blob: 1e9c303eef188709315e25153d49f6bb27af9b4a [file] [log] [blame]
// 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.
import 'base/context.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 custom devices are enabled.
bool get areCustomDevicesEnabled => false;
/// Whether WebAssembly compilation for Flutter Web is enabled.
bool get isFlutterWebWasmEnabled => false;
/// Whether animations are used in the command line interface.
bool get isCliAnimationEnabled => true;
/// 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);
/// All current Flutter feature flags.
const List<Feature> allFeatures = <Feature>[
/// All current Flutter feature flags that can be configured.
/// [Feature.configSetting] is not `null`.
Iterable<Feature> get allConfigurableFeatures => allFeatures.where((Feature feature) => feature.configSetting != null);
/// The [Feature] for flutter web.
const Feature flutterWebFeature = Feature.fullyEnabled(
name: 'Flutter for web',
configSetting: 'enable-web',
environmentOverride: 'FLUTTER_WEB',
/// The [Feature] for macOS desktop.
const Feature flutterMacOSDesktopFeature = Feature.fullyEnabled(
name: 'support for desktop on macOS',
configSetting: 'enable-macos-desktop',
environmentOverride: 'FLUTTER_MACOS',
/// The [Feature] for Linux desktop.
const Feature flutterLinuxDesktopFeature = Feature.fullyEnabled(
name: 'support for desktop on Linux',
configSetting: 'enable-linux-desktop',
environmentOverride: 'FLUTTER_LINUX',
/// The [Feature] for Windows desktop.
const Feature flutterWindowsDesktopFeature = Feature.fullyEnabled(
name: 'support for desktop on Windows',
configSetting: 'enable-windows-desktop',
environmentOverride: 'FLUTTER_WINDOWS',
/// The [Feature] for Android devices.
const Feature flutterAndroidFeature = Feature.fullyEnabled(
name: 'Flutter for Android',
configSetting: 'enable-android',
/// The [Feature] for iOS devices.
const Feature flutterIOSFeature = Feature.fullyEnabled(
name: 'Flutter for iOS',
configSetting: 'enable-ios',
/// The [Feature] for Fuchsia support.
const Feature flutterFuchsiaFeature = Feature(
name: 'Flutter for Fuchsia',
configSetting: 'enable-fuchsia',
environmentOverride: 'FLUTTER_FUCHSIA',
master: FeatureChannelSetting(
available: true,
const Feature flutterCustomDevicesFeature = Feature(
name: 'early support for custom device types',
configSetting: 'enable-custom-devices',
environmentOverride: 'FLUTTER_CUSTOM_DEVICES',
master: FeatureChannelSetting(
available: true,
beta: FeatureChannelSetting(
available: true,
stable: FeatureChannelSetting(
available: true,
/// Enabling WebAssembly compilation from `flutter build web`
const Feature flutterWebWasm = Feature(
name: 'WebAssembly compilation from flutter build web',
environmentOverride: 'FLUTTER_WEB_WASM',
master: FeatureChannelSetting(
available: true,
enabledByDefault: true,
/// The [Feature] for CLI animations.
/// The TERM environment variable set to "dumb" turns this off.
const Feature cliAnimation = Feature.fullyEnabled(
name: 'animations in the command line interface',
configSetting: 'cli-animations',
/// 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({
this.master = const FeatureChannelSetting(),
this.beta = const FeatureChannelSetting(),
this.stable = const FeatureChannelSetting()
/// Creates a [Feature] that is fully enabled across channels.
const Feature.fullyEnabled(
: master = const FeatureChannelSetting(
available: true,
enabledByDefault: true,
beta = const FeatureChannelSetting(
available: true,
enabledByDefault: true,
stable = const FeatureChannelSetting(
available: true,
enabledByDefault: true,
/// 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 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.');
final List<String> channels = <String>[
if (master.available) 'master',
if (beta.available) 'beta',
if (stable.available) 'stable',
// Add channel info for settings only on some channels.
if (channels.length == 1) {
buffer.write('\nThis setting applies only to the ${channels.single} channel.');
} else if (channels.length == 2) {
buffer.write('\nThis setting applies only to the ${channels.join(' and ')} 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 'master':
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;