Re: How to use guix-for-channels together with -L without errors?

[Tomas Volf <~@wolfsden.cz>]

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On 2024-08-15 19:14:52 +0200, Nils Landt wrote:
> > Tomas Volf <~@wolfsden.cz> hat am 15.08.2024 00:24 CEST geschrieben:
> >
> > Now, what I do not understand is why this error:
> >
> >     no code for module (foo)
> >
> > is there.  I am building guix from %default-channels, why is it even loading
> > files in the local directory?  And how do I make it stop?  In this case, I could
> > just drop `-L .', but in real code I need the argument to load modules required
> > for the system.
>
> When that happened to me, it took me forever to find out, so I'm happy to save
> you some pain: The -L adds to the *package* module search path. Guix loads all
> the scm files there to get the package definitions, I'm guessing so there
> doesn't need to be empty modules with a huge "requires" list of every
> package-containing module.
>
> So I put my package definitions in a subdirectory of the channels directory,
> add that subdirectory to GUIX_PACKAGE_PATH, and add the channel root directory
> to GUILE_LOAD_PATH.

Yes!  That is it, when I use GUILE_LOAD_PATH instead of -L the errors go away.
Thank you so much.  You have saved me so much time. ^_^

Now I have a different problem however.  Given a channel list with commits,
hence resolving to the same code every time, it still gets pulled every time,
and Guix derivation computed every time.  Illustrated here:

    /tmp/repro $ cat x.scm
    (use-modules (guix channels)
                 (gnu packages package-management))

    (guix-for-channels (list (channel
                              (name 'guix)
                              (url "https://git.wolfsden.cz/.git/guix")
                              (commit
                               "b03eddc326ee4eb26b25743faee2080de6aded7e")
                              (introduction
                               (make-channel-introduction
                                "028e445a2028068e3c83996daa281057f19141a0"
                                (openpgp-fingerprint
                                 "B783 49B3 8C14 7D36 2988  68A4 2FBF EE7D B67F C1A9"))))))
    /tmp/repro $ guix build -f x.scm
    Updating channel 'guix' from Git repository at 'https://git.wolfsden.cz/.git/guix'...
    Computing Guix derivation for 'x86_64-linux'... |
    /gnu/store/9i597ckynirxy4w5iv2wbmy288vc7gf0-profile
    /tmp/repro $ guix build -f x.scm
    Updating channel 'guix' from Git repository at 'https://git.wolfsden.cz/.git/guix'...
    Computing Guix derivation for 'x86_64-linux'... |
    /gnu/store/9i597ckynirxy4w5iv2wbmy288vc7gf0-profile

This does not seem necessary (it uses commit, so it does not change) and makes
re-deploys *much* slower.  Would you happen to have magical trick for this as
well?

Tomas

--
There are only two hard things in Computer Science:
cache invalidation, naming things and off-by-one errors.

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