Re: Using symlinks in 'local-file'

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> If one uses a relative symlink in 'local-file', it will lead to a broken
> symlink in the store as illustrated in the attached example.  So I think
> it either:
>
> - should be documented explicitly that 'local-file' adds a specified
>   file to the store blindly, which may lead to the problem with a broken
>   symlink.
>
> - or 'local-file' (or a deeper procedure) should take care of that case
>   and dereference a symlink if needed.
>
> WDYT?

Actually, this only happens with #:recursive? #t, which is currently the
default.

With #:recursive? #f, you get an error:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,enter-store-monad
store-monad@(guile-user) [1]> (gexp->derivation "foo" #~(symlink #$(local-file "/tmp/symlink1" #:recursive? #f) #$output))
guix/store.scm:604:22: In procedure add-to-store:
guix/store.scm:604:22: Throw to key `srfi-34' with args `(#<condition &nix-protocol-error [message: "regular file expected" status: 1] 30c5ab0>)'.
--8<---------------cut here---------------end--------------->8---

So I think we should first make #:recursive? default to #f, since that’s
what we want by default, and optionally have the <local-file> gexp
expander resolve symlinks.

WDYT?

> (define (call-derivation drv)
>   (apply system*
>          (cons (derivation-builder drv)
>                (derivation-builder-arguments drv))))

This is quite original.  ;-)

Thanks,
Ludo’.