[Python-Dev] Keyword meanings [was: Accept just PEP-0426] (original) (raw)

Toshio Kuratomi a.badger at gmail.com
Wed Dec 5 16:42:48 CET 2012

On Wed, Dec 05, 2012 at 02:46:11AM -0500, Donald Stufft wrote:

On Wednesday, December 5, 2012 at 2:13 AM, PJ Eby wrote:

On Mon, Dec 3, 2012 at 2:43 PM, Daniel Holth <dholth at 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 wrote: How to use Obsoletes: The author of B decides A is obsolete.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

This is correct.

I believe it refuses to install B if A is already there (and the reverse as well).*

I'd have to test this but I believe you are correct about the first. Not sure about the reverse.

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. In rpm-land, if something depended on A and nothing besides the actual A package provided A, rpm will refuse to install B. But rpm is meant to be used unattended so different package managers could certainly choose to prompt. For package renames, package B would have both an Obsoletes: A <= $OLD_VERSION and a Provides: A = NEW_VERSION

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