From 4453ba0a4d3a6ce5fcf29bb39d1cb3d2360b6874 Mon Sep 17 00:00:00 2001
From: Liam Appelbe <liama@google.com>
Date: Wed, 7 Sep 2022 12:28:52 -0700
Subject: [PATCH] Null safety migration of
 packages/flutter_tools/test/general.shard, part 2/2 (#110712)

* Migrate packages/flutter_tools/test/general.shard, part 2/2

* Fix analysis

* Fix tests

* Fix analysis

* Apply suggestions from code review

Co-authored-by: Christopher Fujino <fujino@google.com>

Co-authored-by: Christopher Fujino <fujino@google.com>
---
 .../lib/src/resident_runner.dart              |   2 +-
 packages/flutter_tools/lib/src/vmservice.dart |   4 +-
 .../application_package_test.dart             | 105 +++++-----
 .../test/general.shard/args_test.dart         |  17 +-
 .../test/general.shard/emulator_test.dart     |  36 +++-
 .../test/general.shard/hot_test.dart          | 123 ++++++-----
 .../resident_web_runner_cold_test.dart        |  32 ++-
 .../resident_web_runner_test.dart             | 198 +++++++++---------
 .../test/general.shard/vmservice_test.dart    |  36 ++--
 .../general.shard/web/devfs_web_test.dart     | 101 +++++----
 .../web/golden_comparator_process_test.dart   |  12 +-
 ...crub_generated_plugin_registrant_test.dart |  12 +-
 .../web/web_asset_server_test.dart            |   4 +-
 .../web/web_expression_compiler_test.dart     |  14 +-
 14 files changed, 343 insertions(+), 353 deletions(-)

diff --git a/packages/flutter_tools/lib/src/resident_runner.dart b/packages/flutter_tools/lib/src/resident_runner.dart
index de428242089..4b493d93c47 100644
--- a/packages/flutter_tools/lib/src/resident_runner.dart
+++ b/packages/flutter_tools/lib/src/resident_runner.dart
@@ -707,7 +707,7 @@ abstract class ResidentHandlers {
       }
       final List<FlutterView> views = await device!.vmService!.getFlutterViews();
       for (final FlutterView view in views) {
-        final Map<String, Object>? rasterData =
+        final Map<String, Object?>? rasterData =
           await device.vmService!.renderFrameWithRasterStats(
             viewId: view.id,
             uiIsolateId: view.uiIsolate!.id,
diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index 1d1d5c7fc17..95429336fe0 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -557,7 +557,7 @@ class FlutterVmService {
   /// for rasterization which is not reflective of how long the frame takes in
   /// production. This is primarily intended to be used to identify the layers
   /// that result in the most raster perf degradation.
-  Future<Map<String, Object>?> renderFrameWithRasterStats({
+  Future<Map<String, Object?>?> renderFrameWithRasterStats({
     required String? viewId,
     required String? uiIsolateId,
   }) async {
@@ -568,7 +568,7 @@ class FlutterVmService {
         'viewId': viewId,
       },
     );
-    return response?.json as Map<String, Object>?;
+    return response?.json;
   }
 
   Future<String> flutterDebugDumpApp({
diff --git a/packages/flutter_tools/test/general.shard/application_package_test.dart b/packages/flutter_tools/test/general.shard/application_package_test.dart
index 5b94432d32c..fe1bb0fff41 100644
--- a/packages/flutter_tools/test/general.shard/application_package_test.dart
+++ b/packages/flutter_tools/test/general.shard/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/android/android_sdk.dart';
@@ -30,10 +28,10 @@ import '../src/fakes.dart';
 
 void main() {
   group('Apk with partial Android SDK works', () {
-    FakeAndroidSdk sdk;
-    FakeProcessManager fakeProcessManager;
-    MemoryFileSystem fs;
-    Cache cache;
+    late FakeAndroidSdk sdk;
+    late FakeProcessManager fakeProcessManager;
+    late MemoryFileSystem fs;
+    late Cache cache;
 
     final Map<Type, Generator> overrides = <Type, Generator>{
       AndroidSdk: () => sdk,
@@ -79,11 +77,10 @@ void main() {
         )
       );
 
-      final ApplicationPackage applicationPackage = await ApplicationPackageFactory.instance.getPackageForPlatform(
+      final ApplicationPackage applicationPackage = (await ApplicationPackageFactory.instance!.getPackageForPlatform(
         TargetPlatform.android_arm,
-        buildInfo: null,
         applicationBinary: apkFile,
-      );
+      ))!;
       expect(applicationPackage.name, 'app.apk');
       expect(applicationPackage, isA<PrebuiltApplicationPackage>());
       expect((applicationPackage as PrebuiltApplicationPackage).applicationPackage.path, apkFile.path);
@@ -104,9 +101,8 @@ void main() {
       gradleWrapperDir.childFile('gradlew').writeAsStringSync('irrelevant');
       gradleWrapperDir.childFile('gradlew.bat').writeAsStringSync('irrelevant');
 
-      await ApplicationPackageFactory.instance.getPackageForPlatform(
+      await ApplicationPackageFactory.instance!.getPackageForPlatform(
         TargetPlatform.android_arm,
-        buildInfo: null,
         applicationBinary: globals.fs.file('app.apk'),
       );
       expect(fakeProcessManager, hasNoRemainingExpectations);
@@ -116,19 +112,16 @@ void main() {
       final AndroidSdkVersion sdkVersion = FakeAndroidSdkVersion();
       sdk.latestVersion = sdkVersion;
 
-      await ApplicationPackageFactory.instance.getPackageForPlatform(
+      await ApplicationPackageFactory.instance!.getPackageForPlatform(
         TargetPlatform.android_arm,
-        buildInfo: null,
       );
       expect(fakeProcessManager, hasNoRemainingExpectations);
     }, overrides: overrides);
 
     testWithoutContext('returns null when failed to extract manifest', () async {
-      final AndroidSdkVersion sdkVersion = FakeAndroidSdkVersion();
-      sdk.latestVersion = sdkVersion;
       final Logger logger = BufferLogger.test();
-      final AndroidApk androidApk = AndroidApk.fromApk(
-        null,
+      final AndroidApk? androidApk = AndroidApk.fromApk(
+        fs.file(''),
         processManager: fakeProcessManager,
         logger: logger,
         userMessages: UserMessages(),
@@ -146,7 +139,7 @@ void main() {
       final ApkManifestData data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithExplicitEnabledAndMainLauncherActivity,
         BufferLogger.test(),
-      );
+      )!;
 
       expect(data, isNotNull);
       expect(data.packageName, 'io.flutter.examples.hello_world');
@@ -157,7 +150,7 @@ void main() {
       final ApkManifestData data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithDefaultEnabledAndMainLauncherActivity,
         BufferLogger.test(),
-      );
+      )!;
 
       expect(data, isNotNull);
       expect(data.packageName, 'io.flutter.examples.hello_world');
@@ -168,7 +161,7 @@ void main() {
       final ApkManifestData data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithDistNamespace,
         BufferLogger.test(),
-      );
+      )!;
 
       expect(data, isNotNull);
       expect(data.packageName, 'io.flutter.examples.hello_world');
@@ -177,7 +170,7 @@ void main() {
 
     testWithoutContext('Error when parsing manifest with no Activity that has enabled set to true nor has no value for its enabled field', () {
       final BufferLogger logger = BufferLogger.test();
-      final ApkManifestData data = ApkManifestData.parseFromXmlDump(
+      final ApkManifestData? data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithNoEnabledActivity,
         logger,
       );
@@ -191,7 +184,7 @@ void main() {
 
     testWithoutContext('Error when parsing manifest with no Activity that has action set to android.intent.action.MAIN', () {
       final BufferLogger logger = BufferLogger.test();
-      final ApkManifestData data = ApkManifestData.parseFromXmlDump(
+      final ApkManifestData? data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithNoMainActivity,
         logger,
       );
@@ -205,7 +198,7 @@ void main() {
 
     testWithoutContext('Error when parsing manifest with no Activity that has category set to android.intent.category.LAUNCHER', () {
       final BufferLogger logger = BufferLogger.test();
-      final ApkManifestData data = ApkManifestData.parseFromXmlDump(
+      final ApkManifestData? data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithNoLauncherActivity,
         logger,
       );
@@ -221,7 +214,7 @@ void main() {
       final ApkManifestData data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithLauncherAndDefaultActivity,
         BufferLogger.test(),
-      );
+      )!;
 
       expect(data, isNotNull);
       expect(data.packageName, 'io.flutter.examples.hello_world');
@@ -229,7 +222,7 @@ void main() {
     });
 
     testWithoutContext('Parses manifest with missing application tag', () async {
-      final ApkManifestData data = ApkManifestData.parseFromXmlDump(
+      final ApkManifestData? data = ApkManifestData.parseFromXmlDump(
         _aaptDataWithoutApplication,
         BufferLogger.test(),
       );
@@ -239,8 +232,8 @@ void main() {
   });
 
   group('PrebuiltIOSApp', () {
-    FakeOperatingSystemUtils os;
-    FakePlistParser testPlistParser;
+    late FakeOperatingSystemUtils os;
+    late FakePlistParser testPlistParser;
 
     final Map<Type, Generator> overrides = <Type, Generator>{
       FileSystem: () => MemoryFileSystem.test(),
@@ -255,8 +248,8 @@ void main() {
     });
 
     testUsingContext('Error on non-existing file', () {
-      final PrebuiltIOSApp iosApp =
-          IOSApp.fromPrebuiltApp(globals.fs.file('not_existing.ipa')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp =
+          IOSApp.fromPrebuiltApp(globals.fs.file('not_existing.ipa')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(
         testLogger.errorText,
@@ -266,8 +259,8 @@ void main() {
 
     testUsingContext('Error on non-app-bundle folder', () {
       globals.fs.directory('regular_folder').createSync();
-      final PrebuiltIOSApp iosApp =
-          IOSApp.fromPrebuiltApp(globals.fs.file('regular_folder')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp =
+          IOSApp.fromPrebuiltApp(globals.fs.file('regular_folder')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(
           testLogger.errorText, 'Folder "regular_folder" is not an app bundle.\n');
@@ -275,7 +268,7 @@ void main() {
 
     testUsingContext('Error on no info.plist', () {
       globals.fs.directory('bundle.app').createSync();
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(
         testLogger.errorText,
@@ -286,7 +279,7 @@ void main() {
     testUsingContext('Error on bad info.plist', () {
       globals.fs.directory('bundle.app').createSync();
       globals.fs.file('bundle.app/Info.plist').createSync();
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(
         testLogger.errorText,
@@ -299,7 +292,7 @@ void main() {
       globals.fs.directory('bundle.app').createSync();
       globals.fs.file('bundle.app/Info.plist').createSync();
       testPlistParser.setProperty('CFBundleIdentifier', 'fooBundleId');
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp iosApp = (IOSApp.fromPrebuiltApp(globals.fs.file('bundle.app')) as PrebuiltIOSApp?)!;
       expect(testLogger.errorText, isEmpty);
       expect(iosApp.uncompressedBundle.path, 'bundle.app');
       expect(iosApp.id, 'fooBundleId');
@@ -309,7 +302,7 @@ void main() {
 
     testUsingContext('Bad ipa zip-file, no payload dir', () {
       globals.fs.file('app.ipa').createSync();
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(
         testLogger.errorText,
@@ -330,7 +323,7 @@ void main() {
         globals.fs.directory(bundlePath1).createSync(recursive: true);
         globals.fs.directory(bundlePath2).createSync(recursive: true);
       };
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp? iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp?;
       expect(iosApp, isNull);
       expect(testLogger.errorText,
           'Invalid prebuilt iOS ipa. Does not contain a single app bundle.\n');
@@ -350,7 +343,7 @@ void main() {
             .file(globals.fs.path.join(bundleAppDir.path, 'Info.plist'))
             .createSync();
       };
-      final PrebuiltIOSApp iosApp = IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp;
+      final PrebuiltIOSApp iosApp = (IOSApp.fromPrebuiltApp(globals.fs.file('app.ipa')) as PrebuiltIOSApp?)!;
       expect(testLogger.errorText, isEmpty);
       expect(iosApp.uncompressedBundle.path, endsWith('bundle.app'));
       expect(iosApp.id, 'fooBundleId');
@@ -361,8 +354,8 @@ void main() {
     testUsingContext('returns null when there is no ios or .ios directory', () async {
       globals.fs.file('pubspec.yaml').createSync();
       globals.fs.file('.packages').createSync();
-      final BuildableIOSApp iosApp = await IOSApp.fromIosProject(
-        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp;
+      final BuildableIOSApp? iosApp = await IOSApp.fromIosProject(
+        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp?;
 
       expect(iosApp, null);
     }, overrides: overrides);
@@ -371,8 +364,8 @@ void main() {
       globals.fs.file('pubspec.yaml').createSync();
       globals.fs.file('.packages').createSync();
       globals.fs.file('ios/FooBar.xcodeproj').createSync(recursive: true);
-      final BuildableIOSApp iosApp = await IOSApp.fromIosProject(
-        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp;
+      final BuildableIOSApp? iosApp = await IOSApp.fromIosProject(
+        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp?;
 
       expect(iosApp, null);
     }, overrides: overrides);
@@ -381,8 +374,8 @@ void main() {
       globals.fs.file('pubspec.yaml').createSync();
       globals.fs.file('.packages').createSync();
       globals.fs.file('ios/Runner.xcodeproj').createSync(recursive: true);
-      final BuildableIOSApp iosApp = await IOSApp.fromIosProject(
-        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp;
+      final BuildableIOSApp? iosApp = await IOSApp.fromIosProject(
+        FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp?;
 
       expect(iosApp, null);
     }, overrides: overrides);
@@ -392,8 +385,8 @@ void main() {
       globals.fs.file('.packages').createSync();
       final Directory project = globals.fs.directory('ios/Runner.xcodeproj')..createSync(recursive: true);
       project.childFile('project.pbxproj').createSync();
-      final BuildableIOSApp iosApp = await IOSApp.fromIosProject(
-          FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp;
+      final BuildableIOSApp? iosApp = await IOSApp.fromIosProject(
+          FlutterProject.fromDirectory(globals.fs.currentDirectory).ios, null) as BuildableIOSApp?;
 
       expect(iosApp, null);
     }, overrides: overrides);
@@ -407,8 +400,8 @@ void main() {
     };
 
     testUsingContext('Error on non-existing file', () {
-      final PrebuiltFuchsiaApp fuchsiaApp =
-          FuchsiaApp.fromPrebuiltApp(globals.fs.file('not_existing.far')) as PrebuiltFuchsiaApp;
+      final PrebuiltFuchsiaApp? fuchsiaApp =
+          FuchsiaApp.fromPrebuiltApp(globals.fs.file('not_existing.far')) as PrebuiltFuchsiaApp?;
       expect(fuchsiaApp, isNull);
       expect(
         testLogger.errorText,
@@ -418,8 +411,8 @@ void main() {
 
     testUsingContext('Error on non-far file', () {
       globals.fs.directory('regular_folder').createSync();
-      final PrebuiltFuchsiaApp fuchsiaApp =
-          FuchsiaApp.fromPrebuiltApp(globals.fs.file('regular_folder')) as PrebuiltFuchsiaApp;
+      final PrebuiltFuchsiaApp? fuchsiaApp =
+          FuchsiaApp.fromPrebuiltApp(globals.fs.file('regular_folder')) as PrebuiltFuchsiaApp?;
       expect(fuchsiaApp, isNull);
       expect(
         testLogger.errorText,
@@ -429,7 +422,7 @@ void main() {
 
     testUsingContext('Success with far file', () {
       globals.fs.file('bundle.far').createSync();
-      final PrebuiltFuchsiaApp fuchsiaApp = FuchsiaApp.fromPrebuiltApp(globals.fs.file('bundle.far')) as PrebuiltFuchsiaApp;
+      final PrebuiltFuchsiaApp fuchsiaApp = (FuchsiaApp.fromPrebuiltApp(globals.fs.file('bundle.far')) as PrebuiltFuchsiaApp?)!;
       expect(testLogger.errorText, isEmpty);
       expect(fuchsiaApp.id, 'bundle.far');
       expect(fuchsiaApp.applicationPackage.path, globals.fs.file('bundle.far').path);
@@ -438,7 +431,7 @@ void main() {
     testUsingContext('returns null when there is no fuchsia', () async {
       globals.fs.file('pubspec.yaml').createSync();
       globals.fs.file('.packages').createSync();
-      final BuildableFuchsiaApp fuchsiaApp = FuchsiaApp.fromFuchsiaProject(FlutterProject.fromDirectory(globals.fs.currentDirectory).fuchsia) as BuildableFuchsiaApp;
+      final BuildableFuchsiaApp? fuchsiaApp = FuchsiaApp.fromFuchsiaProject(FlutterProject.fromDirectory(globals.fs.currentDirectory).fuchsia) as BuildableFuchsiaApp?;
 
       expect(fuchsiaApp, null);
     }, overrides: overrides);
@@ -707,7 +700,7 @@ N: android=http://schemas.android.com/apk/res/android
 ''';
 
 class FakeOperatingSystemUtils extends Fake implements OperatingSystemUtils {
-  void Function(File, Directory) onUnzip;
+  void Function(File, Directory)? onUnzip;
 
   @override
   void unzip(File file, Directory targetDirectory) {
@@ -717,16 +710,16 @@ class FakeOperatingSystemUtils extends Fake implements OperatingSystemUtils {
 
 class FakeAndroidSdk extends Fake implements AndroidSdk {
   @override
-  bool platformToolsAvailable;
+  late bool platformToolsAvailable;
 
   @override
-  bool licensesAvailable;
+  late bool licensesAvailable;
 
   @override
-  AndroidSdkVersion latestVersion;
+  AndroidSdkVersion? latestVersion;
 }
 
 class FakeAndroidSdkVersion extends Fake implements AndroidSdkVersion {
   @override
-  String aaptPath;
+  late String aaptPath;
 }
diff --git a/packages/flutter_tools/test/general.shard/args_test.dart b/packages/flutter_tools/test/general.shard/args_test.dart
index 4725e37d2aa..683a4df7088 100644
--- a/packages/flutter_tools/test/general.shard/args_test.dart
+++ b/packages/flutter_tools/test/general.shard/args_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/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:flutter_tools/executable.dart' as executable;
@@ -111,7 +109,7 @@ void main() {
   });
 }
 
-void verifyCommandRunner(CommandRunner<Object> runner) {
+void verifyCommandRunner(CommandRunner<Object?> runner) {
   expect(runner.argParser, isNotNull, reason: '${runner.runtimeType} has no argParser');
   expect(runner.argParser.allowsAnything, isFalse, reason: '${runner.runtimeType} allows anything');
   expect(runner.argParser.allowTrailingOptions, isFalse, reason: '${runner.runtimeType} allows trailing options');
@@ -119,7 +117,7 @@ void verifyCommandRunner(CommandRunner<Object> runner) {
   runner.commands.values.forEach(verifyCommand);
 }
 
-void verifyCommand(Command<Object> runner) {
+void verifyCommand(Command<Object?> runner) {
   expect(runner.argParser, isNotNull, reason: 'command ${runner.name} has no argParser');
   verifyOptions(runner.name, runner.argParser.options.values);
 
@@ -161,7 +159,7 @@ const String _needHelp = "Every option must have help explaining what it does, e
 
 const String _header = ' Comment: ';
 
-void verifyOptions(String command, Iterable<Option> options) {
+void verifyOptions(String? command, Iterable<Option> options) {
   String target;
   if (command == null) {
     target = 'the global argument "';
@@ -191,10 +189,11 @@ void verifyOptions(String command, Iterable<Option> options) {
     if (option.defaultsTo != null) {
       expect(option.help, isNot(contains('Default')), reason: '${_header}Help for $target--${option.name}" mentions the default value but that is redundant with the defaultsTo option which is also specified (and preferred).');
 
-      if (option.allowedHelp != null) {
-        for (final String allowedValue in option.allowedHelp.keys) {
+      final Map<String, String>? allowedHelp = option.allowedHelp;
+      if (allowedHelp != null) {
+        for (final String allowedValue in allowedHelp.keys) {
           expect(
-            option.allowedHelp[allowedValue],
+            allowedHelp[allowedValue],
             isNot(anyOf(contains('default'), contains('Default'))),
             reason: '${_header}Help for $target--${option.name} $allowedValue" mentions the default value but that is redundant with the defaultsTo option which is also specified (and preferred).',
           );
@@ -202,7 +201,7 @@ void verifyOptions(String command, Iterable<Option> options) {
       }
     }
     expect(option.help, isNot(matches(_bannedArgumentReferencePatterns)), reason: '${_header}Help for $target--${option.name}" contains the string "--" in an unexpected way. If it\'s trying to mention another argument, it should be quoted, as in "--foo".');
-    for (final String line in option.help.split('\n')) {
+    for (final String line in option.help!.split('\n')) {
       if (!line.startsWith('    ')) {
         expect(line, isNot(contains('  ')), reason: '${_header}Help for $target--${option.name}" has excessive whitespace (check e.g. for double spaces after periods or round line breaks in the source).');
         expect(line, matches(_allowedTrailingPatterns), reason: '${_header}A line in the help for $target--${option.name}" does not end with the expected period that a full sentence should end with. (If the help ends with a URL, place it after a colon, don\'t leave a trailing period; if it\'s sample code, prefix the line with four spaces.)');
diff --git a/packages/flutter_tools/test/general.shard/emulator_test.dart b/packages/flutter_tools/test/general.shard/emulator_test.dart
index 0657786b9e3..24905d9c7fe 100644
--- a/packages/flutter_tools/test/general.shard/emulator_test.dart
+++ b/packages/flutter_tools/test/general.shard/emulator_test.dart
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
@@ -45,10 +45,10 @@ const FakeCommand kListEmulatorsCommand = FakeCommand(
 );
 
 void main() {
-  FakeProcessManager fakeProcessManager;
-  FakeAndroidSdk sdk;
-  FileSystem fileSystem;
-  Xcode xcode;
+  late FakeProcessManager fakeProcessManager;
+  late FakeAndroidSdk sdk;
+  late FileSystem fileSystem;
+  late Xcode xcode;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -110,7 +110,16 @@ void main() {
     });
 
     testWithoutContext('getEmulatorsById', () async {
-      final TestEmulatorManager testEmulatorManager = TestEmulatorManager(emulators);
+      final TestEmulatorManager testEmulatorManager = TestEmulatorManager(emulators,
+        logger: BufferLogger.test(),
+        processManager: fakeProcessManager,
+        androidWorkflow: AndroidWorkflow(
+          androidSdk: sdk,
+          featureFlags: TestFeatureFlags(),
+          operatingSystemUtils: FakeOperatingSystemUtils(),
+        ),
+        fileSystem: fileSystem,
+      );
 
       expect(await testEmulatorManager.getEmulatorsMatching('Nexus_5'), <Emulator>[emulator1]);
       expect(await testEmulatorManager.getEmulatorsMatching('Nexus_5X'), <Emulator>[emulator2]);
@@ -340,7 +349,12 @@ void main() {
 }
 
 class TestEmulatorManager extends EmulatorManager {
-  TestEmulatorManager(this.allEmulators);
+  TestEmulatorManager(this.allEmulators, {
+    required super.logger,
+    required super.processManager,
+    required super.androidWorkflow,
+    required super.fileSystem,
+  });
 
   final List<Emulator> allEmulators;
 
@@ -374,16 +388,16 @@ class FakeEmulator extends Emulator {
 
 class FakeAndroidSdk extends Fake implements AndroidSdk {
   @override
-  String avdManagerPath;
+  String? avdManagerPath;
 
   @override
-  String emulatorPath;
+  String? emulatorPath;
 
   @override
-  String adbPath;
+  String? adbPath;
 
   @override
-  String getAvdManagerPath() => avdManagerPath;
+  String? getAvdManagerPath() => avdManagerPath;
 
   @override
   String getAvdPath() => 'avd';
diff --git a/packages/flutter_tools/test/general.shard/hot_test.dart b/packages/flutter_tools/test/general.shard/hot_test.dart
index 4ffa42a1775..721032efb9e 100644
--- a/packages/flutter_tools/test/general.shard/hot_test.dart
+++ b/packages/flutter_tools/test/general.shard/hot_test.dart
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/application_package.dart';
@@ -21,7 +21,6 @@ import 'package:flutter_tools/src/resident_devtools_handler.dart';
 import 'package:flutter_tools/src/resident_runner.dart';
 import 'package:flutter_tools/src/run_hot.dart';
 import 'package:flutter_tools/src/vmservice.dart';
-import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 import 'package:test/fake.dart';
 import 'package:vm_service/vm_service.dart' as vm_service;
@@ -116,8 +115,8 @@ void main() {
 
   group('hotRestart', () {
     final FakeResidentCompiler residentCompiler = FakeResidentCompiler();
-    FileSystem fileSystem;
-    TestUsage testUsage;
+    late FileSystem fileSystem;
+    late TestUsage testUsage;
 
     setUp(() {
       fileSystem = MemoryFileSystem.test();
@@ -125,7 +124,7 @@ void main() {
     });
 
     group('fails to setup', () {
-      TestHotRunnerConfig failingTestingConfig;
+      late TestHotRunnerConfig failingTestingConfig;
       setUp(() {
         failingTestingConfig = TestHotRunnerConfig(
           successfulHotRestartSetup: false,
@@ -174,13 +173,13 @@ void main() {
           target: 'main.dart',
           devtoolsHandler: createNoOpHandler,
           reassembleHelper: (
-            List<FlutterDevice> flutterDevices,
-            Map<FlutterDevice, List<FlutterView>> viewCache,
-            void Function(String message) onSlow,
+            List<FlutterDevice?> flutterDevices,
+            Map<FlutterDevice?, List<FlutterView>> viewCache,
+            void Function(String message)? onSlow,
             String reloadMessage,
-            String fastReassembleClassName,
+            String? fastReassembleClassName,
           ) async => ReassembleResult(
-              <FlutterView, FlutterVmService>{null: null},
+              <FlutterView?, FlutterVmService?>{null: null},
               false,
               true,
             ),
@@ -198,7 +197,7 @@ void main() {
     });
 
     group('shutdown hook tests', () {
-      TestHotRunnerConfig shutdownTestingConfig;
+      late TestHotRunnerConfig shutdownTestingConfig;
 
       setUp(() {
         shutdownTestingConfig = TestHotRunnerConfig();
@@ -250,7 +249,7 @@ void main() {
     });
 
     group('successful hot restart', () {
-      TestHotRunnerConfig testingConfig;
+      late TestHotRunnerConfig testingConfig;
       setUp(() {
         testingConfig = TestHotRunnerConfig(
           successfulHotRestartSetup: true,
@@ -279,7 +278,7 @@ void main() {
           },
         );
 
-        (fakeFlutterDevice.devFS as FakeDevFs).baseUri = Uri.parse('file:///base_uri');
+        (fakeFlutterDevice.devFS! as FakeDevFs).baseUri = Uri.parse('file:///base_uri');
 
         final OperationResult result = await HotRunner(
           devices,
@@ -318,7 +317,7 @@ void main() {
     });
 
     group('successful hot reload', () {
-      TestHotRunnerConfig testingConfig;
+      late TestHotRunnerConfig testingConfig;
       setUp(() {
         testingConfig = TestHotRunnerConfig(
           successfulHotReloadSetup: true,
@@ -349,7 +348,7 @@ void main() {
           },
         );
 
-        (fakeFlutterDevice.devFS as FakeDevFs).baseUri = Uri.parse('file:///base_uri');
+        (fakeFlutterDevice.devFS! as FakeDevFs).baseUri = Uri.parse('file:///base_uri');
 
         final OperationResult result = await HotRunner(
           devices,
@@ -359,13 +358,13 @@ void main() {
           stopwatchFactory: fakeStopwatchFactory,
           reloadSourcesHelper: (
             HotRunner hotRunner,
-            List<FlutterDevice> flutterDevices,
-            bool pause,
+            List<FlutterDevice?> flutterDevices,
+            bool? pause,
             Map<String, dynamic> firstReloadDetails,
-            String targetPlatform,
-            String sdkName,
-            bool emulator,
-            String reason,
+            String? targetPlatform,
+            String? sdkName,
+            bool? emulator,
+            String? reason,
           ) async {
             firstReloadDetails['finalLibraryCount'] = 2;
             firstReloadDetails['receivedLibraryCount'] = 3;
@@ -374,13 +373,13 @@ void main() {
             return OperationResult.ok;
           },
           reassembleHelper: (
-            List<FlutterDevice> flutterDevices,
-            Map<FlutterDevice, List<FlutterView>> viewCache,
-            void Function(String message) onSlow,
+            List<FlutterDevice?> flutterDevices,
+            Map<FlutterDevice?, List<FlutterView>> viewCache,
+            void Function(String message)? onSlow,
             String reloadMessage,
-            String fastReassembleClassName,
+            String? fastReassembleClassName,
           ) async => ReassembleResult(
-              <FlutterView, FlutterVmService>{null: null},
+              <FlutterView?, FlutterVmService?>{null: null},
               false,
               true,
             ),
@@ -421,7 +420,7 @@ void main() {
     });
 
     group('hot restart that failed to sync dev fs', () {
-      TestHotRunnerConfig testingConfig;
+      late TestHotRunnerConfig testingConfig;
       setUp(() {
         testingConfig = TestHotRunnerConfig(
           successfulHotRestartSetup: true,
@@ -455,7 +454,7 @@ void main() {
     });
 
     group('hot reload that failed to sync dev fs', () {
-      TestHotRunnerConfig testingConfig;
+      late TestHotRunnerConfig testingConfig;
       setUp(() {
         testingConfig = TestHotRunnerConfig(
           successfulHotReloadSetup: true,
@@ -490,7 +489,7 @@ void main() {
   });
 
   group('hot attach', () {
-    FileSystem fileSystem;
+    late FileSystem fileSystem;
 
     setUp(() {
       fileSystem = MemoryFileSystem.test();
@@ -561,10 +560,10 @@ class FakeDevFs extends Fake implements DevFS {
   List<Uri> sources = <Uri>[];
 
   @override
-  DateTime lastCompiled;
+  DateTime? lastCompiled;
 
   @override
-  PackageConfig lastPackageConfig;
+  PackageConfig? lastPackageConfig;
 
   @override
   Set<String> assetPathsToEvict = <String>{};
@@ -573,7 +572,7 @@ class FakeDevFs extends Fake implements DevFS {
   Set<String> shaderPathsToEvict= <String>{};
 
   @override
-  Uri baseUri;
+  Uri? baseUri;
 }
 
 // Unfortunately Device, despite not being immutable, has an `operator ==`.
@@ -608,8 +607,8 @@ class FakeDevice extends Fake implements Device {
 
   @override
   Future<bool> stopApp(
-    covariant ApplicationPackage app, {
-    String userIdentifier,
+    covariant ApplicationPackage? app, {
+    String? userIdentifier,
   }) async {
     return true;
   }
@@ -624,7 +623,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   FakeFlutterDevice(this.device);
 
   bool stoppedEchoingDeviceLog = false;
-  Future<UpdateFSReport> Function() updateDevFSReportCallback;
+  late Future<UpdateFSReport> Function() updateDevFSReportCallback;
 
   @override
   final FakeDevice device;
@@ -635,36 +634,36 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   }
 
   @override
-  DevFS devFS = FakeDevFs();
+  DevFS? devFS = FakeDevFs();
 
   @override
   FlutterVmService get vmService => FakeFlutterVmService();
 
   @override
-  ResidentCompiler generator;
+  ResidentCompiler? generator;
 
   @override
   Future<UpdateFSReport> updateDevFS({
-    Uri mainUri,
-    String target,
-    AssetBundle bundle,
-    DateTime firstBuildTime,
+    Uri? mainUri,
+    String? target,
+    AssetBundle? bundle,
+    DateTime? firstBuildTime,
     bool bundleFirstUpload = false,
     bool bundleDirty = false,
     bool fullRestart = false,
-    String projectRootPath,
-    String pathToReload,
-    @required String dillOutputPath,
-    @required List<Uri> invalidatedFiles,
-    @required PackageConfig packageConfig,
+    String? projectRootPath,
+    String? pathToReload,
+    required String dillOutputPath,
+    required List<Uri> invalidatedFiles,
+    required PackageConfig packageConfig,
   }) => updateDevFSReportCallback();
 }
 
 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, developmentShaderCompiler: const FakeShaderCompiler());
 
@@ -673,17 +672,17 @@ 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 disableServiceAuthCodes = false,
     bool enableDds = true,
     bool cacheStartupProfile = false,
-    bool ipv6 = false,
-    int hostVmServicePort,
-    int ddsPort,
+    bool? ipv6 = false,
+    int? hostVmServicePort,
+    int? ddsPort,
     bool allowExistingDdsInstance = false,
   }) async {
     throw exception;
@@ -692,19 +691,19 @@ class TestFlutterDevice extends FlutterDevice {
 
 class TestHotRunnerConfig extends HotRunnerConfig {
   TestHotRunnerConfig({this.successfulHotRestartSetup, this.successfulHotReloadSetup});
-  bool successfulHotRestartSetup;
-  bool successfulHotReloadSetup;
+  bool? successfulHotRestartSetup;
+  bool? successfulHotReloadSetup;
   bool shutdownHookCalled = false;
   bool updateDevFSCompleteCalled = false;
 
   @override
-  Future<bool> setupHotRestart() async {
+  Future<bool?> setupHotRestart() async {
     assert(successfulHotRestartSetup != null, 'setupHotRestart is not expected to be called in this test.');
     return successfulHotRestartSetup;
   }
 
   @override
-  Future<bool> setupHotReload() async {
+  Future<bool?> setupHotReload() async {
     assert(successfulHotReloadSetup != null, 'setupHotReload is not expected to be called in this test.');
     return successfulHotReloadSetup;
   }
@@ -749,7 +748,7 @@ class FakeShaderCompiler implements DevelopmentShaderCompiler {
   const FakeShaderCompiler();
 
   @override
-  void configureCompiler(TargetPlatform platform, { @required bool enableImpeller }) { }
+  void configureCompiler(TargetPlatform? platform, { required bool enableImpeller }) { }
 
   @override
   Future<DevFSContent> recompileShader(DevFSContent inputShader) {
diff --git a/packages/flutter_tools/test/general.shard/resident_web_runner_cold_test.dart b/packages/flutter_tools/test/general.shard/resident_web_runner_cold_test.dart
index 88e7007562a..f4352e5780e 100644
--- a/packages/flutter_tools/test/general.shard/resident_web_runner_cold_test.dart
+++ b/packages/flutter_tools/test/general.shard/resident_web_runner_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 'dart:async';
 
 import 'package:file/memory.dart';
@@ -28,9 +26,9 @@ import '../src/context.dart';
 import '../src/test_build_system.dart';
 
 void main() {
-  FakeFlutterDevice mockFlutterDevice;
-  FakeWebDevFS mockWebDevFS;
-  FileSystem fileSystem;
+  late FakeFlutterDevice mockFlutterDevice;
+  late FakeWebDevFS mockWebDevFS;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -191,22 +189,22 @@ class FakeWebDevice extends Fake implements Device {
 
   @override
   Future<bool> stopApp(
-    covariant ApplicationPackage app, {
-    String userIdentifier,
+    covariant ApplicationPackage? app, {
+    String? userIdentifier,
   }) async {
     return true;
   }
 
   @override
   Future<LaunchResult> startApp(
-    covariant ApplicationPackage package, {
-    String mainPath,
-    String route,
-    DebuggingOptions debuggingOptions,
-    Map<String, dynamic> platformArgs,
+    covariant ApplicationPackage? package, {
+    String? mainPath,
+    String? route,
+    DebuggingOptions? debuggingOptions,
+    Map<String, dynamic>? platformArgs,
     bool prebuiltApplication = false,
     bool ipv6 = false,
-    String userIdentifier,
+    String? userIdentifier,
   }) async {
     return LaunchResult.succeeded();
   }
@@ -219,14 +217,14 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   final FakeWebDevice device;
 
 
-  DevFS _devFS;
+  DevFS? _devFS;
 
   @override
-  DevFS get devFS => _devFS;
+  DevFS? get devFS => _devFS;
 
   @override
-  set devFS(DevFS value) { }
+  set devFS(DevFS? value) { }
 
   @override
-  FlutterVmService vmService;
+  FlutterVmService? vmService;
 }
diff --git a/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart b/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart
index 8a492d3d480..8958d04e065 100644
--- a/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart
+++ b/packages/flutter_tools/test/general.shard/resident_web_runner_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';
@@ -32,7 +30,6 @@ import 'package:flutter_tools/src/resident_runner.dart';
 import 'package:flutter_tools/src/vmservice.dart';
 import 'package:flutter_tools/src/web/chrome.dart';
 import 'package:flutter_tools/src/web/web_device.dart';
-import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 import 'package:package_config/package_config_types.dart';
 import 'package:test/fake.dart';
@@ -90,20 +87,20 @@ const List<VmServiceExpectation> kAttachExpectations = <VmServiceExpectation>[
 ];
 
 void main() {
-  FakeDebugConnection debugConnection;
-  FakeChromeDevice chromeDevice;
-  FakeAppConnection appConnection;
-  FakeFlutterDevice flutterDevice;
-  FakeWebDevFS webDevFS;
-  FakeResidentCompiler residentCompiler;
-  FakeChromeConnection chromeConnection;
-  FakeChromeTab chromeTab;
-  FakeWebServerDevice webServerDevice;
-  FakeDevice mockDevice;
-  FakeVmServiceHost fakeVmServiceHost;
-  FileSystem fileSystem;
-  ProcessManager processManager;
-  TestUsage testUsage;
+  late FakeDebugConnection debugConnection;
+  late FakeChromeDevice chromeDevice;
+  late FakeAppConnection appConnection;
+  late FakeFlutterDevice flutterDevice;
+  late FakeWebDevFS webDevFS;
+  late FakeResidentCompiler residentCompiler;
+  late FakeChromeConnection chromeConnection;
+  late FakeChromeTab chromeTab;
+  late FakeWebServerDevice webServerDevice;
+  late FakeDevice mockDevice;
+  late FakeVmServiceHost fakeVmServiceHost;
+  late FileSystem fileSystem;
+  late ProcessManager processManager;
+  late TestUsage testUsage;
 
   setUp(() {
     testUsage = TestUsage();
@@ -114,6 +111,7 @@ void main() {
     appConnection = FakeAppConnection();
     webDevFS = FakeWebDevFS();
     residentCompiler = FakeResidentCompiler();
+    chromeDevice = FakeChromeDevice();
     chromeConnection = FakeChromeConnection();
     chromeTab = FakeChromeTab('index.html');
     webServerDevice = FakeWebServerDevice();
@@ -161,7 +159,7 @@ void main() {
 
     expect(profileResidentWebRunner.debuggingEnabled, false);
 
-    flutterDevice.device = FakeChromeDevice();
+    flutterDevice.device = chromeDevice;
 
     expect(residentWebRunner.debuggingEnabled, true);
     expect(fakeVmServiceHost.hasRemainingExpectations, false);
@@ -897,7 +895,7 @@ void main() {
     setupMocks();
     final Completer<DebugConnectionInfo> connectionInfoCompleter =
         Completer<DebugConnectionInfo>();
-    final Future<int> result = residentWebRunner.run(
+    final Future<int?> result = residentWebRunner.run(
       connectionInfoCompleter: connectionInfoCompleter,
     );
     await connectionInfoCompleter.future;
@@ -1192,7 +1190,9 @@ flutter:
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
     setupMocks();
 
-    webDevFS.exception = ChromeDebugException(<String, dynamic>{});
+    webDevFS.exception = ChromeDebugException(<String, Object?>{
+      'text': 'error',
+    });
 
     await expectLater(residentWebRunner.run, throwsToolExit());
     expect(fakeVmServiceHost.hasRemainingExpectations, false);
@@ -1232,9 +1232,9 @@ flutter:
 
 ResidentRunner setUpResidentRunner(
   FlutterDevice flutterDevice, {
-  Logger logger,
-  SystemClock systemClock,
-  DebuggingOptions debuggingOptions,
+  Logger? logger,
+  SystemClock? systemClock,
+  DebuggingOptions? debuggingOptions,
 }) {
   return ResidentWebRunner(
     flutterDevice,
@@ -1261,7 +1261,7 @@ class FakeWebServerDevice extends FakeDevice implements WebServerDevice {}
 // ignore: avoid_implementing_value_types
 class FakeDevice extends Fake implements Device {
   @override
-  String name;
+  String name = 'FakeDevice';
 
   int count = 0;
 
@@ -1269,26 +1269,26 @@ class FakeDevice extends Fake implements Device {
   Future<String> get sdkNameAndVersion async => 'SDK Name and Version';
 
   @override
-  DartDevelopmentService dds;
+  late DartDevelopmentService dds;
 
   @override
   Future<LaunchResult> startApp(
-    covariant ApplicationPackage package, {
-    String mainPath,
-    String route,
-    DebuggingOptions debuggingOptions,
-    Map<String, dynamic> platformArgs,
+    covariant ApplicationPackage? package, {
+    String? mainPath,
+    String? route,
+    DebuggingOptions? debuggingOptions,
+    Map<String, dynamic>? platformArgs,
     bool prebuiltApplication = false,
     bool ipv6 = false,
-    String userIdentifier,
+    String? userIdentifier,
   }) async {
     return LaunchResult.succeeded();
   }
 
   @override
   Future<bool> stopApp(
-    covariant ApplicationPackage app, {
-    String userIdentifier,
+    covariant ApplicationPackage? app, {
+    String? userIdentifier,
   }) async {
     if (count > 0) {
       throw StateError('stopApp called more than once.');
@@ -1299,14 +1299,14 @@ class FakeDevice extends Fake implements Device {
 }
 
 class FakeDebugConnection extends Fake implements DebugConnection {
-  FakeVmServiceHost Function() fakeVmServiceHost;
+  late FakeVmServiceHost Function() fakeVmServiceHost;
 
   @override
   vm_service.VmService get vmService =>
       fakeVmServiceHost.call().vmService.service;
 
   @override
-  String uri;
+  late String uri;
 
   final Completer<void> completer = Completer<void>();
   bool didClose = false;
@@ -1340,14 +1340,14 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
   @override
   Future<CompilerOutput> recompile(
     Uri mainUri,
-    List<Uri> invalidatedFiles, {
-    @required String outputPath,
-    @required PackageConfig packageConfig,
-    @required String projectRootPath,
-    @required FileSystem fs,
+    List<Uri>? invalidatedFiles, {
+    required String outputPath,
+    required PackageConfig packageConfig,
+    required FileSystem fs,
+    String? projectRootPath,
     bool suppressErrors = false,
     bool checkDartPluginRegistry = false,
-    File dartPluginRegistrant,
+    File? dartPluginRegistrant,
   }) async {
     return const CompilerOutput('foo.dill', 0, <Uri>[]);
   }
@@ -1368,11 +1368,11 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
 }
 
 class FakeWebDevFS extends Fake implements WebDevFS {
-  Object exception;
-  ConnectionResult result;
-  UpdateFSReport report;
+  Object? exception;
+  ConnectionResult? result;
+  late UpdateFSReport report;
 
-  Uri mainUri;
+  Uri? mainUri;
 
   @override
   List<Uri> sources = <Uri>[];
@@ -1381,10 +1381,10 @@ class FakeWebDevFS extends Fake implements WebDevFS {
   Uri baseUri = Uri.parse('http://localhost:12345');
 
   @override
-  DateTime lastCompiled = DateTime.now();
+  DateTime? lastCompiled = DateTime.now();
 
   @override
-  PackageConfig lastPackageConfig = PackageConfig.empty;
+  PackageConfig? lastPackageConfig = PackageConfig.empty;
 
   @override
   Future<Uri> create() async {
@@ -1393,33 +1393,33 @@ class FakeWebDevFS extends Fake implements WebDevFS {
 
   @override
   Future<UpdateFSReport> update({
-    @required Uri mainUri,
-    @required ResidentCompiler generator,
-    @required bool trackWidgetCreation,
-    @required String pathToReload,
-    @required List<Uri> invalidatedFiles,
-    @required PackageConfig packageConfig,
-    @required String dillOutputPath,
-    @required DevelopmentShaderCompiler shaderCompiler,
-    DevFSWriter devFSWriter,
-    String target,
-    AssetBundle bundle,
-    DateTime firstBuildTime,
+    required Uri mainUri,
+    required ResidentCompiler generator,
+    required bool trackWidgetCreation,
+    required String pathToReload,
+    required List<Uri> invalidatedFiles,
+    required PackageConfig packageConfig,
+    required String dillOutputPath,
+    required DevelopmentShaderCompiler shaderCompiler,
+    DevFSWriter? devFSWriter,
+    String? target,
+    AssetBundle? bundle,
+    DateTime? firstBuildTime,
     bool bundleFirstUpload = false,
     bool fullRestart = false,
-    String projectRootPath,
-    File dartPluginRegistrant,
+    String? projectRootPath,
+    File? dartPluginRegistrant,
   }) async {
     this.mainUri = mainUri;
     return report;
   }
 
   @override
-  Future<ConnectionResult> connect(bool useDebugExtension, {VmServiceFactory vmServiceFactory = createVmServiceDelegate}) async {
+  Future<ConnectionResult?> connect(bool useDebugExtension, {VmServiceFactory vmServiceFactory = createVmServiceDelegate}) async {
     if (exception != null) {
       assert(exception is Exception || exception is Error);
       // ignore: only_throw_errors, exception is either Error or Exception here.
-      throw exception;
+      throw exception!;
     }
     return result;
   }
@@ -1430,12 +1430,12 @@ class FakeChromeConnection extends Fake implements ChromeConnection {
 
   @override
   Future<ChromeTab> getTab(bool Function(ChromeTab tab) accept,
-      {Duration retryFor}) async {
+      {Duration? retryFor}) async {
     return tabs.firstWhere(accept);
   }
 
   @override
-  Future<List<ChromeTab>> getTabs({Duration retryFor}) async {
+  Future<List<ChromeTab>> getTabs({Duration? retryFor}) async {
     return tabs;
   }
 }
@@ -1448,7 +1448,7 @@ class FakeChromeTab extends Fake implements ChromeTab {
   final FakeWipConnection connection = FakeWipConnection();
 
   @override
-  Future<WipConnection> connect({Function/*?*/ onError}) async {
+  Future<WipConnection> connect({Function? onError}) async {
     return connection;
   }
 }
@@ -1491,9 +1491,9 @@ class TestChromiumLauncher implements ChromiumLauncher {
   Future<Chromium> launch(
     String url, {
     bool headless = false,
-    int debugPort,
+    int? debugPort,
     bool skipCheck = false,
-    Directory cacheDir,
+    Directory? cacheDir,
     List<String> webBrowserFlags = const <String>[],
   }) async {
     return currentCompleter.future;
@@ -1506,35 +1506,35 @@ class TestChromiumLauncher implements ChromiumLauncher {
 }
 
 class FakeFlutterDevice extends Fake implements FlutterDevice {
-  Uri testUri;
+  Uri? testUri;
   UpdateFSReport report = UpdateFSReport(
     success: true,
     invalidatedSourcesCount: 1,
   );
-  Exception reportError;
+  Exception? reportError;
 
   @override
-  ResidentCompiler generator;
+  ResidentCompiler? generator;
 
   @override
-  Stream<Uri> get observatoryUris => Stream<Uri>.value(testUri);
+  Stream<Uri?> get observatoryUris => Stream<Uri?>.value(testUri);
 
   @override
   DevelopmentShaderCompiler get developmentShaderCompiler => const FakeShaderCompiler();
 
   @override
-  FlutterVmService vmService;
+  FlutterVmService? vmService;
 
-  DevFS _devFS;
+  DevFS? _devFS;
 
   @override
-  DevFS get devFS => _devFS;
+  DevFS? get devFS => _devFS;
 
   @override
-  set devFS(DevFS value) {}
+  set devFS(DevFS? value) {}
 
   @override
-  Device device;
+  Device? device;
 
   @override
   Future<void> stopEchoingDeviceLog() async {}
@@ -1543,7 +1543,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   Future<void> initLogReader() async {}
 
   @override
-  Future<Uri> setupDevFS(String fsName, Directory rootDirectory) async {
+  Future<Uri?> setupDevFS(String fsName, Directory rootDirectory) async {
     return testUri;
   }
 
@@ -1553,38 +1553,38 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
 
   @override
   Future<void> connect({
-    ReloadSources reloadSources,
-    Restart restart,
-    CompileExpression compileExpression,
-    GetSkSLMethod getSkSLMethod,
-    PrintStructuredErrorLogMethod printStructuredErrorLogMethod,
-    int hostVmServicePort,
-    int ddsPort,
+    ReloadSources? reloadSources,
+    Restart? restart,
+    CompileExpression? compileExpression,
+    GetSkSLMethod? getSkSLMethod,
+    PrintStructuredErrorLogMethod? printStructuredErrorLogMethod,
+    int? hostVmServicePort,
+    int? ddsPort,
     bool disableServiceAuthCodes = false,
     bool enableDds = true,
     bool cacheStartupProfile = false,
-    @required bool allowExistingDdsInstance,
-    bool ipv6 = false,
+    required bool allowExistingDdsInstance,
+    bool? ipv6 = false,
   }) async {}
 
   @override
   Future<UpdateFSReport> updateDevFS({
-    Uri mainUri,
-    String target,
-    AssetBundle bundle,
-    DateTime firstBuildTime,
+    Uri? mainUri,
+    String? target,
+    AssetBundle? bundle,
+    DateTime? firstBuildTime,
     bool bundleFirstUpload = false,
     bool bundleDirty = false,
     bool fullRestart = false,
-    String projectRootPath,
-    String pathToReload,
-    String dillOutputPath,
-    List<Uri> invalidatedFiles,
-    PackageConfig packageConfig,
-    File dartPluginRegistrant,
+    String? projectRootPath,
+    String? pathToReload,
+    String? dillOutputPath,
+    List<Uri>? invalidatedFiles,
+    PackageConfig? packageConfig,
+    File? dartPluginRegistrant,
   }) async {
     if (reportError != null) {
-      throw reportError;
+      throw reportError!;
     }
     return report;
   }
@@ -1597,7 +1597,7 @@ class FakeShaderCompiler implements DevelopmentShaderCompiler {
   const FakeShaderCompiler();
 
   @override
-  void configureCompiler(TargetPlatform platform, { @required bool enableImpeller }) { }
+  void configureCompiler(TargetPlatform? platform, { required bool enableImpeller }) { }
 
   @override
   Future<DevFSContent> recompileShader(DevFSContent inputShader) {
diff --git a/packages/flutter_tools/test/general.shard/vmservice_test.dart b/packages/flutter_tools/test/general.shard/vmservice_test.dart
index fb4e87de7e9..837706b9c37 100644
--- a/packages/flutter_tools/test/general.shard/vmservice_test.dart
+++ b/packages/flutter_tools/test/general.shard/vmservice_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:fake_async/fake_async.dart';
@@ -62,7 +60,7 @@ final FakeVmServiceRequest listViewsRequest = FakeVmServiceRequest(
 
 void main() {
   testWithoutContext('VmService registers reloadSources', () async {
-    Future<void> reloadSources(String isolateId, { bool pause, bool force}) async {}
+    Future<void> reloadSources(String isolateId, { bool? pause, bool? force}) async {}
 
     final MockVMService mockVMService = MockVMService();
     await setUpVmService(
@@ -217,7 +215,7 @@ void main() {
       windows: false,
     ));
 
-    final Map<String, Object> rawRequest = json.decode(await completer.future) as Map<String, Object>;
+    final Map<String, Object?>? rawRequest = json.decode(await completer.future) as Map<String, Object?>?;
 
     expect(rawRequest, allOf(<Matcher>[
       containsPair('method', kSetAssetBundlePathMethod),
@@ -245,7 +243,7 @@ void main() {
       windows: true,
     ));
 
-    final Map<String, Object> rawRequest = json.decode(await completer.future) as Map<String, Object>;
+    final Map<String, Object?>? rawRequest = json.decode(await completer.future) as Map<String, Object?>?;
 
     expect(rawRequest, allOf(<Matcher>[
       containsPair('method', kSetAssetBundlePathMethod),
@@ -269,7 +267,7 @@ void main() {
       viewId: 'abc',
     ));
 
-    final Map<String, Object> rawRequest = json.decode(await completer.future) as Map<String, Object>;
+    final Map<String, Object?>? rawRequest = json.decode(await completer.future) as Map<String, Object?>?;
 
     expect(rawRequest, allOf(<Matcher>[
       containsPair('method', kGetSkSLsMethod),
@@ -291,7 +289,7 @@ void main() {
       uiIsolateId: 'def',
     ));
 
-    final Map<String, Object> rawRequest = json.decode(await completer.future) as Map<String, Object>;
+    final Map<String, Object?>? rawRequest = json.decode(await completer.future) as Map<String, Object?>?;
 
     expect(rawRequest, allOf(<Matcher>[
       containsPair('method', kFlushUIThreadTasksMethod),
@@ -469,7 +467,7 @@ void main() {
       ]
     );
 
-    final Map<String, Object> skSLs = await fakeVmServiceHost.vmService.getSkSLs(
+    final Map<String, Object?>? skSLs = await fakeVmServiceHost.vmService.getSkSLs(
       viewId: '1234',
     );
     expect(skSLs, isNull);
@@ -477,19 +475,19 @@ void main() {
     final List<FlutterView> views = await fakeVmServiceHost.vmService.getFlutterViews();
     expect(views, isEmpty);
 
-    final vm_service.Response screenshot = await fakeVmServiceHost.vmService.screenshot();
+    final vm_service.Response? screenshot = await fakeVmServiceHost.vmService.screenshot();
     expect(screenshot, isNull);
 
-    final vm_service.Response screenshotSkp = await fakeVmServiceHost.vmService.screenshotSkp();
+    final vm_service.Response? screenshotSkp = await fakeVmServiceHost.vmService.screenshotSkp();
     expect(screenshotSkp, isNull);
 
     // Checking that this doesn't throw.
     await fakeVmServiceHost.vmService.setTimelineFlags(<String>['test']);
 
-    final vm_service.Response timeline = await fakeVmServiceHost.vmService.getTimeline();
+    final vm_service.Response? timeline = await fakeVmServiceHost.vmService.getTimeline();
     expect(timeline, isNull);
 
-    final Map<String, Object> rasterStats =
+    final Map<String, Object?>? rasterStats =
       await fakeVmServiceHost.vmService.renderFrameWithRasterStats(viewId: '1', uiIsolateId: '12');
     expect(rasterStats, isNull);
 
@@ -505,7 +503,7 @@ void main() {
       ]
     );
 
-    final vm_service.Isolate isolate = await fakeVmServiceHost.vmService.getIsolateOrNull(
+    final vm_service.Isolate? isolate = await fakeVmServiceHost.vmService.getIsolateOrNull(
       'isolate/123',
     );
     expect(isolate, null);
@@ -535,7 +533,7 @@ void main() {
       ]
     );
 
-    final Map<String, Object> rasterStats =
+    final Map<String, Object?>? rasterStats =
       await fakeVmServiceHost.vmService.renderFrameWithRasterStats(viewId: 'view/1', uiIsolateId: 'isolate/123');
     expect(rasterStats, equals(response));
 
@@ -629,7 +627,7 @@ void main() {
         isolate.toJson()
           ..['id'] = '2'
           ..['extensionRPCs'] = <String>[otherExtensionName],
-      );
+      )!;
 
       final FlutterView fakeFlutterView2 = FlutterView(
         id: '2',
@@ -680,7 +678,7 @@ void main() {
 
     testWithoutContext('does not rethrow a sentinel exception if the initially queried flutter view disappears', () async {
       const String otherExtensionName = 'ext.flutter.test.otherExtension';
-      final vm_service.Isolate isolate2 = vm_service.Isolate.parse(
+      final vm_service.Isolate? isolate2 = vm_service.Isolate.parse(
         isolate.toJson()
           ..['id'] = '2'
           ..['extensionRPCs'] = <String>[otherExtensionName],
@@ -836,7 +834,7 @@ void main() {
 
   testUsingContext('WebSocket URL construction uses correct URI join primitives', () async {
     final Completer<String> completer = Completer<String>();
-    openChannelForTesting = (String url, {io.CompressionOptions compression, Logger logger}) async {
+    openChannelForTesting = (String url, {io.CompressionOptions compression = io.CompressionOptions.compressionDefault, required Logger logger}) async {
       completer.complete(url);
       throw Exception('');
     };
@@ -883,8 +881,8 @@ class FakeDevice extends Fake implements Device { }
 /// A [WebSocketConnector] that always throws an [io.SocketException].
 Future<io.WebSocket> failingWebSocketConnector(
   String url, {
-  io.CompressionOptions compression,
-  Logger logger,
+  io.CompressionOptions? compression,
+  Logger? logger,
 }) {
   throw const io.SocketException('Failed WebSocket connection');
 }
diff --git a/packages/flutter_tools/test/general.shard/web/devfs_web_test.dart b/packages/flutter_tools/test/general.shard/web/devfs_web_test.dart
index 70f5a805daa..6455221ec15 100644
--- a/packages/flutter_tools/test/general.shard/web/devfs_web_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/devfs_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 'dart:async';
 import 'dart:io' hide Directory, File;
 
@@ -23,7 +21,6 @@ import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:flutter_tools/src/isolated/devfs_web.dart';
 import 'package:flutter_tools/src/web/compile.dart';
 import 'package:logging/logging.dart' as logging;
-import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 import 'package:shelf/shelf.dart';
 import 'package:test/fake.dart';
@@ -41,14 +38,14 @@ const List<int> kTransparentImage = <int>[
 ];
 
 void main() {
-  Testbed testbed;
-  WebAssetServer webAssetServer;
-  ReleaseAssetServer releaseAssetServer;
-  Platform linux;
-  PackageConfig packages;
-  Platform windows;
-  FakeHttpServer httpServer;
-  BufferLogger logger;
+  late Testbed testbed;
+  late WebAssetServer webAssetServer;
+  late ReleaseAssetServer releaseAssetServer;
+  late Platform linux;
+  late PackageConfig packages;
+  late Platform windows;
+  late FakeHttpServer httpServer;
+  late BufferLogger logger;
 
   setUpAll(() async {
     packages = PackageConfig(<Package>[
@@ -66,15 +63,15 @@ void main() {
         httpServer,
         packages,
         InternetAddress.loopbackIPv4,
-        null,
-        null,
-        null,
+        <String, String>{},
+        <String, String>{},
+        NullSafetyMode.unsound,
       );
       releaseAssetServer = ReleaseAssetServer(
         globals.fs.file('main.dart').uri,
-        fileSystem: null, // ignore: avoid_redundant_argument_values
+        fileSystem: globals.fs,
         flutterRoot: null, // ignore: avoid_redundant_argument_values
-        platform: null, // ignore: avoid_redundant_argument_values
+        platform: FakePlatform(),
         webBuildDirectory: null, // ignore: avoid_redundant_argument_values
         basePath: null,
       );
@@ -183,10 +180,10 @@ void main() {
       }));
     webAssetServer.write(source, manifest, sourcemap, metadata);
 
-    final String merged = await webAssetServer.metadataContents('main_module.ddc_merged_metadata');
+    final String? merged = await webAssetServer.metadataContents('main_module.ddc_merged_metadata');
     expect(merged, equals(metadataContents));
 
-    final String single = await webAssetServer.metadataContents('foo.js.metadata');
+    final String? single = await webAssetServer.metadataContents('foo.js.metadata');
     expect(single, equals(metadataContents));
   }, overrides: <Type, Generator>{
     Platform: () => linux,
@@ -292,9 +289,9 @@ void main() {
       httpServer,
       packages,
       InternetAddress.loopbackIPv4,
-      null,
-      null,
-      null,
+      <String, String>{},
+      <String, String>{},
+      NullSafetyMode.unsound,
     );
 
     expect(webAssetServer.basePath, 'foo/bar');
@@ -311,9 +308,9 @@ void main() {
       httpServer,
       packages,
       InternetAddress.loopbackIPv4,
-      null,
-      null,
-      null,
+      <String, String>{},
+      <String, String>{},
+      NullSafetyMode.unsound,
     );
 
     // Defaults to "/" when there's no base element.
@@ -332,9 +329,9 @@ void main() {
         httpServer,
         packages,
         InternetAddress.loopbackIPv4,
-        null,
-        null,
-        null,
+        <String, String>{},
+        <String, String>{},
+        NullSafetyMode.unsound,
       ),
       throwsToolExit(),
     );
@@ -352,9 +349,9 @@ void main() {
         httpServer,
         packages,
         InternetAddress.loopbackIPv4,
-        null,
-        null,
-        null,
+        <String, String>{},
+        <String, String>{},
+        NullSafetyMode.unsound,
       ),
       throwsToolExit(),
     );
@@ -380,7 +377,7 @@ void main() {
 
     final Response response = await webAssetServer
       .handleRequest(Request('GET', Uri.parse('http://foobar/foo.js')));
-    final String etag = response.headers[HttpHeaders.etagHeader];
+    final String etag = response.headers[HttpHeaders.etagHeader]!;
 
     final Response cachedResponse = await webAssetServer
       .handleRequest(Request('GET', Uri.parse('http://foobar/foo.js'), headers: <String, String>{
@@ -622,14 +619,14 @@ void main() {
 
     final Response response = await webAssetServer
       .handleRequest(Request('GET', Uri.parse('http://foobar/assets/fooπ')));
-    final String etag = response.headers[HttpHeaders.etagHeader];
+    final String etag = response.headers[HttpHeaders.etagHeader]!;
 
     expect(etag.runes, everyElement(predicate((int char) => char < 255)));
   }));
 
   test('serves /packages/<package>/<path> files as if they were '
        'package:<package>/<path> uris', () => testbed.run(() async {
-    final Uri expectedUri = packages.resolve(
+    final Uri? expectedUri = packages.resolve(
         Uri.parse('package:flutter_tools/foo.dart'));
     final File source = globals.fs.file(globals.fs.path.fromUri(expectedUri))
       ..createSync(recursive: true)
@@ -691,13 +688,13 @@ void main() {
 
     final Uri uri = await webDevFS.create();
     webDevFS.webAssetServer.entrypointCacheDirectory = globals.fs.currentDirectory;
-    final String webPrecompiledSdk = globals.artifacts
+    final String webPrecompiledSdk = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledSdk).path;
-    final String webPrecompiledSdkSourcemaps = globals.artifacts
+    final String webPrecompiledSdkSourcemaps = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledSdkSourcemaps).path;
-    final String webPrecompiledCanvaskitSdk = globals.artifacts
+    final String webPrecompiledCanvaskitSdk = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledCanvaskitSdk).path;
-    final String webPrecompiledCanvaskitSdkSourcemaps = globals.artifacts
+    final String webPrecompiledCanvaskitSdkSourcemaps = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledCanvaskitSdkSourcemaps).path;
     globals.fs.currentDirectory
       .childDirectory('lib')
@@ -808,13 +805,13 @@ void main() {
       .childFile('web_entrypoint.dart')
       ..createSync(recursive: true)
       ..writeAsStringSync('GENERATED');
-    final String webPrecompiledSdk = globals.artifacts
+    final String webPrecompiledSdk = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledSoundSdk).path;
-    final String webPrecompiledSdkSourcemaps = globals.artifacts
+    final String webPrecompiledSdkSourcemaps = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledSoundSdkSourcemaps).path;
-    final String webPrecompiledCanvaskitSdk = globals.artifacts
+    final String webPrecompiledCanvaskitSdk = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledCanvaskitSoundSdk).path;
-    final String webPrecompiledCanvaskitSdkSourcemaps = globals.artifacts
+    final String webPrecompiledCanvaskitSdkSourcemaps = globals.artifacts!
       .getHostArtifact(HostArtifact.webPrecompiledCanvaskitSoundSdkSourcemaps).path;
     globals.fs.file(webPrecompiledSdk)
       ..createSync(recursive: true)
@@ -917,7 +914,7 @@ void main() {
         webDevFS.webAssetServer.dwds = FakeDwds(<AppConnection>[firstConnection, secondConnection]);
 
         int vmServiceFactoryInvocationCount = 0;
-        Future<vm_service.VmService> vmServiceFactory(Uri uri, {CompressionOptions compression, @required Logger logger}) {
+        Future<vm_service.VmService> vmServiceFactory(Uri uri, {CompressionOptions? compression, required Logger logger}) {
           if (vmServiceFactoryInvocationCount > 0) {
             fail('Called vmServiceFactory twice!');
           }
@@ -927,7 +924,7 @@ void main() {
             () => FakeVmService(),
           );
         }
-        return webDevFS.connect(false, vmServiceFactory: vmServiceFactory).then<void>((ConnectionResult firstConnectionResult) {
+        return webDevFS.connect(false, vmServiceFactory: vmServiceFactory).then<void>((ConnectionResult? firstConnectionResult) {
           return webDevFS.destroy();
         });
       });
@@ -1078,7 +1075,7 @@ void main() {
       false,
       Uri.base,
       null,
-      null,
+      NullSafetyMode.unsound,
       testMode: true);
 
     expect(webAssetServer.defaultResponseHeaders['x-frame-options'], null);
@@ -1179,20 +1176,20 @@ class FakeHttpServer extends Fake implements HttpServer {
 }
 
 class FakeResidentCompiler extends Fake implements ResidentCompiler {
-  CompilerOutput output;
+  CompilerOutput? output;
 
   @override
   void addFileSystemRoot(String root) { }
 
   @override
-  Future<CompilerOutput> recompile(Uri mainUri, List<Uri> invalidatedFiles, {
-    String outputPath,
-    PackageConfig packageConfig,
-    String projectRootPath,
-    FileSystem fs,
+  Future<CompilerOutput?> recompile(Uri mainUri, List<Uri>? invalidatedFiles, {
+    String? outputPath,
+    PackageConfig? packageConfig,
+    String? projectRootPath,
+    FileSystem? fs,
     bool suppressErrors = false,
     bool checkDartPluginRegistry = false,
-    File dartPluginRegistrant,
+    File? dartPluginRegistrant,
   }) async {
     return output;
   }
@@ -1202,7 +1199,7 @@ class FakeShaderCompiler implements DevelopmentShaderCompiler {
   const FakeShaderCompiler();
 
   @override
-  void configureCompiler(TargetPlatform platform, { @required bool enableImpeller }) { }
+  void configureCompiler(TargetPlatform? platform, { required bool enableImpeller }) { }
 
   @override
   Future<DevFSContent> recompileShader(DevFSContent inputShader) {
diff --git a/packages/flutter_tools/test/general.shard/web/golden_comparator_process_test.dart b/packages/flutter_tools/test/general.shard/web/golden_comparator_process_test.dart
index 300747bd2d2..3e653572b23 100644
--- a/packages/flutter_tools/test/general.shard/web/golden_comparator_process_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/golden_comparator_process_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/file_system.dart';
@@ -16,11 +14,11 @@ import '../../src/fakes.dart';
 
 void main() {
   group('Test that TestGoldenComparatorProcess', () {
-    File imageFile;
-    Uri goldenKey;
-    File imageFile2;
-    Uri goldenKey2;
-    FakeProcess Function(String) createFakeProcess;
+    late File imageFile;
+    late Uri goldenKey;
+    late File imageFile2;
+    late Uri goldenKey2;
+    late FakeProcess Function(String) createFakeProcess;
 
     setUpAll(() {
       imageFile = globals.fs.file('test_image_file');
diff --git a/packages/flutter_tools/test/general.shard/web/migrations/scrub_generated_plugin_registrant_test.dart b/packages/flutter_tools/test/general.shard/web/migrations/scrub_generated_plugin_registrant_test.dart
index 0fbd6d24260..0bc1066f5f7 100644
--- a/packages/flutter_tools/test/general.shard/web/migrations/scrub_generated_plugin_registrant_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/migrations/scrub_generated_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 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
@@ -22,13 +20,13 @@ void main() {
 
   group('ScrubGeneratedPluginRegistrant', () {
     // The files this migration deals with
-    File gitignore;
-    File registrant;
+    late File gitignore;
+    late File registrant;
 
     // Environment overrides
-    FileSystem fileSystem;
-    ProcessManager processManager;
-    BuildSystem buildSystem;
+    late FileSystem fileSystem;
+    late ProcessManager processManager;
+    late BuildSystem buildSystem;
 
     setUp(() {
       // Prepare environment overrides
diff --git a/packages/flutter_tools/test/general.shard/web/web_asset_server_test.dart b/packages/flutter_tools/test/general.shard/web/web_asset_server_test.dart
index 97fb1dd6375..df2c36094ec 100644
--- a/packages/flutter_tools/test/general.shard/web/web_asset_server_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/web_asset_server_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';
@@ -28,7 +26,7 @@ final Platform platform = FakePlatform(
 );
 
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
diff --git a/packages/flutter_tools/test/general.shard/web/web_expression_compiler_test.dart b/packages/flutter_tools/test/general.shard/web/web_expression_compiler_test.dart
index fc06eb8a903..d1e7c06daf1 100644
--- a/packages/flutter_tools/test/general.shard/web/web_expression_compiler_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/web_expression_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:dwds/dwds.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -14,7 +12,7 @@ import 'package:test/fake.dart';
 import '../../src/common.dart';
 
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   setUp(() {
     fileSystem = MemoryFileSystem.test();
@@ -27,7 +25,7 @@ void main() {
 
     final ExpressionCompilationResult result =
       await expressionCompiler.compileExpressionToJs(
-        null, null, 1, 1, null, null, null, null);
+        '', '', 1, 1, <String, String>{}, <String, String>{}, '', '');
 
     expectResult(result, false, 'a');
   });
@@ -39,7 +37,7 @@ void main() {
 
     final ExpressionCompilationResult result =
       await expressionCompiler.compileExpressionToJs(
-        null, null, 1, 1, null, null, null, null);
+        '', '', 1, 1, <String, String>{}, <String, String>{}, '', '');
 
     expectResult(result, true, 'Error: a');
   });
@@ -50,7 +48,7 @@ void main() {
 
     final ExpressionCompilationResult result =
       await expressionCompiler.compileExpressionToJs(
-        null, null, 1, 1, null, null, null, 'a');
+        '', '', 1, 1, <String, String>{}, <String, String>{}, '', 'a');
 
     expectResult(result, true, "InternalError: frontend server failed to compile 'a'");
   });
@@ -66,10 +64,10 @@ void expectResult(ExpressionCompilationResult result, bool isError, String value
 class FakeResidentCompiler extends Fake implements ResidentCompiler {
   FakeResidentCompiler(this.output);
 
-  final CompilerOutput output;
+  final CompilerOutput? output;
 
   @override
-  Future<CompilerOutput> compileExpressionToJs(
+  Future<CompilerOutput?> compileExpressionToJs(
     String libraryUri,
     int line,
     int column,