Documentation guidelines
========================

This guide contains instructions for building the scikit-bio documentation, as well as guidelines for contributing to the documentation. If you would like to contribute to the documentation, whether by adding something entirely new or by modifying existing documentation, please first review :doc:`../contribute`.

.. note:: If you're only interested in viewing the scikit-bio documentation, please visit the `documentation site <https://scikit.bio/docs/latest/index.html>`_.


Build the documentation
-----------------------

To build the documentation, you'll need a scikit-bio development environment set up. See :doc:`../contribute` for instructions. In addition, you will also need to install `Sphinx <https://www.sphinx-doc.org/>`_ and relevant extensions within the same environment for the documentation, you can do that with::

    conda install -c conda-forge --file ci/requirements.doc.txt

.. warning:: The documentation will be built for whatever version of scikit-bio is *currently installed* on your system (i.e., the version imported by ``import skbio``). This may not match the code located in this repository. You will need to either install this version of scikit-bio somewhere (e.g., in a virtualenv) or point your ``PYTHONPATH`` environment variable to this code, *before* building the documentation.

To build the documentation, assuming you are at the top-level scikit-bio directory::

    make -C doc clean html

The built HTML documentation will be at ``doc/build/html/index.html``.

.. warning:: Before submitting your changes, ensure that the documentation builds without errors or warnings.


Docstring style
---------------

Most of scikit-bio's API documentation is automatically generated from `docstrings <https://legacy.python.org/dev/peps/pep-0257/#what-is-a-docstring>`_.
The advantage to this approach is that users can access the documentation in an interactive Python session or from our website as HTML. Other output formats are also possible, such as PDF.

scikit-bio docstrings follow the `numpydoc style guide <https://numpydoc.readthedocs.io/en/latest/format.html>`_. This ensures that the docstrings are easily readable both from the interpreter and HTML, PDF, etc. Please read the numpydoc guidelines before continuing.


Documenting a module
--------------------

In addition to following the numpydoc conventions for docstrings, we have a few more conventions that will ensure your documentation is correctly built and
linked within our website, and that it maintains consistency with the rest of the scikit-bio docs.

The easiest way to get started with documenting your code is to look at the docstrings in existing scikit-bio modules. A couple of modules to start with are ``skbio.sequence`` and ``skbio.stats.distance``. Go ahead and look through those now. We've structured our docs in a similar way to `SciPy's documentation <https://docs.scipy.org/doc/scipy/reference/>`_, so that may be another good place to look for examples.

We'll take a top-down approach by discussing how to document a new module that you'd like to add to scikit-bio (let's call it ``skbio/example.py``).

Module docstring
^^^^^^^^^^^^^^^^

The first thing you'll need to add is a docstring for the module. The docstring must start at the first line of the file. It should start with a title for the module::

    """
    Documentation examples (:mod:`skbio.example`)
    =============================================

It is important to include the ``:mod:`` Sphinx directive in the title, as this title will be included in the table of contents. Also make sure that the title underline is the same length as the title.

We also need to include another Sphinx directive below this::

    .. currentmodule:: skbio.example

This directive tells Sphinx that other classes, functions, etc. that we will reference are located in the ``skbio.example`` module.

Next, include a more detailed description of the module. For example::

    This module consists of several example classes and functions to illustrate
    the scikit-bio documentation system.

Following that, list any classes, functions, and exceptions that you'd like documentation generated for. Note that you do *not* need to include every single class, function, or exception that is defined in the module. Also, you do not need to list class methods, as those will be automatically included in the generated class documentation. Only include objects that should be exposed as part of the public API.

For example::

    Classes
    -------

    .. autosummary::
       :toctree: generated/

       ExampleClass1
       ExampleClass2

    Functions
    ---------

    .. autosummary::
       :toctree: generated/

       example_function1
       example_function2

    Exceptions
    ----------

    .. autosummary::
       :toctree: generated/

       ExampleError

The ``autosummary`` directives are important as they generate RST files in the ``generated/`` directory for each object. A single-line summary and link to each object is inserted into the page for you.

After listing public module members, we encourage a usage example section showing how to use some of the module's functionality. Examples should be written in `doctest <https://docs.python.org/3/library/doctest.html>`_ format so that they can be automatically tested (e.g., using ``make test`` or ``python -m skbio.test``)::

    Examples
    --------

    Run the ``example_function1`` function:

    >>> from skbio.example import example_function1
    >>> example_function1("hello", "world")
    hello world!

You can also embed the plots that an example generates into the built documentation with the ``.. plot::`` directive. For example::

    .. plot::

       >>> import pandas as pd
       >>> df = pd.DataFrame({'col1': [1, 2, 3, 4], 'col2': [10, 11, 12, 13]})
       >>> fig = df.boxplot()

This will include the plot, a link to the source code used to generate the plot, and links to different image formats (e.g., PNG and PDF) so that users can easily download the plot.

You're now ready to document the members of your module.

Documenting module members
^^^^^^^^^^^^^^^^^^^^^^^^^^

When documenting the members of a module (e.g., classes, methods, attributes, functions, and exceptions), follow the numpydoc conventions. In addition to these conventions, there are a few things to keep in mind:

- When documenting a class, only public methods and attributes are included in the built documentation. If a method or attribute starts with an underscore, it is assumed to be private.

- When documenting a class, include the ``Parameters`` section in the class docstring, instead of in the ``__init__`` docstring. While numpydoc technically supports either form, ``__init__`` is not included in the list of methods by default and thus should have its documentation included in the class docstring.

Including the module in the docs
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Until now, we've only been editing docstrings, which are attached to Python code. The final step is to hook up this new module's docstrings to the documentation build system:

1. Make sure you're within the ``scikit-bio/doc`` directory.

2. Create a new file with the same name as your module under the ``source`` directory. Do not include ``skbio`` as part of the name, and use ``.rst`` as the suffix. For example, ``source/example.rst``.

3. Add the following line to ``source/example.rst`` to have your module's docstring pulled into the document::

    ``
    .. automodule:: skbio.example
    ``

4. Add the following line to ``source/index.rst`` to add the new page to the top-level table of contents::

    ``
    example
    ``

That's it! You can now try building the documentation, which should include the documentation for your new module!


Documenting a subpackage
------------------------

The process of documenting a subpackage is very similar to documenting a module in scikit-bio. The only difference is that the module docstring goes in the subpackage's ``__init__.py``.


Troubleshooting
---------------

If things aren't working correctly, try running ``make clean`` and then rebuild the docs. If things still aren't working, try building the docs *without* your changes, and see if there are any Sphinx errors or warnings. Make note of these, and then see what new errors or warnings are generated when you add your changes again.
