User:Breton/GSoC2014/Melange

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Your name
    Boris Bobrov

Your email address
    breton@cynicmansion.ru

The name of the project
    Mediagoblin: Python 3 port + switch to Alembic

Summary
    Port all of MediaGoblin's code to python 3: https://issues.mediagoblin.org/ticket/813
    Currently MediaGoblin uses sqlalchemy-migrate, but it's fairly outdated and unmaintained.
    Port the migration infrastructure to using Alembic instead. Which is also python3-compatible.

Benefits
    Python 3 is a new modern language that gaines popularity.
    Also sqlalchemy-migrate used there is old and should be changed to a new shiny Alembic

Deliverables
    All code will be python3.3-compatible, it means, that there the whole codebase will work with python 2.6, 2.7, 3.3+, maybe 3.2.
    Minimal requirements' versions will be determined and the code will be ported to use them.
    Alembic will be switched to sqlalchemy-migrate. Alembic is a database-schema migration tool.

Plan
    A rough plan:
        1. do something about Paste. Paste as well as pastescript is python3-incompatible.
            - Drop it!
        2. sort out versions of dependencies. Babel < 1.0 does not support py3. Maybe switch to newer versions of babel? Etc.
        3. adopt tox -- https://bitbucket.org/hpk42/tox, use it for different Python versions and interpreters.
        4. follow suggestion on #813: "Start porting MediaGoblin's code to python 3 generally. Ignore migrations, just support MediaGoblin "starting with the latest database schema", or even easier, set up your database on the python 2 branch before you git checkout the python 3 branch. ;)"
            - There is an option to use "six". I suggest not to use it, for code cleanness. If some compatibility code will be required, it will be shipped in _compat module.
            - http://python3porting.com/noconv.html suggests to convert to python3 and then convert back to python2. I agree with that and will do so.
            - Hold up to ideas listed on http://lucumr.pocoo.org/2013/5/21/porting-to-python-3-redux/, like "Test for 2.x not 3.x".
            - The conversion will look like this: 3.3 -> 2.7 -> 2.6 [-> 3.2] [-> 3.4?].
            - To minimize the number of errors need to be fixed during an iteration, the conversion will be done by a number of fixes. A fix is a line from "2to3 -l". Every "fix" will be tested in order mentioned above, after it gives 0 errors, another one will be applied.
        5. Write migrations
            - Switch to Alembic
            - It still doesn't support hacks around SQLite migrations.
            - But there is a workaround which looks small and which we could use perhaps -- https://github.com/klugjohannes/alembic-sqlite
        6. if time left, backport to 3.2
    A little script involving 2to3 shows that these types of changes are required:
        import, set_literal, input, idioms, print, dict, ws_comma (sorted asc).
    Timeline:
        Bonding period: getting to know architecture better, reading requirements' changelogs, experimenting.
        19 May -- 27 May: drop Paste, drop sqlalchemy-migrate, getting dependencies, fix tests
        28 May -- 1 June: adopting tox, making current tests pass and getting failures on python 3.
        2 June -- 15 June: porting
        15 June -- 27 June (mid-term): if everything is done, porting to python 3.2. Else finishing what remains. Or start switching to Alembic.
        30 June -- 20 Jule: integrating Alembic
        31 Jule -- 11 August: backporting old migrations to Alembic

Communication
    We are going to chat in email, mailing lists and IRC. My nick in IRC is breton, I already hang out in #mediagoblin on freenode.
    I use git, mediagoblin is stored in git, we shall work using it.

Qualification
    Experience:
        3.5 years of Python
        3 years of Django
        3.5 years of C in university
        1.5 years of C++ in university
        4 years of javascript (though I don't write too much in it); with jQuery and pure
        6 years of HTML and CSS
        1.5 year of Scheme and 12 months of Common Lisp
        basic knowledge of system administration (set up nginx, uwsgi etc, familiar with cron, shell scripting)
        a couple of FreeBSD kernel modules
    I use
        Debian as main OS
        git (mercurial where required)
        vim
    I liked the project because it's:
        1. MediaGoblin. I like it's idea and what people do there;
        2. Python;
        3. Python 3. I don't have too much experience in Python 3, and I want to a) learn it better and b) learn how to port to it.
    You can find my github repo here: https://github.com/bretonium/
    I don't know some of the tools used there, such as Paste. I don't think it's a problem, because one of the subtasks is to drop it.