pelican/docs/contribute.rst

Contributing and feedback guidelines
####################################

There are many ways to contribute to Pelican. You can improve the
documentation, add missing features, and fix bugs (or just report them). You
can also help out by reviewing and commenting on
`existing issues <https://github.com/getpelican/pelican/issues>`_.

Don't hesitate to fork Pelican and submit an issue or pull request on GitHub.
When doing so, please consider the following guidelines.

.. include:: ../CONTRIBUTING.rst

Setting up the development environment
======================================

While there are many ways to set up one's development environment, the following
instructions will utilize Pip_ and Poetry_. These tools facilitate managing
virtual environments for separate Python projects that are isolated from one
another, so you can use different packages (and package versions) for each.

Please note that Python 3.6+ is required for Pelican development.

*(Optional)* If you prefer to install Poetry once for use with multiple projects,
you can install it via::

    curl -sSL https://raw.githubusercontent.com/sdispater/poetry/master/get-poetry.py | python

Point your web browser to the `Pelican repository`_ and tap the **Fork** button
at top-right. Then clone the source for your fork and add the upstream project
as a Git remote::

    mkdir ~/projects
    git clone https://github.com/YOUR_USERNAME/pelican.git ~/projects/pelican
    cd ~/projects/pelican
    git remote add upstream https://github.com/getpelican/pelican.git

While Poetry can dynamically create and manage virtual environments, we're going
to manually create and activate a virtual environment::

    mkdir ~/virtualenvs
    python3 -m venv ~/virtualenvs/pelican
    source ~/virtualenvs/pelican/bin/activate

Install the needed dependencies and set up the project::

    python -m pip install invoke
    invoke setup
    python -m pip install -e ~/projects/pelican

Your local environment should now be ready to go!

.. _Pip: https://pip.pypa.io/
.. _Poetry: https://poetry.eustace.io/docs/#installation
.. _Pelican repository: https://github.com/getpelican/pelican

Development
===========

Once Pelican has been set up for local development, create a topic branch for
your bug fix or feature::

    git checkout -b name-of-your-bugfix-or-feature

Now you can make changes to Pelican, its documentation, and/or other aspects of
the project.

Running the test suite
----------------------

Each time you make changes to Pelican, there are two things to do regarding
tests: check that the existing tests pass, and add tests for any new features
or bug fixes. The tests are located in ``pelican/tests``, and you can run them
via::

    invoke tests

In addition to running the test suite, it is important to also ensure that any
lines you changed conform to code style guidelines. You can check that via::

    invoke lint

If code style violations are found in lines you changed, correct those lines
and re-run the above lint command until they have all been fixed. You do not
need to address style violations, if any, for code lines you did not touch.

After making your changes and running the tests, you may see a test failure
mentioning that "some generated files differ from the expected functional tests
output." If you have made changes that affect the HTML output generated by
Pelican, and the changes to that output are expected and deemed correct given
the nature of your changes, then you should update the output used by the
functional tests. To do so, **make sure you have both** ``en_EN.utf8`` **and**
``fr_FR.utf8`` **locales installed**, and then run the following command::

    invoke update-functional-tests

You may also find that some tests are skipped because some dependency (e.g.,
Pandoc) is not installed. This does not automatically mean that these tests
have passed; you should at least verify that any skipped tests are not affected
by your changes.

You should run the test suite under each of the supported versions of Python.
This is best done by creating a separate Python environment for each version.
Tox_ is a useful tool to automate running tests inside ``virtualenv``
environments.

.. _Tox: https://tox.readthedocs.io/en/latest/

Building the docs
-----------------

If you make changes to the documentation, you should build and inspect your
changes before committing them::

    invoke docserve

Open http://localhost:8000 in your browser to review the documentation. While
the above task is running, any changes you make and save to the documentation
should automatically appear in the browser, as it live-reloads when it detects
changes to the documentation source files.

Plugin development
------------------

To create a *new* Pelican plugin, please refer to the `plugin template`_
repository for detailed instructions.

If you want to contribute to an *existing* Pelican plugin, follow the steps
above to set up Pelican for local development, and then create a directory to
store cloned plugin repositories::

   mkdir -p ~/projects/pelican-plugins

Assuming you wanted to contribute to the Simple Footnotes plugin, you would
first browse to the `Simple Footnotes`_ repository on GitHub and tap the **Fork**
button at top-right. Then clone the source for your fork and add the upstream
project as a Git remote::

    git clone https://github.com/YOUR_USERNAME/simple-footnotes.git ~/projects/pelican-plugins/simple-footnotes
    cd ~/projects/pelican-plugins/simple-footnotes
    git remote add upstream https://github.com/pelican-plugins/simple-footnotes.git

Install the needed dependencies and set up the project::

    invoke setup

Create a topic branch for your plugin bug fix or feature::

    git checkout -b name-of-your-bugfix-or-feature

After writing new tests for your plugin changes, run the plugin test suite::

    invoke tests

.. _plugin template: https://github.com/getpelican/cookiecutter-pelican-plugin
.. _Simple Footnotes: https://github.com/pelican-plugins/simple-footnotes

Submitting your changes
-----------------------

Assuming linting validation and tests pass, add a ``RELEASE.md`` file in the root
of the project that contains the release type (major, minor, patch) and a
summary of the changes that will be used as the release changelog entry.
For example::

    Release type: patch

    Fix browser reloading upon changes to content, settings, or theme

Commit your changes and push your topic branch::

    git add .
    git commit -m "Your detailed description of your changes"
    git push origin name-of-your-bugfix-or-feature

Finally, browse to your repository fork on GitHub and submit a pull request.


Logging tips
============

Try to use logging with appropriate levels.

For logging messages that are not repeated, use the usual Python way::

    # at top of file
    import logging
    logger = logging.getLogger(__name__)

    # when needed
    logger.warning("A warning with %s formatting", arg_to_be_formatted)

Do not format log messages yourself. Use ``%s`` formatting in messages and pass
arguments to logger. This is important, because the Pelican logger will
preprocess some arguments, such as exceptions.

Limiting extraneous log messages
--------------------------------

If the log message can occur several times, you may want to limit the log to
prevent flooding. In order to do that, use the ``extra`` keyword argument for
the logging message in the following format::

    logger.warning("A warning with %s formatting", arg_to_be_formatted,
        extra={'limit_msg': 'A generic message for too many warnings'})

Optionally, you can also set ``'limit_args'`` as a tuple of arguments in
``extra`` dict if your generic message needs formatting.

Limit is set to ``5``, i.e, first four logs with the same ``'limit_msg'`` are
outputted normally but the fifth one will be logged using ``'limit_msg'`` (and
``'limit_args'`` if present). After the fifth, corresponding log messages will
be ignored.

For example, if you want to log missing resources, use the following code::

    for resource in resources:
        if resource.is_missing:
            logger.warning(
                'The resource %s is missing', resource.name,
                extra={'limit_msg': 'Other resources were missing'})

The log messages will be displayed as follows::

    WARNING: The resource prettiest_cat.jpg is missing
    WARNING: The resource best_cat_ever.jpg is missing
    WARNING: The resource cutest_cat.jpg is missing
    WARNING: The resource lolcat.jpg is missing
    WARNING: Other resources were missing


Outputting traceback in the logs
--------------------------------

If you're logging inside an ``except`` block, you may want to provide the
traceback information as well. You can do that by setting ``exc_info`` keyword
argument to ``True`` during logging. However, doing so by default can be
undesired because tracebacks are long and can be confusing to regular users.
Try to limit them to ``--debug`` mode like the following::

    try:
        some_action()
    except Exception as e:
        logger.error('Exception occurred: %s', e,
            exc_info=settings.get('DEBUG', False))