[Distutils] OS X and PEP 425 / wheels

[MinRK]

Hello,

I proposed a patch <https://github.com/pypa/pip/pull/1465> to pip, with
respect to treatment of the platform tag on OS X, and Chris Barker proposed
that I bring the discussion here.

The situation:

PEP 425 describes the platform tag as:

The platform tag is simply distutils.util.get*platform() with all hyphens -
and periods . replaced with underscore *.

but the PEP makes no mention of what should be done on OS X. On OS X,
get_platform() has the form:

macosx_10_6_intel

where 10_6 indicates that the OS X deployment target (of Python) is 10.6,
and intel indicates that it is a fat binary with both x86_64 and i386.
Other values for the arch include ‘ppc’, ‘ppc64’, and ‘universal’, another
multi-arch tag indicating a fat binary with all four of 32/64bit intel and
ppc.

Where PEP 425 causes problems (or pip’s implementation thereof), is in
testing strict equality of this value, not taking into account the meaning
of its contents. I proposed two changes:

   1.

   Use >= comparison for the deployment target

   From the OS X platform
documentation<https://developer.apple.com/library/mac/documentation/DeveloperTools/Conceptual/cross_development/Configuring/configuring.html>
   :

   Choose a deployment target. This identifies the earliest OS version on
   which your software can run.

   so a binary with deployment target = 10.6 should be installable on OS X
   >= 10.6.

   This change restores the longstanding behavior of easy_install, where
   10.6 eggs are installable on >= 10.6.
    2.

   support multi-arch names (intel, universal) on their respective
   components
    - intel is valid on {x86_64, i386}
      - universal is valid on {intel, x86_64, i386, ppc64, ppc}

   easy_install, like pip, also does strict comparison here, so this would
   be new behavior.

My actual use case:

I have a wheel (pyzmq), which works on any intel-based Python targeting OS
X >= 10.6. To express this with pip-1.5, the filename has to be:

pyzmq-14.1.0-cp27-none-macosx_10_6_intel.macosx_10_6_x86_64.macosx_10_6_i386.macosx_10_7_intel.macosx_10_7_x86_64.macosx_10_7_i386.macosx_10_8_intel.macosx_10_8_x86_64.macosx_10_8_i386.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_9_i386.whl

and it has to grow every time there is a new OS release.

With both proposed changes, I could communicate the same information with
just one tag:

pyzmq-14.1.0-cp27-none-macosx_10_6_intel.whl

With just the first change, it would need three:

pyzmq-14.1.0-cp27-none-macosx_10_6_intel.macosx_10_6_x86_64.macosx_10_6_i386.whl

Any feedback from experts, especially if my understanding of deployment
targets or fat binaries is incorrect, would be much appreciated.

Thanks,

-MinRK
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/distutils-sig/attachments/20140306/94ded214/attachment.html>