Reland "[Android] Add mechanism for setting Android engine flags via Android manifest (take 2)" (#182522) ### Overview Re-lands https://github.com/flutter/flutter/pull/181632 which TLDR does the following: **Same old same old changes from original PR** - Refactors all engine flags recognized by the Flutter Android embedding (specifically those previously recognized by [`FlutterShellArgs`](https://github.com/flutter/flutter/blob/4f5478cce38d837e14b7a032a12500d3fc0f1310/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/FlutterShellArgs.java) and all of those used to initialize the engine in `FlutterLoader`) into a new class `FlutterEngineFlags` (`FlutterShellArgs` is kept for now to maintain backwards compatibility; see https://github.com/flutter/flutter/issues/182153 for details) - Adds the ability to set engine flags (that are recognized by `FlutterEngineFlags`) via the manifest - Adds warnings for developers that set engine flags via `Intent`s as this will be disabled as part of https://github.com/flutter/flutter/issues/180686. - Disallows debug/test only flags in release mode **New changes/fixes** > [!NOTE] > This re-land was required because when previously submitted, it caused b/483299339. I have confirmed that this bug has been fixed in this PR; see go/flutter-android-setting-flags-in-manifest-perf-comparison for A/B test results with the previous version of this PR (https://github.com/flutter/flutter/pull/181632) and commit https://github.com/flutter/flutter/pull/182522/commits/d6d4a07ede2052db4a861528ff05df8175bd9d37 of this PR. - [Critical change] To fix the bug caught by b/483299339, `--merged-platform-ui-thread` flag is added to `FlutterEngineFlag`s - [Behavior change, not critical] To avoid more bugs like b/483299339, `FlutterLoader` allows unrecognized flags specified by the command line or `Intent` extras to be used to initialize the engine for now (same behavior as before my original change but I plan to secure this in the future; see https://github.com/flutter/flutter/issues/182557) - [Small refactor] To speed up manifest argument processing time, `FlutterLoader` loops through all recognized `FlutterEngineFlag`s to check if they are present in an application's manifest versus looping through all metadata in an application's manifest and looking for recognized `FlutterEngineFlag`s (small improvement for apps with large manifests) - [Small refactor] To speed up command line argument processing time, `FlutterLoader` processes the `--aot-shared-library-name` flag in the same loop as the other flags, reducing the number of loops `ensureInitializationComplete` has to do (minimal improvement perf-wise but kept it in because it's more readable to me) ### Full description (Mostly copied from https://github.com/flutter/flutter/pull/181632) > [!NOTE] > This PR is based on conversation & feedback on go/flutter-android-harden-engine-shell-arguments. Adds a mechanism for setting Android engine flags via the manifest. If a flag is specified on the command line and in manifest metadata, the value specified on the command line will take precedence. Documentation is added on this mechanism Additionally, this PR removes the exposure of`--cache-sksl` command line flag as per [https://github.com/flutter/flutter/issues/140310#issuecomment-2708459007](https://www.google.com/url?q=https://github.com/flutter/flutter/issues/140310%23issuecomment-2708459007&sa=D&source=docs&ust=1761156167162464&usg=AOvVaw3a8ubXTtv3apknY2-P9dKe). Additionally, this PR adds documentation for the only two supported ways of setting engine flags moving forward -- via the command line or manifest. The `Intent` mechanism will be removed when https://github.com/flutter/flutter/issues/180686 is completed (intended to be a follow up to this PR). As the unit tests in this PR only cover setting flags via manifest in debug mode, I will follow up this PR with an integration test to test that flags are appropriately respected/ignored in release mode. See https://github.com/flutter/flutter/pull/178383 for my currently working but WIP draft. Part of https://github.com/flutter/flutter/issues/172553. # Follow up work: - [ ] **Migrate flags all un-migrated flags `FlutterEngineFlags`** https://github.com/flutter/flutter/issues/182852 - [ ] **Add integration test for this new added mechanism.** This will land as an immediate follow-up to this PR. WIP in https://github.com/flutter/flutter/pull/182241. - [ ] **Remove support for setting shell arguments via `Intent`.** This task will be a follow up to this work + the integration test landing, and will complete work for https://github.com/flutter/flutter/issues/172553. See https://github.com/flutter/flutter/issues/180686 for details. - [ ] **Only allow known engine flags to be passed to the engine.** This is more of a P2 but would be a nice additional security feature; see https://github.com/flutter/flutter/issues/182557. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md --------- Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> https://dart.googlesource.com/external/github.com/flutter/flutter/+/994b73f795ee7c5d0026d52c4b8be25334d673e4
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.