[Distutils] Finding dependencies and Limiting download

Phillip J. Eby pje at telecommunity.com
Thu Mar 16 21:31:49 CET 2006

At 10:13 AM 3/16/2006 -0600, Ian Bicking wrote:
>It occurs to me that maybe it would be easiest to create an RPM that 
>includes Paste, PasteDeploy, and PasteScript all together?  That would 
>simplify all of this, it seems.

That would certainly fix the conflict problem in the short term.

In the long run, I'd like a better solution, though.  Separate components 
for namespace packages are too good a thing to give up on without a 
fight.  I'm tempted to see if there isn't a way to create an import hook in 
pkg_resources that would allow namespace packages to work without having an 
__init__.py.  That would eliminate the file conflicts, albeit at the 
expense of requiring pkg_resources to be imported before any namespace 

That seems problematic, though, since it would only be needed for --svem 
pacakges.  The fundamental problem is that you end up having to have dummy 
packages to hold the __init__.py, or else you have to have something that 
gets imported first.  It seems a bit fragile.

One hack would be to add a .pth file for each --svem install of a namespace 
package, something like "PasteDeploy-nspkg.pth", that contains some code to 
activate the namespace package, like:

     import sys,new; \
     m = sys.modules.setdefault('paste',new.module('paste')); \
     p = os.path.join(sys._getframe(1).f_locals['sitedir'], 'paste'); \
     mp = m.__path__ = getattr(m,'__path__',[]); \
     (p not in mp) and mp.append(p)

Yeah, that would do the trick, if --svem installs left out the __init__.py 
for declared namespace packages.  Of course, this slows down Python startup 
time when you have a lot of --svem namespace packages installed, and 
doesn't work with "python -S", but what else can we do?

If a given system packager wants to handle namespace packages differently, 
we could probably accomodate that via modifiers to the --svem 
mode.  Really, the hardest part of implementing this is going to be the 
bits of setuptools that need to munge the build_py and install_lib commands 
to leave out __init__ files for namespace packages.  I'll probably also 
need to document how to deal with certain legacy situations where there is 
an official package that "owns" the namespace and needs to install an 
__init__.py that actually contains code.

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