Issues using opam .locked files

Ecosystem
1

Here’s what I’m trying to do:

  • I have a local project (arm) with a my_project.opam.locked
  • I’m copying all config files to a docker/podman container (amd64): *.opam* dune-project dune Makefile*
  • I run opam install --yes --locked --deps-only -- . with the expectation of getting a 1:1 build env as my local project

The first error was that arm-amd64 dependencies were included in locked files (Cross compile and opam lock files with conflicting dependencies - #2 by kit-ty-kate), which seems fixed

I’m getting the following error:

The following dependencies couldn't be met:
  - my_project -> ocaml-system = 5.2.1
      unmet availability conditions: sys-ocaml-version = "5.2.1" & (os != "win32"
    | sys-ocaml-libc = "msvc")

even though opam switch list is:

5.2     ocaml-base-compiler.5.2.1  5.2

and ocam --version is The OCaml toplevel, version 5.2.1

I’m not sure what to make out of this error?
(opam install . --deps-only runs fine)

Is there an alternative to opam .locked files?

2

It looks like the system you locked the project on was using a preinstalled version of OCaml 5.2.1 (so the .locked file contains a reference to ocaml-system version 5.2.1 instead of ocaml-base-compiler 5.2.1).

It’s another manifestation of the weakness of the current lockfile implementation - the workaround here would be either to edit the lock file to replace the ocaml-system package with ocaml-base-compiler or to re-create the lockfile on a system where you’re using ocaml-base-compiler instead of the preinstalled compiler.

3

What is the difference between ocaml system and ocaml base compiler?
on the host machine the switch from which the lock file is generated is:

→  /Users/my_user/my_project ocaml-system.5.2.1
 ocaml-base-compiler = 5.2.1 | ocaml-system = 5.2.1
4

The difference is whether the compiler is provided by your system (e.g. in /usr/bin) and just used by OCaml or whether it’s built from sources and installed in the switch (in $(opam var bin)).

On the host, you should be able to change it with opam switch set-invariant ocaml-base-compiler.5.2.1 which should then build the compiler (and will rebuild the entire switch with it) and then if you recreate the lock then it should use ocaml-base-compiler.5.2.1 instead of ocaml-system.5.2.1.

5

In the Octez repository, the script which updates the lock file actually removes the definition of the ocaml-system package so that Opam cannot use it. This is only possible because the script actually clones the opam repository (see lines 52-72).