Added "How to get a new feature into Docutils".

[docutils.git] / docs / dev / policies.txt

===========================
 Docutils Project Policies
===========================

:Author: David Goodger; open to all Docutils developers
:Contact: docutils-develop@lists.sourceforge.net
:Date: $Date$
:Revision: $Revision$
:Copyright: This document has been placed in the public domain.

.. contents::

The Docutils project group is a meritocracy based on code contribution
and lots of discussion [#bcs]_.  A few quotes sum up the policies of
the Docutils project.  The IETF's classic credo (by MIT professor Dave
Clark) is an ideal we can aspire to:

    We reject: kings, presidents, and voting.  We believe in: rough
    consensus and running code.

As architect, chief cook and bottle-washer, David Goodger currently
functions as BDFN (Benevolent Dictator For Now).  (But he would
happily abdicate the throne given a suitable candidate.  Any takers?)

Eric S. Raymond, anthropologist of the hacker subculture, writes in
his essay `The Magic Cauldron`_:

    The number of contributors [to] projects is strongly and inversely
    correlated with the number of hoops each project makes a user go
    through to contribute.

We will endeavour to keep the barrier to entry as low as possible.
The policies below should not be thought of as barriers, but merely as
a codification of experience to date.  These are "best practices";
guidelines, not absolutes.  Exceptions are expected, tolerated, and
used as a source of improvement.  Feedback and criticism is welcome.

As for control issues, Emmett Plant (CEO of the Xiph.org Foundation,
originators of Ogg Vorbis) put it well when he said:

    Open source dictates that you lose a certain amount of control
    over your codebase, and that's okay with us.

.. [#bcs] Phrase borrowed from `Ben Collins-Sussman of the Subversion
   project <http://www.red-bean.com/sussman/svn-anti-fud.html>`__.

.. _The Magic Cauldron:
   http://www.catb.org/~esr/writings/magic-cauldron/


How to get a new feature into Docutils
========================================

Question:
   I would very much like to have this new feature in the Docutils core.
   What exactly do I have to do to make this possible?

* Present your idea at the Docutils-develop_ mailing list,

  +1  usually triggers a fast response,
  -1  may be forgotten later,

  and/or file a feature request at the `docutils tracker`_

  +1  there is a permanent record,
  -1  it may stay forgotten among all the other feature requests.


* Convince a Docutils developer that this is a valuable addition worth the
  effort.

* Contribute. The developers will make sure that the contribution fits
  nicely into Docutils (cf. the `review criteria`_). This might involve
  discussing (and compromising on) design and implementation details. It
  might also lead to the conclusion that the addition fits better in `the
  sandbox`_ than in the Docutils core.

* Be patient, and be persistent.  None of us are paid to do this,
  it's all in our spare time -- which is precious and rare.

How to make code contributions that are easily accepted:

* Have a look at the `Python coding conventions`_ and `documentation
  conventions`_ below.

* **Prepare test cases.** This vastly helps when integrating new code. Test
  cases are also examples and showcases for new features. See `Docutils
  Testing`_ for a description of the test suite in ``docutils/test/``.

  Ensure the addition works with all supported Python versions
  (2.3 ... 3.2).

* Look at the Docutils sources to see how similar features are implemented,
  learn to do it "the Docutils way".

* Prepare the a patch or an addition to the existing documentation.
  Include links.

* If you are familiar with version control, consider creating a `feature
  branch`_ in a Docutils repository_ checkout. (Working with branches is
  *much* easier with git_. You can get a git clone of the repository from
  http://repo.or.cz/w/docutils.git or with git-svn.)

.. _docutils-develop: ../user/mailing-lists.html#docutils-develop
.. _docutils tracker: http://sourceforge.net/tracker/?group_id=38414
.. _git: http://git-scm.com/
.. _Docutils testing: testing.html


Python Coding Conventions
=========================

Contributed code will not be refused merely because it does not
strictly adhere to these conditions; as long as it's internally
consistent, clean, and correct, it probably will be accepted.  But
don't be surprised if the "offending" code gets fiddled over time to
conform to these conventions.

The Docutils project shall follow the generic coding conventions as
specified in the `Style Guide for Python Code`_ and `Docstring
Conventions`_ PEPs, summarized, clarified, and extended as follows:

* 4 spaces per indentation level.  No hard tabs.

* Use only 7-bit ASCII, no 8-bit strings.  See `Docutils
  Internationalization`_.

* No one-liner compound statements (i.e., no ``if x: return``: use two
  lines & indentation), except for degenerate class or method
  definitions (i.e., ``class X: pass`` is OK.).

* Lines should be no more than 78 characters long.

* Use "StudlyCaps" for class names (except for element classes in
  docutils.nodes).

* Use "lowercase" or "lowercase_with_underscores" for function,
  method, and variable names.  For short names, maximum two words,
  joined lowercase may be used (e.g. "tagname").  For long names with
  three or more words, or where it's hard to parse the split between
  two words, use lowercase_with_underscores (e.g.,
  "note_explicit_target", "explicit_target").  If in doubt, use
  underscores.

* Avoid lambda expressions, which are inherently difficult to
  understand.  Named functions are preferable and superior: they're
  faster (no run-time compilation), and well-chosen names serve to
  document and aid understanding.

* Avoid functional constructs (filter, map, etc.).  Use list
  comprehensions instead.

* Avoid ``from __future__ import`` constructs.  They are inappropriate
  for production code.

* Use 'single quotes' for string literals, and """triple double
  quotes""" for docstrings.

.. _Style Guide for Python Code:
   http://www.python.org/peps/pep-0008.html
.. _Docstring Conventions: http://www.python.org/peps/pep-0257.html
.. _Docutils Internationalization: ../howto/i18n.html#python-code


Documentation Conventions
=========================

* Docutils documentation is written using reStructuredText, of course.

* Use 7-bit ASCII if at all possible, and Unicode substitutions when
  necessary.

* Use the following section title adornment styles::

      ================
       Document Title
      ================

      --------------------------------------------
       Document Subtitle, or Major Division Title
      --------------------------------------------

      Section
      =======

      Subsection
      ----------

      Sub-Subsection
      ``````````````

      Sub-Sub-Subsection
      ..................

* Use two blank lines before each section/subsection/etc. title.  One
  blank line is sufficient between immediately adjacent titles.

* Add a bibliographic field list immediately after the document
  title/subtitle.  See the beginning of this document for an example.

* Add an Emacs "local variables" block in a comment at the end of the
  document.  See the end of this document for an example.


Copyrights and Licensing
========================

The majority of the Docutils project code and documentation has been
placed in the public domain.  Unless clearly and explicitly indicated
otherwise, any patches (modifications to existing files) submitted to
the project for inclusion (via Subversion, SourceForge trackers,
mailing lists, or private email) are assumed to be in the public
domain as well.

Any new files contributed to the project should clearly state their
intentions regarding copyright, in one of the following ways:

* Public domain (preferred): include the statement "This
  module/document has been placed in the public domain."

* Copyright & open source license: include a copyright notice, along
  with either an embedded license statement, a reference to an
  accompanying license file, or a license URL.

  The license should be well known, simple and compatible with other
  open source software licenses. To keep the number of different
  licenses at a minimum, using the `2-Clause BSD license`_
  (also known as "Simplified" or `FreeBSD license`_) is recommended.

  .. _2-Clause BSD license: http://www.opensource.org/licenses/BSD-2-Clause
  .. _FreeBSD license:  http://www.freebsd.org/copyright/freebsd-license.html

..

  The following licenses are described as simple
  and permissible on `Various Licenses and Comments about Them`_ by
  the GNU Project and listed as popular in `OSI Approved Licenses`_:

  Expat License / MIT License

    http://www.jclark.com/xml/copying.txt
    http://www.opensource.org/licenses/MIT
    http://www.spdx.org/licenses/MIT

    The term MIT License is ambiguous and may accurately refer to the
    Expat license or the X11 license
    [http://en.wikipedia.org/wiki/MIT_License]

    -1  called `MIT license` by OSI and in the
        `SPDX Open Source License Registry`_
        but `Expat license` by GNU

  2-Clause BSD license / FreeBSD license

    http://www.freebsd.org/copyright/freebsd-license.html
    http://www.opensource.org/licenses/BSD-2-Clause
    http://www.spdx.org/licenses/BSD-2-Clause

      If you want a simple, permissive non-copyleft free software
      license, the FreeBSD license is a reasonable choice. However,
      please don't call it a “BSD” or “BSD-style” license, because
      that is likely to cause confusion which could lead to use of the
      flawed original BSD license.

      -- `Various Licenses and Comments about Them`_

     +1  license used by the closely related Sphinx project
     +1  "2-Clause BSD license" is a non-ambiguous name,
         used by both, OSI and GNU.
     +1  clear wording, structured text

  .. _Various Licenses and Comments about Them:
     http://www.gnu.org/licenses/license-list.html
  .. _OSI Approved Licenses: http://www.opensource.org/licenses/category
  .. _SPDX Open Source License Registry: http://www.spdx.org/licenses/
  .. _pypi: http://pypi.python.org/pypi?:action=browse&c=54


.. _Subversion Repository:

Repository
==========

Please see the `repository documentation`_ for details on how to
access Docutils' Subversion repository.  Anyone can access the
repository anonymously.  Only project developers can make changes.
(If you would like to become a project developer, just ask!)  Also see
`Setting Up For Docutils Development`_ below for some useful info.

Unless you really *really* know what you're doing, please do *not* use
``svn import``.  It's quite easy to mess up the repository with an
import.

.. _repository documentation: repository.html


Branches
--------

(These branch policies go into effect with Docutils 0.4.)

The "docutils" directory of the **trunk** (a.k.a. the **Docutils
core**) is used for active -- but stable, fully tested, and reviewed
-- development.

There will be at least one active **maintenance branch** at a time,
based on at least the latest feature release.  For example, when
Docutils 0.5 is released, its maintenance branch will take over, and
the 0.4.x maintenance branch may be retired.  Maintenance branches
will receive bug fixes only; no new features will be allowed here.

Obvious and uncontroversial bug fixes *with tests* can be checked in
directly to the core and to the maintenance branches.  Don't forget to
add test cases!  Many (but not all) bug fixes will be applicable both
to the core and to the maintenance branches; these should be applied
to both.  No patches or dedicated branches are required for bug fixes,
but they may be used.  It is up to the discretion of project
developers to decide which mechanism to use for each case.

.. _feature branches:
.. _feature branch:

Feature additions and API changes will be done in **feature
branches**.  Feature branches will not be managed in any way.
Frequent small checkins are encouraged here.  Feature branches must be
discussed on the `docutils-develop mailing list`_ and reviewed before
being merged into the core.

.. _docutils-develop mailing list:
   http://lists.sourceforge.net/lists/listinfo/docutils-develop


Review Criteria
```````````````

Before a new feature, an API change, or a complex, disruptive, or
controversial bug fix can be checked in to the core or into a
maintenance branch, it must undergo review.  These are the criteria:

* The branch must be complete, and include full documentation and
  tests.

* There should ideally be one branch merge commit per feature or
  change.  In other words, each branch merge should represent a
  coherent change set.

* The code must be stable and uncontroversial.  Moving targets and
  features under debate are not ready to be merged.

* The code must work.  The test suite must complete with no failures.
  See `Docutils Testing`_.

The review process will ensure that at least one other set of eyeballs
& brains sees the code before it enters the core.  In addition to the
above, the general `Check-ins`_ policy (below) also applies.


Check-ins
---------

Changes or additions to the Docutils core and maintenance branches
carry a commitment to the Docutils user community.  Developers must be
prepared to fix and maintain any code they have committed.

The Docutils core (``trunk/docutils`` directory) and maintenance
branches should always be kept in a stable state (usable and as
problem-free as possible).  All changes to the Docutils core or
maintenance branches must be in `good shape`_, usable_, documented_,
tested_, and `reasonably complete`_.

* _`Good shape` means that the code is clean, readable, and free of
  junk code (unused legacy code; by analogy to "junk DNA").

* _`Usable` means that the code does what it claims to do.  An "XYZ
  Writer" should produce reasonable XYZ output.

* _`Documented`: The more complete the documentation the better.
  Modules & files must be at least minimally documented internally.
  `Docutils Front-End Tools`_ should have a new section for any
  front-end tool that is added.  `Docutils Configuration Files`_
  should be modified with any settings/options defined.  For any
  non-trivial change, the HISTORY.txt_ file should be updated.

* _`Tested` means that unit and/or functional tests, that catch all
  bugs fixed and/or cover all new functionality, have been added to
  the test suite.  These tests must be checked by running the test
  suite under all supported Python versions, and the entire test suite
  must pass.  See `Docutils Testing`_.

* _`Reasonably complete` means that the code must handle all input.
  Here "handle" means that no input can cause the code to fail (cause
  an exception, or silently and incorrectly produce nothing).
  "Reasonably complete" does not mean "finished" (no work left to be
  done).  For example, a writer must handle every standard element
  from the Docutils document model; for unimplemented elements, it
  must *at the very least* warn that "Output for element X is not yet
  implemented in writer Y".

If you really want to check code directly into the Docutils core,
you can, but you must ensure that it fulfills the above criteria
first.  People will start to use it and they will expect it to work!
If there are any issues with your code, or if you only have time for
gradual development, you should put it on a branch or in the sandbox
first.  It's easy to move code over to the Docutils core once it's
complete.

It is the responsibility and obligation of all developers to keep the
Docutils core and maintenance branches stable.  If a commit is made to
the core or maintenance branch which breaks any test, the solution is
simply to revert the change.  This is not vindictive; it's practical.
We revert first, and discuss later.

Docutils will pursue an open and trusting policy for as long as
possible, and deal with any aberrations if (and hopefully not when)
they happen.  We'd rather see a torrent of loose contributions than
just a trickle of perfect-as-they-stand changes.  The occasional
mistake is easy to fix.  That's what Subversion is for!

.. _Docutils Front-End Tools: ../user/tools.html
.. _Docutils Configuration Files: ../user/config.html
.. _HISTORY.txt: ../../HISTORY.txt


Version Numbering
=================

Docutils version numbering uses a ``major.minor.micro`` scheme (x.y.z;
for example, 0.4.1).

**Major releases** (x.0, e.g. 1.0) will be rare, and will represent
major changes in API, functionality, or commitment.  For example, as
long as the major version of Docutils is 0, it is to be considered
*experimental code*.  When Docutils reaches version 1.0, the major
APIs will be considered frozen and backward compatibility will become
of paramount importance.

Releases that change the minor number (x.y, e.g. 0.5) will be
**feature releases**; new features from the `Docutils core`_ will be
included.

Releases that change the micro number (x.y.z, e.g. 0.4.1) will be
**bug-fix releases**.  No new features will be introduced in these
releases; only bug fixes off of `maintenance branches`_ will be
included.

This policy was adopted in October 2005, and will take effect with
Docutils version 0.4.  Prior to version 0.4, Docutils didn't have an
official version numbering policy, and micro releases contained both
bug fixes and new features.

.. _Docutils core:
   http://docutils.svn.sourceforge.net/viewvc/docutils/trunk/docutils/
.. _maintenance branches:
   http://docutils.svn.sourceforge.net/viewvc/docutils/branches/


Snapshots
=========

Snapshot tarballs will be generated regularly from

* the Docutils core, representing the current cutting-edge state of
  development;

* each active maintenance branch, for bug fixes;

* each development branch, representing the unstable
  seat-of-your-pants bleeding edge.

The ``sandbox/infrastructure/docutils-update`` shell script, run as an
hourly cron job on the BerliOS server, is responsible for
automatically generating the snapshots and updating the web site.  See
the `web site docs <website.html>`__.


Setting Up For Docutils Development
===================================

When making changes to the code, testing is a must.  The code should
be run to verify that it produces the expected results, and the entire
test suite should be run too.  The modified Docutils code has to be
accessible to Python for the tests to have any meaning.  There are two
ways to keep the Docutils code accessible during development:

1. Update your ``PYTHONPATH`` environment variable so that Python
   picks up your local working copy of the code.  This is the
   recommended method.

   We'll assume that the Docutils trunk is checked out under your
   ~/projects/ directory as follows::

       svn co https://<user>@docutils.svn.sourceforge.net/svnroot/docutils/trunk \
           docutils

   For the bash shell, add this to your ``~/.profile``::

       PYTHONPATH=$HOME/projects/docutils/docutils
       PYTHONPATH=$PYTHONPATH:$HOME/projects/docutils/docutils/extras
       export PYTHONPATH

   The first line points to the directory containing the ``docutils``
   package.  The second line adds the directory containing the
   third-party modules Docutils depends on.  The third line exports
   this environment variable.  You may also wish to add the ``tools``
   directory to your ``PATH``::

       PATH=$PATH:$HOME/projects/docutils/docutils/tools
       export PATH

2. Before you run anything, every time you make a change, reinstall
   Docutils::

       python setup.py install

   .. CAUTION::

      This method is **not** recommended for day-to-day development;
      it's too easy to forget.  Confusion inevitably ensues.

      If you install Docutils this way, Python will always pick up the
      last-installed copy of the code.  If you ever forget to
      reinstall the "docutils" package, Python won't see your latest
      changes.

A useful addition to the ``docutils`` top-level directory in branches
and alternate copies of the code is a ``set-PATHS`` file
containing the following lines::

    # source this file
    export PYTHONPATH=$PWD:$PWD/extras
    export PATH=$PWD/tools:$PATH

Open a shell for this branch, ``cd`` to the ``docutils`` top-level
directory, and "source" this file.  For example, using the bash
shell::

    $ cd some-branch/docutils
    $ . set-PATHS


Mailing Lists
=============

Developers are recommended to subscribe to all `Docutils mailing
lists`_.

.. _Docutils mailing lists: ../user/mailing-lists.html


The Wiki
========

There is a development wiki at http://docutils.python-hosting.com/ as
a scratchpad for transient notes.  Please use the repository for
permament document storage.


The Sandbox
===========

The `sandbox directory`_ is a place to play around, to try out and
share ideas.  It's a part of the Subversion repository but it isn't
distributed as part of Docutils releases.  Feel free to check in code
to the sandbox; that way people can try it out but you won't have to
worry about it working 100% error-free, as is the goal of the Docutils
core.  A project-specific subdirectory should be created for each new
project.  Any developer who wants to play in the sandbox may do so,
but project directories are recommended over personal directories,
which discourage collaboration.  It's OK to make a mess in the
sandbox!  But please, play nice.

Please update the `sandbox README`_ file with links and a brief
description of your work.

In order to minimize the work necessary for others to install and try
out new, experimental components, the following sandbox directory
structure is recommended::

    sandbox/
        project_name/ # For a collaborative project.
            README.txt  # Describe the requirements, purpose/goals, usage,
                        # and list the maintainers.
            docs/
                ...
            component.py    # The component is a single module.
                            # *OR* (but *not* both)
            component/      # The component is a package.
                __init__.py  # Contains the Reader/Writer class.
                other1.py    # Other modules and data files used
                data.txt     # by this component.
                ...
            test/       # Test suite.
                ...
            tools/      # For front ends etc.
                ...
            setup.py    # Use Distutils to install the component
                        # code and tools/ files into the right
                        # places in Docutils.
        userid/       # For *temporary* personal space.

Some sandbox projects are destined to move to the Docutils core once
completed.  Others, such as add-ons to Docutils or applications of
Docutils, may graduate to become `parallel projects`_.

.. _sandbox README: http://docutils.sf.net/sandbox/README.html
.. _sandbox directory:
   http://docutils.svn.sourceforge.net/viewvc/docutils/trunk/sandbox/


.. _parallel project:

Parallel Projects
=================

Parallel projects contain useful code that is not central to the
functioning of Docutils.  Examples are specialized add-ons or
plug-ins, and applications of Docutils.  They use Docutils, but
Docutils does not require their presence to function.

An official parallel project will have its own directory beside (or
parallel to) the main ``docutils`` directory in the Subversion
repository.  It can have its own web page in the
docutils.sourceforge.net domain, its own file releases and
downloadable snapshots, and even a mailing list if that proves useful.
However, an official parallel project has implications: it is expected
to be maintained and continue to work with changes to the core
Docutils.

A parallel project requires a project leader, who must commit to
coordinate and maintain the implementation:

* Answer questions from users and developers.
* Review suggestions, bug reports, and patches.
* Monitor changes and ensure the quality of the code and
  documentation.
* Coordinate with Docutils to ensure interoperability.
* Put together official project releases.

Of course, related projects may be created independently of Docutils.
The advantage of a parallel project is that the SourceForge
environment and the developer and user communities are already
established.  Core Docutils developers are available for consultation
and may contribute to the parallel project.  It's easier to keep the
projects in sync when there are changes made to the core Docutils
code.

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