts;
+    late FileSystem fs;
 
     setUp(() {
       fs = MemoryFileSystem.test();
@@ -211,7 +209,7 @@ void main() {
       });
     }
 
-    String propertyFor(String key, File file) {
+    String? propertyFor(String key, File file) {
       final Iterable<String> result = file.readAsLinesSync()
           .where((String line) => line.startsWith('$key='))
           .map((String line) => line.split('=')[1]);
@@ -219,10 +217,10 @@ void main() {
     }
 
     Future<void> checkBuildVersion({
-      String manifest,
-      BuildInfo buildInfo,
-      String expectedBuildName,
-      String expectedBuildNumber,
+      required String manifest,
+      BuildInfo? buildInfo,
+      String? expectedBuildName,
+      String? expectedBuildNumber,
     }) async {
       final File manifestFile = globals.fs.file('path/to/project/pubspec.yaml');
       manifestFile.createSync(recursive: true);
@@ -457,7 +455,7 @@ flutter:
   });
 
   group('isAppUsingAndroidX', () {
-    FileSystem fs;
+    late FileSystem fs;
 
     setUp(() {
       fs = MemoryFileSystem.test();
@@ -503,8 +501,8 @@ flutter:
   });
 
   group('printHowToConsumeAar', () {
-    BufferLogger logger;
-    FileSystem fileSystem;
+    late BufferLogger logger;
+    late FileSystem fileSystem;
 
     setUp(() {
       logger = BufferLogger.test();
@@ -694,8 +692,8 @@ flutter:
     // If this test fails, you probably edited templates/app/android.tmpl.
     // That's fine, but you now need to add a copy of that file to gradle/settings.gradle.legacy_versions, separated
     // from the previous versions by a line that just says ";EOF".
-    final File templateSettingsDotGradle = globals.fs.file(globals.fs.path.join(Cache.flutterRoot, 'packages', 'flutter_tools', 'templates', 'app', 'android.tmpl', 'settings.gradle'));
-    final File legacySettingsDotGradleFiles = globals.fs.file(globals.fs.path.join(Cache.flutterRoot, 'packages','flutter_tools', 'gradle', 'settings.gradle.legacy_versions'));
+    final File templateSettingsDotGradle = globals.fs.file(globals.fs.path.join(Cache.flutterRoot!, 'packages', 'flutter_tools', 'templates', 'app', 'android.tmpl', 'settings.gradle'));
+    final File legacySettingsDotGradleFiles = globals.fs.file(globals.fs.path.join(Cache.flutterRoot!, 'packages','flutter_tools', 'gradle', 'settings.gradle.legacy_versions'));
     expect(
       legacySettingsDotGradleFiles.readAsStringSync().split(';EOF').map<String>((String body) => body.trim()),
       contains(templateSettingsDotGradle.readAsStringSync().trim()),

packages/flutter_tools/test/general.shard/android/multidex_test.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:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/multidex.dart';

packages/flutter_tools/test/general.shard/asset_bundle_package_fonts_test.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:convert';
 
 import 'package:file/file.dart';
@@ -24,9 +22,9 @@ void main() {
     // fixed we fix them here.
     // TODO(dantup): Remove this function once the above issue is fixed and
     // rolls into Flutter.
-    return path?.replaceAll('/', globals.fs.path.separator);
+    return path.replaceAll('/', globals.fs.path.separator);
   }
-  void writePubspecFile(String path, String name, { String fontsSection }) {
+  void writePubspecFile(String path, String name, { String? fontsSection }) {
     if (fontsSection == null) {
       fontsSection = '';
     } else {
@@ -61,14 +59,14 @@ $fontsSection
     String expectedAssetManifest,
   ) async {
     final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-    await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+    await bundle.build(packagesPath: '.packages');
 
     for (final String packageName in packages) {
       for (final String packageFont in packageFonts) {
         final String entryKey = 'packages/$packageName/$packageFont';
         expect(bundle.entries.containsKey(entryKey), true);
         expect(
-          utf8.decode(await bundle.entries[entryKey].contentsAsBytes()),
+          utf8.decode(await bundle.entries[entryKey]!.contentsAsBytes()),
           packageFont,
         );
       }
@@ -76,14 +74,14 @@ $fontsSection
       for (final String localFont in localFonts) {
         expect(bundle.entries.containsKey(localFont), true);
         expect(
-          utf8.decode(await bundle.entries[localFont].contentsAsBytes()),
+          utf8.decode(await bundle.entries[localFont]!.contentsAsBytes()),
           localFont,
         );
       }
     }
 
     expect(
-      json.decode(utf8.decode(await bundle.entries['FontManifest.json'].contentsAsBytes())),
+      json.decode(utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes())),
       json.decode(expectedAssetManifest),
     );
   }
@@ -95,7 +93,7 @@ $fontsSection
   }
 
   group('AssetBundle fonts from packages', () {
-    FileSystem testFileSystem;
+    FileSystem? testFileSystem;
 
     setUp(() async {
       testFileSystem = MemoryFileSystem(
@@ -103,7 +101,7 @@ $fontsSection
           ? FileSystemStyle.windows
           : FileSystemStyle.posix,
       );
-      testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
+      testFileSystem!.currentDirectory = testFileSystem!.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
     });
 
     testUsingContext('App includes neither font manifest nor fonts when no defines fonts', () async {
@@ -112,7 +110,7 @@ $fontsSection
       writePubspecFile('p/p/pubspec.yaml', 'test_package');
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
       expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
       expect(bundle.entries.containsKey('FontManifest.json'), isTrue);
     }, overrides: <Type, Generator>{

packages/flutter_tools/test/general.shard/asset_bundle_package_test.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:convert';
 
 import 'package:file/file.dart';
@@ -24,9 +22,9 @@ void main() {
     // fixed we fix them here.
     // TODO(dantup): Remove this function once the above issue is fixed and
     // rolls into Flutter.
-    return path?.replaceAll('/', globals.fs.path.separator);
+    return path.replaceAll('/', globals.fs.path.separator);
   }
-  void writePubspecFile(String path, String name, { List<String> assets }) {
+  void writePubspecFile(String path, String name, { List<String>? assets }) {
     String assetsSection;
     if (assets == null) {
       assetsSection = '';
@@ -65,11 +63,11 @@ $assetsSection
   Future<void> buildAndVerifyAssets(
     List<String> assets,
     List<String> packages,
-    String expectedAssetManifest, {
+    String? expectedAssetManifest, {
     bool expectExists = true,
   }) async {
     final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-    await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+    await bundle.build(packagesPath: '.packages');
 
     for (final String packageName in packages) {
       for (final String asset in assets) {
@@ -78,7 +76,7 @@ $assetsSection
           reason: 'Cannot find key on bundle: $entryKey');
         if (expectExists) {
           expect(
-            utf8.decode(await bundle.entries[entryKey].contentsAsBytes()),
+            utf8.decode(await bundle.entries[entryKey]!.contentsAsBytes()),
             asset,
           );
         }
@@ -87,7 +85,7 @@ $assetsSection
 
     if (expectExists) {
       expect(
-        utf8.decode(await bundle.entries['AssetManifest.json'].contentsAsBytes()),
+        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
         expectedAssetManifest,
       );
     }
@@ -103,7 +101,7 @@ $assetsSection
     }
   }
 
-  FileSystem testFileSystem;
+  late FileSystem testFileSystem;
 
   setUp(() async {
     testFileSystem = MemoryFileSystem(
@@ -121,15 +119,15 @@ $assetsSection
       writePubspecFile('p/p/pubspec.yaml', 'test_package');
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
       expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
       const String expectedAssetManifest = '{}';
       expect(
-        utf8.decode(await bundle.entries['AssetManifest.json'].contentsAsBytes()),
+        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
         expectedAssetManifest,
       );
       expect(
-        utf8.decode(await bundle.entries['FontManifest.json'].contentsAsBytes()),
+        utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
         '[]',
       );
     }, overrides: <Type, Generator>{
@@ -146,15 +144,15 @@ $assetsSection
       writeAssets('p/p/', assets);
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
       expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
       const String expectedAssetManifest = '{}';
       expect(
-        utf8.decode(await bundle.entries['AssetManifest.json'].contentsAsBytes()),
+        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
         expectedAssetManifest,
       );
       expect(
-        utf8.decode(await bundle.entries['FontManifest.json'].contentsAsBytes()),
+        utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
         '[]',
       );
     }, overrides: <Type, Generator>{
@@ -540,7 +538,7 @@ $assetsSection
       writeAssets('p/p/', assetsOnDisk);
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
 
       expect(bundle.entries['AssetManifest.json'], isNull,
         reason: 'Invalid pubspec.yaml should not generate AssetManifest.json'  );

packages/flutter_tools/test/general.shard/asset_bundle_variant_test.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:convert';
 
 import 'package:file/file.dart';
@@ -24,11 +22,11 @@ void main() {
     // fixed we fix them here.
     // TODO(dantup): Remove this function once the above issue is fixed and
     // rolls into Flutter.
-    return path?.replaceAll('/', globals.fs.path.separator);
+    return path.replaceAll('/', globals.fs.path.separator);
   }
 
   group('AssetBundle asset variants', () {
-    FileSystem testFileSystem;
+    late FileSystem testFileSystem;
     setUp(() async {
       testFileSystem = MemoryFileSystem(
         style: globals.platform.isWindows
@@ -67,24 +65,24 @@ flutter:
       }
 
       AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
 
       // The main asset file, /a/b/c/foo, and its variants exist.
       for (final String asset in assets) {
         expect(bundle.entries.containsKey(asset), true);
-        expect(utf8.decode(await bundle.entries[asset].contentsAsBytes()), asset);
+        expect(utf8.decode(await bundle.entries[asset]!.contentsAsBytes()), asset);
       }
 
       globals.fs.file(fixPath('a/b/c/foo')).deleteSync();
       bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(manifestPath: 'pubspec.yaml', packagesPath: '.packages');
+      await bundle.build(packagesPath: '.packages');
 
       // Now the main asset file, /a/b/c/foo, does not exist. This is OK because
       // the /a/b/c/*/foo variants do exist.
       expect(bundle.entries.containsKey('a/b/c/foo'), false);
       for (final String asset in assets.skip(1)) {
         expect(bundle.entries.containsKey(asset), true);
-        expect(utf8.decode(await bundle.entries[asset].contentsAsBytes()), asset);
+        expect(utf8.decode(await bundle.entries[asset]!.contentsAsBytes()), asset);
       }
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,

packages/flutter_tools/test/general.shard/asset_test.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:flutter_tools/src/asset.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/cache.dart';
@@ -86,5 +84,5 @@ void main() {
 }
 
 Future<String> getValueAsString(String key, AssetBundle asset) async {
-  return String.fromCharCodes(await asset.entries[key].contentsAsBytes());
+  return String.fromCharCodes(await asset.entries[key]!.contentsAsBytes());
 }

packages/flutter_tools/test/general.shard/build_system/source_test.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:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
@@ -21,9 +19,9 @@ final Platform windowsPlatform = FakePlatform(
 );
 
 void main() {
-  Testbed testbed;
-  SourceVisitor visitor;
-  Environment environment;
+  late Testbed testbed;
+  late SourceVisitor visitor;
+  late Environment environment;
 
   setUp(() {
     testbed = Testbed(setup: () {
@@ -33,7 +31,7 @@ void main() {
       environment = Environment.test(
         globals.fs.currentDirectory,
         outputDir: outputs,
-        artifacts: globals.artifacts, // using real artifacts
+        artifacts: globals.artifacts!, // using real artifacts
         processManager: FakeProcessManager.any(),
         fileSystem: globals.fs,
         // engineVersion being null simulates a local engine.

packages/flutter_tools/test/general.shard/build_system/targets/android_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -21,10 +19,10 @@ import '../../../src/context.dart';
 import '../../../src/fake_process_manager.dart';
 
 void main() {
-  FakeProcessManager processManager;
-  FileSystem fileSystem;
-  Artifacts artifacts;
-  Logger logger;
+  late FakeProcessManager processManager;
+  late FileSystem fileSystem;
+  late Artifacts artifacts;
+  late Logger logger;
 
   setUp(() {
     logger = BufferLogger.test();

packages/flutter_tools/test/general.shard/build_system/targets/assets_test.dart

@@ -2,8 +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:collection/collection.dart' show IterableExtension;
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -21,8 +20,8 @@ import '../../../src/common.dart';
 import '../../../src/context.dart';
 
 void main() {
-  Environment environment;
-  FileSystem fileSystem;
+  late Environment environment;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -75,7 +74,7 @@ flutter:
     final Depfile dependencies = depfileService.parse(depfile);
 
     expect(
-      dependencies.inputs.firstWhere((File file) => file.path == '/bar/LICENSE', orElse: () => null),
+      dependencies.inputs.firstWhereOrNull((File file) => file.path == '/bar/LICENSE'),
       isNotNull,
     );
   }, overrides: <Type, Generator>{
@@ -124,7 +123,6 @@ flutter:
       targetPlatform: TargetPlatform.android,
       fileSystem: MemoryFileSystem.test(),
       logger: BufferLogger.test(),
-      engineVersion: null,
     ), isNull);
   });
 
@@ -136,7 +134,6 @@ flutter:
       targetPlatform: TargetPlatform.android,
       fileSystem: MemoryFileSystem.test(),
       logger: BufferLogger.test(),
-      engineVersion: null,
     ), throwsException);
   });
 
@@ -152,7 +149,6 @@ flutter:
       targetPlatform: TargetPlatform.android,
       fileSystem: fileSystem,
       logger: logger,
-      engineVersion: null,
     ), throwsException);
     expect(logger.errorText, contains('was not a JSON object'));
   });
@@ -169,7 +165,6 @@ flutter:
       targetPlatform: TargetPlatform.android,
       fileSystem: fileSystem,
       logger: logger,
-      engineVersion: null,
     ), throwsException);
     expect(logger.errorText, contains('was not a JSON object'));
   });
@@ -214,7 +209,7 @@ flutter:
       fileSystem: fileSystem,
       logger: logger,
       engineVersion: '2',
-    );
+    )!;
 
     expect(await content.contentsAsBytes(), utf8.encode('{"data":{}}'));
     expect(logger.errorText, contains('This may lead to less efficient shader caching'));
@@ -238,7 +233,7 @@ flutter:
       fileSystem: fileSystem,
       logger: logger,
       engineVersion: '2',
-    );
+    )!;
 
     expect(await content.contentsAsBytes(), utf8.encode('{"data":{}}'));
     expect(logger.errorText, isEmpty);

packages/flutter_tools/test/general.shard/build_system/targets/common_test.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:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -26,12 +24,12 @@ const String kAssemblyAot = '--snapshot_kind=app-aot-assembly';
 
 final Platform macPlatform = FakePlatform(operatingSystem: 'macos', environment: <String, String>{});
 void main() {
-  FakeProcessManager processManager;
-  Environment androidEnvironment;
-  Environment iosEnvironment;
-  Artifacts artifacts;
-  FileSystem fileSystem;
-  Logger logger;
+  late FakeProcessManager processManager;
+  late Environment androidEnvironment;
+  late Environment iosEnvironment;
+  late Artifacts artifacts;
+  late FileSystem fileSystem;
+  late Logger logger;
 
   setUp(() {
     processManager = FakeProcessManager.empty();

packages/flutter_tools/test/general.shard/build_system/targets/dart_plugin_registrant_test.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
-
 // TODO(gspencergoog): Remove this tag once this test's state leaks/test
 // dependencies have been fixed.
 // https://github.com/flutter/flutter/issues/85160

packages/flutter_tools/test/general.shard/build_system/targets/deferred_components_test.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:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -19,8 +17,8 @@ import '../../../src/context.dart';
 // These tests perform a simple check to verify if the check/task was executed at all.
 // Detailed per-check tests are in android/deferred_components_setup_validator_test.dart.
 void main() {
-  FileSystem fileSystem;
-  BufferLogger logger;
+  late FileSystem fileSystem;
+  late BufferLogger logger;
 
   setUp(() {
     logger = BufferLogger.test();
@@ -55,9 +53,9 @@ void main() {
     await validatorTarget.build(environment);
 
     // We check the inputs to determine if the task was executed.
-    expect(validatorTarget.validator.inputs.length, 3);
-    expect(validatorTarget.validator.inputs[0].path, 'project/pubspec.yaml');
-    expect(validatorTarget.validator.inputs[1].path, 'project/android/app/src/main/AndroidManifest.xml');
+    expect(validatorTarget.validator!.inputs.length, 3);
+    expect(validatorTarget.validator!.inputs[0].path, 'project/pubspec.yaml');
+    expect(validatorTarget.validator!.inputs[1].path, 'project/android/app/src/main/AndroidManifest.xml');
   });
 
   testUsingContext('checkAgainstLoadingUnitsCache checks runs', () async {
@@ -88,8 +86,8 @@ void main() {
     await validatorTarget.build(environment);
 
     // We check the inputs to determine if the task was executed.
-    expect(validatorTarget.validator.inputs.length, 3);
-    expect(validatorTarget.validator.inputs[2].path, 'project/deferred_components_loading_units.yaml');
+    expect(validatorTarget.validator!.inputs.length, 3);
+    expect(validatorTarget.validator!.inputs[2].path, 'project/deferred_components_loading_units.yaml');
   });
 
   testUsingContext('writeLoadingUnitsCache task runs', () async {
@@ -120,7 +118,7 @@ void main() {
     await validatorTarget.build(environment);
 
     // We check the inputs to determine if the task was executed.
-    expect(validatorTarget.validator.outputs.length, 1);
-    expect(validatorTarget.validator.outputs[0].path, 'project/deferred_components_loading_units.yaml');
+    expect(validatorTarget.validator!.outputs.length, 1);
+    expect(validatorTarget.validator!.outputs[0].path, 'project/deferred_components_loading_units.yaml');
   });
 }

packages/flutter_tools/test/general.shard/build_system/targets/ios_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -39,11 +37,11 @@ const List<String> _kSharedConfig = <String>[
 ];
 
 void main() {
-  Environment environment;
-  FileSystem fileSystem;
-  FakeProcessManager processManager;
-  Artifacts artifacts;
-  BufferLogger logger;
+  late Environment environment;
+  late FileSystem fileSystem;
+  late FakeProcessManager processManager;
+  late Artifacts artifacts;
+  late BufferLogger logger;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -323,13 +321,13 @@ void main() {
   });
 
   group('copies Flutter.framework', () {
-    Directory outputDir;
-    File binary;
-    FakeCommand copyPhysicalFrameworkCommand;
-    FakeCommand lipoCommandNonFatResult;
-    FakeCommand lipoVerifyArm64Command;
-    FakeCommand bitcodeStripCommand;
-    FakeCommand adHocCodesignCommand;
+    late Directory outputDir;
+    late File binary;
+    late FakeCommand copyPhysicalFrameworkCommand;
+    late FakeCommand lipoCommandNonFatResult;
+    late FakeCommand lipoVerifyArm64Command;
+    late FakeCommand bitcodeStripCommand;
+    late FakeCommand adHocCodesignCommand;
 
     setUp(() {
       final FileSystem fileSystem = MemoryFileSystem.test();

packages/flutter_tools/test/general.shard/build_system/targets/linux_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -90,7 +88,8 @@ void main() {
   });
 
   // Only required for the test below that still depends on the context.
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
+
   setUp(() {
     fileSystem = MemoryFileSystem.test();
   });

packages/flutter_tools/test/general.shard/build_system/targets/macos_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -19,16 +17,16 @@ import '../../../src/context.dart';
 import '../../../src/fake_process_manager.dart';
 
 void main() {
-  Environment environment;
-  FileSystem fileSystem;
-  Artifacts artifacts;
-  FakeProcessManager processManager;
-  File binary;
-  BufferLogger logger;
-  FakeCommand copyFrameworkCommand;
-  FakeCommand lipoInfoNonFatCommand;
-  FakeCommand lipoInfoFatCommand;
-  FakeCommand lipoVerifyX86_64Command;
+  late Environment environment;
+  late FileSystem fileSystem;
+  late Artifacts artifacts;
+  late FakeProcessManager processManager;
+  late File binary;
+  late BufferLogger logger;
+  late FakeCommand copyFrameworkCommand;
+  late FakeCommand lipoInfoNonFatCommand;
+  late FakeCommand lipoInfoFatCommand;
+  late FakeCommand lipoVerifyX86_64Command;
 
   setUp(() {
     processManager = FakeProcessManager.empty();

packages/flutter_tools/test/general.shard/build_system/targets/web_test.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:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -30,9 +28,9 @@ const List<String> kDart2jsLinuxArgs = <String>[
 ];
 
 void main() {
-  Testbed testbed;
-  Environment environment;
-  FakeProcessManager processManager;
+  late Testbed testbed;
+  late Environment environment;
+  late FakeProcessManager processManager;
   final Platform linux = FakePlatform(
     environment: <String, String>{},
   );
@@ -40,7 +38,7 @@ void main() {
     operatingSystem: 'windows',
     environment: <String, String>{},
   );
-  DepfileService depfileService;
+  late DepfileService depfileService;
 
   setUp(() {
     testbed = Testbed(setup: () {

packages/flutter_tools/test/general.shard/build_system/targets/windows_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -120,7 +118,7 @@ void main() {
   });
 
   // AssetBundleFactory still uses context injection
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test(style: FileSystemStyle.windows);

packages/flutter_tools/test/general.shard/bundle_builder_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/config.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -71,7 +69,7 @@ void main() {
     final String mainPath = globals.fs.path.join('lib', 'main.dart');
     const String assetDirPath = 'example';
     const String depfilePath = 'example.d';
-    Environment env;
+    Environment? env;
     final BuildSystem buildSystem = TestBuildSystem.all(
       BuildResult(success: true),
       (Target target, Environment environment) {
@@ -104,17 +102,17 @@ void main() {
     );
 
     expect(env, isNotNull);
-    expect(env.defines[kBuildMode], 'debug');
-    expect(env.defines[kTargetPlatform], 'ios');
-    expect(env.defines[kTargetFile], mainPath);
-    expect(env.defines[kTrackWidgetCreation], 'true');
-    expect(env.defines[kExtraFrontEndOptions], 'test1,test2');
-    expect(env.defines[kExtraGenSnapshotOptions], 'test3,test4');
-    expect(env.defines[kFileSystemRoots], 'test5,test6');
-    expect(env.defines[kFileSystemScheme], 'test7');
-    expect(env.defines[kDartDefines], encodeDartDefines(<String>['test8', 'test9']));
-    expect(env.defines[kIconTreeShakerFlag], 'true');
-    expect(env.defines[kDeferredComponents], 'false');
+    expect(env!.defines[kBuildMode], 'debug');
+    expect(env!.defines[kTargetPlatform], 'ios');
+    expect(env!.defines[kTargetFile], mainPath);
+    expect(env!.defines[kTrackWidgetCreation], 'true');
+    expect(env!.defines[kExtraFrontEndOptions], 'test1,test2');
+    expect(env!.defines[kExtraGenSnapshotOptions], 'test3,test4');
+    expect(env!.defines[kFileSystemRoots], 'test5,test6');
+    expect(env!.defines[kFileSystemScheme], 'test7');
+    expect(env!.defines[kDartDefines], encodeDartDefines(<String>['test8', 'test9']));
+    expect(env!.defines[kIconTreeShakerFlag], 'true');
+    expect(env!.defines[kDeferredComponents], 'false');
   }, overrides: <Type, Generator>{
     FileSystem: () => MemoryFileSystem.test(),
     ProcessManager: () => FakeProcessManager.any(),

packages/flutter_tools/test/general.shard/cache_test.dart

@@ -2,8 +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:collection/collection.dart' show IterableExtension;
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
@@ -17,7 +16,6 @@ import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/dart/pub.dart';
 import 'package:flutter_tools/src/flutter_cache.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
-import 'package:meta/meta.dart';
 import 'package:test/fake.dart';
 
 import '../src/common.dart';
@@ -41,7 +39,7 @@ const FakeCommand unameCommandForArm64 = FakeCommand(
 );
 
 void main() {
-  FakeProcessManager fakeProcessManager;
+  late FakeProcessManager fakeProcessManager;
 
   setUp(() {
     fakeProcessManager = FakeProcessManager.empty();
@@ -79,7 +77,7 @@ void main() {
     });
 
     testWithoutContext('should not throw when lock is acquired', () async {
-      final String oldRoot = Cache.flutterRoot;
+      final String? oldRoot = Cache.flutterRoot;
       Cache.flutterRoot = '';
       try {
         final FileSystem fileSystem = MemoryFileSystem.test();
@@ -365,7 +363,7 @@ void main() {
     final Directory dir = fileSystem.systemTempDirectory
         .listSync(recursive: true)
         .whereType<Directory>()
-        .singleWhere((Directory directory) => directory.basename == 'bin_dir', orElse: () => null);
+        .singleWhereOrNull((Directory directory) => directory.basename == 'bin_dir')!;
 
     expect(dir, isNotNull);
     expect(dir.path, artifactDir.childDirectory('bin_dir').path);
@@ -458,6 +456,7 @@ void main() {
   testWithoutContext('FlutterRunnerDebugSymbols downloads Flutter runner debug symbols', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
     final Cache cache = FakeSecondaryCache()
+      ..artifactDirectory = fileSystem.currentDirectory
       ..version = '123456';
 
     final FakeVersionedPackageResolver packageResolver = FakeVersionedPackageResolver();
@@ -974,9 +973,9 @@ void main() {
   });
 
   group('AndroidMavenArtifacts', () {
-    MemoryFileSystem memoryFileSystem;
-    Cache cache;
-    FakeAndroidSdk fakeAndroidSdk;
+    MemoryFileSystem? memoryFileSystem;
+    Cache? cache;
+    FakeAndroidSdk? fakeAndroidSdk;
 
     setUp(() {
       memoryFileSystem = MemoryFileSystem.test();
@@ -988,25 +987,25 @@ void main() {
     });
 
     testWithoutContext('AndroidMavenArtifacts has a specified development artifact', () async {
-      final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache, platform: FakePlatform());
+      final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache!, platform: FakePlatform());
       expect(mavenArtifacts.developmentArtifact, DevelopmentArtifact.androidMaven);
     });
 
     testUsingContext('AndroidMavenArtifacts can invoke Gradle resolve dependencies if Android SDK is present', () async {
-      final String oldRoot = Cache.flutterRoot;
+      final String? oldRoot = Cache.flutterRoot;
       Cache.flutterRoot = '';
       try {
-        final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache, platform: FakePlatform());
-        expect(await mavenArtifacts.isUpToDate(memoryFileSystem), isFalse);
+        final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache!, platform: FakePlatform());
+        expect(await mavenArtifacts.isUpToDate(memoryFileSystem!), isFalse);
 
-        final Directory gradleWrapperDir = cache.getArtifactDirectory('gradle_wrapper')..createSync(recursive: true);
+        final Directory gradleWrapperDir = cache!.getArtifactDirectory('gradle_wrapper')..createSync(recursive: true);
         gradleWrapperDir.childFile('gradlew').writeAsStringSync('irrelevant');
         gradleWrapperDir.childFile('gradlew.bat').writeAsStringSync('irrelevant');
 
-        await mavenArtifacts.update(FakeArtifactUpdater(), BufferLogger.test(), memoryFileSystem, FakeOperatingSystemUtils());
+        await mavenArtifacts.update(FakeArtifactUpdater(), BufferLogger.test(), memoryFileSystem!, FakeOperatingSystemUtils());
 
-        expect(await mavenArtifacts.isUpToDate(memoryFileSystem), isFalse);
-        expect(fakeAndroidSdk.reinitialized, true);
+        expect(await mavenArtifacts.isUpToDate(memoryFileSystem!), isFalse);
+        expect(fakeAndroidSdk!.reinitialized, true);
       } finally {
         Cache.flutterRoot = oldRoot;
       }
@@ -1028,12 +1027,12 @@ void main() {
     });
 
     testUsingContext('AndroidMavenArtifacts is a no-op if the Android SDK is absent', () async {
-      final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache, platform: FakePlatform());
-      expect(await mavenArtifacts.isUpToDate(memoryFileSystem), isFalse);
+      final AndroidMavenArtifacts mavenArtifacts = AndroidMavenArtifacts(cache!, platform: FakePlatform());
+      expect(await mavenArtifacts.isUpToDate(memoryFileSystem!), isFalse);
 
-      await mavenArtifacts.update(FakeArtifactUpdater(), BufferLogger.test(), memoryFileSystem, FakeOperatingSystemUtils());
+      await mavenArtifacts.update(FakeArtifactUpdater(), BufferLogger.test(), memoryFileSystem!, FakeOperatingSystemUtils());
 
-      expect(await mavenArtifacts.isUpToDate(memoryFileSystem), isFalse);
+      expect(await mavenArtifacts.isUpToDate(memoryFileSystem!), isFalse);
     }, overrides: <Type, Generator>{
       Cache: () => cache,
       FileSystem: () => memoryFileSystem,
@@ -1046,8 +1045,8 @@ void main() {
 class FakeCachedArtifact extends EngineCachedArtifact {
   FakeCachedArtifact({
     String stampName = 'STAMP',
-    @required Cache cache,
-    DevelopmentArtifact requiredArtifacts,
+    required Cache cache,
+    required DevelopmentArtifact requiredArtifacts,
     this.binaryDirs = const <List<String>>[],
     this.licenseDirs = const <String>[],
     this.packageDirs = const <String>[],
@@ -1081,7 +1080,7 @@ class FakeSimpleArtifact extends CachedArtifact {
 class FakeSecondaryCachedArtifact extends Fake implements CachedArtifact {
   bool upToDate = false;
   bool didUpdate = false;
-  Exception updateException;
+  Exception? updateException;
 
   @override
   Future<bool> isUpToDate(FileSystem fileSystem) async => upToDate;
@@ -1089,7 +1088,7 @@ class FakeSecondaryCachedArtifact extends Fake implements CachedArtifact {
   @override
   Future<void> update(ArtifactUpdater artifactUpdater, Logger logger, FileSystem fileSystem, OperatingSystemUtils operatingSystemUtils, {bool offline = false}) async {
     if (updateException != null) {
-      throw updateException;
+      throw updateException!;
     }
     didUpdate = true;
   }
@@ -1107,10 +1106,10 @@ class FakeIosUsbArtifacts extends Fake implements IosUsbArtifacts {
 }
 
 class FakeSecondaryCache extends Fake implements Cache {
-  Directory downloadDir;
-  Directory artifactDirectory;
-  String version;
-  void Function(String artifactName, String version) onSetStamp;
+  Directory? downloadDir;
+  late Directory artifactDirectory;
+  String? version;
+  late void Function(String artifactName, String version) onSetStamp;
 
   @override
   String get storageBaseUrl => 'https://storage.googleapis.com';
@@ -1132,7 +1131,7 @@ class FakeSecondaryCache extends Fake implements Cache {
   }
 
   @override
-  String getVersionFor(String artifactName) => version;
+  String? getVersionFor(String artifactName) => version;
 
   @override
   void setStampFor(String artifactName, String version) {
@@ -1155,13 +1154,13 @@ class FakePub extends Fake implements Pub {
 
   @override
   Future<void> get({
-    PubContext context,
-    String directory,
+    PubContext? context,
+    String? directory,
     bool skipIfAbsent = false,
     bool upgrade = false,
     bool offline = false,
     bool generateSyntheticPackage = false,
-    String flutterRootOverride,
+    String? flutterRootOverride,
     bool checkUpToDate = false,
     bool shouldSkipThirdPartyGenerator = true,
     bool printProgress = true,
@@ -1172,19 +1171,15 @@ class FakePub extends Fake implements Pub {
 
 class FakeCache extends Cache {
   FakeCache({
-    @required Logger logger,
-    @required FileSystem fileSystem,
-    @required Platform platform,
-    @required OperatingSystemUtils osUtils,
+    required super.logger,
+    required super.fileSystem,
+    required super.platform,
+    required super.osUtils,
   }) : super(
-    logger: logger,
-    fileSystem: fileSystem,
-    platform: platform,
-    osUtils: osUtils,
     artifacts: <ArtifactSet>[],
   );
 
-  File stampFile;
+  late File stampFile;
 
   @override
   File getStampFileFor(String artifactName) {
@@ -1202,8 +1197,8 @@ class FakeAndroidSdk extends Fake implements AndroidSdk {
 }
 
 class FakeArtifactUpdater extends Fake implements ArtifactUpdater {
-  void Function(String, Uri, Directory) onDownloadZipArchive;
-  void Function(String, Uri, Directory) onDownloadZipTarball;
+  void Function(String, Uri, Directory)? onDownloadZipArchive;
+  void Function(String, Uri, Directory)? onDownloadZipTarball;
 
   @override
   Future<void> downloadZippedTarball(String message, Uri url, Directory location) async {

packages/flutter_tools/test/general.shard/channel_test.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
-
 // TODO(gspencergoog): Remove this tag once this test's state leaks/test
 // dependencies have been fixed.
 // https://github.com/flutter/flutter/issues/85160
@@ -24,7 +22,7 @@ import '../src/test_flutter_command_runner.dart';
 
 void main() {
   group('channel', () {
-    FakeProcessManager fakeProcessManager;
+    late FakeProcessManager fakeProcessManager;
 
     setUp(() {
       fakeProcessManager = FakeProcessManager.empty();
@@ -159,7 +157,7 @@ void main() {
       final Iterable<String> rows = testLogger.statusText
         .split('\n')
         .map((String line) => line.trim())
-        .where((String line) => line?.isNotEmpty == true)
+        .where((String line) => line.isNotEmpty == true)
         .skip(1); // remove `Flutter channels:` line
 
       expect(rows, <String>['beta', 'stable', 'Currently not on an official channel.']);
@@ -190,7 +188,7 @@ void main() {
       final Iterable<String> rows = testLogger.statusText
         .split('\n')
         .map((String line) => line.trim())
-        .where((String line) => line?.isNotEmpty == true)
+        .where((String line) => line.isNotEmpty == true)
         .skip(1); // remove `Flutter channels:` line
 
       expect(rows, <String>['beta', 'stable', 'Currently not on an official channel.']);

packages/flutter_tools/test/general.shard/cmake_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -17,11 +15,11 @@ const String _kTestFlutterRoot = '/flutter';
 const String _kTestWindowsFlutterRoot = r'C:\flutter';
 
 void main() {
-  FileSystem fileSystem;
-
-  ProcessManager processManager;
+  late FileSystem fileSystem;
+  late ProcessManager processManager;
 
   setUp(() {
+    processManager = FakeProcessManager.any();
     fileSystem = MemoryFileSystem.test();
   });
 
@@ -33,7 +31,7 @@ void main() {
       ..createSync(recursive: true)
       ..writeAsStringSync('set(BINARY_NAME "hello")');
 
-    final String name = getCmakeExecutableName(cmakeProject);
+    final String? name = getCmakeExecutableName(cmakeProject);
 
     expect(name, 'hello');
   }, overrides: <Type, Generator>{
@@ -45,7 +43,7 @@ void main() {
     final FlutterProject project = FlutterProject.fromDirectoryTest(fileSystem.currentDirectory);
     final CmakeBasedProject cmakeProject = _FakeProject.fromFlutter(project);
 
-    final String name = getCmakeExecutableName(cmakeProject);
+    final String? name = getCmakeExecutableName(cmakeProject);
 
     expect(name, isNull);
   }, overrides: <Type, Generator>{

packages/flutter_tools/test/general.shard/cold_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -15,7 +13,6 @@ import 'package:flutter_tools/src/resident_runner.dart';
 import 'package:flutter_tools/src/run_cold.dart';
 import 'package:flutter_tools/src/tracing.dart';
 import 'package:flutter_tools/src/vmservice.dart';
-import 'package:meta/meta.dart';
 import 'package:test/fake.dart';
 import 'package:vm_service/vm_service.dart';
 
@@ -68,8 +65,9 @@ void main() {
   });
 
   group('cold run', () {
-    MemoryFileSystem memoryFileSystem;
-    FakePlatform fakePlatform;
+    late MemoryFileSystem memoryFileSystem;
+    late FakePlatform fakePlatform;
+
     setUp(() {
       memoryFileSystem = MemoryFileSystem();
       fakePlatform = FakePlatform(environment: <String, String>{});
@@ -159,7 +157,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   int runColdCode = 0;
 
   @override
-  Future<int> runCold({ColdRunner coldRunner, String route}) async {
+  Future<int> runCold({ColdRunner? coldRunner, String? route}) async {
     return runColdCode;
   }
 
@@ -175,10 +173,10 @@ class FakeDevice extends Fake implements Device {
   bool isSupported() => true;
 
   @override
-  bool supportsHotReload;
+  bool supportsHotReload = false;
 
   @override
-  bool supportsHotRestart;
+  bool supportsHotRestart = false;
 
   @override
   Future<String> get sdkNameAndVersion async => 'Android 10';
@@ -199,9 +197,9 @@ class FakeDevice extends Fake implements Device {
 
 class TestFlutterDevice extends FlutterDevice {
   TestFlutterDevice({
-    @required Device device,
-    @required this.exception,
-    @required ResidentCompiler generator,
+    required Device device,
+    required this.exception,
+    required ResidentCompiler generator,
   })  : assert(exception != null),
         super(device, buildInfo: BuildInfo.debug, generator: generator);
 
@@ -210,17 +208,17 @@ class TestFlutterDevice extends FlutterDevice {
 
   @override
   Future<void> connect({
-    ReloadSources reloadSources,
-    Restart restart,
-    CompileExpression compileExpression,
-    GetSkSLMethod getSkSLMethod,
-    PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
+    ReloadSources? reloadSources,
+    Restart? restart,
+    CompileExpression? compileExpression,
+    GetSkSLMethod? getSkSLMethod,
+    PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
     bool enableDds = true,
     bool cacheStartupProfile = false,
     bool disableServiceAuthCodes = false,
-    int hostVmServicePort,
-    int ddsPort,
-    bool ipv6 = false,
+    int? hostVmServicePort,
+    int? ddsPort,
+    bool? ipv6 = false,
     bool allowExistingDdsInstance = false,
   }) async {
     throw exception;
@@ -239,10 +237,10 @@ class FakeFlutterVmService extends Fake implements FlutterVmService {
   }
 
   @override
-  Future<bool> flutterAlreadyPaintedFirstUsefulFrame({String isolateId}) async => true;
+  Future<bool> flutterAlreadyPaintedFirstUsefulFrame({String? isolateId}) async => true;
 
   @override
-  Future<Response> getTimeline() async {
+  Future<Response?> getTimeline() async {
     return Response.parse(<String, dynamic>{
       'traceEvents': <dynamic>[
         <String, dynamic>{

packages/flutter_tools/test/general.shard/coverage_collector_test.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:flutter_tools/src/test/coverage_collector.dart';
 import 'package:vm_service/vm_service.dart';
 
@@ -20,11 +18,11 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'getVM',
-          jsonResponse: (VM.parse(<String, Object>{})
+          jsonResponse: (VM.parse(<String, Object>{})!
             ..isolates = <IsolateRef>[
               IsolateRef.parse(<String, Object>{
                 'id': '1',
-              }),
+              })!,
             ]
           ).toJson(),
         ),
@@ -40,10 +38,10 @@ void main() {
       ],
     );
 
-    final Map<String, Object> result = await collect(
+    final Map<String, Object?> result = await collect(
       null,
       <String>{'foo'},
-      connector: (Uri uri) async {
+      connector: (Uri? uri) async {
         return fakeVmServiceHost.vmService;
       },
     );
@@ -61,11 +59,11 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'getVM',
-          jsonResponse: (VM.parse(<String, Object>{})
+          jsonResponse: (VM.parse(<String, Object>{})!
             ..isolates = <IsolateRef>[
               IsolateRef.parse(<String, Object>{
                 'id': '1',
-              }),
+              })!,
             ]
           ).toJson(),
         ),
@@ -112,10 +110,10 @@ void main() {
       ],
     );
 
-    final Map<String, Object> result = await collect(
+    final Map<String, Object?> result = await collect(
       null,
       <String>{'foo'},
-      connector: (Uri uri) async {
+      connector: (Uri? uri) async {
         return fakeVmServiceHost.vmService;
       },
     );
@@ -148,11 +146,11 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'getVM',
-          jsonResponse: (VM.parse(<String, Object>{})
+          jsonResponse: (VM.parse(<String, Object>{})!
             ..isolates = <IsolateRef>[
               IsolateRef.parse(<String, Object>{
                 'id': '1',
-              }),
+              })!,
             ]
           ).toJson(),
         ),
@@ -229,10 +227,10 @@ void main() {
       ],
     );
 
-    final Map<String, Object> result = await collect(
+    final Map<String, Object?> result = await collect(
       null,
       null,
-      connector: (Uri uri) async {
+      connector: (Uri? uri) async {
         return fakeVmServiceHost.vmService;
       },
     );
@@ -276,11 +274,11 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'getVM',
-          jsonResponse: (VM.parse(<String, Object>{})
+          jsonResponse: (VM.parse(<String, Object>{})!
             ..isolates = <IsolateRef>[
               IsolateRef.parse(<String, Object>{
                 'id': '1',
-              }),
+              })!,
             ]
           ).toJson(),
         ),
@@ -317,10 +315,10 @@ void main() {
       ],
     );
 
-    final Map<String, Object> result = await collect(
+    final Map<String, Object?> result = await collect(
       null,
       <String>{'foo'},
-      connector: (Uri uri) async {
+      connector: (Uri? uri) async {
         return fakeVmServiceHost.vmService;
       },
     );
@@ -353,11 +351,11 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'getVM',
-          jsonResponse: (VM.parse(<String, Object>{})
+          jsonResponse: (VM.parse(<String, Object>{})!
             ..isolates = <IsolateRef>[
               IsolateRef.parse(<String, Object>{
                 'id': '1',
-              }),
+              })!,
             ]
           ).toJson(),
         ),
@@ -393,10 +391,10 @@ void main() {
       ],
     );
 
-    final Map<String, Object> result = await collect(
+    final Map<String, Object?> result = await collect(
       null,
       null,
-      connector: (Uri uri) async {
+      connector: (Uri? uri) async {
         return fakeVmServiceHost.vmService;
       },
     );

packages/flutter_tools/test/general.shard/create_config_test.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:flutter_tools/src/commands/create_base.dart';
 
 import '../src/common.dart';

packages/flutter_tools/test/general.shard/custom_devices/custom_device_test.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:file/file.dart';
@@ -116,9 +114,7 @@ void main() {
   final CustomDeviceConfig disabledTestConfig = testConfig.copyWith(enabled: false);
   final CustomDeviceConfig testConfigNonForwarding = testConfig.copyWith(
     explicitForwardPortCommand: true,
-    forwardPortCommand: null,
     explicitForwardPortSuccessRegex: true,
-    forwardPortSuccessRegex: null,
   );
 
   testUsingContext('CustomDevice defaults',
@@ -339,12 +335,12 @@ void main() {
 
     final CustomDevicePortForwarder forwarder = CustomDevicePortForwarder(
       deviceName: 'testdevicename',
-      forwardPortCommand: testConfig.forwardPortCommand,
-      forwardPortSuccessRegex: testConfig.forwardPortSuccessRegex,
+      forwardPortCommand: testConfig.forwardPortCommand!,
+      forwardPortSuccessRegex: testConfig.forwardPortSuccessRegex!,
       logger: BufferLogger.test(),
       processManager: FakeProcessManager.list(<FakeCommand>[
         FakeCommand(
-          command: testConfig.forwardPortCommand,
+          command: testConfig.forwardPortCommand!,
           stdout: testConfigForwardPortSuccessOutput,
           completer: forwardPortCommandCompleter,
         ),
@@ -373,7 +369,7 @@ void main() {
         stdout: 'The Dart VM service is listening on http://127.0.0.1:12345/abcd/\n',
       ),
       FakeCommand(
-        command: testConfig.forwardPortCommand,
+        command: testConfig.forwardPortCommand!,
         completer: forwardPortCompleter,
         stdout: testConfigForwardPortSuccessOutput,
       ),
@@ -450,7 +446,7 @@ void main() {
             command: testConfig.pingCommand,
             stdout: testConfigPingSuccessOutput
           ),
-          FakeCommand(command: testConfig.postBuildCommand),
+          FakeCommand(command: testConfig.postBuildCommand!),
           FakeCommand(command: testConfig.uninstallCommand),
           FakeCommand(command: testConfig.installCommand),
           FakeCommand(
@@ -459,7 +455,7 @@ void main() {
             stdout: 'The Dart VM service is listening on http://127.0.0.1:12345/abcd/\n',
           ),
           FakeCommand(
-            command: testConfig.forwardPortCommand,
+            command: testConfig.forwardPortCommand!,
             completer: forwardPortCompleter,
             stdout: testConfigForwardPortSuccessOutput,
           ),
@@ -524,7 +520,7 @@ void main() {
 
     final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
       FakeCommand(
-        command: testConfig.screenshotCommand,
+        command: testConfig.screenshotCommand!,
         onRun: () => screenshotCommandWasExecuted = true,
       ),
     ]);
@@ -550,7 +546,7 @@ void main() {
 
     final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
       FakeCommand(
-        command: testConfig.screenshotCommand,
+        command: testConfig.screenshotCommand!,
         onRun: () => screenshotCommandWasExecuted = true,
       ),
     ]);
@@ -560,8 +556,7 @@ void main() {
 
     final CustomDevice device = CustomDevice(
         config: testConfig.copyWith(
-          explicitScreenshotCommand: true,
-          screenshotCommand: null
+          explicitScreenshotCommand: true
         ),
         logger: BufferLogger.test(),
         processManager: processManager
@@ -640,14 +635,14 @@ class MyFakeStreamSubscription<T> extends Fake implements StreamSubscription<T>
 class FakeBundleBuilder extends Fake implements BundleBuilder {
   @override
   Future<void> build({
-    TargetPlatform platform,
-    BuildInfo buildInfo,
-    FlutterProject project,
-    String mainPath,
+    TargetPlatform? platform,
+    BuildInfo? buildInfo,
+    FlutterProject? project,
+    String? mainPath,
     String manifestPath = defaultManifestPath,
-    String applicationKernelFilePath,
-    String depfilePath,
-    String assetDirPath,
-    @visibleForTesting BuildSystem buildSystem
+    String? applicationKernelFilePath,
+    String? depfilePath,
+    String? assetDirPath,
+    @visibleForTesting BuildSystem? buildSystem
   }) async {}
 }

packages/flutter_tools/test/general.shard/dart_plugin_test.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:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/dart/package_map.dart';
@@ -22,9 +20,9 @@ import '../src/context.dart';
 
 void main() {
   group('Dart plugin registrant', () {
-    FileSystem fs;
-    FakeFlutterProject flutterProject;
-    FakeFlutterManifest flutterManifest;
+    late FileSystem fs;
+    late FakeFlutterProject flutterProject;
+    late FakeFlutterManifest flutterManifest;
 
     setUp(() async {
       fs = MemoryFileSystem.test();
@@ -1023,35 +1021,35 @@ class FakeFlutterProject extends Fake implements FlutterProject {
   bool isModule = false;
 
   @override
-  FlutterManifest manifest;
+  late FlutterManifest manifest;
 
   @override
-  Directory directory;
+  late Directory directory;
 
   @override
-  File flutterPluginsFile;
+  late File flutterPluginsFile;
 
   @override
-  File flutterPluginsDependenciesFile;
+  late File flutterPluginsDependenciesFile;
 
   @override
-  File dartPluginRegistrant;
+  late File dartPluginRegistrant;
 
   @override
-  IosProject ios;
+  late IosProject ios;
 
   @override
-  AndroidProject android;
+  late AndroidProject android;
 
   @override
-  WebProject web;
+  late WebProject web;
 
   @override
-  MacOSProject macos;
+  late MacOSProject macos;
 
   @override
-  LinuxProject linux;
+  late LinuxProject linux;
 
   @override
-  WindowsProject windows;
+  late WindowsProject windows;
 }

packages/flutter_tools/test/general.shard/devfs_test.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 'dart:convert';
 import 'dart:io' as io show ProcessSignal, Process;
@@ -101,7 +99,6 @@ void main() {
     final DateTime fiveSecondsAgo = file.statSync().modified.subtract(const Duration(seconds: 5));
     expect(content.isModifiedAfter(fiveSecondsAgo), isTrue);
     expect(content.isModifiedAfter(fiveSecondsAgo), isTrue);
-    expect(content.isModifiedAfter(null), isTrue);
 
     file.writeAsBytesSync(<int>[2, 3, 4], flush: true);
 
@@ -186,7 +183,7 @@ void main() {
       requests: <VmServiceExpectation>[createDevFSRequest],
       httpAddress: Uri.parse('http://localhost'),
     );
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       fileSystem.file('lib/foo.dill')
         ..createSync(recursive: true)
         ..writeAsBytesSync(<int>[1, 2, 3, 4, 5]);
@@ -250,10 +247,10 @@ void main() {
     );
 
     await devFS.create();
-    final DateTime previousCompile = devFS.lastCompiled;
+    final DateTime? previousCompile = devFS.lastCompiled;
 
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       return const CompilerOutput('lib/foo.dill', 2, <Uri>[]);
     };
 
@@ -289,10 +286,10 @@ void main() {
     );
 
     await devFS.create();
-    final DateTime previousCompile = devFS.lastCompiled;
+    final DateTime? previousCompile = devFS.lastCompiled;
 
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       fileSystem.file('lib/foo.txt.dill').createSync(recursive: true);
       return const CompilerOutput('lib/foo.txt.dill', 0, <Uri>[]);
     };
@@ -330,10 +327,10 @@ void main() {
     );
 
     await devFS.create();
-    final DateTime previousCompile = devFS.lastCompiled;
+    final DateTime? previousCompile = devFS.lastCompiled;
 
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       fileSystem.file('lib/foo.txt.dill').createSync(recursive: true);
       return const CompilerOutput('lib/foo.txt.dill', 0, <Uri>[]);
     };
@@ -380,7 +377,7 @@ void main() {
     await devFS.create();
 
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       fileSystem.file('example').createSync();
       return const CompilerOutput('lib/foo.txt.dill', 0, <Uri>[]);
     };
@@ -456,7 +453,7 @@ void main() {
     await devFS.create();
 
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    residentCompiler.onRecompile = (Uri mainUri, List<Uri> invalidatedFiles) async {
+    residentCompiler.onRecompile = (Uri mainUri, List<Uri>? invalidatedFiles) async {
       fileSystem.file('lib/foo.txt.dill').createSync(recursive: true);
       return const CompilerOutput('lib/foo.txt.dill', 0, <Uri>[]);
     };
@@ -506,7 +503,7 @@ void main() {
           await Future<dynamic>.delayed(const Duration(milliseconds: 5));
         }
 
-        String boundaryKey;
+        String? boundaryKey;
         while(processed < frontendServerStdIn.writes.length) {
           final List<int> data = frontendServerStdIn.writes[processed];
           final String stringData = utf8.decode(data);
@@ -581,10 +578,10 @@ void main() {
 }
 
 class FakeResidentCompiler extends Fake implements ResidentCompiler {
-  Future<CompilerOutput> Function(Uri mainUri, List<Uri> invalidatedFiles) onRecompile;
+  Future<CompilerOutput> Function(Uri mainUri, List<Uri>? invalidatedFiles)? onRecompile;
 
   @override
-  Future<CompilerOutput> recompile(Uri mainUri, List<Uri> invalidatedFiles, {String outputPath, PackageConfig packageConfig, String projectRootPath, FileSystem fs, bool suppressErrors = false, bool checkDartPluginRegistry = false}) {
+  Future<CompilerOutput> recompile(Uri mainUri, List<Uri>? invalidatedFiles, {String? outputPath, PackageConfig? packageConfig, String? projectRootPath, FileSystem? fs, bool suppressErrors = false, bool checkDartPluginRegistry = false}) {
     return onRecompile?.call(mainUri, invalidatedFiles)
       ?? Future<CompilerOutput>.value(const CompilerOutput('', 1, <Uri>[]));
   }
@@ -605,12 +602,12 @@ class LoggingLogger extends BufferLogger {
   List<String> messages = <String>[];
 
   @override
-  void printError(String message, {StackTrace stackTrace, bool emphasis, TerminalColor color, int indent, int hangingIndent, bool wrap}) {
+  void printError(String message, {StackTrace? stackTrace, bool? emphasis, TerminalColor? color, int? indent, int? hangingIndent, bool? wrap}) {
     messages.add(message);
   }
 
   @override
-  void printStatus(String message, {bool emphasis, TerminalColor color, bool newline, int indent, int hangingIndent, bool wrap}) {
+  void printStatus(String message, {bool? emphasis, TerminalColor? color, bool? newline, int? indent, int? hangingIndent, bool? wrap}) {
     messages.add(message);
   }
 
@@ -625,7 +622,7 @@ class FakeBundle extends AssetBundle {
   List<File> get additionalDependencies => <File>[];
 
   @override
-  Future<int> build({String manifestPath = defaultManifestPath, String assetDirPath, String packagesPath, bool deferredComponentsEnabled = false, TargetPlatform targetPlatform}) async {
+  Future<int> build({String manifestPath = defaultManifestPath, String? assetDirPath, String? packagesPath, bool deferredComponentsEnabled = false, TargetPlatform? targetPlatform}) async {
     return 0;
   }
 
@@ -657,7 +654,7 @@ class AnsweringFakeProcessManager implements ProcessManager {
   final IOSink stdin;
 
   @override
-  bool canRun(dynamic executable, {String workingDirectory}) {
+  bool canRun(dynamic executable, {String? workingDirectory}) {
     return true;
   }
 
@@ -667,17 +664,17 @@ class AnsweringFakeProcessManager implements ProcessManager {
   }
 
   @override
-  Future<ProcessResult> run(List<Object> command, {String workingDirectory, Map<String, String> environment, bool includeParentEnvironment = true, bool runInShell = false, Encoding stdoutEncoding = systemEncoding, Encoding stderrEncoding = systemEncoding}) async {
+  Future<ProcessResult> run(List<Object> command, {String? workingDirectory, Map<String, String>? environment, bool includeParentEnvironment = true, bool runInShell = false, Encoding? stdoutEncoding = systemEncoding, Encoding? stderrEncoding = systemEncoding}) async {
     throw UnimplementedError();
   }
 
   @override
-  ProcessResult runSync(List<Object> command, {String workingDirectory, Map<String, String> environment, bool includeParentEnvironment = true, bool runInShell = false, Encoding stdoutEncoding = systemEncoding, Encoding stderrEncoding = systemEncoding}) {
+  ProcessResult runSync(List<Object> command, {String? workingDirectory, Map<String, String>? environment, bool includeParentEnvironment = true, bool runInShell = false, Encoding? stdoutEncoding = systemEncoding, Encoding? stderrEncoding = systemEncoding}) {
     throw UnimplementedError();
   }
 
   @override
-  Future<Process> start(List<Object> command, {String workingDirectory, Map<String, String> environment, bool includeParentEnvironment = true, bool runInShell = false, ProcessStartMode mode = ProcessStartMode.normal}) async {
+  Future<Process> start(List<Object> command, {String? workingDirectory, Map<String, String>? environment, bool includeParentEnvironment = true, bool runInShell = false, ProcessStartMode mode = ProcessStartMode.normal}) async {
     return AnsweringFakeProcess(stdout, stderr, stdin);
   }
 }

packages/flutter_tools/test/general.shard/devtools_launcher_test.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:flutter_tools/src/base/io.dart';
@@ -17,7 +15,7 @@ import '../src/fake_process_manager.dart';
 import '../src/fakes.dart';
 
 void main() {
-  BufferLogger logger;
+  late BufferLogger logger;
 
   Cache.flutterRoot = '';
 
@@ -44,9 +42,9 @@ void main() {
       ]),
     );
 
-    final DevToolsServerAddress address = await launcher.serve();
-    expect(address.host, '127.0.0.1');
-    expect(address.port, 9100);
+    final DevToolsServerAddress? address = await launcher.serve();
+    expect(address?.host, '127.0.0.1');
+    expect(address?.port, 9100);
   });
 
   testWithoutContext('DevtoolsLauncher does not launch a new DevTools instance if one is already active', () async {
@@ -68,14 +66,14 @@ void main() {
       ]),
     );
 
-    DevToolsServerAddress address = await launcher.serve();
-    expect(address.host, '127.0.0.1');
-    expect(address.port, 9100);
+    DevToolsServerAddress? address = await launcher.serve();
+    expect(address?.host, '127.0.0.1');
+    expect(address?.port, 9100);
 
     // Call `serve` again and verify that the already running server is returned.
     address = await launcher.serve();
-    expect(address.host, '127.0.0.1');
-    expect(address.port, 9100);
+    expect(address?.host, '127.0.0.1');
+    expect(address?.port, 9100);
   });
 
   testWithoutContext('DevtoolsLauncher can launch devtools with a memory profile', () async {

packages/flutter_tools/test/general.shard/flutter_platform_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -17,12 +15,11 @@ import '../src/common.dart';
 import '../src/context.dart';
 
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
-    fileSystem
-      .file('.dart_tool/package_config.json')
+    fileSystem.file('.dart_tool/package_config.json')
       ..createSync(recursive: true)
       ..writeAsStringSync('{"configVersion":2,"packages":[]}');
   });
@@ -80,7 +77,7 @@ void main() {
         ),
       ), throwsAssertionError);
 
-      FlutterPlatform capturedPlatform;
+      FlutterPlatform? capturedPlatform;
       final Map<String, String> expectedPrecompiledDillFiles = <String, String>{'Key': 'Value'};
       final FlutterPlatform flutterPlatform = installHook(
         shellPath: 'abc',

packages/flutter_tools/test/general.shard/flutter_tester_device_test.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';
@@ -16,7 +14,6 @@ import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/device.dart';
 import 'package:flutter_tools/src/test/flutter_tester_device.dart';
 import 'package:flutter_tools/src/test/font_config_manager.dart';
-import 'package:meta/meta.dart';
 import 'package:stream_channel/stream_channel.dart';
 import 'package:test/fake.dart';
 
@@ -25,10 +22,10 @@ import '../src/context.dart';
 import '../src/fake_process_manager.dart';
 
 void main() {
-  FakePlatform platform;
-  FileSystem fileSystem;
-  FakeProcessManager processManager;
-  FlutterTesterTestDevice device;
+  late FakePlatform platform;
+  late FileSystem fileSystem;
+  late FakeProcessManager processManager;
+  late FlutterTesterTestDevice device;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -265,17 +262,14 @@ void main() {
 /// Uses a mock HttpServer. We don't want to bind random ports in our CI hosts.
 class TestFlutterTesterDevice extends FlutterTesterTestDevice {
   TestFlutterTesterDevice({
-    @required Platform platform,
-    @required FileSystem fileSystem,
-    @required ProcessManager processManager,
-    @required bool enableObservatory,
-    @required List<String> dartEntrypointArgs,
+    required super.platform,
+    required super.fileSystem,
+    required super.processManager,
+    required super.enableObservatory,
+    required List<String> dartEntrypointArgs,
   }) : super(
     id: 999,
     shellPath: '/',
-    platform: platform,
-    fileSystem: fileSystem,
-    processManager: processManager,
     logger: BufferLogger.test(),
     debuggingOptions: DebuggingOptions.enabled(
       const BuildInfo(
@@ -286,7 +280,6 @@ class TestFlutterTesterDevice extends FlutterTesterTestDevice {
       hostVmServicePort: 1234,
       dartEntrypointArgs: dartEntrypointArgs,
     ),
-    enableObservatory: enableObservatory,
     machine: false,
     host: InternetAddress.loopbackIPv6,
     testAssetDirectory: null,
@@ -307,7 +300,7 @@ class TestFlutterTesterDevice extends FlutterTesterTestDevice {
   }
 
   @override
-  Future<HttpServer> bind(InternetAddress host, int port) async => FakeHttpServer();
+  Future<HttpServer> bind(InternetAddress? host, int port) async => FakeHttpServer();
 
   @override
   Future<StreamChannel<String>> get remoteChannel async => StreamChannelController<String>().foreign;

packages/flutter_tools/test/general.shard/fuchsia/fuchsia_pm_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/fuchsia/fuchsia_pm.dart';
@@ -16,13 +14,12 @@ import '../../src/fake_process_manager.dart';
 
 void main() {
   group('FuchsiaPM', () {
-    File pm;
-    FakeProcessManager fakeProcessManager;
-    FakeFuchsiaArtifacts fakeFuchsiaArtifacts;
+    late File pm;
+    late FakeProcessManager fakeProcessManager;
+    late FakeFuchsiaArtifacts fakeFuchsiaArtifacts;
 
     setUp(() {
       pm = MemoryFileSystem.test().file('pm');
-
       fakeFuchsiaArtifacts = FakeFuchsiaArtifacts(pm);
       fakeProcessManager = FakeProcessManager.empty();
     });

packages/flutter_tools/test/general.shard/github_template_test.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:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -16,8 +14,9 @@ import '../src/common.dart';
 import '../src/context.dart';
 
 void main() {
-  BufferLogger logger;
-  FileSystem fs;
+  late BufferLogger logger;
+  late FileSystem fs;
+
   setUp(() {
     logger = BufferLogger.test();
     fs = MemoryFileSystem.test();
@@ -144,8 +143,8 @@ void main() {
     });
 
     group('new issue template URL', () {
-      StackTrace stackTrace;
-      Error error;
+      late StackTrace stackTrace;
+      late Error error;
       const String command = 'flutter test';
       const String doctorText = ' [✓] Flutter (Channel report';
 
@@ -220,7 +219,7 @@ project_type: app
         ''');
 
         final String actualURL = await creator.toolCrashIssueTemplateGitHubURL(command, error, stackTrace, doctorText);
-        final String actualBody = Uri.parse(actualURL).queryParameters['body'];
+        final String? actualBody = Uri.parse(actualURL).queryParameters['body'];
         const String expectedBody = '''
 ## Command
 ```

packages/flutter_tools/test/general.shard/integration_test_device_test.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:file/file.dart';
 import 'package:flutter_tools/src/application_package.dart';
 import 'package:flutter_tools/src/base/io.dart' as io;
@@ -64,8 +62,8 @@ final FakeVmServiceRequest listViewsRequest = FakeVmServiceRequest(
 final Uri observatoryUri = Uri.parse('http://localhost:1234');
 
 void main() {
-  FakeVmServiceHost fakeVmServiceHost;
-  TestDevice testDevice;
+  late FakeVmServiceHost fakeVmServiceHost;
+  late TestDevice testDevice;
 
   setUp(() {
     testDevice = IntegrationTestTestDevice(
@@ -133,14 +131,14 @@ void main() {
   }, overrides: <Type, Generator>{
     ApplicationPackageFactory: () => FakeApplicationPackageFactory(),
     VMServiceConnector: () => (Uri httpUri, {
-      ReloadSources reloadSources,
-      Restart restart,
-      CompileExpression compileExpression,
-      GetSkSLMethod getSkSLMethod,
-      PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-      io.CompressionOptions compression,
-      Device device,
-      Logger logger,
+      ReloadSources? reloadSources,
+      Restart? restart,
+      CompileExpression? compileExpression,
+      GetSkSLMethod? getSkSLMethod,
+      PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+      io.CompressionOptions? compression,
+      Device? device,
+      Logger? logger,
     }) async => fakeVmServiceHost.vmService,
   });
 
@@ -152,14 +150,14 @@ void main() {
   }, overrides: <Type, Generator>{
     ApplicationPackageFactory: () => FakeApplicationPackageFactory(),
     VMServiceConnector: () => (Uri httpUri, {
-      ReloadSources reloadSources,
-      Restart restart,
-      CompileExpression compileExpression,
-      GetSkSLMethod getSkSLMethod,
-      PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-      io.CompressionOptions compression,
-      Device device,
-      Logger logger,
+      ReloadSources? reloadSources,
+      Restart? restart,
+      CompileExpression? compileExpression,
+      GetSkSLMethod? getSkSLMethod,
+      PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+      io.CompressionOptions? compression,
+      Device? device,
+      Logger? logger,
     }) async => fakeVmServiceHost.vmService,
   });
 
@@ -181,13 +179,13 @@ void main() {
     expect(() => testDevice.start('entrypointPath'), throwsA(isA<TestDeviceException>()));
   }, overrides: <Type, Generator>{
     VMServiceConnector: () => (Uri httpUri, {
-      ReloadSources reloadSources,
-      Restart restart,
-      CompileExpression compileExpression,
-      GetSkSLMethod getSkSLMethod,
-      PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-      io.CompressionOptions compression,
-      Device device,
+      ReloadSources? reloadSources,
+      Restart? restart,
+      CompileExpression? compileExpression,
+      GetSkSLMethod? getSkSLMethod,
+      PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+      io.CompressionOptions? compression,
+      Device? device,
     }) async => fakeVmServiceHost.vmService,
   });
 
@@ -209,13 +207,13 @@ void main() {
     expect(() => testDevice.start('entrypointPath'), throwsA(isA<TestDeviceException>()));
   }, overrides: <Type, Generator>{
     VMServiceConnector: () => (Uri httpUri, {
-      ReloadSources reloadSources,
-      Restart restart,
-      CompileExpression compileExpression,
-      GetSkSLMethod getSkSLMethod,
-      PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-      io.CompressionOptions compression,
-      Device device,
+      ReloadSources? reloadSources,
+      Restart? restart,
+      CompileExpression? compileExpression,
+      GetSkSLMethod? getSkSLMethod,
+      PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+      io.CompressionOptions? compression,
+      Device? device,
     }) async => fakeVmServiceHost.vmService,
   });
 
@@ -226,14 +224,14 @@ void main() {
   }, overrides: <Type, Generator>{
     ApplicationPackageFactory: () => FakeApplicationPackageFactory(),
     VMServiceConnector: () => (Uri httpUri, {
-      ReloadSources reloadSources,
-      Restart restart,
-      CompileExpression compileExpression,
-      GetSkSLMethod getSkSLMethod,
-      PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-      io.CompressionOptions compression,
-      Device device,
-      Logger logger,
+      ReloadSources? reloadSources,
+      Restart? restart,
+      CompileExpression? compileExpression,
+      GetSkSLMethod? getSkSLMethod,
+      PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+      io.CompressionOptions? compression,
+      Device? device,
+      Logger? logger,
     }) async => fakeVmServiceHost.vmService,
   });
 }
@@ -242,8 +240,8 @@ class FakeApplicationPackageFactory extends Fake implements ApplicationPackageFa
   @override
   Future<ApplicationPackage> getPackageForPlatform(
     TargetPlatform platform, {
-    BuildInfo buildInfo,
-    File applicationBinary,
+    BuildInfo? buildInfo,
+    File? applicationBinary,
   }) async => FakeApplicationPackage();
 }
 

packages/flutter_tools/test/general.shard/ios/ios_device_project_test.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:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -22,7 +20,7 @@ import '../../src/context.dart';
 
 // FlutterProject still depends on context.
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   // This setup is required to inject the context.
   setUp(() {

packages/flutter_tools/test/general.shard/ios/simulators_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -34,9 +32,9 @@ final Platform macosPlatform = FakePlatform(
 );
 
 void main() {
-  FakePlatform osx;
-  FileSystemUtils fsUtils;
-  MemoryFileSystem fileSystem;
+  late FakePlatform osx;
+  late FileSystemUtils fsUtils;
+  late MemoryFileSystem fileSystem;
 
   setUp(() {
     osx = FakePlatform(
@@ -48,8 +46,8 @@ void main() {
   });
 
   group('_IOSSimulatorDevicePortForwarder', () {
-    FakeSimControl simControl;
-    Xcode xcode;
+    late FakeSimControl simControl;
+    late Xcode xcode;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -100,7 +98,7 @@ void main() {
   });
 
   group('logFilePath', () {
-    FakeSimControl simControl;
+    late FakeSimControl simControl;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -163,7 +161,7 @@ void main() {
   });
 
   group('sdkMajorVersion', () {
-    FakeSimControl simControl;
+    late FakeSimControl simControl;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -205,7 +203,7 @@ void main() {
   });
 
   group('IOSSimulator.isSupported', () {
-    FakeSimControl simControl;
+    late FakeSimControl simControl;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -368,8 +366,8 @@ void main() {
   });
 
   group('device log tool', () {
-    FakeProcessManager fakeProcessManager;
-    FakeSimControl simControl;
+    late FakeProcessManager fakeProcessManager;
+    late FakeSimControl simControl;
 
     setUp(() {
       fakeProcessManager = FakeProcessManager.empty();
@@ -472,10 +470,10 @@ void main() {
   });
 
   group('log reader', () {
-    FakeProcessManager fakeProcessManager;
-    FakeIosProject mockIosProject;
-    FakeSimControl simControl;
-    Xcode xcode;
+    late FakeProcessManager fakeProcessManager;
+    late FakeIosProject mockIosProject;
+    late FakeSimControl simControl;
+    late Xcode xcode;
 
     setUp(() {
       fakeProcessManager = FakeProcessManager.empty();
@@ -616,7 +614,7 @@ Dec 20 17:04:32 md32-11-vm1 Another App[88374]: Ignore this text'''
     });
 
     group('unified logging', () {
-      BufferLogger logger;
+      late BufferLogger logger;
 
       setUp(() {
         logger = BufferLogger.test();
@@ -754,9 +752,9 @@ Dec 20 17:04:32 md32-11-vm1 Another App[88374]: Ignore this text'''
 }
     ''';
 
-    FakeProcessManager fakeProcessManager;
+    late FakeProcessManager fakeProcessManager;
     Xcode xcode;
-    SimControl simControl;
+    late SimControl simControl;
     const String deviceId = 'smart-phone';
     const String appId = 'flutterApp';
 
@@ -895,10 +893,10 @@ Dec 20 17:04:32 md32-11-vm1 Another App[88374]: Ignore this text'''
   });
 
   group('startApp', () {
-    FakePlistParser testPlistParser;
-    FakeSimControl simControl;
-    Xcode xcode;
-    BufferLogger logger;
+    late FakePlistParser testPlistParser;
+    late FakeSimControl simControl;
+    late Xcode xcode;
+    late BufferLogger logger;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -1027,8 +1025,8 @@ Dec 20 17:04:32 md32-11-vm1 Another App[88374]: Ignore this text'''
   });
 
   group('IOSDevice.isSupportedForProject', () {
-    FakeSimControl simControl;
-    Xcode xcode;
+    late FakeSimControl simControl;
+    late Xcode xcode;
 
     setUp(() {
       simControl = FakeSimControl();
@@ -1113,17 +1111,17 @@ flutter:
 
 class FakeIosProject extends Fake implements IosProject {
   @override
-  Future<String> productBundleIdentifier(BuildInfo buildInfo) async => 'com.example.test';
+  Future<String> productBundleIdentifier(BuildInfo? buildInfo) async => 'com.example.test';
 
   @override
-  Future<String> hostAppBundleName(BuildInfo buildInfo) async => 'My Super Awesome App.app';
+  Future<String> hostAppBundleName(BuildInfo? buildInfo) async => 'My Super Awesome App.app';
 }
 
 class FakeSimControl extends Fake implements SimControl {
   final List<LaunchRequest> requests = <LaunchRequest>[];
 
   @override
-  Future<RunResult> launch(String deviceId, String appIdentifier, [ List<String> launchArgs ]) async {
+  Future<RunResult> launch(String deviceId, String appIdentifier, [ List<String>? launchArgs ]) async {
     requests.add(LaunchRequest(deviceId, appIdentifier, launchArgs));
     return RunResult(ProcessResult(0, 0, '', ''), <String>['test']);
   }
@@ -1139,5 +1137,5 @@ class LaunchRequest {
 
   final String deviceId;
   final String appIdentifier;
-  final List<String> launchArgs;
+  final List<String>? launchArgs;
 }

packages/flutter_tools/test/general.shard/ios/xcodeproj_test.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:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -56,11 +54,11 @@ void main() {
     stdout: 'hw.optional.arm64: 1',
   );
 
-  FakeProcessManager fakeProcessManager;
-  XcodeProjectInterpreter xcodeProjectInterpreter;
-  FakePlatform platform;
-  FileSystem fileSystem;
-  BufferLogger logger;
+  late FakeProcessManager fakeProcessManager;
+  late XcodeProjectInterpreter xcodeProjectInterpreter;
+  late FakePlatform platform;
+  late FileSystem fileSystem;
+  late BufferLogger logger;
 
   setUp(() {
     fakeProcessManager = FakeProcessManager.empty();
@@ -660,7 +658,7 @@ Information about project "Runner":
     expect(info.buildConfigurationFor(const BuildInfo(BuildMode.release, 'Paid', treeShakeIcons: false), 'Paid'), null);
   });
  group('environmentVariablesAsXcodeBuildSettings', () {
-    FakePlatform platform;
+    late FakePlatform platform;
 
     setUp(() {
       platform = FakePlatform();
@@ -679,9 +677,9 @@ Information about project "Runner":
   });
 
   group('updateGeneratedXcodeProperties', () {
-    Artifacts localIosArtifacts;
-    FakePlatform macOS;
-    FileSystem fs;
+    late Artifacts localIosArtifacts;
+    late FakePlatform macOS;
+    late FileSystem fs;
 
     setUp(() {
       fs = MemoryFileSystem.test();
@@ -691,8 +689,8 @@ Information about project "Runner":
     });
 
     group('arm simulator', () {
-      FakeProcessManager fakeProcessManager;
-      XcodeProjectInterpreter xcodeProjectInterpreter;
+      late FakeProcessManager fakeProcessManager;
+      late XcodeProjectInterpreter xcodeProjectInterpreter;
 
       setUp(() {
         fakeProcessManager = FakeProcessManager.empty();
@@ -1047,7 +1045,7 @@ Build settings for action build and target plugin2:
       });
     });
 
-    String propertyFor(String key, File file) {
+    String? propertyFor(String key, File file) {
       final List<String> properties = file
           .readAsLinesSync()
           .where((String line) => line.startsWith('$key='))
@@ -1057,10 +1055,10 @@ Build settings for action build and target plugin2:
     }
 
     Future<void> checkBuildVersion({
-      String manifestString,
-      BuildInfo buildInfo,
-      String expectedBuildName,
-      String expectedBuildNumber,
+      required String manifestString,
+      required BuildInfo buildInfo,
+      String? expectedBuildName,
+      String? expectedBuildNumber,
     }) async {
       final File manifestFile = fs.file('path/to/project/pubspec.yaml');
       manifestFile.createSync(recursive: true);

packages/flutter_tools/test/general.shard/macos/application_package_test.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:convert';
 
 import 'package:file/file.dart';
@@ -23,9 +21,9 @@ import '../../src/context.dart';
 
 void main() {
 group('PrebuiltMacOSApp', () {
-    FakeOperatingSystemUtils os;
-    FileSystem fileSystem;
-    BufferLogger logger;
+    late FakeOperatingSystemUtils os;
+    late FileSystem fileSystem;
+    late BufferLogger logger;
 
     final Map<Type, Generator> overrides = <Type, Generator>{
       FileSystem: () => fileSystem,
@@ -42,7 +40,7 @@ group('PrebuiltMacOSApp', () {
     });
 
     testUsingContext('Error on non-existing file', () {
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('not_existing.app')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('not_existing.app')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('File "not_existing.app" does not exist.'));
@@ -50,7 +48,7 @@ group('PrebuiltMacOSApp', () {
 
     testUsingContext('Error on non-app-bundle folder', () {
       fileSystem.directory('regular_folder').createSync();
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('regular_folder')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('regular_folder')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Folder "regular_folder" is not an app bundle.'));
@@ -58,7 +56,7 @@ group('PrebuiltMacOSApp', () {
 
     testUsingContext('Error on no info.plist', () {
       fileSystem.directory('bundle.app').createSync();
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Invalid prebuilt macOS app. Does not contain Info.plist.'));
@@ -67,10 +65,9 @@ group('PrebuiltMacOSApp', () {
     testUsingContext('Error on info.plist missing bundle identifier', () {
       final String contentsDirectory = fileSystem.path.join('bundle.app', 'Contents');
       fileSystem.directory(contentsDirectory).createSync(recursive: true);
-      fileSystem
-        .file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
+      fileSystem.file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
         .writeAsStringSync(badPlistData);
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Invalid prebuilt macOS app. Info.plist does not contain bundle identifier'));
@@ -79,10 +76,9 @@ group('PrebuiltMacOSApp', () {
     testUsingContext('Error on info.plist missing executable', () {
       final String contentsDirectory = fileSystem.path.join('bundle.app', 'Contents');
       fileSystem.directory(contentsDirectory).createSync(recursive: true);
-      fileSystem
-        .file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
+      fileSystem.file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
         .writeAsStringSync(badPlistDataNoExecutable);
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Invalid prebuilt macOS app. Info.plist does not contain bundle executable'));
@@ -91,13 +87,11 @@ group('PrebuiltMacOSApp', () {
     testUsingContext('Success with app bundle', () {
       final String appDirectory = fileSystem.path.join('bundle.app', 'Contents', 'MacOS');
       fileSystem.directory(appDirectory).createSync(recursive: true);
-      fileSystem
-        .file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
+      fileSystem.file(fileSystem.path.join('bundle.app', 'Contents', 'Info.plist'))
         .writeAsStringSync(plistData);
-      fileSystem
-        .file(fileSystem.path.join(appDirectory, executableName))
+      fileSystem.file(fileSystem.path.join(appDirectory, executableName))
         .createSync();
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('bundle.app'))! as PrebuiltMacOSApp;
 
       expect(logger.errorText, isEmpty);
       expect(macosApp.uncompressedBundle.path, 'bundle.app');
@@ -107,7 +101,7 @@ group('PrebuiltMacOSApp', () {
 
     testUsingContext('Bad zipped app, no payload dir', () {
       fileSystem.file('app.zip').createSync();
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Archive "app.zip" does not contain a single app bundle.'));
@@ -124,7 +118,7 @@ group('PrebuiltMacOSApp', () {
         fileSystem.directory(bundlePath1).createSync(recursive: true);
         fileSystem.directory(bundlePath2).createSync(recursive: true);
       };
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp? macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltMacOSApp?;
 
       expect(macosApp, isNull);
       expect(logger.errorText, contains('Archive "app.zip" does not contain a single app bundle.'));
@@ -138,18 +132,15 @@ group('PrebuiltMacOSApp', () {
         }
         final Directory bundleAppContentsDir = fileSystem.directory(fileSystem.path.join(targetDirectory.path, 'bundle.app', 'Contents'));
         bundleAppContentsDir.createSync(recursive: true);
-        fileSystem
-          .file(fileSystem.path.join(bundleAppContentsDir.path, 'Info.plist'))
+        fileSystem.file(fileSystem.path.join(bundleAppContentsDir.path, 'Info.plist'))
           .writeAsStringSync(plistData);
-        fileSystem
-          .directory(fileSystem.path.join(bundleAppContentsDir.path, 'MacOS'))
+        fileSystem.directory(fileSystem.path.join(bundleAppContentsDir.path, 'MacOS'))
           .createSync();
-        fileSystem
-          .file(fileSystem.path
+        fileSystem.file(fileSystem.path
           .join(bundleAppContentsDir.path, 'MacOS', executableName))
           .createSync();
       };
-      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltMacOSApp;
+      final PrebuiltMacOSApp macosApp = MacOSApp.fromPrebuiltApp(fileSystem.file('app.zip'))! as PrebuiltMacOSApp;
 
       expect(logger.errorText, isEmpty);
       expect(macosApp.uncompressedBundle.path, endsWith('bundle.app'));
@@ -170,7 +161,7 @@ group('PrebuiltMacOSApp', () {
 class FakeOperatingSystemUtils extends Fake implements OperatingSystemUtils {
   FakeOperatingSystemUtils();
 
-  void Function(File, Directory) unzipOverride;
+  void Function(File, Directory)? unzipOverride;
 
   @override
   void unzip(File file, Directory targetDirectory) {
@@ -181,15 +172,15 @@ class FakeOperatingSystemUtils extends Fake implements OperatingSystemUtils {
 class FakePlistUtils extends Fake implements PlistParser {
   FakePlistUtils(this.fileSystem);
 
-  final FileSystem fileSystem;
+  final FileSystem? fileSystem;
 
   @override
-  Map<String, dynamic> parseFile(String plistFilePath) {
-    final File file = fileSystem.file(plistFilePath);
+  Map<String, Object> parseFile(String plistFilePath) {
+    final File file = fileSystem!.file(plistFilePath);
     if (!file.existsSync()) {
-      return <String, dynamic>{};
+      return <String, Object>{};
     }
-    return castStringKeyedMap(json.decode(file.readAsStringSync()));
+    return castStringKeyedMap(json.decode(file.readAsStringSync()))!.cast();
   }
 }
 

packages/flutter_tools/test/general.shard/macos/cocoapods_test.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:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/logger.dart';
@@ -22,11 +20,11 @@ import '../../src/context.dart';
 import '../../src/fake_process_manager.dart';
 
 void main() {
-  FileSystem fileSystem;
-  FakeProcessManager fakeProcessManager;
-  CocoaPods cocoaPodsUnderTest;
-  BufferLogger logger;
-  TestUsage usage;
+  late FileSystem fileSystem;
+  late FakeProcessManager fakeProcessManager;
+  late CocoaPods cocoaPodsUnderTest;
+  late BufferLogger logger;
+  late TestUsage usage;
 
   void pretendPodVersionFails() {
     fakeProcessManager.addCommand(
@@ -77,17 +75,17 @@ void main() {
       usage: usage,
     );
     fileSystem.file(fileSystem.path.join(
-      Cache.flutterRoot, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-ios-objc',
+      Cache.flutterRoot!, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-ios-objc',
     ))
         ..createSync(recursive: true)
         ..writeAsStringSync('Objective-C iOS podfile template');
     fileSystem.file(fileSystem.path.join(
-      Cache.flutterRoot, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-ios-swift',
+      Cache.flutterRoot!, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-ios-swift',
     ))
         ..createSync(recursive: true)
         ..writeAsStringSync('Swift iOS podfile template');
     fileSystem.file(fileSystem.path.join(
-      Cache.flutterRoot, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-macos',
+      Cache.flutterRoot!, 'packages', 'flutter_tools', 'templates', 'cocoapods', 'Podfile-macos',
     ))
         ..createSync(recursive: true)
         ..writeAsStringSync('macOS podfile template');
@@ -728,7 +726,6 @@ Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by
       final bool didInstall = await cocoaPodsUnderTest.processPods(
         xcodeProject: projectUnderTest.ios,
         buildMode: BuildMode.debug,
-        dependenciesChanged: true,
       );
       expect(didInstall, isTrue);
       expect(fakeProcessManager, hasNoRemainingExpectations);
@@ -828,7 +825,7 @@ class FakeXcodeProjectInterpreter extends Fake implements XcodeProjectInterprete
   @override
   Future<Map<String, String>> getBuildSettings(
     String projectPath, {
-    XcodeProjectBuildContext buildContext,
+    XcodeProjectBuildContext? buildContext,
     Duration timeout = const Duration(minutes: 1),
   }) async => buildSettings;
 

packages/flutter_tools/test/general.shard/macos/xcode_test.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:flutter_tools/src/artifacts.dart';
@@ -24,21 +22,21 @@ import '../../src/common.dart';
 import '../../src/context.dart';
 
 void main() {
-  BufferLogger logger;
+  late BufferLogger logger;
 
   setUp(() {
     logger = BufferLogger.test();
   });
 
   group('FakeProcessManager', () {
-    FakeProcessManager fakeProcessManager;
+    late FakeProcessManager fakeProcessManager;
 
     setUp(() {
       fakeProcessManager = FakeProcessManager.empty();
     });
 
     group('Xcode', () {
-      FakeXcodeProjectInterpreter xcodeProjectInterpreter;
+      late FakeXcodeProjectInterpreter xcodeProjectInterpreter;
 
       setUp(() {
         xcodeProjectInterpreter = FakeXcodeProjectInterpreter();
@@ -94,7 +92,7 @@ void main() {
       });
 
       group('macOS', () {
-        Xcode xcode;
+        late Xcode xcode;
 
         setUp(() {
           xcodeProjectInterpreter = FakeXcodeProjectInterpreter();
@@ -276,8 +274,8 @@ void main() {
     });
 
     group('xcdevice not installed', () {
-      XCDevice xcdevice;
-      Xcode xcode;
+      late XCDevice xcdevice;
+      late Xcode xcode;
 
       setUp(() {
         xcode = Xcode.test(
@@ -310,8 +308,8 @@ void main() {
     });
 
     group('xcdevice', () {
-      XCDevice xcdevice;
-      Xcode xcode;
+      late XCDevice xcdevice;
+      late Xcode xcode;
 
       setUp(() {
         xcode = Xcode.test(processManager: FakeProcessManager.any());
@@ -351,7 +349,7 @@ void main() {
           // Attach: d83d5bc53967baa0ee18626ba87b6254b2ab5418
           // Attach: 00008027-00192736010F802E
           // Detach: d83d5bc53967baa0ee18626ba87b6254b2ab5418
-          xcdevice.observedDeviceEvents().listen((Map<XCDeviceEvent, String> event) {
+          xcdevice.observedDeviceEvents()!.listen((Map<XCDeviceEvent, String> event) {
             expect(event.length, 1);
             if (event.containsKey(XCDeviceEvent.attach)) {
               if (event[XCDeviceEvent.attach] == 'd83d5bc53967baa0ee18626ba87b6254b2ab5418') {

packages/flutter_tools/test/general.shard/preview_device_test.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:file/memory.dart';
@@ -93,15 +91,15 @@ class FakeBundleBuilder extends Fake implements BundleBuilder {
 
   @override
   Future<void> build({
-    @required TargetPlatform platform,
-    @required BuildInfo buildInfo,
-    FlutterProject project,
-    String mainPath,
+    required TargetPlatform platform,
+    required BuildInfo buildInfo,
+    FlutterProject? project,
+    String? mainPath,
     String manifestPath = defaultManifestPath,
-    String applicationKernelFilePath,
-    String depfilePath,
-    String assetDirPath,
-    @visibleForTesting BuildSystem buildSystem
+    String? applicationKernelFilePath,
+    String? depfilePath,
+    String? assetDirPath,
+    @visibleForTesting BuildSystem? buildSystem
   }) async {
     final Directory assetDirectory = fileSystem
       .directory(assetDirPath)

packages/flutter_tools/test/general.shard/project_file_invalidator_test.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:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';

packages/flutter_tools/test/general.shard/resident_devtools_handler_test.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:flutter_tools/src/base/logger.dart';
@@ -107,8 +105,8 @@ void main() {
       flutterDevices: <FlutterDevice>[],
     );
 
-    expect(handler.activeDevToolsServer.host, 'localhost');
-    expect(handler.activeDevToolsServer.port, 8181);
+    expect(handler.activeDevToolsServer!.host, 'localhost');
+    expect(handler.activeDevToolsServer!.port, 8181);
   });
 
   testWithoutContext('serveAndAnnounceDevTools with attached device does not fail on null vm service', () async {
@@ -425,13 +423,13 @@ void main() {
 
 class FakeDevtoolsLauncher extends Fake implements DevtoolsLauncher {
   @override
-  DevToolsServerAddress activeDevToolsServer;
+  DevToolsServerAddress? activeDevToolsServer;
 
   @override
-  Uri devToolsUrl;
+  Uri? devToolsUrl;
 
   @override
-  Future<DevToolsServerAddress> serve() async => null;
+  Future<DevToolsServerAddress?> serve() async => null;
 
   @override
   Future<void> get ready => readyCompleter.future;
@@ -452,7 +450,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   final Device device = FakeDevice();
 
   @override
-  FlutterVmService vmService;
+  FlutterVmService? vmService;
 
   @override
   TargetPlatform targetPlatform = TargetPlatform.android_arm;

packages/flutter_tools/test/general.shard/terminal_handler_test.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:file/file.dart';
@@ -945,14 +943,14 @@ void main() {
       listViews,
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'false',
         },
       ),
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'true',
         },
@@ -971,7 +969,7 @@ void main() {
       listViews,
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'false',
         },
@@ -985,7 +983,7 @@ void main() {
       ),
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'true',
         },
@@ -1005,7 +1003,7 @@ void main() {
       listViews,
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'false',
         },
@@ -1019,7 +1017,7 @@ void main() {
       ),
       FakeVmServiceRequest(
         method: 'ext.flutter.debugAllowBanner',
-        args: <String, Object>{
+        args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
           'enabled': 'true',
         },
@@ -1090,7 +1088,7 @@ void main() {
         listViews,
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'false',
           },
@@ -1115,7 +1113,7 @@ void main() {
         listViews,
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'false',
           },
@@ -1127,7 +1125,7 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'true',
           },
@@ -1150,7 +1148,7 @@ void main() {
         listViews,
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'false',
           },
@@ -1162,7 +1160,7 @@ void main() {
         ),
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'true',
           },
@@ -1186,14 +1184,14 @@ void main() {
         listViews,
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'false',
           },
         ),
         FakeVmServiceRequest(
           method: 'ext.flutter.debugAllowBanner',
-          args: <String, Object>{
+          args: <String, Object?>{
             'isolateId': fakeUnpausedIsolate.id,
             'enabled': 'true',
           },
@@ -1309,7 +1307,7 @@ class FakeResidentRunner extends ResidentHandlers {
   }
 
   @override
-  void printHelp({bool details}) {
+  void printHelp({required bool details}) {
     if (details) {
       calledPrintWithDetails = true;
     } else {
@@ -1321,7 +1319,7 @@ class FakeResidentRunner extends ResidentHandlers {
   Future<void> runSourceGenerators() async {  }
 
   @override
-  Future<OperationResult> restart({bool fullRestart = false, bool pause = false, String reason}) async {
+  Future<OperationResult> restart({bool fullRestart = false, bool pause = false, String? reason}) async {
     if (fullRestart && !supportsRestart) {
       throw StateError('illegal restart');
     }
@@ -1345,7 +1343,7 @@ class FakeResidentDevtoolsHandler extends Fake implements ResidentDevtoolsHandle
   bool calledLaunchDevToolsInBrowser = false;
 
   @override
-  bool launchDevToolsInBrowser({List<FlutterDevice> flutterDevices}) {
+  bool launchDevToolsInBrowser({List<FlutterDevice?>? flutterDevices}) {
     return calledLaunchDevToolsInBrowser = true;
   }
 }
@@ -1382,8 +1380,8 @@ TerminalHandler setUpTerminalHandler(List<FakeVmServiceRequest> requests, {
   bool supportsScreenshot = false,
   int reloadExitCode = 0,
   BuildMode buildMode = BuildMode.debug,
-  Logger logger,
-  FileSystem fileSystem,
+  Logger? logger,
+  FileSystem? fileSystem,
 }) {
   final Logger testLogger = logger ?? BufferLogger.test();
   final Signals signals = Signals.test();
@@ -1440,7 +1438,7 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler { }
 
 class TestRunner extends Fake implements ResidentRunner {
   bool hasHelpBeenPrinted = false;
-  String receivedCommand;
+  String? receivedCommand;
 
   @override
   Future<void> cleanupAfterSignal() async { }
@@ -1449,22 +1447,22 @@ class TestRunner extends Fake implements ResidentRunner {
   Future<void> cleanupAtFinish() async { }
 
   @override
-  void printHelp({ bool details }) {
+  void printHelp({ bool? details }) {
     hasHelpBeenPrinted = true;
   }
 
   @override
-  Future<int> run({
-    Completer<DebugConnectionInfo> connectionInfoCompleter,
-    Completer<void> appStartedCompleter,
+  Future<int?> run({
+    Completer<DebugConnectionInfo>? connectionInfoCompleter,
+    Completer<void>? appStartedCompleter,
     bool enableDevTools = false,
-    String route,
+    String? route,
   }) async => null;
 
   @override
-  Future<int> attach({
-    Completer<DebugConnectionInfo> connectionInfoCompleter,
-    Completer<void> appStartedCompleter,
+  Future<int?> attach({
+    Completer<DebugConnectionInfo>? connectionInfoCompleter,
+    Completer<void>? appStartedCompleter,
     bool allowExistingDdsInstance = false,
     bool enableDevTools = false,
     bool needsFullRestart = true,
@@ -1491,10 +1489,10 @@ class _TestSignals implements Signals {
     if (!_handlersTable.containsKey(signal)) {
       return false;
     }
-    if (!_handlersTable[signal].containsKey(token)) {
+    if (!_handlersTable[signal]!.containsKey(token)) {
       return false;
     }
-    _handlersTable[signal].remove(token);
+    _handlersTable[signal]!.remove(token);
     return true;
   }
 

packages/flutter_tools/test/general.shard/test/test_compiler_test.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:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -33,8 +31,8 @@ final BuildInfo debugBuild = BuildInfo(
 );
 
 void main() {
-  FakeResidentCompiler residentCompiler;
-  FileSystem fileSystem;
+  late FakeResidentCompiler residentCompiler;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -149,8 +147,7 @@ environment:
 
     await testCompiler.compile(Uri.parse('test/foo.dart'));
 
-    final File generatedMain = fileSystem
-      .directory('.dart_tool')
+    final File generatedMain = fileSystem.directory('.dart_tool')
       .childDirectory('flutter_build')
       .childFile('dart_plugin_registrant.dart');
 
@@ -170,17 +167,17 @@ environment:
 /// Override the creation of the Resident Compiler to simplify testing.
 class FakeTestCompiler extends TestCompiler {
   FakeTestCompiler(
-    BuildInfo buildInfo,
-    FlutterProject flutterProject,
+    super.buildInfo,
+    super.flutterProject,
     this.residentCompiler, {
-      String precompiledDillPath,
+      super.precompiledDillPath,
     }
-  ) : super(buildInfo, flutterProject, precompiledDillPath: precompiledDillPath);
+  );
 
-  final FakeResidentCompiler residentCompiler;
+  final FakeResidentCompiler? residentCompiler;
 
   @override
-  Future<ResidentCompiler> createCompiler() async {
+  Future<ResidentCompiler?> createCompiler() async {
     return residentCompiler;
   }
 }
@@ -188,24 +185,24 @@ class FakeTestCompiler extends TestCompiler {
 class FakeResidentCompiler extends Fake implements ResidentCompiler {
   FakeResidentCompiler(this.fileSystem);
 
-  final FileSystem fileSystem;
+  final FileSystem? fileSystem;
 
-  CompilerOutput compilerOutput;
+  CompilerOutput? compilerOutput;
   bool didShutdown = false;
 
   @override
-  Future<CompilerOutput> recompile(
+  Future<CompilerOutput?> recompile(
     Uri mainUri,
-    List<Uri> invalidatedFiles, {
-    String outputPath,
-    PackageConfig packageConfig,
-    String projectRootPath,
-    FileSystem fs,
+    List<Uri>? invalidatedFiles, {
+    String? outputPath,
+    PackageConfig? packageConfig,
+    String? projectRootPath,
+    FileSystem? fs,
     bool suppressErrors = false,
     bool checkDartPluginRegistry = false,
   }) async {
     if (compilerOutput != null) {
-      fileSystem.file(compilerOutput.outputFilename).createSync(recursive: true);
+      fileSystem!.file(compilerOutput!.outputFilename).createSync(recursive: true);
     }
     return compilerOutput;
   }
@@ -217,7 +214,8 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
   void reset() { }
 
   @override
-  Future<void> shutdown() async {
+  Future<Object> shutdown() async {
     didShutdown = true;
+    return Object();
   }
 }

packages/flutter_tools/test/general.shard/testbed_test.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 'dart:io';
 
@@ -24,7 +22,7 @@ void main() {
     test('Can provide default interfaces', () async {
       final Testbed testbed = Testbed();
 
-      FileSystem localFileSystem;
+      late FileSystem localFileSystem;
       await testbed.run(() {
         localFileSystem = globals.fs;
       });
@@ -39,7 +37,7 @@ void main() {
         A: () => A(),
       });
 
-      A instance;
+      A? instance;
       await testbed.run(() {
         instance = context.get<A>();
       });
@@ -52,7 +50,7 @@ void main() {
         A: () => A(),
       });
 
-      A instance;
+      A? instance;
       await testbed.run(() {
         instance = context.get<A>();
       }, overrides: <Type, Generator>{

packages/flutter_tools/test/general.shard/version_test.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:convert';
 
 import 'package:flutter_tools/src/base/logger.dart';
@@ -24,8 +22,8 @@ final DateTime _stampUpToDate = _testClock.ago(VersionFreshnessValidator.checkAg
 final DateTime _stampOutOfDate = _testClock.ago(VersionFreshnessValidator.checkAgeConsideredUpToDate * 2);
 
 void main() {
-  FakeCache cache;
-  FakeProcessManager processManager;
+  late FakeCache cache;
+  late FakeProcessManager processManager;
 
   setUp(() {
     processManager = FakeProcessManager.empty();
@@ -323,15 +321,15 @@ void main() {
       const String flutterNonStandardUrlDotGit = 'https://githubmirror.com/flutter/flutter.git';
       const String flutterStandardSshUrlDotGit = 'git@github.com:flutter/flutter.git';
 
-      VersionCheckError runUpstreamValidator({
-        String versionUpstreamUrl,
-        String flutterGitUrl,
+      VersionCheckError? runUpstreamValidator({
+        String? versionUpstreamUrl,
+        String? flutterGitUrl,
       }){
         final Platform testPlatform = FakePlatform(environment: <String, String> {
           if (flutterGitUrl != null) 'FLUTTER_GIT_URL': flutterGitUrl,
         });
         return VersionUpstreamValidator(
-          version: FakeFlutterVersion(repositoryUrl: versionUpstreamUrl),
+          version: FakeFlutterVersion(repositoryUrl: versionUpstreamUrl, channel: 'master'),
           platform: testPlatform,
         ).run();
       }
@@ -339,7 +337,7 @@ void main() {
       testWithoutContext('returns error if repository url is null', () {
         final VersionCheckError error = runUpstreamValidator(
           // repositoryUrl is null by default
-        );
+        )!;
         expect(error, isNotNull);
         expect(
           error.message,
@@ -352,7 +350,7 @@ void main() {
       });
 
       testWithoutContext('returns error at non-standard remote url with FLUTTER_GIT_URL unset', () {
-        final VersionCheckError error = runUpstreamValidator(versionUpstreamUrl: flutterNonStandardUrlDotGit);
+        final VersionCheckError error = runUpstreamValidator(versionUpstreamUrl: flutterNonStandardUrlDotGit)!;
         expect(error, isNotNull);
         expect(
           error.message,
@@ -375,7 +373,7 @@ void main() {
         final VersionCheckError error = runUpstreamValidator(
             versionUpstreamUrl: flutterStandardUrlDotGit,
             flutterGitUrl: flutterNonStandardUrlDotGit,
-        );
+        )!;
         expect(error, isNotNull);
         expect(
           error.message,
@@ -673,7 +671,7 @@ void main() {
 }
 
 class FakeCache extends Fake implements Cache {
-  String versionStamp;
+  String? versionStamp;
   bool setVersionStamp = false;
 
   @override
@@ -689,7 +687,7 @@ class FakeCache extends Fake implements Cache {
   void checkLockAcquired() { }
 
   @override
-  String getStampFor(String artifactName) {
+  String? getStampFor(String artifactName) {
     if (artifactName == VersionCheckStamp.flutterVersionCheckStampFile) {
       return versionStamp;
     }
@@ -705,11 +703,11 @@ class FakeCache extends Fake implements Cache {
 }
 
 class FakeFlutterVersion extends Fake implements FlutterVersion {
-  FakeFlutterVersion({this.channel, this.repositoryUrl});
+  FakeFlutterVersion({required this.channel, this.repositoryUrl});
 
   @override
   final String channel;
 
   @override
-  final String repositoryUrl;
+  final String? repositoryUrl;
 }

packages/flutter_tools/test/general.shard/windows/application_package_test.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:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -17,9 +15,9 @@ import '../../src/context.dart';
 
 void main() {
   group('PrebuiltWindowsApp', () {
-    FakeOperatingSystemUtils os;
-    FileSystem fileSystem;
-    BufferLogger logger;
+    late FakeOperatingSystemUtils os;
+    late FileSystem fileSystem;
+    late BufferLogger logger;
 
     final Map<Type, Generator> overrides = <Type, Generator>{
       FileSystem: () => fileSystem,
@@ -35,7 +33,7 @@ void main() {
     });
 
     testUsingContext('Error on non-existing exe file', () {
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.exe')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp? windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.exe')) as PrebuiltWindowsApp?;
 
       expect(windowsApp, isNull);
       expect(logger.errorText, contains('File "not_existing.exe" does not exist.'));
@@ -43,13 +41,13 @@ void main() {
 
     testUsingContext('Success on exe file', () {
       fileSystem.file('file.exe').createSync();
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('file.exe')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('file.exe'))! as PrebuiltWindowsApp;
 
       expect(windowsApp.name, 'file.exe');
     }, overrides: overrides);
 
     testUsingContext('Error on non-existing zip file', () {
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.zip')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp? windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.zip')) as PrebuiltWindowsApp?;
 
       expect(windowsApp, isNull);
       expect(logger.errorText, contains('File "not_existing.zip" does not exist.'));
@@ -57,7 +55,7 @@ void main() {
 
     testUsingContext('Bad zipped app, no payload dir', () {
       fileSystem.file('app.zip').createSync();
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp? windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltWindowsApp?;
 
       expect(windowsApp, isNull);
       expect(logger.errorText, contains('Cannot find .exe files in the zip archive.'));
@@ -74,7 +72,7 @@ void main() {
         fileSystem.directory(exePath1).createSync(recursive: true);
         fileSystem.directory(exePath2).createSync(recursive: true);
       };
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp? windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltWindowsApp?;
 
       expect(windowsApp, isNull);
       expect(logger.errorText, contains('Archive "app.zip" contains more than one .exe files.'));
@@ -82,7 +80,7 @@ void main() {
 
     testUsingContext('Success with zipped app', () {
       fileSystem.file('app.zip').createSync();
-      String exePath;
+      String? exePath;
       os.unzipOverride = (File zipFile, Directory targetDirectory) {
         if (zipFile.path != 'app.zip') {
           return;
@@ -90,7 +88,7 @@ void main() {
         exePath = fileSystem.path.join(targetDirectory.path, 'app.exe');
         fileSystem.directory(exePath).createSync(recursive: true);
       };
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('app.zip'))! as PrebuiltWindowsApp;
 
       expect(logger.errorText, isEmpty);
       expect(windowsApp.name, exePath);
@@ -99,7 +97,7 @@ void main() {
 
     testUsingContext('Error on unknown file type', () {
       fileSystem.file('not_existing.app').createSync();
-      final PrebuiltWindowsApp windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.app')) as PrebuiltWindowsApp;
+      final PrebuiltWindowsApp? windowsApp = WindowsApp.fromPrebuiltApp(fileSystem.file('not_existing.app')) as PrebuiltWindowsApp?;
 
       expect(windowsApp, isNull);
       expect(logger.errorText, contains('Unknown windows application type.'));
@@ -110,7 +108,7 @@ void main() {
 class FakeOperatingSystemUtils extends Fake implements OperatingSystemUtils {
   FakeOperatingSystemUtils();
 
-  void Function(File, Directory) unzipOverride;
+  void Function(File, Directory)? unzipOverride;
 
   @override
   void unzip(File file, Directory targetDirectory) {

packages/flutter_tools/test/integration.shard/expression_evaluation_test.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:file/file.dart';
 
 import 'package:vm_service/vm_service.dart';
@@ -16,8 +14,8 @@ import 'test_utils.dart';
 
 void batch1() {
   final BasicProject project = BasicProject();
-  Directory tempDir;
-  FlutterRunTestDriver flutter;
+  late Directory tempDir;
+  late FlutterRunTestDriver flutter;
 
   Future<void> initProject() async {
     tempDir = createResolvedTempDirectorySync('run_expression_eval_test.');
@@ -95,8 +93,8 @@ void batch1() {
 
 void batch2() {
   final TestsProject project = TestsProject();
-  Directory tempDir;
-  FlutterTestTestDriver flutter;
+  late Directory tempDir;
+  late FlutterTestTestDriver flutter;
 
   Future<void> initProject() async {
     tempDir = createResolvedTempDirectorySync('test_expression_eval_test.');
@@ -105,7 +103,7 @@ void batch2() {
   }
 
   Future<void> cleanProject() async {
-    await flutter?.waitForCompletion();
+    await flutter.waitForCompletion();
     tryToDelete(tempDir);
   }
 
@@ -165,14 +163,14 @@ Future<void> evaluateComplexReturningExpressions(FlutterTestDriver flutter) asyn
   final DateTime date = DateTime(2000);
   final ObjRef resp = await flutter.evaluateInFrame('new DateTime(2000)');
   expectInstanceOfClass(resp, 'DateTime');
-  final ObjRef res = await flutter.evaluate(resp.id, r'"$year-$month-$day"');
+  final ObjRef res = await flutter.evaluate(resp.id!, r'"$year-$month-$day"');
   expectValue(res, '${date.year}-${date.month}-${date.day}');
 }
 
 void expectInstanceOfClass(ObjRef result, String name) {
   expect(result,
     const TypeMatcher<InstanceRef>()
-      .having((InstanceRef instance) => instance.classRef.name, 'resp.classRef.name', name));
+      .having((InstanceRef instance) => instance.classRef!.name, 'resp.classRef.name', name));
 }
 
 void expectValueOfType(ObjRef result, String kind, String message) {

packages/flutter_tools/test/integration.shard/migrate_config_test.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:file/file.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/flutter_project_metadata.dart';
@@ -17,9 +15,9 @@ import 'test_utils.dart';
 
 
 void main() {
-  Directory tempDir;
-  FlutterRunTestDriver flutter;
-  Logger logger;
+  late Directory tempDir;
+  late FlutterRunTestDriver flutter;
+  late Logger logger;
 
   setUp(() async {
     tempDir = createResolvedTempDirectorySync('run_test.');
@@ -71,11 +69,11 @@ migration:
 ''', flush: true);
     FlutterProjectMetadata metadata = FlutterProjectMetadata(metadataFile, logger);
 
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root].createRevision, equals('fj19vkla9vnlka9vni3n808v3nch8cd'));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root].baseRevision, equals('93kf9v3njfa90vnidfjvn39nvi3vnie'));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root]!.createRevision, equals('fj19vkla9vnlka9vni3n808v3nch8cd'));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root]!.baseRevision, equals('93kf9v3njfa90vnidfjvn39nvi3vnie'));
 
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android].createRevision, equals('abfj19vkla9vnlka9vni3n808v3nch8cd'));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android].baseRevision, equals('ab93kf9v3njfa90vnidfjvn39nvi3vnie'));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android]!.createRevision, equals('abfj19vkla9vnlka9vni3n808v3nch8cd'));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android]!.baseRevision, equals('ab93kf9v3njfa90vnidfjvn39nvi3vnie'));
 
     expect(metadata.migrateConfig.unmanagedFiles[0], equals('lib/main.dart'));
     expect(metadata.migrateConfig.unmanagedFiles[1], equals('ios/Runner.xcodeproj/project.pbxproj'));
@@ -169,8 +167,6 @@ migration:
       projectDirectory: tempDir,
       currentRevision: currentRevision,
       createRevision: createRevision,
-      create: true,
-      update: true,
       logger: logger,
     );
 
@@ -179,16 +175,16 @@ migration:
     final List<SupportedPlatform> keyList = List<SupportedPlatform>.from(metadata.migrateConfig.platformConfigs.keys);
 
     expect(keyList[0], equals(SupportedPlatform.root));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root].baseRevision, equals(currentRevision));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root].createRevision, equals(createRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root]!.baseRevision, equals(currentRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.root]!.createRevision, equals(createRevision));
 
     expect(keyList[1], equals(SupportedPlatform.android));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android].baseRevision, equals(currentRevision));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android].createRevision, equals(createRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android]!.baseRevision, equals(currentRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.android]!.createRevision, equals(createRevision));
 
     expect(keyList[2], equals(SupportedPlatform.ios));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.ios].baseRevision, equals(currentRevision));
-    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.ios].createRevision, equals(createRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.ios]!.baseRevision, equals(currentRevision));
+    expect(metadata.migrateConfig.platformConfigs[SupportedPlatform.ios]!.createRevision, equals(createRevision));
 
     final File metadataFileOutput = tempDir.childFile('.metadata_output');
     metadata.writeFile(outputFile: metadataFileOutput);

packages/flutter_tools/test/integration.shard/project_validator_integration_test.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/command_runner.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
@@ -15,7 +13,7 @@ import '../src/context.dart';
 import '../src/test_flutter_command_runner.dart';
 
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   group('analyze project command', () {
 

packages/flutter_tools/test/integration.shard/test_driver.dart

@@ -849,9 +849,9 @@ class FlutterTestTestDriver extends FlutterTestDriver {
 
     await resume();
 
-    final Future<Object> timeoutFuture =
-        Future<Object>.delayed(defaultTimeout);
-    await Future.any<Object>(<Future<Object>>[done.future, timeoutFuture]);
+    final Future<void> timeoutFuture =
+        Future<void>.delayed(defaultTimeout);
+    await Future.any<void>(<Future<void>>[done.future, timeoutFuture]);
     await subscription.cancel();
     if (!done.isCompleted) {
       await quit();

packages/flutter_tools/test/integration.shard/web_plugin_registrant_test.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:args/command_runner.dart';
@@ -21,8 +19,8 @@ import '../src/context.dart';
 import '../src/test_flutter_command_runner.dart';
 
 void main() {
-  Directory tempDir;
-  Directory projectDir;
+  late Directory tempDir;
+  late Directory projectDir;
 
   setUpAll(() async {
     Cache.disableLocking();
@@ -195,8 +193,8 @@ Future<void> _createProject(Directory dir, List<String> createArgs) async {
 Future<void> _addDependency(
   Directory projectDir,
   String package, {
-  String version,
-  String path,
+  String? version,
+  String? path,
 }) async {
   assert(version != null || path != null,
       'Need to define a source for the package.');
@@ -249,7 +247,7 @@ Future<void> _analyzeEntity(FileSystemEntity target) async {
   ];
 
   final ProcessResult exec = await Process.run(
-    globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
+    globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path,
     args,
     workingDirectory: target is Directory ? target.path : target.dirname,
   );
@@ -277,7 +275,7 @@ Future<void> _buildWebProject(Directory workingDir) async {
   ];
 
   final ProcessResult exec = await Process.run(
-    globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
+    globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path,
     args,
     workingDirectory: workingDir.path,
   );