On Wednesday, December 5, 2012 at 2:13 AM, PJ Eby wrote: > On Mon, Dec 3, 2012 at 2:43 PM, Daniel Holth <dho...@gmail.com > (mailto:dho...@gmail.com)> wrote: > > How to use Obsoletes: > > > > The author of B decides A is obsolete. > > > > A releases an empty version of itself that Requires: B > > > > B Obsoletes: A > > > > The package manager says "These packages are obsolete: A". Would you like to > > remove them? > > > > User says "OK". > > Um, no. Even if the the author of A and B are the same person, you > can't remove A if there are other things on the user's system using > it. The above scenario does not work *at all*, ever, except in the > case where B is simply an updated version of A (i.e. identical API) -- > in which case, why bother? To change the project name? (Then it > should be "Formerly-named" or something like that, not "Obsoletes".) > >
You can automatically uninstall A from B in an automatic dependency management system. I *think* RPM does this, at the very least I believe it refuses to install B if A is already there (and the reverse as well).* There's nothing preventing an installer from, during it's attempt to install B, see it Obsoletes A, looking at what depends on A and warning the user what is going to happen and prompt it. I think Obsoletes as is an alright bit of information. I think the biggest flaw with Obsoletes isn't in Obsoletes itself, but is in the lack of a Conflicts tag that has the same functionality (minimally refusal to install both, possibly uninstall the previous one with a prompt to the user). Obsoletes has the semantics of a logical successor (typically renames) while Conflicts should have the semantics of a competitor. distribute would conflict with setuptools, foo2 would Obsoletes foo. * I could be wrong about RPM's treatment of Obsoletes > > Please, *please* see the previous Catalog-SIG discussion I linked: > this is only one of multiple metadata fields that were thoroughly > debunked in that discussion as completely useless for automated > dependency management. > > I don't see this in this thread, could you link it again? > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org (mailto:Python-Dev@python.org) > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/donald.stufft%40gmail.com > >
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