Re: Profiles/manifests-related command line interface enhancements

[Pierre Neidhardt]

Hi Mark!

Mark H Weaver <address@hidden> writes:

> It doesn't remove them, but it overwrites them, thus losing the
> information of what the previous environment was.  Now, it's true that
> for *most* of those environment variables, the previous value is a
> suffix of the new value, but that's not always the case.  One notable
> counter-example is GUIX_PROFILE itself, which is simply overwritten.
> Others include GIT_EXEC_PATH and ASPELL_DICT_DIR.

- ASPELL_DICT_DIR is broken: #29686.  We should fix it anyways.

- What's the use of GUIX_PROFILE once a profile is loaded?  I believe
  it's only there for the user to know which was the last loaded
  profile.  Which is a bit broken in my opinion: I believe GUIX_PROFILE
  should point to the default profile, but this is not possible when
  using multiple profiles.

  With my `guix-activate` proposal, GUIX_PROFILE would not have to be
  overridden.

  Although we could also fix this by modifying the etc/profile file so
  that they don't depend on GUIX_PROFILE being set to themselves (which
  is the actual bug here).

- You are right about GIT_EXEC_PATH, any clue why it has to be overridden?

> There's no way to change the environment variable in Emacs without
> running Emacs lisp code, e.g. by running M-x setenv.

Indeed, for Emacs `guix-activate` would run some Elisp code.  It would
essentially work for every program that can edit its own environment.

> Note that I'm not passing judgement on the merits of your proposals, I'm
> merely letting you know that they cannot be implemented as envisioned,
> at least not if I understand correctly.

With the shell/Emacs/etc. specialization we discussed, I believe it
would be :)


To clarify: what I'm proposing is a more universal, better encapsulated
way to activate profiles.

Currently we can do

--8<---------------cut here---------------start------------->8---
GUIX_PROFILE=/path/to/profile ; . $GUIX_PROFILE/etc/profile
--8<---------------cut here---------------end--------------->8---

which has some shortcomings:

- It only works for Bourne-style shells.  Activating profiles for
  different shells / programs require some work from the user; we should
  do this work upstream I believe.
- It exposes too many implementation details.
- It's too long ;)

Cheers!

-- 
Pierre Neidhardt
https://ambrevar.xyz/

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