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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Package transformations
Date: Sun, 21 Feb 2016 22:35:17 +0100
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To: Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de>
Cc: guix-devel@gnu.org

Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de> skribis:

> Ludovic Court=C3=A8s <ludo@gnu.org> writes:
>
>> I=E2=80=99ve pushed my =E2=80=9Ctrain hacks=E2=80=9D, which are a contin=
uation of refactoring
>> work I had done in December (ca. 64ec0e2):
>>
>>   =E2=80=A2 =E2=80=98guix build=E2=80=99 has a new =E2=80=98--with-input=
=E2=80=99 option to rewrite the
>>     dependency graph so you can run:
>>
>>       guix build guix --with-input=3Dguile=3Dguile-next
>>
>>     and guess what it does.  :-)
>>
>>     However, it only works for explicit inputs.
>
> What does it mean that it only works for *explicit* inputs?  Does this
> mean that default inputs added by the build system (e.g. GCC) cannot be
> replaced?

Exactly.

Eventually we should permit it as well but as you know, it=E2=80=99s curren=
tly
less convenient to fiddle with implicit inputs than with explicit inputs
(see =E2=80=98package-with-explicit-inputs=E2=80=99 and co.)  We should imp=
rove the API
in this regard.

> Looking at the code it seems that it is operating on labels.

No, =E2=80=98transform-package-inputs=E2=80=99 in (guix scripts build) matc=
hes packages
by name, not by label, for the reasons you gave.  Maybe the doc should
be clarified?

Thanks for your feedback!

Ludo=E2=80=99.