Re: Package input loop detection

[ludo@gnu.org (Ludovic Courtès)]

Hello!

Ricardo Wurmus <rekado@elephly.net> skribis:

>> I've had this issue for a while now, while adding some packages, I'll
>> create a loop in the package graph, which causes Guix to just loop
>> infinitely when trying to generate derivations.
>
> this is a great initiative.  I’ve been having this issue in the past as
> well, and I’d really like Guix to be a little smarter about it.

+1

>> I'm not particularly fond of the implementation, because the
>> package-derivation function is called from expand-input called from
>> bag->derivation, the information about the part of the graph that has
>> been traversed is passed through each function.
>>
>> The seen-package-list argument could be removed, but the ordering
>> information is really useful when printing out the error message. I
>> think it should be still possible to generate this after finding the
>> issue by searching through the graph of packages, which would allow
>> removing this one argument.
>>
>> One other thought I had is that this could be extracted to something in
>> guix lint, which would at least allow finding these problems, without
>> touching the core derivation related code.
>
> I’d be in favour of keeping it out of the core and stash it away in a
> separate tool.  Not sure if that should be “guix lint” (what about “guix
> graph”?), but I would prefer that over having the code run all the time.

I’d be in favor of keeping it in the core, like Chris did, provided the
code is not too complex and provided there’s no significant performance
penalty.  That way, problems would always be gracefully handled.

I’ll take a look at Chris’ code soonish.

Thanks!

Ludo’.