.. _dev_start_guide:

=====================
Developer Start Guide
=====================

To get up to speed, you'll need to

- Learn some non-basic Python to understand what's going on in some of the
  trickier files (like tensor.py).
- Go through the `NumPy documentation`_.
- Learn to write reStructuredText_ for epydoc_ and Sphinx_.
- Learn about how unittest_ and nose_ work

.. _Sphinx: http://sphinx.pocoo.org/
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
.. _epydoc: http://epydoc.sourceforge.net/
.. _NumPy documentation: http://docs.scipy.org/numpy/
.. _unittest: http://docs.python.org/library/unittest.html
.. _nose: http://somethingaboutorange.com/mrl/projects/nose/

Accounts
--------

To obtain developer access: register with `GitHub
<http://www.github.com/>`_ and create a fork of `Pylearn2
<http://www.github.com/lisa-lab/pylearn2>`_.

Coding style
------------

See the coding style guideline  :doc:`here <api_coding_style>`.

We do not plan to change all existing code to follow this coding
style, but as we modify the code, we update it accordingly.

Documentation
-------------

See the documentation guideline :ref:`here <metadocumentation>`.


Mailing list
------------

See the Pylearn2 main page for the pylearn-dev, theano-buildbot and
pylearn2-github mailing list. They are useful to Pylearn2 contributors.

Git config
----------

.. code-block:: bash

   git config --global user.email you@yourdomain.example.com
   git config --global user.name "Your Name Comes Here"

Typical development workflow
----------------------------

Clone your fork locally with

.. code-block:: bash

    git clone git@github.com:your_github_login/pylearn2.git

and add a reference to the 'central' Pylearn2 repository with

.. code-block:: bash

    git remote add central git://github.com/lisa-lab/pylearn2.git

When working on a new feature in your own fork, start from an up-to-date copy
of the trunk:

.. code-block:: bash

    git fetch central
    git checkout -b my_shiny_feature central/master

Once your code is ready for others to review, push your branch to your github fork:

.. code-block:: bash

    git push -u origin my_shiny_feature

then go to your fork's github page on the github website, select your feature
branch and hit the "Pull Request" button in the top right corner.
If you don't get any feedback, bug us on the pylearn-dev mailing list.

When the your pull request have been merged, you can delete the branch
from the github list of branch. That is usefull to don't have too many
that stay there!

.. code-block:: bash

   git push origin :my_shiny_feature


You can keep you local repo up to date with central/master with those commands:

.. code-block:: bash

   git checkout master
   git fetch central
   git merge central/master

If you want to fix a commit done in a pull request(i.e. fix small
typo) to keep the history clean, you can do it like this:

.. code-block:: bash

   git checkout branch
   git commit --amend
   git push -u origin  my_shiny_feature:my_shiny_feature


Coding Style Auto Check
-----------------------

See the coding style guideline  :doc:`here <api_coding_style>`.
The principal thing to know is that we follow the
`pep8 <http://www.python.org/dev/peps/pep-0008/>`_ coding style.

We use git hooks provided in the project `pygithooks
<https://github.com/lumberlabs/pygithooks>`_ to validate that commits
respect pep8. This happens when each user commits, not when we
push/merge to the Pylearn2 repository. Github doesn't allow us to have
code executed when we push to the repository. So we ask all
contributors to use those hooks.

For historic reason, we currently don't have all files respecting pep8.
We decided to fix everything incrementally. So not all files respect it
now. So we strongly suggest that you use the "increment" pygithooks
config option to have a good workflow. See the pygithooks main page
for how to set it up for Pylearn2 and how to enable this option.

Cleaning up history
-------------------

Sometimes you may have commits in your feature branch that
are not needed in the final pull request. There is a `page
<http://sandofsky.com/blog/git-workflow.html>`_ that talks about
this. In summary:

* Commits to the trunk should be a lot cleaner than commits to your
  feature branch; not just for ease of reviewing but also
  because intermediate commits can break blame (the bisecting tool).
* `git merge --squash` will put all of the commits from your feature branch into one commit.
* There are other tools that are useful if your branch is too big for one squash.


To checkout another user branch in his repo:

.. code-block:: bash

   git remote add REPO_NAME HIS_REPO_PATH
   git checkout -b LOCAL_BRANCH_NAME REPO_NAME/REMOVE_BRANCH_NAME

You can find move information and tips in the `numpy development
<http://docs.scipy.org/doc/numpy/dev/gitwash/development_workflow.html>`_
page.


Details about ``PYTHONPATH``
----------------------------

``$PYTHONPATH`` should contain a ":"-separated list of paths, each of which
contains one or several Python packages, in the order in which you would like
Python to search for them. If a package has sub-packages of interest to you,
do **not** add them to ``$PYTHONPATH``: it is not portable, might shadow other
packages or short-circuit important things in its ``__init__``.

It is advisable to never import Pylearn2's files from outside Pylearn2 itself
(this is good advice for Python packages in general). Use ``from pylearn2 import
module`` instead of ``import module``. ``$PYTHONPATH`` should only contain
paths to complete packages.

When you install a package, only the package name can be imported directly. If
you want a sub-package, you must import it from the main package. That's how
it will work in 99.9% of installs because it is the default. Therefore, if you
stray from this practice, your code will not be portable. Also, some ways to
circumvent circular dependencies might make it so you have to import files in
a certain order, which is best handled by the package's own ``__init__.py``.

More instructions
-----------------

Once you have completed these steps, you should run the by running
``nosetests`` from your checkout directory.

All tests should pass. If some test fails on your machine, you are
encouraged to tell us what went wrong on the `pylearn-dev`_
mailing list.

.. _pylearn-dev: https://groups.google.com/group/pylearn-dev

To update your library to the latest revision, you should have a branch
that tracks the main trunk. You can add one with:

.. code-block:: bash

    git fetch central
    git branch trunk central/master

Once you have such a branch, in order to update it, do:

.. code-block:: bash

    git checkout trunk
    git pull

Keep in mind that this branch should be "read-only": if you want to patch
Pylearn2, do it in another branch like described above.

Optional
--------

You can instruct git to do color diff. For this, you need to add those lines in the file ~/.gitconfig

.. code-block:: bash


    [color]
       branch = auto
       diff = auto
       interactive = auto
       status = auto

Nightly test
------------

Each night we execute all the unit tests automatically.  The result is sent by
email to the `theano-buildbot`_ mailing list.

.. _theano-buildbot: https://groups.google.com/group/theano-buildbot

For more detail, see :ref:`see <metadocumentation_nightly_build>`.

To run all the tests with the same configuration as the buildbot, run this script:

.. code-block:: bash

   pylearn2/misc/do_nightly_build

This function accepts arguments that it forward to nosetests. You can
run only some tests or enable pdb by giving the equivalent nosetests
parameters.