See also: Flutter's code of conduct
For an introduction to contributing to Flutter, see our contributor guide.
For specific instructions regarding building Flutter's engine, see Setting up the Engine development environment on our wiki. Those instructions are part of the broader onboarding instructions described in the contributing guide.
The Flutter engine follows Google style for the languages it uses:
GObject or C++ developers. For example, do not use STL collections or std::string. Exceptions:nullptr rather than NULL.#define; for internal constants use static constexpr instead.C/C++ and Objective-C/C++ files are formatted with clang-format, and GN files with gn format.
The testing policy for contributing to the flutter engine can be found at the Tree Hygiene Wiki. The summary is that all PR's to the engine should be tested or have an explicit test exemption.
Because the engine targets multiple platforms the testing infrastructure is fairly complicated. Here are some more resources to help guide writing tests:
//testing - This is where the run_tests.py script is located. All tests will have the ability to be executed with run_tests.py.//ci/builders - The JSON files that determine how tests are executed on CI.Tests will be executed on CI, but some tests will be executed before PR's can be merged (presubmit) and others after they have been merged (postsubmit). Ideally everything would be presubmit but tests that take up more resources are executed in postsubmit.
The Flutter engine uses Skia Gold for image comparison tests which fail if:
dir_contents_diff).Any untriaged failures will block presubmit and postsubmit tests.
# Configure host build for macOS arm64 debug. $ flutter/tools/gn --runtime-mode=debug --unoptimized --no-lto --mac-cpu=arm64 # Compile default targets (should cover all applicable run_tests.py requirements). $ ninja -j100 -C out/host_debug_unopt_arm64 # Run all cross-platform C++ tests for the debug build arm64 variant. $ cd flutter/testing $ ./run_tests.py --variant=host_debug_unopt_arm64 --type=engine`
| Name | run_tests.py type | Description |
|---|---|---|
| accessibility_unittests | engine | |
| client_wrapper_glfw_unittests | engine | |
| client_wrapper_unittests | engine | |
| common_cpp_core_unittests | engine | |
| common_cpp_unittests | engine | |
| dart_plugin_registrant_unittests | engine | |
| display_list_rendertests | engine | |
| display_list_unittests | engine | |
| embedder_a11y_unittests | engine | |
| embedder_proctable_unittests | engine | |
| embedder_unittests | engine | |
| felt | n/a | The test runner for flutter web. See //lib/web_ui |
| flow_unittests | engine | |
| flutter_tester | dart | Launcher for engine dart tests. |
| fml_arc_unittests | engine | |
| fml_unittests | engine | Unit tests for //fml |
| framework_common_unittests | engine(mac) | |
| gpu_surface_metal_unittests | engine(mac) | |
| impeller_dart_unittests | engine | |
| impeller_golden_tests | engine(mac) | Generates golden images for impeller (vulkan, metal, opengles). |
| impeller_unittests | engine | impeller unit tests and interactive tests |
| ios_test_flutter | objc | dynamic library of objc tests to be run with XCTest |
| jni_unittests | engine(not windows) | |
| no_dart_plugin_registrant_unittests | engine | |
| platform_view_android_delegate_unittests | engine(not windows) | |
| runtime_unittests | engine | |
| shell_unittests | engine(not windows) | |
| scenario_app | android | Integration and golden tests for Android, iOS |
| testing_unittests | engine | |
| tonic_unittests | engine | Unit tests for //third_party/tonic |
| txt_unittests | engine(linux) | |
| ui_unittests | engine |
Googlers contributing to Fuchsia should follow the additional steps at: go/flutter-fuchsia-pr-policy.