home-environment: Stop exporting __HM_SESS_VARS_SOURCED

[wahjava]

Description

If the __HM_SESS_VARS_SOURCED is set in environment of parent process, then the spawned child shell will inherit it, and won't set the session variables one expects to be set in their home environment

And, I don't see any need for exporting environment variable, just setting it is enough for it to be a guard.

P.S. This is essentially a re-open of #2328 which I messed up.

Checklist

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[berbiche]

If I understand correctly, if the environment (home.sessionVariables, etc.) is changed after it has been loaded (for instance before starting your window manager) then new shells won't see the new environment variables?

[wahjava]

If I understand correctly, if the environment (home.sessionVariables, etc.) is changed after it has been loaded (for instance before starting your window manager) then new shells won't see the new environment variables?

Exactly

[subterfugue]

Hey, any progress on this PR? I've encountered this issue myself and this would be the solution. What's stopping this from being merged?

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[ncfavier]

Won't this introduce duplicated entries in PATH-like variables? I think this might be a problem?

[wahjava]

Won't this introduce duplicated entries in PATH-like variables? I think this might be a problem?

I've been using it for an year on multiple systems, and haven't experienced what you're pointing. Could you please elaborate why/how that may happen ?

Thanks

[ncfavier]

Things like export PATH=foo:$PATH will result in duplicated foo entries in nested shells. I don't know if this is a problem.

[wahjava]

Things like export PATH=foo:$PATH will result in duplicated foo entries in nested shells. I don't know if this is a problem.

Well, I've not noticed it in practice, it did make switching home-manager profiles more deterministic for me when I was experimenting with session variables. And yes, I'd noticed NixOS uses similar concept (environment variable).

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