It's a follow-up for #672 (comment).

• I have searched the issues of this repo and believe that this is not a duplicate.

Issue

So setuptools have this nice hook points system where they allow replacing certain utils by some third-party implementations.
It can catch up with what's available by iterating through a list of entrypoints with names corresponding to hooks.
This is a fairly popular technique among setuptools-based dists. For example, pytest and tox support having third-party dists being automatically activated and used when installed given they "advertise" their entry points as required by the plugin system. These two tools use https://github.com/pytest-dev/pluggy to achieve this.

Back to Poetry, I think lots of people agree that providing ability to extend such a great tool is a widely wanted feature.
This would allow adding custom dist/package format generators, custom metadata generators etc. They could be used to retrieve long description from some esoteric formats or places converting that into supported markups. This would also make possible having a custom version constructor like popular plugins to setuptools facilitating version sourcing from Git/Hg (#140/#672). Or, another example, exporting a pinned env and direct dependencies into pip-friendly formatted requirements. And who knows, maybe someone will even try out having another resolver replacement?

Any thoughts on how this might look like?