So, consider I want to target my library foo as Elixir ~> 1.12

This has a dependency bar, which in v1 has a dependency to Elixir~> 1.10, but in v2 it has a dependency to Elixir ~> 1.18. This is totally fine so far.

But when I use mix to lock the dependencies (mix deps.get), it will always generate a mix.lock file using the newest version (v2), and naturally when I run CI using my target minimum Elixir version of 1.12, CI fails because standard lib functions are used that do not exist in 1.12.

Now, most of this is still correct - I target Elixir ~> 1.12, so it is correct to retrieve the newest compatible dependency for the given version, because Elixir 1.18 does match ~> 1.12.

But not, if I’m running it using an Elixir 1.12 toolchain, which I am.

How do I deal with this properly? Maybe I’m missing something?

Currently I have to manually search through every revision of every direct dependency to find a useable version, then do the same for every single transitive dependency, and then manually set said version. That’s quite the effort for something the dependency solver already does for every dependency (except Elixir itself)