Re: python 2.2 to python 2.3 transition

[Donovan Baarda <abo@minkirri.apana.org.au>]

On Mon, 2003-08-11 at 22:03, Matthias Urlichs wrote:
> Hi, Josselin Mouette wrote:
> 
> > Hrm, this could be achieved quite simply, /methinks. It needs little
> > changes in dh_python and some prerm/postinst stuff in the python package
> > (not the pythonX.Y package) to rebuild all .pyc's and .pyo's in this
> > directory upon upgrade.
> > 
> > Matthias, do you think it is feasible ?
> 
> Would work for me. /usr/lib/site-python is supposed to have "clean" python
> scripts only, so running compileall.py on all subdirectories thereof
> should pose no problem.

The problem I have with it is it doesn't take into account programs with
python modules outside /usr/lib/site-python. Probably mailman is the
prime example.

Currently packages with python modules are responsible for compiling and
removing their own pyc's and pyo's. Having the python package "take
over" and re-compile them might be risky.

I personally favour having the python package identify all packages that
depend on "python" and getting them to do the recompilation by
re-configuring them. This will work for packages that install *.py's
anywhere. The python package should do the same on removal, so packages
that have things like "Depends: python | python2.1" can recompile
themselves with python2.1 if "python" disappears.

The pythonX.Y packages should do the same to "notify" packages that
optionally depend/support them that the pythonX.Y packages have been
installed/removed.

I know this is more complicated, but if we don't do this, we end up with
yet another half-solution, where version independent packages are only
supported if they put their modules in /usr/lib/site-python, and only
for multiple versions of "python", not "pythonX.Y".

The following is a code fragment for identifying all the installed
packages to be "notified" on install/remove of any python or pythonX.Y
package

# get_dependants <package>
# echo to stdout installed packages that depend on the specified package
# in any way.
get_dependants () {
    PYTHONXY=$1
    QUERYFORMAT='${Status}:${Package}:${Depends}\n'
    dpkg-query --show-format=$QUERYFORMAT -W | \
        egrep "^install ok installed:[^:]*:.*$PYTHONXY([ ,]|$)" | \
        cut -f 2 -d':'
}
 
Using this the python package can "notify" all packages that depend on
it by calling dpkg-reconfigure on them;

for p in `get_dependants python`; do
  dpkg-reconfigure --priority=critical $p
done

This assumes packages will compile their own *.py's using a suitable
python when they are "dpkg-reconfigured". Note this means packages that
have things like "Depends: python (<<2.3) | python2.2" can choose to
fall-back to compiling with python2.2 when python (2.3) is installed.

I'm not sure if dpkg-reconfigure only does stuff for packages that use
debconf. If it does, than an alternative would be to call
"/var/lib/dpkg/info/$p.postinst configure" directly.

-- 
Donovan Baarda <abo@minkirri.apana.org.au>
http://minkirri.apana.org.au/~abo/