[flutter_tools] split features into 2 libraries, migrate to null safety (#79603)

packages/flutter_tools/lib/src/context_runner.dart

@@ -40,6 +40,7 @@ import 'emulator.dart';
 import 'features.dart';
 import 'flutter_application_package.dart';
 import 'flutter_device_manager.dart';
+import 'flutter_features.dart';
 import 'fuchsia/fuchsia_device.dart' show FuchsiaDeviceTools;
 import 'fuchsia/fuchsia_sdk.dart' show FuchsiaSdk, FuchsiaArtifacts;
 import 'fuchsia/fuchsia_workflow.dart' show FuchsiaWorkflow, fuchsiaWorkflow;

packages/flutter_tools/lib/src/features.dart

@@ -2,19 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
-import 'package:meta/meta.dart';
-
-import 'base/config.dart';
 import 'base/context.dart';
-import 'base/platform.dart';
-import 'version.dart';
 
 /// The current [FeatureFlags] implementation.
 ///
 /// If not injected, a default implementation is provided.
-FeatureFlags get featureFlags => context.get<FeatureFlags>();
+FeatureFlags get featureFlags => context.get<FeatureFlags>()!;
 
 /// The interface used to determine if a particular [Feature] is enabled.
 ///
@@ -66,75 +59,6 @@ abstract class FeatureFlags {
   bool isEnabled(Feature feature) => false;
 }
 
-class FlutterFeatureFlags implements FeatureFlags {
-  FlutterFeatureFlags({
-    @required FlutterVersion flutterVersion,
-    @required Config config,
-    @required Platform platform,
-  }) : _flutterVersion = flutterVersion,
-       _config = config,
-       _platform = platform;
-
-  final FlutterVersion _flutterVersion;
-  final Config _config;
-  final Platform _platform;
-
-  @override
-  bool get isLinuxEnabled => isEnabled(flutterLinuxDesktopFeature);
-
-  @override
-  bool get isMacOSEnabled => isEnabled(flutterMacOSDesktopFeature);
-
-  @override
-  bool get isWebEnabled => isEnabled(flutterWebFeature);
-
-  @override
-  bool get isWindowsEnabled => isEnabled(flutterWindowsDesktopFeature);
-
-  @override
-  bool get isAndroidEnabled => isEnabled(flutterAndroidFeature);
-
-  @override
-  bool get isIOSEnabled => isEnabled(flutterIOSFeature);
-
-  @override
-  bool get isFuchsiaEnabled => isEnabled(flutterFuchsiaFeature);
-
-  @override
-  bool get areCustomDevicesEnabled => isEnabled(flutterCustomDevicesFeature);
-
-  @override
-  bool get isSingleWidgetReloadEnabled => isEnabled(singleWidgetReload);
-
-  @override
-  bool get isExperimentalInvalidationStrategyEnabled => isEnabled(experimentalInvalidationStrategy);
-
-  @override
-  bool get isWindowsUwpEnabled => isEnabled(windowsUwpEmbedding);
-
-  @override
-  bool isEnabled(Feature feature) {
-    final String currentChannel = _flutterVersion.channel;
-    final FeatureChannelSetting featureSetting = feature.getSettingForChannel(currentChannel);
-    if (!featureSetting.available) {
-      return false;
-    }
-    bool isEnabled = featureSetting.enabledByDefault;
-    if (feature.configSetting != null) {
-      final bool configOverride = _config.getValue(feature.configSetting) as bool;
-      if (configOverride != null) {
-        isEnabled = configOverride;
-      }
-    }
-    if (feature.environmentOverride != null) {
-      if (_platform.environment[feature.environmentOverride]?.toLowerCase() == 'true') {
-        isEnabled = true;
-      }
-    }
-    return isEnabled;
-  }
-}
-
 /// All current Flutter feature flags.
 const List<Feature> allFeatures = <Feature>[
   flutterWebFeature,
@@ -393,7 +317,7 @@ const Feature windowsUwpEmbedding = Feature(
 class Feature {
   /// Creates a [Feature].
   const Feature({
-    @required this.name,
+    required this.name,
     this.environmentOverride,
     this.configSetting,
     this.extraHelpText,
@@ -425,20 +349,20 @@ class Feature {
   /// a feature.
   ///
   /// If not provided, defaults to `null` meaning there is no override.
-  final String environmentOverride;
+  final String? environmentOverride;
 
   /// The name of a setting that can be used to enable this feature.
   ///
   /// If not provided, defaults to `null` meaning there is no config setting.
-  final String configSetting;
+  final String? configSetting;
 
   /// Additional text to add to the end of the help message.
   ///
   /// If not provided, defaults to `null` meaning there is no additional text.
-  final String extraHelpText;
+  final String? extraHelpText;
 
   /// A help message for the `flutter config` command, or null if unsupported.
-  String generateHelpMessage() {
+  String? generateHelpMessage() {
     if (configSetting == null) {
       return null;
     }

packages/flutter_tools/lib/src/flutter_features.dart

@@ -0,0 +1,81 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.8
+
+import 'package:meta/meta.dart';
+
+import 'base/config.dart';
+import 'base/platform.dart';
+import 'features.dart';
+import 'version.dart';
+
+class FlutterFeatureFlags implements FeatureFlags {
+  FlutterFeatureFlags({
+    @required FlutterVersion flutterVersion,
+    @required Config config,
+    @required Platform platform,
+  }) : _flutterVersion = flutterVersion,
+       _config = config,
+       _platform = platform;
+
+  final FlutterVersion _flutterVersion;
+  final Config _config;
+  final Platform _platform;
+
+  @override
+  bool get isLinuxEnabled => isEnabled(flutterLinuxDesktopFeature);
+
+  @override
+  bool get isMacOSEnabled => isEnabled(flutterMacOSDesktopFeature);
+
+  @override
+  bool get isWebEnabled => isEnabled(flutterWebFeature);
+
+  @override
+  bool get isWindowsEnabled => isEnabled(flutterWindowsDesktopFeature);
+
+  @override
+  bool get isAndroidEnabled => isEnabled(flutterAndroidFeature);
+
+  @override
+  bool get isIOSEnabled => isEnabled(flutterIOSFeature);
+
+  @override
+  bool get isFuchsiaEnabled => isEnabled(flutterFuchsiaFeature);
+
+  @override
+  bool get areCustomDevicesEnabled => isEnabled(flutterCustomDevicesFeature);
+
+  @override
+  bool get isSingleWidgetReloadEnabled => isEnabled(singleWidgetReload);
+
+  @override
+  bool get isExperimentalInvalidationStrategyEnabled => isEnabled(experimentalInvalidationStrategy);
+
+  @override
+  bool get isWindowsUwpEnabled => isEnabled(windowsUwpEmbedding);
+
+  @override
+  bool isEnabled(Feature feature) {
+    final String currentChannel = _flutterVersion.channel;
+    final FeatureChannelSetting featureSetting = feature.getSettingForChannel(currentChannel);
+    if (!featureSetting.available) {
+      return false;
+    }
+    bool isEnabled = featureSetting.enabledByDefault;
+    if (feature.configSetting != null) {
+      final bool configOverride = _config.getValue(feature.configSetting) as bool;
+      if (configOverride != null) {
+        isEnabled = configOverride;
+      }
+    }
+    if (feature.environmentOverride != null) {
+      if (_platform.environment[feature.environmentOverride]?.toLowerCase() == 'true') {
+        isEnabled = true;
+      }
+    }
+    return isEnabled;
+  }
+}

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

@@ -7,6 +7,7 @@
 import 'package:flutter_tools/src/base/config.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/features.dart';
+import 'package:flutter_tools/src/flutter_features.dart';
 
 import '../src/common.dart';
 import '../src/fakes.dart';