[Python-Dev] PEP 376 - Open questions

[P.J. Eby]

At 07:38 PM 7/6/2009 +0100, Paul Moore wrote:
>As promised, here are some open questions on PEP 376.
>
>- Will the public API names be changed from *egginfo* to *metadata*?

+1 (FWIW, 'metadata' is what pkg_resources API refers to this kind of 
stuff as.)


>- What precisely are the use cases for absolute path names? Concrete
>examples are needed. With the current spec, some things can go wrong
>(e.g., see below), so we need real use cases to know how to address
>this.

The purpose is to be able to remove scripts, data files, 
documentation, etc. that's stored in some place that's not 
package-relative, and survive a move of the package directory itself.

For example, suppose I install with --prefix=~, and have files in 
~/bin and ~/lib.  I then move ~/lib/python2.7 to ~/pylib.  If the 
scripts were installed with a relative path, this would break the 
link to the script still living in ~/bin.

Now that I'm thinking about this, it occurs to me that there is 
another way to address this besides mixing relative and absolute 
paths in RECORD, and that is to make *all* the paths relative, and 
include an original installation location in INSTALLER.  Then, it 
would be possible to detect whether the installation location had 
been moved and handle it accordingly...  for some definition of "accordingly".

I agree that further discussion is probably needed to resolve this.


>- How will bdist_wininst/bdist_msi/bdist_rpm be updated?

bdist_wininst, bdist_dumb, and various others use 'install --root' 
pattern to generate files for installation, which means that they 
would transparently end up writing a correct RECORD file, except for 
the inclusion of incorrect absolute paths for non-libdir-relative 
files.  However, if we used the "all relative in RECORD, with a base 
in INSTALLER", these cases could transparently be treated as another 
instance of install directory relocation.

I don't know if bdist_msi does a --root install before generating the 
.msi; if it does, then it should work the same way.


>- Can distutils be made to install files in places the current RECORD
>file spec can't handle? (I think the answer is "yes"). What happens
>then?

Surely an absolute path is sufficient?


>- Should distribution names be case insensitive on case insensitive
>filesystems? For comparison, module/package names are always case
>sensitive even on case insensitive systems.

IMO, they should be case-insensitive *regardless* of filesystem case, 
and I believe PyPI has already begun disallowing packages with only 
case-distinct names (e.g. 'Zope' vs. 'ZoPe') to be registered.