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// 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/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>();
/// The interface used to determine if a particular [Feature] is enabled.
///
/// The rest of the tools code should use this class instead of looking up
/// features directly. To facilitate rolls to google3 and other clients, all
/// flags should be provided with a default implementation here. Clients that
/// use this class should extent instead of implement, so that new flags are
/// picked up automatically.
abstract class FeatureFlags {
/// const constructor so that subclasses can be const.
const FeatureFlags();
/// Whether flutter desktop for linux is enabled.
bool get isLinuxEnabled => false;
/// Whether flutter desktop for macOS is enabled.
bool get isMacOSEnabled => false;
/// Whether flutter web is enabled.
bool get isWebEnabled => false;
/// Whether flutter desktop for Windows is enabled.
bool get isWindowsEnabled => false;
/// Whether android is enabled.
bool get isAndroidEnabled => true;
/// Whether iOS is enabled.
bool get isIOSEnabled => true;
/// Whether fuchsia is enabled.
bool get isFuchsiaEnabled => true;
/// Whether fast single widget reloads are enabled.
bool get isSingleWidgetReloadEnabled => false;
/// Whether the CFE experimental invalidation strategy is enabled.
bool get isExperimentalInvalidationStrategyEnabled => false;
/// Whether a particular feature is enabled for the current channel.
///
/// Prefer using one of the specific getters above instead of this API.
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 isSingleWidgetReloadEnabled => isEnabled(singleWidgetReload);
@override
bool get isExperimentalInvalidationStrategyEnabled => isEnabled(experimentalInvalidationStrategy);
@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,
flutterLinuxDesktopFeature,
flutterMacOSDesktopFeature,
flutterWindowsDesktopFeature,
singleWidgetReload,
flutterAndroidFeature,
flutterIOSFeature,
flutterFuchsiaFeature,
experimentalInvalidationStrategy,
];
/// The [Feature] for flutter web.
const Feature flutterWebFeature = Feature(
name: 'Flutter for web',
configSetting: 'enable-web',
environmentOverride: 'FLUTTER_WEB',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: flutterNext,
),
beta: FeatureChannelSetting(
available: true,
enabledByDefault: flutterNext,
),
stable: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: flutterNext,
),
);
/// The [Feature] for macOS desktop.
const Feature flutterMacOSDesktopFeature = Feature(
name: 'beta-quality support for desktop on macOS',
configSetting: 'enable-macos-desktop',
environmentOverride: 'FLUTTER_MACOS',
extraHelpText: flutterNext ?
'Newer beta versions are available on the beta channel.' : null,
master: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
beta: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
stable: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
);
/// The [Feature] for Linux desktop.
const Feature flutterLinuxDesktopFeature = Feature(
name: 'beta-quality support for desktop on Linux',
configSetting: 'enable-linux-desktop',
environmentOverride: 'FLUTTER_LINUX',
extraHelpText: flutterNext ?
'Newer beta versions are available on the beta channel.' : null,
master: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
beta: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
stable: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
);
/// The [Feature] for Windows desktop.
const Feature flutterWindowsDesktopFeature = Feature(
name: 'beta-quality support for desktop on Windows',
configSetting: 'enable-windows-desktop',
environmentOverride: 'FLUTTER_WINDOWS',
extraHelpText: flutterNext ?
'Newer beta versions are available on the beta channel.' : null,
master: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
beta: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
stable: FeatureChannelSetting(
available: flutterNext,
enabledByDefault: false,
),
);
/// The [Feature] for Android devices.
const Feature flutterAndroidFeature = Feature(
name: 'Flutter for Android',
configSetting: 'enable-android',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
beta: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
stable: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
);
/// The [Feature] for iOS devices.
const Feature flutterIOSFeature = Feature(
name: 'Flutter for iOS',
configSetting: 'enable-ios',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
beta: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
stable: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
);
/// The [Feature] for Fuchsia support.
const Feature flutterFuchsiaFeature = Feature(
name: 'Flutter for Fuchsia',
configSetting: 'enable-fuchsia',
environmentOverride: 'FLUTTER_FUCHSIA',
master: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
);
/// The fast hot reload feature for https://github.com/flutter/flutter/issues/61407.
const Feature singleWidgetReload = Feature(
name: 'Hot reload optimization for changes to class body of a single widget',
configSetting: 'single-widget-reload-optimization',
environmentOverride: 'FLUTTER_SINGLE_WIDGET_RELOAD',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
beta: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
stable: FeatureChannelSetting(
available: false,
enabledByDefault: false,
),
);
/// The CFE experimental invalidation strategy.
const Feature experimentalInvalidationStrategy = Feature(
name: 'Hot reload optimization that reduces incremental artifact size',
configSetting: 'experimental-invalidation-strategy',
environmentOverride: 'FLUTTER_CFE_EXPERIMENTAL_INVALIDATION',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
),
dev: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
beta: FeatureChannelSetting(
available: true,
enabledByDefault: false,
),
stable: FeatureChannelSetting(
available: false,
enabledByDefault: false,
),
);
/// A [Feature] is a process for conditionally enabling tool features.
///
/// All settings are optional, and if not provided will generally default to
/// a "safe" value, such as being off.
///
/// The top level feature settings can be provided to apply to all channels.
/// Otherwise, more specific settings take precedence over higher level
/// settings.
class Feature {
/// Creates a [Feature].
const Feature({
@required this.name,
this.environmentOverride,
this.configSetting,
this.extraHelpText,
this.master = const FeatureChannelSetting(),
this.dev = const FeatureChannelSetting(),
this.beta = const FeatureChannelSetting(),
this.stable = const FeatureChannelSetting(),
});
/// The user visible name for this feature.
final String name;
/// The settings for the master branch and other unknown channels.
final FeatureChannelSetting master;
/// The settings for the dev branch.
final FeatureChannelSetting dev;
/// The settings for the beta branch.
final FeatureChannelSetting beta;
/// The settings for the stable branch.
final FeatureChannelSetting stable;
/// The name of an environment variable that can override the setting.
///
/// The environment variable needs to be set to the value 'true'. This is
/// only intended for usage by CI and not as an advertised method to enable
/// a feature.
///
/// If not provided, defaults to `null` meaning there is no override.
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;
/// 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;
/// A help message for the `flutter config` command, or null if unsupported.
String generateHelpMessage() {
if (configSetting == null) {
return null;
}
final StringBuffer buffer = StringBuffer('Enable or disable $name. '
'This setting will take effect on ');
final List<String> channels = <String>[
if (master.available) 'master',
if (dev.available) 'dev',
if (beta.available) 'beta',
if (stable.available) 'stable',
];
if (channels.length == 1) {
buffer.write('the ${channels.single} channel.');
} else if (channels.length == 2) {
buffer.write('the ${channels.join(' and ')} channels.');
} else {
final String prefix = (channels.toList()
..removeLast()).join(', ');
buffer.write('the $prefix, and ${channels.last} channels.');
}
if (extraHelpText != null) {
buffer.write(' $extraHelpText');
}
return buffer.toString();
}
/// Retrieve the correct setting for the provided `channel`.
FeatureChannelSetting getSettingForChannel(String channel) {
switch (channel) {
case 'stable':
return stable;
case 'beta':
return beta;
case 'dev':
return dev;
case 'master':
default:
return master;
}
}
}
/// A description of the conditions to enable a feature for a particular channel.
class FeatureChannelSetting {
const FeatureChannelSetting({
this.available = false,
this.enabledByDefault = false,
});
/// Whether the feature is available on this channel.
///
/// If not provided, defaults to `false`. This implies that the feature
/// cannot be enabled even by the settings below.
final bool available;
/// Whether the feature is enabled by default.
///
/// If not provided, defaults to `false`.
final bool enabledByDefault;
}
const bool flutterNext = true;