depext: is there support for passing options to the OS package manager?

[anton-trunov]

Hi! I have a use case where to build an OCaml package depending on an foreign library, I need to pass a CLI option to the Homebrew package manager:

brew install <package> --with-foobar-support

Is it possible to do using depext in opam? Thanks in advance.

[dra27]

Not yet - this is a feature we're looking at for opam 2.2 next year.

[dra27]

At the moment, you can emulate this with depopts - so you have a dummy package to enable foobar support. In opam-repository, ctypes-foreign is an example of this - https://opam.ocaml.org/packages/ctypes/

[AltGr]

If it's purely for local use, as opposed to having it in the repository as suggested by @dra27, you can always let opam pause instead of running the package manager itself, run the commands, and then let it continue.

Seems quite ugly, but wouldn't it actually work to have the following ?

depexts: [
  ["<package>" "--with-foobar-support"] {os-distribution = "homebrew" & os = "macos"}
]

opam is pretty lax on what is in the list to the left IIRC

[anton-trunov]

@dra27 @AltGr Awesome suggestions, thank you very much!

[dra27]

An update, following review of issues yesterday: @AltGr's suggested workaround definitely won't work now with the integrated depext in opam 2.1, since it will attempt to detect the presence of a package called --with-foobar-support.

Other package managers either have, or have recently added, features like this, so this is something we should come to. A note at this stage to remember that however this is done it creates a dependency on the setting, so in order to pass a --with-flag in, we'd also need the depext subsystem to be able to detect whether the package was built/installed with that flag and know how to reinstall the package with that flag if necessary.