Feature request: command to show env status

[rymdhund]

I'm always having trouble with is keeping track of when I need to run eval $(opam env). For example when cd-ing between a local switches. If there was a quick way to query opam about when I needed to update my env it would be easy to write a shell plugin that automatically reconfigures the env when needed.

For example a command like this would do the trick:

opam env --status

That returns Env is up to date or Run 'eval $(opam env)'

This might also be useful for dune to give a hint that you forgot to configure the env when your build fails.

Does this feature make sense? In that case I could try to put together some kind of pull request.

[hcarty]

opam 2 supports automatically changing switches as you navigate in your shell. I'm not sure where that code lives in the source tree, but it should provide a good starting point if the built-in support doesn't work for your setup.

[rjbou]

Indeed, at opam init (or replaying it) you can enable a shell hook that evaluates opam env at each prompt, making it constantly up to date.
You can find in this initial PR #3304 discussion, example of use, and involved files.
Does that cover your case?

[rymdhund]

@rjbou Ah, yes I'm not using the hooks that opam init wants to create since I like to manage my shell config myself. But you're right that I could probably just update the env on every command.

However what I really want to do is show a flag in my prompt when my opam env is out of sync. And I don't think this is possible using any existing commands?

[rjbou]

Usually, one easy way that covers most of the cases (not some tricky ones) is that your env is out of sync when the switch prefix doesn't match opam's one. So, a light check is to add on your prompt command something like

[ "x`opam var prefix`" = "x$OPAM_SWITCH_PREFIX" ] || echo "Update!"

Shell hook files can be found in <opam>/opam-init/env_hook.{sh,csh,zsh,fish}, you can take a look and add at you convenience in you config

[AltGr]

opam switch does print such a warning, but probably not in an easily usable format