Pin the dependencies from dart-lang/native to a specific version during testing (rather than having them auto-upgrade during pub resolution). This will prevent tests using the template to start failing if a bad version is published to pub.
Closes: https://github.com/flutter/flutter/issues/137418
Also bumps dep in flutter_tools.
Reverts flutter/flutter#137191
Initiated by: camsim99
This change reverts the following previous change:
Original Description:
Adds support for Android 34 in the following ways:
- Bumps integration tests compile SDK versions 33 --> 34
- Bumps template compile SDK version 33 --> 34
- Also changes deprecated `compileSdkVersion` to `compileSdk`
Part of https://github.com/flutter/flutter/issues/134220
Adds support for Android 34 in the following ways:
- Bumps integration tests compile SDK versions 33 --> 34
- Bumps template compile SDK version 33 --> 34
- Also changes deprecated `compileSdkVersion` to `compileSdk`
Part of https://github.com/flutter/flutter/issues/134220
Fixes https://github.com/flutter/flutter/issues/130808. Short context is that the migration guide doesn't help when a user has a newer java version than 17, and this tells them how to fix the error in that situation.
This is an alternative to https://github.com/flutter/flutter/pull/131354, because I think it is a bad idea to introduce branching in how we handle this error with some specialized regexp.
Analyzer's dependency on autosnapshotting causes issues.
Because every version of integration_test from sdk depends on leak_tracker from hosted and autosnapshotting depends on leak_tracker from path, integration_test from sdk is forbidden.
So, because autosnapshotting depends on integration_test from sdk, version solving failed.
Relands #136851, which was rolled back in #137121
package:coverage has been rolled, so the breakages should be fixed.
Also, in this reland I've changed the `coverableLineCache` parameter to
be optional, which is safer.
## Description
This PR adds a `nonce` parameter to flutter.js' `loadEntrypoint` method.
When set, loadEntrypoint will add a `nonce` attribute to the `main.dart.js` script tag, which allows Flutter to run in environments slightly more restricted by CSP; those that don't add `'self'` as a valid source for `script-src`.
----
### CSP directive
After this change, the CSP directive for a Flutter Web index.html can be:
```
script-src 'nonce-YOUR_NONCE_VALUE' 'wasm-unsafe-eval';
font-src https://fonts.gstatic.com;
style-src 'nonce-YOUR_NONCE_VALUE';
```
When CSP is set via a `meta` tag (like in the test accompanying this change), and to use a service worker, the CSP needs an additional directive: [`worker-src 'self';`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/worker-src)
When CSP set via response headers, the CSP that applies to `flutter_service_worker.js` is determined by its response headers. See **Web Workers API > [Content security policy](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers#content_security_policy)** in MDN.)
----
### Initialization
If the CSP is set to disallow `script-src 'self'`, a nonce needs to also be passed to `loadEntrypoint`:
```javascript
_flutter.loader.loadEntrypoint({
nonce: 'SOME_NONCE',
onEntrypointLoaded: (engineInitializer) async {
const appRunner = await engineInitializer.initializeEngine({
nonce: 'SOME_NONCE',
});
appRunner.runApp();
},
});
```
(`nonce` shows twice for now, because the entrypoint loader script doesn't have direct access to the `initializeEngine` call.)
----
## Tests
* Added a smoke test to ensure an app configured as described above starts.
## Issues
* Fixes https://github.com/flutter/flutter/issues/126977
Reverts flutter/flutter#136880
Initiated by: camsim99
This change reverts the following previous change:
Original Description:
Since the original PR that supposedly enabled proguard, it was using the android proguard rules that disable optimizations. See initial PR in [0]
This PR changes the flutter gradle plugin to use the `proguard-android-optimize.txt` (instead of `proguard-android.txt`) which will enable optimizations/shrinking of platform code (i.e. java/kotlin).
For a simple flutter hello world this results in a 25% reduction in the resulting DEX file (`classes.dex` of the APK).
[0] f098de1fde
Fixes https://github.com/flutter/flutter/issues/136879
Since the original PR that supposedly enabled proguard, it was using the
android proguard rules that disable optimizations. See initial PR in [0]
This PR changes the flutter gradle plugin to use the
`proguard-android-optimize.txt` (instead of `proguard-android.txt`)
which will enable optimizations/shrinking of platform code (i.e.
java/kotlin).
For a simple flutter hello world this results in a 25% reduction in the
resulting DEX file (`classes.dex` of the APK).
Note for users:
For some users this may result in issues because their java/kotlin code is
now better optimized & tree shaken and thereby symbols may be no longer
available or being obfuscated.
To fix those issues it's best to craft precise proguard rules describing the
extra symbols that are needed by the app (see [1]). But it's also possible to
opt out entirely of optimizations by using the unoptimized proguard rules.
To add custom proguard rules or use the unoptimized android rules, one can
update `android/app/build.gradle`:
```
android {
...
buildTypes {
release {
...
+ proguardFiles(
+ // Not ideal: Disables optimizations by using unoptimized android rules.
+ getDefaultProguardFile("proguard-android.txt"),
+
+ // Better: Have precise keep rules to only keep things that are needed.
+ "custom-rules.pro",
+ )
}
}
}
```
[0] f098de1fde
[1] https://developer.android.com/build/shrink-code
Fixes https://github.com/flutter/flutter/issues/136879
Fixes https://github.com/flutter/flutter/issues/136698.
Alters how `throwToolExit` creates its matcher. This results is an improved description of the matcher.
The mismatch description isn't improved by this, but I writing an entirely custom matcher to fix this isn't ideal either. We can instead mitigate the issue by augmenting the `toString` implementation of `ToolExit` to include the exit code, if it is non-null.
With these changes, the first few lines of output from a test would look like this:
```
Expected: throws <Instance of 'ToolExit'> with `exitCode`: <42> and `message`: contains 'message'
Actual: <Closure: () => Never>
Which: threw ToolExit:<Exit code: 41232. Error: message>
```
Related to tracking issue:
- https://github.com/flutter/flutter/issues/128251
This PR sends analytic events for each of the doctor validators.
This PR below will need to land first in `dart-lang/tools` before this merges.
Extracts out _shouldWriteCodeSizeAnalysis and _writeCodeSizeAnalysis from the main buildMacOS function.
No tets changes sine this is a simple restructuring for readability and does not change any tool logic.
Reverts flutter/flutter#136851
Initiated by: CaseyHillers
This change reverts the following previous change:
Original Description:
One of the reasons gathering coverage information is expensive is that we have to force compile every function in the libraries we're interested in. Without this, functions that haven't been invoked (so haven't been compiled) won't have any line number information, so the coverage tool doesn't know which lines to add to the list of misses. In flutter's case, the test infra spawns many VMs, and each of these needs to recompile all those libraries.
To fix this, we need a way of skipping force compilation for libraries we've already seen in previous tests, without losing the information about which lines in each library are coverable. So I [added](https://github.com/dart-lang/coverage/pull/466) the `coverableLineCache` to `coverage.collect` in package:coverage v1.7.0. This cache starts out empty, but fills up with lists of all the lines that are coverable for every library as coverage is gathered. package:coverage can then tell the VM not to force compile any libraries in this cache (using `getSourceReport`'s `librariesAlreadyCompiled` param). So the first test suite will still have to compile everything, but subsequent test suites will be much faster.
This speeds up coverage collection significantly, for large test suites:
| Running flutter/packages/flutter tests... | Time | Overhead |
| --- | --- | --- |
| without coverage | 8:53 | - |
| with coverage | 20:25 | 130% |
| with `coverableLineCache` | 12:21 | 40% |
Bug: https://github.com/flutter/flutter/issues/100751
One of the reasons gathering coverage information is expensive is that we have to force compile every function in the libraries we're interested in. Without this, functions that haven't been invoked (so haven't been compiled) won't have any line number information, so the coverage tool doesn't know which lines to add to the list of misses. In flutter's case, the test infra spawns many VMs, and each of these needs to recompile all those libraries.
To fix this, we need a way of skipping force compilation for libraries we've already seen in previous tests, without losing the information about which lines in each library are coverable. So I [added](https://github.com/dart-lang/coverage/pull/466) the `coverableLineCache` to `coverage.collect` in package:coverage v1.7.0. This cache starts out empty, but fills up with lists of all the lines that are coverable for every library as coverage is gathered. package:coverage can then tell the VM not to force compile any libraries in this cache (using `getSourceReport`'s `librariesAlreadyCompiled` param). So the first test suite will still have to compile everything, but subsequent test suites will be much faster.
This speeds up coverage collection significantly, for large test suites:
| Running flutter/packages/flutter tests... | Time | Overhead |
| --- | --- | --- |
| without coverage | 8:53 | - |
| with coverage | 20:25 | 130% |
| with `coverableLineCache` | 12:21 | 40% |
Bug: https://github.com/flutter/flutter/issues/100751
Reverts flutter/flutter#135249
Initiated by: zanderso
This change reverts the following previous change:
Original Description:
Changes golden tests on CanvasKit to use Layer.toImage instead of browser APIs for screenshots. This brings it more in line with other platforms and should also fix some async timing bugs with tests.
The code with out the null assertion is legal as per the type signature, but will throw a runtime exception if the nullable value is null. To make this exception more explicit, the value must be null-checked before completing the completer with the value.
The analyzer will soon enforce such checks. See https://github.com/dart-lang/sdk/issues/53253.
Fixes https://github.com/flutter/flutter/issues/136775
This was added because the dispose method doesn't seem to be called - something must still have a reference to the application after shutdown.
Solution for https://github.com/flutter/flutter/issues/136582
Fixes https://github.com/flutter/flutter/issues/130277
This PR does two things:
1. introduce a hidden `flutter build _preview` command, that will build a debug windows desktop app and copy it into the SDK's binary cache. This command is only intended to be run during packaging.
2. introduce a new device type, called `PreviewDevice`, which relies on the prebuilt desktop debug app from step 1, copies it into the target app's assets build folder, and then hot reloads their dart code into it.
Fixes https://github.com/flutter/flutter/issues/134279.
Changes:
* Moves all tests of `--dart-define-from-file` behavior from `build_bundle_test.dart` and `assemble_test.dart` to `flutter_command_test.dart`.
* Deletes a duplicate test of malformed JSON detection behavior.
* Renames the `useDartDefineFromFileOption` method of `FlutterCommand` to `_usesDartDefineFromFileOption`. This 1) makes the name more consistent with the other `uses*Option` methods and 2) hides the method since it is not used outside of the file.
* Renames several tests to better articulate what is under test and what the expected result is.
* Adds a test for the case where a `.env` file with a malformed line is provided to `--dart-define-from-file`.
Adds support for a new --web-header option to flutter run.
Creates a workaround for https://github.com/flutter/flutter/issues/127902
This PR allows adding additional headers for the flutter run web server. This is useful to add headers like Cross-Origin-Embedder-Policy and Cross-Origin-Opener-Policy without the use of a proxy server. These headers are required enable advanced web features. This approach provides flexibility to the developer to make use of the feature as they see fit and is backward-compatible. One tradeoff is that it increases the surface area to support for future changes to the flutter web server.
https://github.com/flutter/flutter/issues/127902 is not fully addressed by this change. The solution for that task will be more opinionated. This PR creates a general-purpose workaround for anyone who needs a solution sooner while the bigger solution is developed.
Reverts flutter/flutter#136562
Initiated by: vashworth
This change reverts the following previous change:
Original Description:
Some of our tests in CI are triggering the `NSLocalNetworkUsageDescription` dialog when they're not supposed to (https://github.com/flutter/flutter/issues/129836) since it's disabled via flags (`--no-publish-port` for flutter/flutter and `--disable-vm-service-publication` for flutter/engine).
Normally, we inject `NSLocalNetworkUsageDescription` (and other bonjour settings) to the Info.plist during the project build for debug and profile mode since by default they will publish the VM Service port over mDNS.
To help diagnose the issue, though, this PR changes it so that we don't inject `NSLocalNetworkUsageDescription` (and other bonjour settings) when port publication is disabled since it shouldn't be needed. Hopefully, this will give us better error messages or cause the app to crash and end the test early (rather than timeout after 30 minutes).
Some of our tests in CI are triggering the `NSLocalNetworkUsageDescription` dialog when they're not supposed to (https://github.com/flutter/flutter/issues/129836) since it's disabled via flags (`--no-publish-port` for flutter/flutter and `--disable-vm-service-publication` for flutter/engine).
Normally, we inject `NSLocalNetworkUsageDescription` (and other bonjour settings) to the Info.plist during the project build for debug and profile mode since by default they will publish the VM Service port over mDNS.
To help diagnose the issue, though, this PR changes it so that we don't inject `NSLocalNetworkUsageDescription` (and other bonjour settings) when port publication is disabled since it shouldn't be needed. Hopefully, this will give us better error messages or cause the app to crash and end the test early (rather than timeout after 30 minutes).
Specifies that compatible Java range stated in warning when Java version is incompatible with our template AGP & Gradle versions notes an exclusive upper bound Java version. This was a bug from https://github.com/flutter/flutter/pull/131444, and I will file a CP request to stable once this lands.
The warning uses [`getJavaVersionFor`](b5c8fd11e4/packages/flutter_tools/lib/src/android/gradle_utils.dart (L606)), which returns an exclusive upper bound, which is why this fix is necessary.
This is the final change needed to address https://github.com/flutter/flutter/issues/133467
This allows us to use the platform dill that is built by the engine when compiling apps. This also fixes the `--local-web-sdk` flag when compiling to wasm (which previously didn't work without some serious tweaking of the engine build output).
Some upcoming engine changes will bind to a function provided by the emscripten JS wrapper around skwasm, rather than just the wasm module itself. This will make sure not to break the benchmarks when those engine changes land. See https://github.com/flutter/engine/pull/46388
Part of:
- https://github.com/flutter/flutter/issues/128251
Currently, when we want to use the analytics instance from `package:unified_analytics`, we are just grabbing it from globals. However, with the legacy analytics instance, there are some things we check to return a no-op version of the instance.. for example, if we are running on bots or a non standard branch, we use a no-op instance
This PR uses the same previous checks for the new analytics instance
* This is completely broken on the Impeller renderer, see: https://github.com/flutter/flutter/issues/135052
* Even on the Skia renderer, this gives a software rasterized screenshot which will absolutely look different from a native rendering screenshot.
I plan to remove this functionality from the engine.
This implements https://github.com/flutter/flutter/issues/132654#issuecomment-1738221257, namely:
Make `Chromium.close` more robust:
* Send `SIGTERM` and wait up to 5 seconds, if the process exited, great! Return from the function.
* If the process has not exited, then send a `SIGKILL`, which is a much firmer way to exit a process. Same as before, wait up to 5 seconds, if the process exited, great! Return from the function.
* If it still hasn't exited then give up trying to exit Chromium, just print a warning to the console and return from the function.
Bonus: a few nullability fixes and extra `-v` logging.
Fixes https://github.com/flutter/flutter/issues/132654
Resolves#128046.
Adds a services API that allows flutter app developers to write app code that determines `--flavor` the app was built with.
This is implemented by having the tool adding the value of `--flavor` to its list of dart environment declarations, which will be available to the app at run time. Specifically,`FLUTTER_APP_FLAVOR` is set. I chose this implementation for its simplicity. There is some precedent for this, but only for web ([example](cd2f3f5e78/packages/flutter_tools/lib/src/runner/flutter_command.dart (L1231))).
Support for FFI calls with `@Native external` functions through Native assets on Windows. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Windows.
Mainly follows the design of https://github.com/flutter/flutter/pull/134031.
Specifically for Windows in this PR is the logic for finding the compiler `cl.exe` and environment variables that contain the paths to the Windows headers `vcvars.bat` based on `vswhere.exe`.
Resolves#81831.
The PR improves the `config` command in below ways:
- Does not print the settings in usages or other options.
- Adds the `--list` flag to print the full settings list.
- Separates usages for settings and analytics.
- Prints the restart tip when clearing features.
So there appears to be a race situation between the flutter CLI and Xcode. In the CLI, we update the `CONFIGURATION_BUILD_DIR` in the Xcode build settings and then tell Xcode to install, launch, and debug the app. When Xcode installs the app, it should use the `CONFIGURATION_BUILD_DIR` to find the bundle. However, it appears that sometimes Xcode hasn't processed the change to the build settings before the install happens, which causes it to not be able to find the bundle.
Fixes https://github.com/flutter/flutter/issues/135442
---
Since it's a timing issue, there's not really a consistent way to test it.
I was able to confirm that it works, though, by using the following steps:
1. Create a flutter project
2. Open the project in Xcode
3. `flutter clean`
4. `flutter run --profile -v`
If I saw a print line `stderr: CONFIGURATION_BUILD_DIR: build/Debug-iphoneos`, that means it first found the old and incorrect `CONFIGURATION_BUILD_DIR` before updating to the the new, so I was able to confirm that it would wait until it updated.
Reland of #134031. (Reverted in #135069.) Contains the fix for b/301051367 together with cl/567233346.
Support for FFI calls with `@Native external` functions through Native assets on Linux. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Linux.
Mainly follows the design of https://github.com/flutter/flutter/pull/130494.
Some differences are:
* Linux does not support cross compiling or compiling for multiple architectures, so this has not been implemented.
* Linux has no add2app.
The assets copying is done in the install-phase of the CMake build of a flutter app.
CMake requires the native assets folder to exist, so we create it also when the feature is disabled or there are no assets.
### Tests
This PR adds new tests to cover the various use cases.
* packages/flutter_tools/test/general.shard/linux/native_assets_test.dart
* Unit tests the Linux-specific part of building native assets.
It also extends various existing tests:
* packages/flutter_tools/test/integration.shard/native_assets_test.dart
* Runs (incl hot reload/hot restart), builds, builds frameworks for Linux and flutter-tester.
Removes an ignore about overriding fields. Instead we just assign the value to the original field in the super class.
Related to https://github.com/dart-lang/language/issues/3332 (discovered during investigations into the violation of that lint).
This analytics event only records the value of the plist entry on
`build` commands. This will give an idea of the proportion of users who
are disabling Impeller when shipping apps.
Adds warning to `flutter create` command that checks if detected Java version is compatible with the template AGP and template Gradle versions. If a developer is building for Android and their Java version is incompatible with either the AGP or Gradle versions that Flutter currently supports by default for new Flutter projects, then
- a warning will show noting the incompatibility and
- steps will be shown to fix the issue, the recommended option being to configure a new compatible Java version given that Flutter knows we can support the template Gradle/AGP versions and updating them manually may be risky (feedback on this approach would be greatly appreciated!)
Given that the template AGP and Gradle versions are compatible, this PR assumes that the detected Java version may only conflict with one of the template AGP or Gradle versions because:
- the minimum Java version for a given AGP version is less than the maximum Java version compatible for the minimum Gradle version required for that AGP version (too low a Java version will fail AGP compatibility test, but not Gradle compatibility).
- the maximum Java version compatible with minimum Gradle version for a given AGP version is higher than minimum Java version required for that AGP version (too high a Java version will fail Gradle compatibility test, but not AGP compatibility test).
Fixes https://github.com/flutter/flutter/issues/130515 in the sense that `flutter create foo`; `cd foo`; `flutter run` should always be successful.
Reverts flutter/flutter#134031
context: b/301051367
Looked at the error message from the broken TAP target, but seems like the failure might be non trivial to resolve. Would it be okay if we revert this for now while it is being triaged?
This PR modifies the web build slightly to create an `AssetManifest.json`, that is a JSON(base64)-encoded version of the `AssetManifest.bin` file.
_(This should enable all browsers to download the file without any interference, and all servers to serve it with the correct headers.)_
It also modifies Flutter's `AssetManifest` class so it loads and uses said file `if (kIsWeb)`.
### Issues
* Fixes https://github.com/flutter/flutter/issues/124883
### Tests
* Unit tests added.
* Some tests that run on the Web needed to be informed of the new filename, but their behavior didn't have to change (binary contents are the same across all platforms).
* I've deployed a test app, so users affected by the BIN issue may take a look at the PR in action:
* https://dit-tests.web.app
## Description
This removes all of the comments that are of the form "so-and-so must not be null" or "so-and-so must be non-null" from the cases where those values are defines as non-nullable values.
This PR removes them from the library in the repo that don't have anything to do with the framework.
This was done by hand, since it really didn't lend itself to scripting, so it needs to be more than just spot-checked, I think. I was careful to leave any comment that referred to parameters that were nullable, but I may have missed some.
In addition to being no longer relevant after null safety has been made the default, these comments were largely fragile, in that it was easy for them to get out of date, and not be accurate anymore anyhow.
This did create a number of constructor comments which basically say "Creates a [Foo].", but I don't really know how to avoid that in a large scale change, since there's not much you can really say in a lot of cases. I think we might consider some leniency for constructors to the "Comment must be meaningful" style guidance (which we de facto have already, since there are a bunch of these).
## Related PRs
- https://github.com/flutter/flutter/pull/134984
- https://github.com/flutter/flutter/pull/134991
- https://github.com/flutter/flutter/pull/134992
- https://github.com/flutter/flutter/pull/134993
## Tests
- Documentation only change.
Support for FFI calls with `@Native external` functions through Native assets on Linux. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Linux.
Mainly follows the design of https://github.com/flutter/flutter/pull/130494.
Some differences are:
* Linux does not support cross compiling or compiling for multiple architectures, so this has not been implemented.
* Linux has no add2app.
The assets copying is done in the install-phase of the CMake build of a flutter app.
CMake requires the native assets folder to exist, so we create it also when the feature is disabled or there are no assets.
### Tests
This PR adds new tests to cover the various use cases.
* packages/flutter_tools/test/general.shard/linux/native_assets_test.dart
* Unit tests the Linux-specific part of building native assets.
It also extends various existing tests:
* packages/flutter_tools/test/integration.shard/native_assets_test.dart
* Runs (incl hot reload/hot restart), builds, builds frameworks for Linux and flutter-tester.
Speeds up the native assets target in the backend by
1. changing other targets `gen_dart_plugin_registrant` and
`release_unpack_ios` to do async I/O,
2. not reparsing the package config, and
3. not calling `dart pub deps --json` for 0 or 1 packages (fixed
package:native_assets_builder).
* https://github.com/flutter/flutter/issues/134427
```
[ +2 ms] native_assets: Starting due to {}
[ +2 ms] Skipping target: gen_localizations
[ +1 ms] gen_dart_plugin_registrant: Starting due to {InvalidatedReasonKind.inputChanged: The following inputs have updated contents: /Users/dacoharkes/flt/engine/flutter/examples/hello_world/.dart_tool/package_config_subset}
[ +33 ms] gen_dart_plugin_registrant: Complete
[ +107 ms] release_unpack_ios: Complete
[ +60 ms] Writing native_assets.yaml.
[ +7 ms] Writing /Users/dacoharkes/flt/engine/flutter/examples/hello_world/.dart_tool/flutter_build/be2692bbfbc0b9a27fcd2422d52354c6/native_assets.yaml done.
[ ] native_assets: Complete
```
->
```
[ +4 ms] native_assets: Starting due to {}
[ ] Skipping target: gen_localizations
[ +1 ms] gen_dart_plugin_registrant: Starting due to {InvalidatedReasonKind.inputChanged: The following inputs have updated contents: /Users/dacoharkes/flt/engine/flutter/examples/hello_world/.dart_tool/package_config_subset}
[ +31 ms] Writing native_assets.yaml.
[ +8 ms] Writing /Users/dacoharkes/flt/engine/flutter/examples/hello_world/.dart_tool/flutter_build/f9451a65a465bfab70d004e21d6cc1d6/native_assets.yaml done.
[ +1 ms] native_assets: Complete
```
## 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 `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.
<!-- Links -->
[Contributor Guide]:
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[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
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