[Distutils] Making commands extensible by default

[Tarek Ziadé]

Hello,

This is a side discussion but quiet important ihmo.

== Problem ==

Some people complained about the fact that is was hard to extend
Distutils commands.
You end up rewriting the whole command most of the time.

So what's a command ? It's a class that is used by the distribution
instance when you run Distutils.

roughly:

cmd = Command(distribution)
cmd.initialize_options()
cmd.finalize_options()        <---  allows to check the options if
subcommands where run
cmd.run()                            <---  runs the code

each command can define sub commands, but most of the time it's a
harcoded list, so you need to inherit the command
if you want to add a new behavior.

== work in progress, ==

What we want to do here is being able to define subsets in run(),
sharing the same options environment.

so basically, a rough, generic run() method could be:

def run():
   for func in some_funcs:
      func(self, options)

If "some_funcs" could be defined by a registery with simple names,
anyone could provide new functions
and configure the registery to run a sequence of function.

Given a command name, Distutils can get this list of function, through
a registery.
Each function could register itself into Distutils, like in what I
have started to work here for the manifest file:
see http://wiki.python.org/moin/Distutils/ManifestPluginSystem

The ordering would be configurable through the setup.cfg file.

Any opinion, idea for this part ?

Cheers
Tarek