Contributing to python-apt ========================== :Author: Julian Andres Klode :Release: |release| :Date: |today| Let's say you need a new feature, you can develop it, and you want to get it included in python-apt. Then be sure to follow the following guidelines. Available branches ------------------- First of all, let's talk a bit about the bzr branches of python-apt. In the following parts, we will assume that you use bzr to create your changes and submit them. Distribution branches ^^^^^^^^^^^^^^^^^^^^^ **debian-sid:** http://bzr.debian.org/apt/python-apt/debian-sid This is the official Debian branch of python-apt. All code which will be uploaded to Debian is here. It is not as up-to-date as the mvo branch, because this branch often gets updated just right before the release happens. VCS-Browser: http://bzr.debian.org/loggerhead/apt/python-apt/debian-sid/changes **debian-experimental:** http://bzr.debian.org/apt/python-apt/debian-experimental This is another official Debian branch of python-apt, for releases targetted at Debian experimental. This branch may contain unstable code and may thus not work correctly. VCS-Browser: http://bzr.debian.org/loggerhead/apt/python-apt/debian-experimental/changes **ubuntu:** ``lp:~ubuntu-core-dev/python-apt/ubuntu`` This is the official Ubuntu development branch. The same notes apply as for the debian-sid branch above. For the Ubuntu release branches, replace ``ubuntu`` with the version you want; for example, for lucid: ``lp:~ubuntu-core-dev/python-apt/lucid``. VCS-Browser: https://code.launchpad.net/~ubuntu-core-dev/python-apt/ubuntu Important Personal branches ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ **mvo:** lp:~mvo/python-apt/mvo This is Michael Vogt's branch. Most of the development of apt happens here, as he is the lead maintainer of python-apt. This branch is also available from Launchpads super mirror, via ``lp:python-apt``. Checkouts from Launchpad are generally faster and can use the bzr protocoll. VCS-Browser: http://bazaar.launchpad.net/~mvo/python-apt/mvo/ **jak:** http://bzr.debian.org/users/jak/python-apt/jak This is Julian Andres Klode's (the documentation author's) branch. This is the place where cleanup and documentation updates happen. It is based off debian-sid. Most stuff happens in debian-sid now. VCS-Browser: http://bzr.debian.org/loggerhead/users/jak/python-apt/jak/ .. highlightlang:: c C++ Coding style ---------------- This document gives coding conventions for the C++ code comprising the C++ extensions of Python APT. Please see the companion informational PEP describing style guidelines for Python code (:PEP:`8`). Note, rules are there to be broken. Two good reasons to break a particular rule: (1) When applying the rule would make the code less readable, even for someone who is used to reading code that follows the rules. (2) To be consistent with surrounding code that also breaks it (maybe for historic reasons) -- although this is also an opportunity to clean up someone else's mess (in true XP style). This part of the document is derived from :PEP:`7` which was written by Guido van Rossum. C++ dialect ^^^^^^^^^^^ - Use ISO standard C++ (the 1998 version of the standard). - Use C++ style // one-line comments for single-line comments. - No compiler warnings with ``gcc -std=c++98 -Wall -Wno-write-strings``. There should also be no errors with ``-pedantic`` added. Code lay-out ^^^^^^^^^^^^ - Use 3-space indents, in files that already use them. In new source files, that were created after this rule was introduced, use 4-space indents. At some point, the whole codebase may be converted to use only 4-space indents. - No line should be longer than 79 characters. If this and the previous rule together don't give you enough room to code, your code is too complicated -- consider using subroutines. - No line should end in whitespace. If you think you need significant trailing whitespace, think again -- somebody's editor might delete it as a matter of routine. - Function definition style: function name in column 2, outermost curly braces in column 1, blank line after local variable declarations:: static int extra_ivars(PyTypeObject *type, PyTypeObject *base) { int t_size = PyType_BASICSIZE(type); int b_size = PyType_BASICSIZE(base); assert(t_size >= b_size); /* type smaller than base! */ ... return 1; } - Code structure: one space between keywords like 'if', 'for' and the following left paren; no spaces inside the paren; braces as shown:: if (mro != NULL) { ... } else { ... } - The return statement should *not* get redundant parentheses:: return Py_None; /* correct */ return(Py_None); /* incorrect */ - Function and macro call style: ``foo(a, b, c)`` -- no space before the open paren, no spaces inside the parens, no spaces before commas, one space after each comma. - Always put spaces around assignment, Boolean and comparison operators. In expressions using a lot of operators, add spaces around the outermost (lowest-priority) operators. - Breaking long lines: if you can, break after commas in the outermost argument list. Always indent continuation lines appropriately, e.g.:: PyErr_Format(PyExc_TypeError, "cannot create '%.100s' instances", type->tp_name); - When you break a long expression at a binary operator, the operator goes at the end of the previous line, e.g.:: if (type->tp_dictoffset != 0 && base->tp_dictoffset == 0 && type->tp_dictoffset == b_size && (size_t)t_size == b_size + sizeof(PyObject *)) return 0; /* "Forgive" adding a __dict__ only */ - Put blank lines around functions, structure definitions, and major sections inside functions. - Comments go before the code they describe. - All functions and global variables should be declared static unless they are to be part of a published interface Naming conventions ^^^^^^^^^^^^^^^^^^ - Use a ``Py`` prefix for public functions; never for static functions. The ``Py_`` prefix is reserved for global service routines like ``Py_FatalError``; specific groups of routines (e.g. specific object type APIs) use a longer prefix, e.g. ``PyString_`` for string functions. - Public functions and variables use MixedCase with underscores, like this: ``PyObject_GetAttr``, ``Py_BuildValue``, ``PyExc_TypeError``. - Internal functions and variables use lowercase with underscores, like this: ``hashes_get_sha1.`` - Occasionally an "internal" function has to be visible to the loader; we use the _Py prefix for this, e.g.: ``_PyObject_Dump``. - Macros should have a MixedCase prefix and then use upper case, for example: ``PyString_AS_STRING``, ``Py_PRINT_RAW``. Documentation Strings ^^^^^^^^^^^^^^^^^^^^^ - The first line of each function docstring should be a "signature line" that gives a brief synopsis of the arguments and return value. For example:: PyDoc_STRVAR(myfunction__doc__, "myfunction(name: str, value) -> bool\n\n" "Determine whether name and value make a valid pair."); The signature line should be formatted using the format for function annotations described in :PEP:`3107`, whereas the annotations shall reflect the name of the type (e.g. ``str``). The leading ``def`` and the trailing ``:`` as used for function definitions must not be included. Always include a blank line between the signature line and the text of the description. If the return value for the function is always ``None`` (because there is no meaningful return value), do not include the indication of the return type. - When writing multi-line docstrings, be sure to always use string literal concatenation:: PyDoc_STRVAR(myfunction__doc__, "myfunction(name, value) -> bool\n\n" "Determine whether name and value make a valid pair."); Python Coding Style ------------------- The coding style for all code written in python is :PEP:`8`. Exceptions from this rule are the documentation, where code is sometimes formatted differently to explain aspects, and functions provided for 0.7 compatibility purposes. When writing code, use tools like pylint, pyflakes, pychecker and pep8.py (all available from Debian/Ubuntu) to verify that your code is OK. Fix all the problems which seem reasonable, and mention the unfixed issues when asking for merge. In order to make the automatic generation of Python 3 code using 2to3 possible, code written in Python may not utilize any functionality unsupported by 2to3 or deprecated as of Python 2.6. Submitting your patch --------------------- First of all, the patch you create should be based against the most current branch of python-apt (debian-sid or debian-experimental). If it is a bugfix, you should probably use debian-sid. If you choose the wrong branch, we will ask you to rebase your patches against the correct one. Once you have made your change, check that it: * conforms to :PEP:`8` (checked with pep8.py). It should, at least not introduce new errors. (and never have whitespace at end of line) * produces no new errors in pychecker, pyflakes and pylint (unless you can't fix them, but please tell so when requesting the merge, so it can be fixed before hitting one of the main branches). * does not change the behaviour of existing code in a non-compatible way. If your change follows all points of the checklist, you can commit it to your repository. (You could commit it first, and check later, and then commit the fixes, but commits should be logical and it makes no sense to have to commits for one logical unit). Once you have made all your changes, you can run ``bzr send -o patch-name`` to create a so called *merge-directive*, which contains your changes and allows us to preserve the history of your changes. (But please replace patch-name with something useful). Now report a bug against the python-apt package, attach the merge directive you created in the previous step, and tag it with 'patch'. It might also be a good idea to prefix the bug report with '[PATCH]'. If your patch introduces new functions, parameters, etc. , but does not update the content of this documentation, please CC. jak@debian.org, and add a short notice to the bug report. Also see `Documentation updates` Once your patch got merged, you can *pull* the branch into which it has been merged into your local one. If you have made changes since you submitted your patch, you may need to *merge* the branch instead. .. note:: If you plan to work on python-apt for a longer time, it may be a good idea to publish your branch somewhere. Alioth (http://alioth.debian.org) and Launchpad (https://launchpad.net) provide bzr hosting. You can also use any webspace with ftp or sftp connection (for the upload). Then you do not need to send *merge directives*, but you can point to your branch instead. Documentation updates --------------------- If you want to update the documentation, please follow the procedure as written above. You can send your content in plain text, but reStructuredText is the preferred format. I (Julian Andres Klode) will review your patch and include it. .. highlightlang:: sh Example patch session ---------------------- In the following example, we edit a file, create a merge directive (an enhanced patch), and report a wishlist bug with this patch against the python-apt package:: user@pc:~$ bzr clone http://bzr.debian.org/apt/python-apt/debian-sid/ user@pc:~$ cd debian-sid user@pc:~/debian-sid$ editor FILES user@pc:~/debian-sid$ pep8.py FILES # PEP 8 check, see above. user@pc:~/debian-sid$ pylint -e FILES # Check with pylint user@pc:~/debian-sid$ pyflakes FILES # Check with pyflakes user@pc:~/debian-sid$ pychecker FILES # Check with pychecker user@pc:~/debian-sid$ bzr commit user@pc:~/debian-sid$ bzr send -o my-patch user@pc:~/debian-sid$ reportbug --severity=wishlist --tag=patch --attach=my-patch python-apt user@pc:~/debian-sid$ # Add --list-cc=jak@debian.org if you change docs.