| commit | 6860b88a9fd713c02233259a3ea1bda5a8ac769a | [log] [tgz] |
|---|---|---|
| author | Loïc Sharma <737941+loic-sharma@users.noreply.github.com> | Mon Jul 14 17:02:16 2025 -0700 |
| committer | dart-internal-monorepo <dart-internal-monorepo@dart-ci-internal.iam.gserviceaccount.com> | Mon Jul 14 17:36:37 2025 -0700 |
| tree | d6cd43826b8b7157b0e04c98567f478faee1a770 | |
| parent | f2991025f29cbddf564a1e755ab1128e32555251 [diff] |
Reland "Add feature flags to the framework" (#171545) This relands https://github.com/flutter/flutter/pull/168437. The google3 fixes were landed in: https://github.com/flutter/flutter/pull/171547, https://critique.corp.google.com/cl/781275353, https://github.com/flutter/flutter/pull/171933. This PR is split into two commits: 1. d6253794e8982348c5c21cb63e8f6bf785664be6, code from https://github.com/flutter/flutter/pull/168437 without any changes 2. f35d29e4af630d2d4fdb0cda8686b6ff9f77227a, updates the PR to omit obvious types. Original PR description: ## Motivation We'd like to let users opt-in to experimental features so that they can give early feedback while we iterate on the feature. For example: Example feature flags: 1. Android sensitive content: https://github.com/flutter/flutter/pull/158473. When enabled, Flutter will tell Android when the view contains sensitive content like a password. 3. Desktop multi-window. When enabled, Flutter will use child windows to allow things like a context menu to "escape" outside of the current window. ### Use case Users will be able to turn on features by: * **Option 1**: Run `flutter config --enable-my-feature`. This enables the feature for all projects on the machine * **Option 2**: Add `enable-my-feature: true` in their `pubspec.yaml`, under the `flutter` section. This would enable the for a single project on the machine. Turning on a feature affects _both_ development-time (`flutter run`) and deployment-time (`flutter build x`). For example, I can `flutter build windows` to create an `.exe` with multi-window features enabled. ## How this works This adds a new [`runtimeId`](https://github.com/flutter/flutter/pull/168437/files#diff-0ded384225f19a4c34d43c7c11f7cb084ff3db947cfa82d8d52fc94c112bb2a7R243-R247) property to the tool's `Feature` class. If a feature is on and has a `runtimeId`, its `runtimeId` will be [stamped into the Dart application as a Dart define](https://github.com/flutter/flutter/pull/168437/files#diff-bd662448bdc2e6f50e47cd3b20b22b41a828561bce65cb4d54ea4f5011cc604eR293-R327). The framework uses this Dart define to [determine which features are enabled](https://github.com/flutter/flutter/pull/168437/files#diff-c8dbd5cd3103bc5be53c4ac5be8bdb9bf73e10cd5d8e4ac34e737fd1f8602d45). ### Multi-window example https://github.com/flutter/flutter/pull/168697 shows how this new feature flag system can be used to add a multi-window feature flag: 1. It adds a new [multi-window feature](https://github.com/flutter/flutter/pull/168697/files#diff-0ded384225f19a4c34d43c7c11f7cb084ff3db947cfa82d8d52fc94c112bb2a7R189-R198) to the Flutter tool. This can be turned on using `flutter config --enable-multi-window` or by putting `enable-multi-window: true` in an app's .pubspec, under the `flutter` section. 2. It adds a new [`isMultiWindowEnabled`](https://github.com/flutter/flutter/pull/168697/files#diff-c8dbd5cd3103bc5be53c4ac5be8bdb9bf73e10cd5d8e4ac34e737fd1f8602d45R7-R11) property to the framework. 4. The Material library can use this new property to determine whether it should create a new window. [Example](https://github.com/flutter/flutter/pull/168697/files#diff-2cbc1634ed6b61d61dfa090e7bfbbb7c60b74c8abc3a28df6f79eee691fd1b73). ## Limitations ### Tool and framework only For now, these feature flags are available only to the Flutter tool and Flutter framework. The flags are not automatically available to the embedder or the engine. For example, embedders need to configure their surfaces differently if Impeller is enabled. This configuration must happen before the Dart isolate is launched. As a result, the framework's feature flags is not a viable solution for this scenario for now. For these kinds of scenarios, we should continue to use platform-specific configuration like the `AndroidManifest.xml` or `Info.plist` files. This is a fixable limitation, we just need to invest in this plumbing :) ### Tree shaking Feature flags are not designed to help tree shaking. For example, you cannot conditionally import Dart code depending on the enabled feature flags. Code that is feature flagged off will still be imported into user's apps. https://dart.googlesource.com/external/github.com/flutter/flutter/+/6474b04e6dbab551ad7147f6da108695e3fbb36e
Monorepo is:
With depot_tools installed and on your path, create a directory for your monorepo checkout and run these commands to create a gclient solution in that directory:
mkdir monorepo cd monorepo gclient config --unmanaged https://dart.googlesource.com/monorepo gclient sync -D
This gives you a checkout in the monorepo directory that contains:
monorepo/ DEPS - the DEPS used for this gclient checkout commits.json - the pinned commits for Dart, flutter/engine, and flutter/flutter tools/ - scripts used to create monorepo DEPS engine/src/ - the flutter/buildroot repo flutter/ - the flutter/engine repo out/ - the build directory, where Flutter engine builds are created third_party/ - Flutter dependencies checked out by DEPS dart/ - the Dart SDK checkout. third_party - Dart dependencies, also used by Flutter flutter/ - the flutter/flutter repo
Flutter's instructions for building the engine are at Compiling the engine
They can be followed closely, with a few changes:
goma_ctl ensure_start is sufficient.Example build commands that work on linux:
MONOREPO_PATH=$PWD if [[ ! $PATH =~ (^|:)$MONOREPO_PATH/flutter/bin(:|$) ]]; then PATH=$MONOREPO_PATH/flutter/bin:$PATH fi export GOMA_DIR=$(dirname $(command -v gclient))/.cipd_bin goma_ctl ensure_start pushd engine/src flutter/tools/gn --goma --no-prebuilt-dart-sdk --unoptimized --full-dart-sdk autoninja -C out/host_debug_unopt popd
The Flutter commands used to build and run apps will use the locally built Flutter engine and Dart SDK, instead of the one downloaded by the Flutter tool, if the --local-engine option is provided.
For example, to build and run the Flutter spinning square sample on the web platform,
MONOREPO_PATH=$PWD cd flutter/examples/layers flutter --local-engine=host_debug_unopt \ -d chrome run widgets/spinning_square.dart cd $MONOREPO_PATH
To build for desktop, specify the desktop platform device in flutter run as -d macos or -d linux or -d windows. You may also need to run the command
flutter create --platforms=windows,macos,linux
on existing apps, such as sample apps. New apps created with flutter create already include these support files. Details of desktop support are at Desktop Support for Flutter
Tests in the Flutter source tree can be run with the flutter test command, run in the directory of a package containing tests. For example:
MONOREPO_PATH=$PWD cd flutter/packages/flutter flutter test --local-engine=host_debug_unopt cd $MONOREPO_PATH
Please file an issue or email the dart-engprod team with any problems with or questions about using monorepo.
We will update this documentation to address them.
flutter commands may download the engine and Dart SDK files for the configured channel, even though they will be using the local engine and its SDK.gclient sync needs to be run in an administrator session, because some installed dependencies create symlinks.