On 16 December 2015 at 04:59, Robert Collins <[email protected]> wrote: > Some issues with reusing extras are: > - extras refer to things in the dependency graph, but as > distributions are the installable things and the graph nodes are > distributions, foo[fast] is - in widespread deployment - entirely and > only a list of additional distributions. > - there's no concept of 'default extra', and there is no clear path > for bringing it in compatibly, at least so far > - we haven't worked through the ui implications about which end of > the relation this should be configured: should consumers be specifying > them, or providers? > - negative operators on extras are as yet undefined, and due to the > dependencies of an install being a graph, not a tree, a naive > definition is likely very hard to use IMO
One of the other challenges posed by the current extras system is how best to map it to alternate packaging systems. It *can* be done, but it's not particularly clean (the main approaches I'm aware of involves defining a meta-package for each extra, which is rather horrible, or just translating them to Recommends or Suggests and accepting the loss of granularity). > Recommends and suggests are an interesting way of modelling this, and > its possible we don't need an exclude relation- rather users should > blacklist them globally in the target environment somehow, which would > contain that partcular complexity. I doubt it will surprise anyone to learn I'd be a fan of aiming to learn from Linux distro experience with describing complex dependency graphs on this front :) The RPM folks recently decided the Debian design was essentially a good one, so the new(ish) weak dependency support in that ecosystem has a lot of similarities to Debian's approach: http://www.rpm.org/wiki/PackagerDocs/DependenciesOverview#Weakdependencies Cheers, Nick. P.S. I had to check the actual degree of similarity myself, so for reference, the relevant Debian docs link is at https://www.debian.org/doc/debian-policy/ch-relationships.html#s-binarydeps -- Nick Coghlan | [email protected] | Brisbane, Australia _______________________________________________ Distutils-SIG maillist - [email protected] https://mail.python.org/mailman/listinfo/distutils-sig
