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

MRAB python at mrabarnett.plus.com
Sat Dec 8 22:14:19 CET 2012

On 2012-12-08 20:18, PJ Eby wrote:

On Sat, Dec 8, 2012 at 5:06 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

On Sat, Dec 8, 2012 at 4:46 PM, PJ Eby <pje at telecommunity.com> wrote:

So if package A includes a "Conflicts: B" declaration, I recommend the following: * An attempt to install A with B already present refuses to install A without a warning and confirmation * An attempt to install B informs the user of the conflict, and optionally offers to uninstall A In this way, any collateral damage to B is avoided, while still making the intended "lack of support" declaration clear. How does that sound? No, that's not the way it works. A conflict is always symmetric, no matter who declares it. But that precisely contradicts what you said in your previous email: It's to allow a project to say they don't support installing in parallel with another package. Just because A doesn't support being installed next to B, doesn't mean B doesn't support being installed next to A. B might work just fine with A installed, and even be explicitly supported by the author of B. Why should the author of A get to decide what happens to B? Just because I trust A about A, doesn't mean I should have to trust them about B. [snip] If package A says that it conflicts with package B, it may or may not be symmetrical, because it's possible that package B has been updated since the author of package A discovered the conflict, so it's important that the user is told which package is complaining about the conflict, the one that is being installed or the one that is already installed.

It may also be helpful if the package that includes the "Conflicts" declaration specifies which version of the other package it was last tested against in case there is a more recent version of the other package that does not cause the conflict, or, indeed, that there's a more recent version of the package that includes the "Conflicts" declaration that does not cause the conflict.

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