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On Wednesday, December 5, 2012 at 2:13 AM, PJ Eby wrote:
On Mon, Dec 3, 2012 at 2:43 PM, Daniel Holth <dholth@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The author of B decides A is obsolete.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?
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