[Distutils] PEP 426: proposed metadata caching convention

[Donald Stufft]

On Wednesday, February 27, 2013 at 1:47 PM, Glyph wrote:
> 
> On Feb 27, 2013, at 2:52 AM, Vinay Sajip <vinay_sajip at yahoo.co.uk (mailto:vinay_sajip at yahoo.co.uk)> wrote:
> > Nick Coghlan <ncoghlan <at> gmail.com (http://gmail.com/)> writes:
> > 
> > > I'm not a fan of post-install hooks - that way lies setup.py. If
> > > people want to run arbitrary code at install time, they can publish a
> > > platform specific installer.
> > > 
> > > *Maybe* we can go down that path in the Python 3.5 timeframe, but for now, no.
> > 
> > I'm concerned that this might affect adoption: there are a lot of projects that
> > have non-trivial custom code in setup.py - often doing mundane stuff like copying
> > files around before the actual setup() call. Having hooks will enable easier
> > migration for such projects (which include, for example, Twisted, Cython, NumPy).
> > I don't believe it's realistic to expect them all to create platform-specific
> > installers; they'll just carry on using setuptools/distribute.
> Quite so.
> 
> Post-install hooks are a requirement for Twisted and for many projects which depend on Twisted.  The hook is always the same on every platform, so it's not a platform-specific installer issue.
> 
> Frankly, a big appeal of some next-generation package distribution system is the introduction of a proper set of events we can hook into, instead of assuming that by some accident of timing we can work out when the software is being "installed" and call some random function from the bottom of setup.py with a bunch of state scooped out of distutils' internals.  The current situation is a total mess.
> 
> -glyph
> 
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> 
> 

I'm generally +1 on hooks, the failure of setup.py isn't particularly that
it's executable, it's that you can't access the metadata without executing
it. In general hooks also allow people to easily disable them during install
if they don't wish for that (of course packages have no reason to support that
if they don't want to).
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