translation/OpenNMT-py/CONTRIBUTING.md

# Contributors

OpenNMT-py is a community developed project and we love developer contributions.

## Guidelines
Before sending a PR, please do this checklist first:

- Please run `onmt/tests/pull_request_chk.sh` and fix any errors. When adding new functionality, also add tests to this script. Included checks:
    1. flake8 check for coding style;
    2. unittest;
    3. continuous integration tests listed in `.travis.yml`.
- When adding/modifying class constructor, please make the arguments as same naming style as its superclass in PyTorch.
- If your change is based on a paper, please include a clear comment and reference in the code (more on that below).

### Docstrings
Above all, try to follow the Google docstring format
([Napoleon example](https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html),
[Google styleguide](http://google.github.io/styleguide/pyguide.html)).
This makes it easy to include your contributions in the Sphinx documentation. And, do feel free
to autodoc your contributions in the API ``.rst`` files in the `docs/source` folder! If you do, check that
your additions look right.

```bash
cd docs
# install some dependencies if necessary:
# recommonmark, sphinx_rtd_theme, sphinxcontrib-bibtex
make html
firefox build/html/main.html  # or your browser of choice
```

Some particular advice:
- Try to follow Python 3 [``typing`` module](https://docs.python.org/3/library/typing.html) conventions when documenting types.
    - Exception: use "or" instead of unions for more readability
    - For external types, use the full "import name". Common abbreviations (e.g. ``np``) are acceptable.
      For ``torch.Tensor`` types, the ``torch.`` is optional.
    - Please don't use tics like `` (`str`) `` or rst directives like `` (:obj:`str`) ``. Napoleon handles types
      very well without additional help, so avoid the clutter.
- [Google docstrings don't support multiple returns](https://stackoverflow.com/questions/29221551/can-sphinx-napoleon-document-function-returning-multiple-arguments).
For multiple returns, the following works well with Sphinx and is still very readable.
  ```python
  def foo(a, b):
      """This is my docstring.

      Args:
          a (object): Something.
          b (class): Another thing.

      Returns:
          (object, class):

          * a: Something or rather with a long
            description that spills over.
          * b: And another thing.
      """

      return a, b
  ```
- When citing a paper, avoid directly linking in the docstring! Add a Bibtex entry to `docs/source/refs.bib`.
E.g., to cite "Attention Is All You Need", visit [arXiv](https://arxiv.org/abs/1706.03762), choose the
[bibtext](https://dblp.uni-trier.de/rec/bibtex/journals/corr/VaswaniSPUJGKP17) link, search `docs/source/refs.bib`
using `CTRL-F` for `DBLP:journals/corr/VaswaniSPUJGKP17`, and if you do not find it then copy-paste the
citation into `refs.bib`. Then, in your docstring, use ``:cite:`DBLP:journals/corr/VaswaniSPUJGKP17` ``.
    - However, a link is better than nothing.
- Please document tensor shapes. Prefer the format
  ``` ``(a, b, c)`` ```. This style is easy to read, allows using ``x`` for multplication, and is common
  (PyTorch uses a few variations on the parentheses format, AllenNLP uses exactly this format, Fairseq uses
  the parentheses format with single ticks).
    - Again, a different style is better than no shape documentation.
- Please avoid unnecessary space characters, try to capitalize, and try to punctuate.

  For multi-line docstrings, add a blank line after the closing ``"""``.
  Don't use a blank line before the closing quotes.

  ``""" not this """`` ``"""This."""``

  ```python
  """
      Not this.
  """
  ```
  ```python
  """This."""
  ```

  This note is the least important. Focus on content first, but remember that consistent docs look good.
- Be sensible about the first line. Generally, one stand-alone summary line (per the Google guidelines) is good.
  Sometimes, it's better to cut directly to the args or an extended description. It's always acceptable to have a
  "trailing" citation.