(guix modules) and ‘source-module-closure’

(guix modules) and ‘source-module-closure’

[Ludovic Courtès]

Hi!

Commit 7ca87354db53fd1e1a7a3dfeddb9a598ea064bbe adds (guix module),
which provides a way to compute the closure of a Scheme module by
looking at its source code.

This has to do with typical ‘with-imported-modules’ usage, as explained
in the manual:

--8<---------------cut here---------------start------------->8---
   Usually you want the _closure_ of the module to be imported—i.e., the
module itself and all the modules it depends on—rather than just the
module; failing to do that, attempts to use the module will fail because
of missing dependent modules.  The ‘source-module-closure’ procedure
computes the closure of a module by looking at its source file headers,
which comes in handy in this case:

     (use-modules (guix modules))   ;for 'source-module-closure'

     (with-imported-modules (source-module-closure
                              '((guix build utils)
                                (gnu build vm)))
       (gexp->derivation "something-with-vms"
                         #~(begin
                             (use-modules (guix build utils)
                                          (gnu build vm))
                             ...)))
--8<---------------cut here---------------end--------------->8---

The benefit can be seen in the next commit:

  http://git.savannah.gnu.org/cgit/guix.git/commit/?id=239c6e276214813f59f761c9dc5cc0e9d266b49b

Comments welcome!

Ludo’.

Re: (guix modules) and ‘source-module-closure’

[Ricardo Wurmus]

Ludovic Courtès <ludo@gnu.org> writes:

> Hi!
>
> Commit 7ca87354db53fd1e1a7a3dfeddb9a598ea064bbe adds (guix module),
> which provides a way to compute the closure of a Scheme module by
> looking at its source code.
>
> This has to do with typical ‘with-imported-modules’ usage, as explained
> in the manual:
>
> --8<---------------cut here---------------start------------->8---
>    Usually you want the _closure_ of the module to be imported—i.e., the
> module itself and all the modules it depends on—rather than just the
> module; failing to do that, attempts to use the module will fail because
> of missing dependent modules.  The ‘source-module-closure’ procedure
> computes the closure of a module by looking at its source file headers,
> which comes in handy in this case:
>
>      (use-modules (guix modules))   ;for 'source-module-closure'
>
>      (with-imported-modules (source-module-closure
>                               '((guix build utils)
>                                 (gnu build vm)))
>        (gexp->derivation "something-with-vms"
>                          #~(begin
>                              (use-modules (guix build utils)
>                                           (gnu build vm))
>                              ...)))
> --8<---------------cut here---------------end--------------->8---
>
> The benefit can be seen in the next commit:
>
>   http://git.savannah.gnu.org/cgit/guix.git/commit/?id=239c6e276214813f59f761c9dc5cc0e9d266b49b

Ah, very nice!

Why is it necessary to read the file and parse the define-module
expression?  Does Guile not keep any of this information?  Should it?
Will something like this become part of Guile eventually?

~~ Ricardo

Re: (guix modules) and ‘source-module-closure’

[Andy Wingo]

On Mon 05 Sep 2016 10:13, Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de> writes:

> Ah, very nice!
>
> Why is it necessary to read the file and parse the define-module
> expression?  Does Guile not keep any of this information?  Should it?
> Will something like this become part of Guile eventually?

If you have the module loaded, there is "live-module-closure" which uses
the information Guile has at run-time.  I guess Ludovic wanted to get
this information without loading the module, for some reason :)

Andy

Re: (guix modules) and ‘source-module-closure’

[Ludovic Courtès]

Andy Wingo <wingo@igalia.com> skribis:

> On Mon 05 Sep 2016 10:13, Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de> writes:
>
>> Ah, very nice!
>>
>> Why is it necessary to read the file and parse the define-module
>> expression?  Does Guile not keep any of this information?  Should it?
>> Will something like this become part of Guile eventually?
>
> If you have the module loaded, there is "live-module-closure" which uses
> the information Guile has at run-time.  I guess Ludovic wanted to get
> this information without loading the module, for some reason :)

Exactly.  Most of the time “build-side” module are not loaded in the
Guile process that uses ‘with-imported-modules’.

It’s a bit of hack but it’s necessary.  Guile could provide this
functionality, but (guix modules) bakes in a few assumptions, notably
that all the source files start with ‘define-module’.

Ludo’.