Re: TODO: user-environment-hook

[Ludovic Courtès]

宋文武 <address@hidden> skribis:

> Currently, (guix profiles) has code to build 'info-dir' for packages in 
> profile.
> As mentioned in TODO, IIUC, we should move the code to 'texinfo'.

Yes, that’s the initial idea.  However, it’s not clear that attaching
“user environment hooks” to packages is the right thing.

For instance, you can install Info files, and if you only ever use the
Info reader of Emacs, you never install Texinfo itself; yet, the ‘dir’
file must be generated.

> Other usecases include:
> * hicolor-icon-theme: use gtk-update-icon-cache to get 'icon-theme.cache'.
> * shared-mime-info: use update-mime-database to get 'mime.cache'.
> * desktop-file-utils: use update-desktop-database to get 'mimeinfo.cache'.
> ? glib: use glib-compile-schemas to get 'gschema.compiled'.

Same problem here: users may never explicitly install GLib, yet these
operations should always be performed.

So I’m tempted to think we could just augment ‘profile-derivation’ to
invoke other hooks similar to ‘info-dir-file’ in (guix profile).  We
could specify a list of “profile hooks” like:

  `(("share/info" . ,info-dir-file)
    ("share/foo/mime.cache" . ,mime-cache-file))

WDYT?

> For schemas, it's always safe for packages in system profile,
> but may broken for user profile:
>   user had install package A
>   user update the guix disto, A -> A' has incompatible schema change
>   user now install package B' which depend on schema of A'
> B' will crash if we have schemas from A and B'.
>
> If we make A a propagated-inputs of B, dose A will be update to A' when
> install B'?

Yes, when installing a package with propagated inputs, said inputs are
installed as well, possibly overriding others.  However, if you look at
collision handling in (guix build union) is minimalist, so anything can
happen.

Thanks,
Ludo’.