Subject: Re: bug#62698: bind:utils

From: Maxim Cournoyer <[email-masked]>
Date: Thu, 04 May 2023 08:43:34 -0400

Hi Brian,

Brian Cully <[email-masked]> writes:

> Maxim Cournoyer <[email-masked]> writes:
>
>> Thanks for finding the problem.  Should we leave this bug open until
>> specification->package+output is properly documented in our manual,
>> with
>> an example?  If yes, would you like to try your hand at adding it?
>
> I've looked at this briefly, and can't figure out a good place to
> document this (I'm also not particularly good with TexInfo).

Hm, looking at '(guix) Packages with Multiple Outputs', we already have
an example, which simply append packages and (list package "output")
lists, so perhaps that should be preferred instead.  The
'specification->package+output' procedure mostly appears to be used
internally, in (guix scripts environment) for example.

> I'm okay with closing the bug. Though I will say that I think this
> procedure is a bit of a foot-gun. Multiple value returns are always
> kind of weird, and in this particular case I don't see the value at
> all; the only reason to use ‘specification->package+output’ would be
> to get both the package and the output, so the minor advantages of
> multi-value returns are obviated. On top of that, does this even get
> used outside of system/home definitions? And in those places you
> always want a list.
>
> I realize a lot of code uses the current semantics, so changing them
> would be extremely difficult at this late stage. It's worth thinking
> about adding another procedure that does the expected thing (returning
> a list of package and output), IMHO, and transitioning over to that.

Note that for user profiles, it seems better to use manifest with the
convenient 'specifications->manifest' procedure that allows directly
providing package name/outputs via a "bind:utils" specification, for
example.

Closing!

-- 
Thanks,
Maxim