Contributing to Flutter ======================= [![Build Status](https://travis-ci.org/flutter/flutter.svg)](https://travis-ci.org/flutter/flutter) _See also: [Flutter's code of conduct](https://flutter.io/design-principles/#code-of-conduct)_ Things you will need -------------------- * Linux, Mac OS X, or Windows * git (used for source version control). * An IDE. We recommend [IntelliJ with the Flutter plugin](https://flutter.io/intellij-ide/). * An ssh client (used to authenticate with GitHub). * Python (used by some of our tools). * The Android platform tools (see [Issue #55](https://github.com/flutter/flutter/issues/55) about downloading the Android platform tools automatically). _If you're also working on the Flutter engine, you can use the copy of the Android platform tools in `.../engine/src/third_party/android_tools/sdk/platform-tools`._ - Mac: `brew install android-platform-tools` - Linux: `sudo apt-get install android-tools-adb` Getting the code and configuring your environment ------------------------------------------------- * Ensure all the dependencies described in the previous section, in particular git, ssh, and python are installed. Ensure that `adb` (from the Android platform tools) is in your path (e.g., that `which adb` prints sensible output). * Fork `https://github.com/flutter/flutter` into your own GitHub account. If you already have a fork, and are now installing a development environment on a new machine, make sure you've updated your fork so that you don't use stale configuration options from long ago. * If you haven't configured your machine with an SSH key that's known to github then follow the directions here: https://help.github.com/articles/generating-ssh-keys/. * `git clone git@github.com:/flutter.git` * `cd flutter` * `git remote add upstream git@github.com:flutter/flutter.git` (So that you fetch from the master repository, not your clone, when running `git fetch` et al.) * Add this repository's `bin` directory to your path. That will let you use the `flutter` command in this directory more easily. * Run `flutter update-packages` This will fetch all the Dart packages that Flutter depends on. You can replicate what this script does by running `pub get` in each directory that contains a `pubspec.yaml` file. * If you plan on using IntelliJ as your IDE, then also run `flutter ide-config --overwrite` to create all of the IntelliJ configuration files so you can open the main flutter directory as a project and run examples from within the IDE. Running the examples -------------------- To run an example, switch to that example's directory, and use `flutter run`. Make sure you have an emulator running, or a device connected over USB and debugging enabled on that device. * `cd examples/hello_world` * `flutter run` You can also specify a particular Dart file to run if you want to run an example that doesn't have a `lib/main.dart` file using the `-t` command-line option. For example, to run the `widgets/spinning_square.dart` example in the [examples/layers](examples/layers) directory on a connected Android device, from that directory you would run: `flutter run -t widgets/spinning_square.dart` When running code from the examples directory, any changes you make to the example code, as well as any changes to Dart code in the [packages/flutter](packages/flutter) directory and subdirectories, will automatically be picked when you relaunch the app. You can do the same for your own code by mimicking the `pubspec.yaml` files in the `examples` subdirectories. Running the analyzer -------------------- When editing Flutter code, it's important to check the code with the analyzer. There are two main ways to run it. In either case you will want to run `flutter update-packages` first, or you will get bogus error messages about core classes like Offset from `dart:ui`. For a one-off, use `flutter analyze --flutter-repo`. This uses the `analysis_options_repo.yaml` file at the root of the repository for its configuration. For continuous analysis, use `flutter analyze --flutter-repo --watch`. This uses normal `analysis_options.yaml` files, and they can differ from package to package. If you want to see how many members are missing dartdocs, you should use the first option, providing the additional command `--dartdocs`. If you omit the `--flutter-repo` option you may end up in a confusing state because that will assume you want to check a single package and the flutter repository has several packages. Running the tests ----------------- To automatically find all files named `_test.dart` inside a package's `test/` subdirectory, and run them inside the flutter shell as a test, use the `flutter test` command, e.g: * `cd examples/stocks` * `flutter test` Individual tests can also be run directly, e.g. `flutter test lib/my_app_test.dart` Flutter tests use [package:flutter_test](https://github.com/flutter/flutter/tree/master/packages/flutter_test) which provides flutter-specific extensions on top of [package:test](https://pub.dartlang.org/packages/test). `flutter test` runs tests inside the flutter shell. To debug tests in Observatory, use the `--start-paused` option to start the test in a paused state and wait for connection from a debugger. This option lets you set breakpoints before the test runs. To run all the tests for the entire Flutter repository, the same way that Travis runs them, run `dart dev/bots/test.dart`. If you've built [your own flutter engine](#working-on-the-engine-and-the-framework-at-the-same-time), you can pass `--local-engine` to change what flutter shell `flutter test` uses. For example, if you built an engine in the `out/host_debug_unopt` directory, you can pass `--local-engine=host_debug_unopt` to run the tests in that engine. Flutter tests are headless, you won't see any UI. You can use `print` to generate console output or you can interact with the DartVM via observatory at [http://localhost:8181/](http://localhost:8181/). Adding a test ------------- To add a test to the Flutter package, create a file whose name ends with `_test.dart` in the `packages/flutter/test` directory. The test should have a `main` function and use the `test` package. Working with flutter tools -------------------------- The flutter tool itself is built when you run `flutter` for the first time and each time you run `flutter upgrade`. If you want to alter and re-test the tool's behavior itself, locally commit your tool changes in git and the tool will be rebuilt from Dart sources in `packages/flutter_tools` the next time you run `flutter`. Alternatively, delete the `bin/cache/flutter_tools.snapshot` file. Doing so will force a rebuild of the tool from your local sources the next time you run `flutter`. flutter_tools' tests run inside the Dart command line VM rather than in the flutter shell. To run the tests, ensure that no devices are connected, then navigate to `flutter_tools` and execute: ```shell ../../bin/cache/dart-sdk/bin/pub run test -j1 ``` The pre-built flutter tool runs in release mode with the observatory off by default. To enable debugging mode and the observatory on the `flutter` tool, uncomment the `FLUTTER_TOOL_ARGS` line in the `bin/flutter` shell script. Contributing code ----------------- We gladly accept contributions via GitHub pull requests. Please peruse our [style guides](https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo) and [design principles](https://flutter.io/design-principles/) before working on anything non-trivial. These guidelines are intended to keep the code consistent and avoid common pitfalls. To start working on a patch: * `git fetch upstream` * `git checkout upstream/master -b name_of_your_branch` * Hack away. * `git commit -a -m ""` * `git push origin name_of_your_branch` To send us a pull request: * `git pull-request` (if you are using [Hub](http://github.com/github/hub/)) or go to `https://github.com/flutter/flutter` and click the "Compare & pull request" button Please make sure all your checkins have detailed commit messages explaining the patch. Once you've gotten an LGTM from a project maintainer and once your PR has received the green light from all our automated testing (Travis, Appveyor, etc), and once the tree is green (see the [design principles](https://flutter.io/design-principles/) document for more details), submit your changes to the `master` branch using one of the following methods: * Wait for one of the project maintainers to submit it for you. * Click the green "Merge pull request" button on the GitHub UI of your pull request (requires commit access) You must complete the [Contributor License Agreement](https://cla.developers.google.com/clas). You can do this online, and it only takes a minute. If you've never submitted code before, you must add your (or your organization's) name and contact info to the [AUTHORS](AUTHORS) file. We grant commit access to people who have gained our trust and demonstrated a commitment to Flutter. Tools for tracking and improving test coverage ---------------------------------------------- We strive for a high degree of test coverage for the Flutter framework. We use Coveralls to [track our test coverage](https://coveralls.io/github/flutter/flutter?branch=master). You can download our current coverage data from cloud storage and visualize it in Atom as follows: * Install [Atom](https://atom.io/). * Install the [lcov-info](https://atom.io/packages/lcov-info) package for Atom. * Open the `packages/flutter` folder in Atom. * Open a Dart file in the `lib` directory an type `Ctrl+Alt+C` to bring up the coverage data. If you don't see any coverage data, check that you have an `lcov.info` file in the `packages/flutter/coverage` directory. It should have been downloaded by the `flutter update-packages` command you ran previously. If you want to iterate quickly on improving test coverage, consider using this workflow: * Open a file and observe that some line is untested. * Write a test that exercises that line. * Run `flutter test --merge-coverage path/to/your/test_test.dart`. * After the test passes, observe that the line is now tested. This workflow merges the coverage data from this test run with the base coverage data downloaded by `flutter update-packages`. See [issue 4719](https://github.com/flutter/flutter/issues/4719) for ideas about how to improve this workflow. Working on the engine and the framework at the same time -------------------------------------------------------- You can work both with this repository (flutter.git) and the Flutter [engine repository](https://github.com/flutter/engine) at the same time using the following steps. 1. Follow the instructions above for creating a working copy of this repository. 2. Follow the [contributing instructions](https://github.com/flutter/engine/blob/master/CONTRIBUTING.md) in the engine repository to create a working copy of the engine. The instructions also explain how to use a locally-built engine instead of the one bundled with your installation of the Flutter framework. Making a breaking change to the engine -------------------------------------- If you make a breaking change to the engine, you'll need to land your change in a few steps: 1. Land your change in the engine repository. 2. Publish a new version of the engine that contains your change. See the engine's [release process](https://github.com/flutter/engine/wiki/Release-process) for instructions about how to publish a new version of the engine. Publishing a new version is important in order to not break folks using prebuilt binaries in their workflow (e.g., our customers). API docs for master branch -------------------------- To view the API docs for the `master` branch, visit https://master-docs-flutter-io.firebaseapp.com/. Those docs should be updated after a successful CI build of Flutter's `master` branch. (Looking for the API docs for our releases? Please visit https://docs.flutter.io.) Build infrastructure -------------------- We build and test Flutter on: - Travis ([details](.travis.yml)) - AppVeyor ([details](appveyor.yml)) - Chromebots (a.k.a. "recipes", [details](dev/bots/README.md)) - Devicelab (a.k.a. "cocoon", [details](dev/devicelab/README.md))