mediapipe/CONTRIBUTING.md

# Contributing guidelines

## Pull Request Checklist

Before sending your pull requests, make sure you followed this list.

- Read [contributing guidelines](CONTRIBUTING.md).
- Read [Code of Conduct](CODE_OF_CONDUCT.md).
- Ensure you have signed the [Contributor License Agreement (CLA)](https://cla.developers.google.com/).
- Check if my changes are consistent with the [guidelines](https://github.com/google/mediapipe/blob/master/CONTRIBUTING.md#general-guidelines-and-philosophy-for-contribution).
- Changes are consistent with the [Coding Style](https://github.com/google/mediapipe/blob/master/CONTRIBUTING.md#c-coding-style).
- Run [Unit Tests](https://github.com/google/mediapipe/blob/master/CONTRIBUTING.md#running-unit-tests).

## How to become a contributor and submit your own code

### Contributor License Agreements

We'd love to accept your patches! Before we can take them, we have to jump a couple of legal hurdles.

Please fill out either the individual or corporate Contributor License Agreement (CLA).

  * If you are an individual writing original source code and you're sure you own the intellectual property, then you'll need to sign an [individual CLA](https://code.google.com/legal/individual-cla-v1.0.html).
  * If you work for a company that wants to allow you to contribute your work, then you'll need to sign a [corporate CLA](https://code.google.com/legal/corporate-cla-v1.0.html).

Follow either of the two links above to access the appropriate CLA and instructions for how to sign and return it. Once we receive it, we'll be able to accept your pull requests.

***NOTE***: Only original source code from you and other people that have signed the CLA can be accepted into the main repository.

### Contributing code

If you have improvements to MediaPipe, send us your pull requests! For those
just getting started, GitHub has a [howto](https://help.github.com/articles/using-pull-requests/).

MediaPipe team members will be assigned to review your pull requests. Once the
pull requests are approved and pass continuous integration checks, a MediaPipe
team member will apply `ready to pull` label to your change. This means we are
working on getting your pull request submitted to our internal repository. After
the change has been submitted internally, your pull request will be merged
automatically on GitHub.

If you want to contribute but you're not sure where to start, take a look at the
[issues with the "contributions welcome" label](https://github.com/google/mediapipe/labels/stat%3Acontributions%20welcome).
These are issues that we believe are particularly well suited for outside
contributions, often because we probably won't get to them right now. If you
decide to start on an issue, leave a comment so that other people know that
you're working on it. If you want to help out, but not alone, use the issue
comment thread to coordinate.

### Contribution guidelines and standards

Before sending your pull request for
[review](https://github.com/google/mediapipe/pulls),
make sure your changes are consistent with the guidelines and follow the
MediaPipe coding style.

#### General guidelines and philosophy for contribution

*   Include unit tests when you contribute new features, as they help to a)
    prove that your code works correctly, and b) guard against future breaking
    changes to lower the maintenance cost.
*   Bug fixes also generally require unit tests, because the presence of bugs
    usually indicates insufficient test coverage.
*   Keep API compatibility in mind when you change code in MediaPipe framework
    e.g., code in
    [mediapipe/framework](https://github.com/google/mediapipe/tree/master/mediapipe/framework)
    and
    [mediapipe/calculators](https://github.com/google/mediapipe/tree/master/mediapipe/calculators).
    Once MediaPipe has reached version 1 and we will not make
    non-backward-compatible API changes without a major release. Reviewers of
    your pull request will comment on any API compatibility issues.
*   When you contribute a new feature to MediaPipe, the maintenance burden is
    (by default) transferred to the MediaPipe team. This means that benefit of
    the contribution must be compared against the cost of maintaining the
    feature.
*   Full new features (e.g., a new op implementing a cutting-edge algorithm)
    typically will live in
    [mediapipe/addons](https://github.com/google/mediapipe/addons) to get some
    airtime before decision is made regarding whether they are to be migrated to
    the core.

#### License

Include a license at the top of new files.

* [C/C++ license example](https://github.com/google/mediapipe/blob/master/mediapipe/framework/calculator_base.cc#L1)
* [Java license example](https://github.com/google/mediapipe/blob/master/mediapipe/java/com/google/mediapipe/components/CameraHelper.java)

Bazel BUILD files also need to include a license section, e.g.,
[BUILD example](https://github.com/google/mediapipe/blob/master/mediapipe/framework/BUILD#L61).

#### C++ coding style

Changes to MediaPipe C++ code should conform to
[Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html).

Use `clang-tidy` to check your C/C++ changes. To install `clang-tidy` on ubuntu:16.04, do:

```bash
apt-get install -y clang-tidy
```

You can check a C/C++ file by doing:


```bash
clang-format <my_cc_file> --style=google > /tmp/my_cc_file.cc
diff <my_cc_file> /tmp/my_cc_file.cc
```

#### Coding style for other languages

* [Google Java Style Guide](https://google.github.io/styleguide/javaguide.html)
* [Google JavaScript Style Guide](https://google.github.io/styleguide/jsguide.html)
* [Google Shell Style Guide](https://google.github.io/styleguide/shell.xml)
* [Google Objective-C Style Guide](https://google.github.io/styleguide/objcguide.html)

#### Running sanity check

If you have Docker installed on your system, you can perform a sanity check on
your changes by running the command:

```bash
mediapipe/tools/ci_build/ci_build.sh CPU mediapipe/tools/ci_build/ci_sanity.sh
```

This will catch most license, Python coding style and BUILD file issues that
may exist in your changes.