[Q] Make OPAM recognize an existing version (manually installed)

[anzhi0708]

After compiling OCaml 5.1 from source, OPAM still recognizes only previously installed switch

~ $ opam switch list
#  switch  compiler
          description
→  4.14.1  ocaml-base-compiler.4.14.1
          4.14.1

I compiled & installed OCaml 5 to bin/ tho

~ $ ocaml --version
The OCaml toplevel, version 4.14.1
~ $ $PREFIX/bin/ocaml --version
The OCaml toplevel, version 5.1.0+dev1-2022-06-09

I want version 5.1 listed in opam switch list too.

These two versions have different installation directories

~ $ which ocaml
/data/data/com.termux/files/home/.opam/4.14.1/bin/ocaml
~ $ which $PREFIX/bin/ocaml
/data/data/com.termux/files/usr/bin/ocaml

Send help :3

(Summary:

• version 5.1 was NOT installed by OPAM
• version 4 WAS installed by OPAM
• Now OPAM does not realize the existence of version 5
  )

[kit-ty-kate]

The problem is not in opam but in opam-repository which lacks the necessary ocaml-system.5.1.0 package.

So far we've never had this package during the development portion because the need didn't really arose as people usually use the builtin ocaml-variants.5.1.0+trunk.

For you though, there is two ways to fix that:

• Add the missing ocaml-system package in opam-repository (but I'm not sure what to use as value to match for the sys-ocaml-version variable so it might be a bit tricky)
• Follow the OCaml compiler documentation: https://github.com/ocaml/ocaml/blob/trunk/HACKING.adoc#testing-with-opam and reinstall it in a switch this way.

I've opened an issue in ocaml/opam-repository#23515
I'll close this discussion as I see you've already opened ocaml/ocaml#12110 for the second solution and you can comment on the new issue if you want to add something for the first solution.

[anzhi0708]

Thank you very much!

[rjbou]

fyi, ocaml-system is a package that you can pin to install custom system packages (that are not in default repository).