https://hackage.haskell.org/package/containers-0.7/changelog
Please note that I am not the author of these changes, I am just posting them here.
Note that while containers is a boot library, you can still override it and test your packages against the new version. Given that this release will probably be packaged with a future GHC version, you might as well implement compatibility now, instead of waiting.
Top marks to the containers maintainers for being so explicit about the breaking changes!
It is quite entertaining that the venerable containers upon which most of Haskell rests is only at 0.7 . But it works well !
However, I feel like PVP versions are cheating, because 0.7 in PVP basically just means 7.0.0 in semver.
In respect of the dropped stack.yaml, if needed, that can be created with command stack init in the package’s root directory. With GHC 9.4.7, its content can be as simple as just:
resolver: lts-21.13
…and once again, HBC was “ahead of its time” :
(…or just the inspiration :-)