Re: Cookbook recipe from "The Repository as a Channel" section does not work for Guix with properly configured GUILE_LOAD_PATH

[Nigko Yerden <nigko.yerden@gmail.com>]

Hello Florian,

pelzflorian (Florian Pelz) wrote:
> While processing guile-package.scm,
> 
> (search-path %load-path "guile-package.scm")
> 
> returns an absolute path if and only if guile-package.scm is in the
> load-path, like when using it from a channel.  Then, your diff makes it
> resolve symlinks.
That's right.

> If the configuration or package file is not in the load-path,
> guile-package.scm is returned, absolute-dirname’s other `if' branch
> calls `canonicalize-path' on all but the basename and directory symlinks
> already got resolved.
No, in this case 'search-path' returns #f. But if 'syntax-source' gives
absolute path, then 'current-source-directory' returns 'dirname' of this
path without calling 'absolute-dirname'.

> Indeed with weird load-paths
> 
> GUILE_LOAD_PATH=${GUILE_LOAD_PATH}:/home/florian/src/home-config/configs guix home reconfigure gnu.scm
> 
> ;;; ("/gnu/store/nanvziq36krgh330yjhwpphcyfz5dyzm-guix-module-union/share/guile/site/3.0")
> 
> because syntax-source says filename is
> "gnu.scm".
> 
> But not normally
> 
> GUILE_LOAD_PATH=${GUILE_LOAD_PATH} guix home reconfigure gnu.scm 
> 
> ;;; ("/home/florian/src/home-config/configs")
> 
> because syntax-source says filename is
> "/home/florian/src/home-config/configs/gnu.scm".
This observation shows that 'current-source-directory' is really bad because
'syntax-source' is bad. Sometimes 'syntax-source' gives an absolute path, and
sometimes a relative one, and I don't understand under what conditions.
And '(module-filename (current-module))' does not seem to be better.
In my experiments it gives exactly the same filename as 'syntax-source'.
But this bad behavior of 'current-source-directory' is unrelated to symlinks and
'if' condition in 'absolute-dirname'. All Guile load paths I have seen before are
absolute paths, and the second branch of 'if' is not executed for them.

Maybe we should leave 'absolute-dirname' alone, as well as 'current-source-directory',
and consider 'local-file' more closely.

Regards,
Nigko