Re: gexps and ‘with-imported-modules’

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> Ludovic Courtès (2016-07-04 01:20 +0300) wrote:
>
>> Hello!
>>
>> The ‘wip-gexp-imported-modules’ branch changes gexps so that each gexp
>> embeds information about which modules need to be imported into its
>> execution environment.
>>
>> Before you would do:
>>
>>   (gexp->derivation "foo"
>>                     #~(begin
>>                         (use-modules (guix build utils))
>>                         …)
>>                     #:modules '((guix build utils)))
>>
>> to specify that (guix build utils) must be imported in the build
>> environment of “foo”.  After, it becomes:
>>
>>   (gexp->derivation "foo"
>>                     (with-imported-modules '((guix build utils))
>>                       #~(begin
>>                           (use-modules (guix build utils))
>>                           …)))
>>
>> The gain (not visible here) is that when you nest gexps, the outermost
>> gexp now contains all the info about modules that need to be imported.
>> That way, no side channel is needed to carry the imported module info
>> (by “side channel”, I mean things like the ‘imported-modules’ field
>> currently found in <shepherd-service> and several other places.)  Thus,
>> it should be easier to compose gexps.
>
> Great!  I like 'with-...' things.  And wow, you did a huge work again!

Thank you.  I think it’ll be beneficial.  It makes more sense to provide
imported-module info at the gexp creation site rather than at the use
site.

>> I plan to merge it within a day or two.
>>
>> Comments welcome!
>
> I see you added the indentation rule for 'with-imported-modules' in
> "emacs/guix-devel.el".  I think it would also be good to add it to
> 'guix-devel-keywords' (as you did in commit cd6f6c22fb) to make it
> highlighted as the other keywords.

Will do!

Ludo’.