[Distutils] PEP 426 installation hooks and conventions

[Vinay Sajip]

I'm looking at PEP 426 specifications for installation hooks and wondering 
whether we need to tighten up the specification a little.

My concern stems from the fact that hook code needs to be installed along 
with other code - at least, the code for preuninstall hooks needs to be in 
the installed code. As it's "only" hook code, the naming of modules which 
contain it may not be done as carefully as the substantive modules and 
packages in a distribution. However, if multiple distributions were to put 
their hooks in a "hooks.py" module, which might seem the simplest thing to 
do, that could lead to problems: if these hook modules get written to site-
packages, the hooks.py from a later installed distribution would override 
that from an earlier installed distribution.

Possible solutions:

1. Constrain the specification so that each distribution must put hook code 
in a subpackage of one of their main packages. This will affect any 
distribution that consists only of modules and which has no packages, as the 
authors will have to create a package just for the hook code.

2. Constrain the specification so that hook code is segregated to a single 
module, perhaps specified by a "hook_module" key in the "install_hooks" 
dict, which is written to the .dist-info directory. An installer could add 
the .dist-info to sys.path before resolving/importing. The code in the hooks 
module could invoke any code it needed from the main body of code in the 
distribution.

Is my concern a valid one? If so, can I please have comments/suggestions 
about how to address it?

Regards,

Vinay Sajip