6 Commits

Author SHA1 Message Date
Loïc Sharma
8a12504a84
Recommend using Flutter feature flags over platform-specific configs (#172324)
See: https://github.com/flutter/flutter/issues/172183
2025-07-18 19:58:23 +00:00
Loïc Sharma
6474b04e6d
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.
2025-07-15 00:02:16 +00:00
Loïc Sharma
5154d16d1f
[tool] Make google3 have to override feature flags (#171933)
_⚠️ Landing this is blocked until: 1)
https://critique.corp.google.com/cl/781275353 lands and 2) google3 is
updated to add the new feature flag introduced in
https://github.com/flutter/flutter/pull/171903._

Currently, google3's `Google3Features` extends `FeatureFlags`. As a
result, google3 automatically gets the same feature flag values as in
Flutter.

This makes Flutter's feature flag values abstract, thereby requiring
that google3's `Google3Features` must explicitly set each feature flag's
value.

Discussion that motivated this change:
https://github.com/flutter/flutter/pull/171797
Internal CL: https://critique.corp.google.com/cl/781275353
Part of: https://github.com/flutter/flutter/issues/167668

## 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].

<!-- 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
2025-07-11 20:42:08 +00:00
auto-submit[bot]
c2cd71309f
Reverts "Add feature flags to the framework (#168437)" (#171542)
<!-- start_original_pr_link -->
Reverts: flutter/flutter#168437
<!-- end_original_pr_link -->
<!-- start_initiating_author -->
Initiated by: chingjun
<!-- end_initiating_author -->
<!-- start_revert_reason -->
Reason for reverting: broke internal customers
<!-- end_revert_reason -->
<!-- start_original_pr_author -->
Original PR Author: loic-sharma
<!-- end_original_pr_author -->

<!-- start_reviewers -->
Reviewed By: {bkonyi, justinmc, matanlurey}
<!-- end_reviewers -->

<!-- start_revert_body -->
This change reverts the following previous change:
## 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.
2. 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.
3. 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.

## 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].

<!-- 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

<!-- end_revert_body -->

Co-authored-by: auto-submit[bot] <flutter-engprod-team@google.com>
2025-07-02 20:31:18 +00:00
Loïc Sharma
c6f9e801b2
Add feature flags to the framework (#168437)
## 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.
2. 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.
3. 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.

## 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].

<!-- 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
2025-07-02 17:13:53 +00:00
Matan Lurey
ea010f3e44
Add an initial "Using feature flags" doc for the team. (#170767)
Closes https://github.com/flutter/flutter/issues/170456.

There are still some TODOs I'd like to address, but in follow-up PRs:

- Update the `# Framework` sub-sections after #168437 merges
- Add known limitations (i.e. embedder/engine)
- Add best practices (using a feature flag versus just using a
parameter, named constructor, etc)
2025-06-18 19:02:33 +00:00