[bug#50755] [PATCH v3] import: Generate list of importers based on available modules

[zimoun]

Hi,

On Thu, 30 Sept 2021 at 10:37, Maxime Devos <maximedevos@telenet.be> wrote:

> The list of importers is only needed for two purposes, right?
>
>    1. to print a list of importers when "guix import --help" is run
>    2. to verify the string actually specifies an importer
>
> Then 'guix import SOME-IMPORTER STUFF' could be optimised:
>
> reolve-importer and guix-import could be modified to skip the validation
> step and let resolve-importer print the error if the module couldn't be
> found.  Possibly (resolve-module '(the possibly undefined module) #:ensure #f)
> might be useful. Then 'importers' would only be required for purpose (1),
> so it could be wrapped in a promise, such that if "guix import some-importer 
> stuff"
> is called, only the required importer module is loaded.

My comment is about the elegance vs the performance loss.  On old
machines, Guix is becoming unpractical for many operations (almost all
the operations indeed) and I would not add another slowness.  I am
fine to sacrifice some performances if it is worth.  However, the
balance is always: what is gain and what is loss?  Here the gain is
small code elegance against the performance lost for end-user.  The
question: does it worth?  From my point of view, no, this change is
not worth.  For what my opinion is worth here. ;-)

Cheers,
simon