Re: importers and input package lookup

[Jelle Licht <jlicht@fsfe.org>]

Ludovic Courtès <ludo@gnu.org> writes:

> Hi!
>
> Attila Lendvai <attila@lendvai.name> skribis:
>
>> there are two, independent namespaces:
>> 1) the scheme one, and
>> 2) the guix package repository.
>>
>> when i work on an importer (golang), it skips the packages that are already available in 2), but then it has no clue under what variable name they are stored in 1), and in which scheme module.
>
> Does the variable name matters though?  In general what matters for the
> importer is whether the package/version exists, regardless of the
> variable name.

Since these packages often end up in a `inputs' list, the variable name
seems pretty relevant.

>> should the dependency lists in the package forms be emitted as (specification->package "pkgname@0.1.0") forms?
>
> No, not for packages in Guix proper.
>
> [...]
>
>> a bit of a tangent here, and a higher-level perspective, but... shouldn't the package definition DSL have support for this? then most package descriptions could be using package specifications instead of scheme variables, and 1) could be phased out. or would that be more error prone? maybe with a tool that warns for the equivalent of undefined variable warnings?
>
> Package specs are ambiguous compared to variable references (they depend
> on external state, on the set of chosen channels, etc.) so in general we
> want to refer to variables.

They are pretty explicit at one point in time: the moment we run an
importer. So at some point in the course of running the importer, we
know we have a package definition somewhere that is pretty much
equivalent to the result of (specification->package "pkgname@0.1.0");
can we somehow serialize this package object, perhaps using a heuristic?

If someone fiddles with GUIX_PACKAGE_PATH, GUILE_LOAD_PATH or any amount
of channels this impacts the result of running an importer, but
importers already can give different results depending on these
settings.