Re: [gentoo-dev] Versioning of Python scripts

[Arfrever Frehtes Taifersar Arahesis <Arfrever@gentoo.org>]

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2009-12-21 11:50:14 Brian Harring napisał(a):
> On Sat, Dec 19, 2009 at 04:24:49PM +0100, Arfrever Frehtes Taifersar Arahesis wrote:
> > Distutils/Setuptools/Distribute modify shebangs of installed Python scripts, so that they
> > contain path of Python interpreter with version included (e.g. "#!/usr/bin/python3.2").
> > This behavior has both advantage and disadvantages:
> >   - Scripts of packages supporting only e.g. Python 2 can be executed (without necessity
> >     of using of e.g. "python2 /usr/bin/${script}") after activating of e.g. Python 3.
> >   - Scripts of packages supporting multiple Python versions ignore active Python version.
> >   - Scripts of packages supporting multiple Python versions cannot be easily (without
> >     necessity of using of e.g. "python3.1 /usr/bin/${script}") executed with a Python
> >     version different than active Python version.
> > The best solution, which removes these 2 disadvantages and preserves the advantage, seems
> > to be to rename Python scripts to include Python version [1] in filenames, and create wrapper
> > scripts, which call appropriate target scripts [2]. Some files sometimes try to execute
> > e.g. "/usr/bin/python /usr/bin/${script}", so wrapper scripts must be implemented in Python.
> > Wrapper scripts try to execute "${wrapper_script}-${PYTHON_ABI}" files (e.g. "py.test" will
> > execute "py.test-3.1", when Python 3.1 is set as active Python version).
> > 
> > distutils.eclass will automatically rename some scripts [3] in "${D}usr/bin" and call
> > the function, which generates wrapper scripts. In case somebody is interested in reading of
> > source code of python_generate_wrapper_scripts() function and potential suggesting of
> > improvements, I'm attaching this function and 2 example wrapper scripts. I'm planning to
> > commit addition of this function in next week.
> 
> Not really a huge fan of the EPYTHON var... can you clarify it's real 
> world usage?

It simplifies development of ebuilds of packages having non-Distutils-based build systems.
E.g. ebuilds of packages, which support only Python2, install some executables or libraries
(e.g. /usr/lib/kvirc/4.0/modules/libkvipythoncore.so of net-irc/kvirc) linked against
libpythonX.Y.so and don't install any Python modules, will be able to simply call
'python_set_active_version 2', which will export EPYTHON variable with appropriate value.
Ebuilds should never manually set EPYTHON variable.

> I can see that causing all sorts of mayhem as it passes 
> it's way down through python scripts invoking other scripts- 
> specifically thinking of a py3k only script being forced to 3.1, then 
> invoking a py2k script.

EPYTHON variable should be respected only by scripts, which are used during building, testing
or installation of other packages and need to be called with appropriate Python version.
Examples: py.test, trial
distutils_src_install() will call python_generate_wrapper_scripts() (at least by default)
without -E option.

> Beyond that, please provide a way to *disable* this for a pkg.

OK.

-- 
Arfrever Frehtes Taifersar Arahesis

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