Opam init complains that sandboxing isn't working on platform macports

[anuragsoni]

Hi,

I'm trying to use the opam 2.1 beta version (I tried both the published beta, and a version compiled from the current trunk) with a clean install. When I run opam init I see an error message about sandboxing not working.

% opam init --bare
[NOTE] Will configure from built-in defaults.
Checking for available remotes: rsync and local, git.
  - you won't be able to use mercurial repositories unless you install the hg command on your system.
  - you won't be able to use darcs repositories unless you install the darcs command on your system.

[ERROR] Sandboxing is not working on your platform macports:
        "~/.opam/opam-init/hooks/sandbox.sh build sh -c echo SUCCESS >/tmp/t && cat /tmp/t" exited with code 1
        "/Users/asoni/.opam/opam-init/hooks/sandbox.sh: line 61: OPAM_SWITCH_PREFIX: unbound variable"
Do you want to disable it?  Note that this will result in less secure package builds, so please ensure that you have some other isolation mechanisms in place
(such as running within a container or virtual machine). [y/N]

If I ignore the warning and continue by pressing N the install seems to succeed without issues. (opam doesn't automatically source the correct switch for me anymore even though the shell hooks have been installed, but the install overall seems to work fine).

I am using macOS 10.15 (Catalina) along with macports. This error wasn't present in the opam 2.0 series.
I'm wondering if this is an environment variable issue and I need to setup something to let Opam know about macports? It seems like the new depext integration is also having trouble finding dependencies like libffi via macports. It complains about them not being installed even though they are.

[AltGr]

This was a bug in the first beta, should be fixed in 2.1.0~beta2

[anuragsoni]

This was a bug in the first beta, should be fixed in 2.1.0~beta2

@AltGr The behavior i reported was seen with both 2.1.0~beta2 and with a version compiled from opam-trunk after the beta2 was released.

[rjbou]

Yes, the variable (OPAM_SWITCH_PREFIX) is not defined at init, in a fresh shell. A fix in opam is needed, not on your side. There is no link with depext, it's the new mechanism to check that the sandbox is usable on the current setup (docker, chroot). cf. #4284.

For depext / macports issues, there is an open one, about variants and their handling #4297. If it is nt the same problem, feel free to open a new one, like that we can investigate on it.

[anuragsoni]

@rjbou I agree that the depext issue is not related to this issue :) Sorry for the noise. #4297 could indeed be related and i'll take a look at that and open a separate issue if needed.

Thanks,
Anurag