[Python-Dev] How we can get rid of eggs for 2.6 and beyond

[Tres Seaver]

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Martin v. Löwis wrote:
>>> Sure, but what is precisely the semantics of uninstallation, in
>>> terms of changes to the system state?
>>>
>>> I think any model where uninstallation is merely the removal
>>> of files is too limited to be practical.
>> The distutils only support the *addition* of files, so I'm not sure 
>> how only removing files is a limit here.  Could you explain?
> 
> For files, yes, it only supports addition. But it supports
> arbitrary other actions, such as:
> - addition of registry keys
> - addition of user accounts
> - creation of database tables in a relational database
> - updating the shared library loader path
> - creation and start of a system service
> - integration of documentation into info
> - registration of DTDs with the system catalog
> - ...
> 
> It's turing-complete, and it has full interface to the operating
> system, so installation of a distutils package can do *much*
> more than merely installing files.

Which is exactly what is wrong with distutils:  turing completeness in
an installer is an *anti* goal, from the perspective of manageability.
I'd be willing to bet that if you asked system packagers to list the
dozen or so packages which they *hate* to maintain, the large majority
of each list would be packages which acutally use the full power of
distutils.

(Note:  I'm aware that people believe it to be necessary to munge the
Windows registry when installing Python packages;  I just don't agree
with the practice, and don't think we should distort Python's process to
coddle it).

> Uninstallation needs to revert anything installation did,
> so it is often more than mere removal of files.

Practically speacking, nobody but the author of the TC-abusing setup.py
is *ever* going to be able to do this, and most of them won't get the
edge cases right.  Maybe we can just punt on such packages, and make a
tool which actually works for the huge majority of distributions which
don't need to do more than install files.



Tres.
- --
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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