When a popular package with many reverse dependencies introduces breaking changes, what practical options exist for the community to manage the transition? An example will be illustrative: in the recent release of ppxlib 0.36, a change to the internal AST required PPX authors to use a different rep…

Without invalidating the more general question you are raising, the ppxlib maintainers opted for an “upgrade the world” approach to compatibility . Ppxlib is in a specific spot where this seems to make sense. (I do not know how it turns out in practice from my personal experience, maybe you are repor…

Thanks @gadmm , I recall that post now that you bring it up. As to how well “upgrade the world” is working out in practice… all I can say is that I didn’t have to look hard to find the version conflict in my example above. I noticed a few others when upgrading packages for one of my projects. I won…

I wonder if we could have a semi-automated way to add upper bounds (only for deps syntactically without upper bounds) to dependencies of packages in the opam repository, at dependency versions where a dependency introduces breakage.

This is manual, but it is already happening. The issue raised above, if I understood correctly, is that now there are no versions of some packages supporting the new library, making it (at least temporarily) impossible to upgrade in some cases

It’s not obvious to me how a versioning policy could help here. Could you elaborate?

We’ve discussed this a bit here: Automate repair of reverse dependencies when package updates introduce breaking changes · Issue #217 · ocurrent/opam-repo-ci · GitHub Not to counter @mseri ’s point about the orthogonality of this feature. :slight_smile:

I am happy to discuss in the thread I started.

The issue raised above, if I understood correctly, is that now there are no versions of some packages supporting the new library, making it (at least temporarily) impossible to upgrade in some cases To build on this a little bit: it might not be possible to use a new package version which contain…

Thanks for raising this point @conroj Speaking with my ppxlib maintainer hat on, this is indeed an unfortunate situation. As others have pointed out, this is a particularly hard problem for ppxlib. The current design means if we want to offer ppx authors with the latest upstream OCaml features, we …

Breaking PPX API changes and the package ecosystem

Ecosystem

yawaramin June 19, 2025, 1:40am 6

See Opam repository package versioning policy?

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Breaking PPX API changes and the package ecosystem

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