## How to Contribute to Apollo

### Contributor License Agreements

You are welcome to contribute to the Apollo project. To contribute, please agree
with the [Apollo individual contributor license agreement]
(https://gist.githubusercontent.com/startcode/f5ccf8887bfc7727a0ae05bf0d601e30/raw/029a11300e987e34a29a9d247ac30caa7f6741a7/Apollo_Individual_Contributor_License_Agreement)
first.

### How do I start contributing

- You can follow the standard
  [Github approach](https://help.github.com/articles/using-pull-requests/) to
  contribute code. There is also a detailed how-to guide on _How to Create Pull
  Request_ in both [English](docs/howto/how_to_create_pull_request.md) and
  [Chinese](docs/howto/how_to_create_pull_request_cn.md).

- There are
  [issues with label "help wanted"](https://github.com/ApolloAuto/apollo/issues?utf8=%E2%9C%93&q=label%3A%22Type%3A+Help+wanted%22+)
  that are best to help you get started.
- If you are currently working on an issue, leave a message to let people know
  that you are working on it.
- Before sending in your pull request for
  [review](https://github.com/ApolloAuto/apollo/pulls), make sure your changes
  follow the guidelines mentioned below, namely: license, testing and coding
  style guidelines.

#### License

For each new file, please include a license at the top of the file.

- C++ code License example [util.h](modules/common/util/util.h);

- Python code License example
  [process.py](modules/tools/vehicle_calibration/process.py);

- Bash code License example [apollo_base.sh](scripts/apollo_base.sh);

#### Testing

Please include unit tests for the contributed code to prove that your code works
correctly, and make sure that your code does not break existing tests. Test
files are always named to end with `_test.cc`, and the test target names in the
BUILD file always end with `test`. Here is an example test file
[file_test.cc](cyber/common/file_test.cc).

You can use command `bash apollo.sh test` to run all unit tests.

#### Coding style

- **C/C++ coding style**: Apollo adopted the
  [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html).
  Make sure your code conforms to this style guide. You can use command
  `bash apollo.sh lint` to check if your code has any style issue.

- **Python coding style**: Apollo adopted the
  [Google Python Style Guide](https://google.github.io/styleguide/pyguide.html).
  You can use the [yapf](https://github.com/google/yapf) command
  `yapf -i --style='{based_on_style: google}' foo.py` to format a file foo.py.

- **Apollo best coding practice**: Please also refer to
  [Apollo Best Coding Practice](docs/technical_tutorial/apollo_best_coding_practice.md)
  for more coding practice disciplines.

- **BUILD file coding style** : you can use command
  `bash apollo.sh format path/to/BUILD/files` to format your BUILD files before
  you submit.

#### Documentation

If your code is not straightforward for other contributors to understand, it is
recommended to implement the code in a clear and efficient way, and provide
sufficient comments and documentation. Apollo uses doxygen to help generate
formatted API Document with command `bash apollo.sh doc generate`. To document
your code, please follow the guide:
[How to document code](docs/howto/how_to_document_code.md).

#### Commit Message

The first line of commit message should be a one-line summary of the change. A
paragraph can be added following the summary to clearly explain the details of
the change. If your code fixed an issue, add the issue number to your commit
message. An example of a good commit message is:

> Control: Replaced algorithm A with algorithm B in modules/control.
>
> Algorithm B is faster than A because it uses binary search. The runtime is
> reduced from O(N) to O(log(N)).
>
> Fixes #1234

### Before Creating Pull Request

After you finish your code and are ready to create a Pull Request, please make
sure your change don't break build/test/lint by running `bash apollo.sh check`,
which is equivalent to a combination of `bash apollo.sh build`,
`bash apollo.sh test` and `bash apollo.sh lint`.