Install files for alternative ocamlfind toolchains are not installed.

[rizo]

I'm running into a cross-compilation related issue with opam and dune.

Currently dune has a pretty good support for cross-compilation via findlib toolchains. It correctly separates compilation artefacts for different targets. When a findlib toolchain is used with -x TOOLCHAIN, dune, in addition to producing a PKG.intsall file for the default context, will also produce a PKG-TOOLCAHIN.install file. This works perfectly!

But, the problem is that opam doesn't know about these -TOOLCHAIN.install files and only looks for PKG.install files.

Is there a way to instruct opam install to look for additional install files described above? I'm looking for a solution that does not require changes to the original package.

Might be related to: #2476.

[rjbou]

On install, opam only check for pkg.install file, and there is no way to specify another filename. The only one is to change the opam file (of called command) to move/copy of the generated install file.

Why and what are the generated pkg-toolchain.install files?

[rizo]

The pkg-toolchain.install files are generated by dune for cross-compiled targets. See ocaml/dune/.../test-cases/cross-compilation/run.t for a short example of that in practice.

The files listed in pkg-toolchain.install are typically installed in ~/.opam/$switch/$toolchain-sysroot.

In short, if pkg-toolchain.install were installed, package cross-compilation with opam would be much easier.