Conflicting Packages Policy (was: python26 note)

[BJ Dierkes]

NOTE: This is likely a topic to revisit/finalize in the next EPEL SIG Meeting (every Monday at 19:30 UTC).

Hello all,

I would like to start an official discussion regarding the current policy on conflicting packages.  Currently, the EPEL documentation [1] is a bit sparse and does not reflect certain situations (such as the discussion on mod_python26/mod_wsgi26).  Per the FPG [1], Fedora packagers should avoid an explicit 'Conflicts: xxxxx' as much as possible.  However, due to some new developments in EPEL 5 (namely python26), some situations may require explicitly conflicting packages.  

As an example, during my package review for mod_python26 [3] the subject was brought up due to my use of 'Conflicts: mod_python' in the spec for mod_python26.  The packages conflict because mod_python and mod_python26 both provide the 'python_module', and the same Apache directives when enabled.  Therefore, the two can not be loaded at the same time.  The issue would be the same for mod_wsgi and mod_wsgi26 (built against/for python26).  In this specific situation, the possible solutions to work around this are:

 * Change policy to account for situations like those related to python26 and allow explicit 'Conflicts: xxxxx'
 * Silently disable mod_python26 if python_module is already loaded via IfModule [4]


Though the second option (IfModule) is a cleaner approach, it hides the fact that mod_python26 just won't load if mod_python is installed/enabled and assumes the user will know to look at /etc/httpd/conf.d/mod_python26.conf for comments on why that might be.  On the other hand, conflicting with mod_python doesn't inform the user why it conflicts... it just conflicts.  In my opinion it would be slightly more obvious why mod_python26 would Conflict: mod_python, but I don't know what is collectively in the best interest of EPEL maintainers.

In Fedora, an explicit 'Conflicts: xxxxx' is unwanted behavior and would be troubling/confusing for a lot of users.  However, being that EPEL is a different audience and different use case... I would like to open discussion regarding current policy and determine, officially, how these situations should be handled.

References:

[1] http://fedoraproject.org/wiki/EPEL/GuidelinesAndPolicies#Policy_for_Conflicting_Packages
[2] http://fedoraproject.org/wiki/Packaging/Guidelines#Conflicts
[3] https://bugzilla.redhat.com/show_bug.cgi?id=638362
[4] http://httpd.apache.org/docs/2.0/mod/core.html#ifmodule

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derks