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.
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?
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.
* Add Linux unit tests to plugin template
Adds an example native unit test to the plugin template for Linux,
matching the structure we use for our 1P plugin unit tests. Once these
have been added for all platforms+languages, they will be documented on
a new plugin development page to explain their use.
While ideally we would adjust the engine APIs first to allow for testing
the method call handler directly, it's unclear when we will have time
for that work, and for a complex plugin most of the testing wouldn't be
at that layer anyway, so having the structure in place with the
limitations documented is still a significant improvement over having
nothing in the template.
Part of https://github.com/flutter/flutter/issues/82458
* Add creation test
* Add integration tests
* Missing newlines
* test owner
* Typo
* Building shared C source code as part of the native build for platforms Android, iOS, Linux desktop, MacOS desktop, and Windows desktop.
* Sample code doing a synchronous FFI call.
* Sample code doing a long running synchronous FFI call on a helper isolate.
* Use of `package:ffigen` to generate the bindings.
