From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Kost <alezost@gmail.com>
Subject: Re: [PATCH 2/6] build-system/emacs: Use "emacs" from native-inputs if
	specified.
Date: Sat, 21 May 2016 00:37:35 +0300
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	(Federico Beffa's message of "Fri, 20 May 2016 09:15:31 +0200")
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To: Federico Beffa <beffa@ieee.org>
Cc: Guix-devel <guix-devel@gnu.org>

Federico Beffa (2016-05-20 10:15 +0300) wrote:

> Alex Kost <alezost@gmail.com> writes:
>
>> * guix/build-system/emacs.scm (lower): Do not add "emacs" to
>>   build-inputs if it is already specified in the native-inputs.
>> @@ -73,8 +75,16 @@
>>
>>                          ;; Keep the standard inputs of 'gnu-build-system'.
>>                          ,@(standard-packages)))
>> -         (build-inputs `(("emacs" ,emacs)
>> -                         ,@native-inputs))
>> +         ;; Add emacs to build-inputs only if native-inputs do not contain
>> +         ;; emacs already.  This allows us to use non-default emacs for
>> +         ;; building.
>> +         (build-inputs (if (find (match-lambda
>> +                                   (("emacs" _ ...) #t)
>> +                                   (_ #f))
>> +                                 native-inputs)
>> +                           native-inputs
>> +                           `(("emacs" ,emacs)
>> +                             ,@native-inputs)))
>
> Note that for the interpreter we normally use a keyword, here #:emacs
> (in a similar way as, say, for the python-build-system there is
> #:python).  Your code overwrites its effect in a non-transparent way.
>
> Please use the keyword in the packages where you need an emacs package
> different from the default one, or remove all the code related to the
> keyword.  If you opt for the second one, please be consistent and do the
> same for all other build systems.

Oh, silly me, now I understand how this keyword works, thanks a lot for
the explanation!  I will adjust this patchset accordingly.  Please
ignore the previous message I sent to this thread :-)

-- 
Alex