From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Question related to outputs
Date: Wed, 15 Mar 2017 17:24:47 +0100
Message-ID: <871sty8q40.fsf@gnu.org>
References: <20170314151402.GA15269@mail.thebird.nl>
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In-Reply-To: <20170314151402.GA15269@mail.thebird.nl> (Pjotr Prins's message
	of "Tue, 14 Mar 2017 15:14:02 +0000")
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To: Pjotr Prins <pjotr.public12@thebird.nl>
Cc: guix-devel <guix-devel@gnu.org>

Hi Pjotr,

Pjotr Prins <pjotr.public12@thebird.nl> skribis:

> In a package I have targets for out and debug. Now I want to tell the
> make file to build different targets
>
>   make -f Makefile.guix build-with-checks
>
>   make -f Makefile.guix build-without-checks
>
> The latter would be the debug with built in bounds checking etc.
>
> After an hour of searching I don't find any example. Packages like git
> have multiple outputs, e.g. git:send-email but I it simply expands
> paths. Is there a way to test for these targets?
>
>   (if build-without-checks (do this) (do that))

Packages with multiple outputs map to derivations with multiple
outputs.  Outputs are unconditional.

So if your package declares =E2=80=9Cout=E2=80=9D and =E2=80=9Cdebug=E2=80=
=9D as its outputs, it must
always produce both.  Then users can choose to install only one or both,
but that=E2=80=99s a different issue.

For instance, =E2=80=98glibc=E2=80=99 always produces both =E2=80=9Cout=E2=
=80=9D and =E2=80=9Cdebug=E2=80=9D, but you
can choose which one to install.

> In gnu/packages/python.scm:L268
>
>  (let ((out (assoc-ref outputs "out"))
>        (tk  (assoc-ref outputs "tk")))
>   (when tk=20
>     (match (find-files out "tkinter.*\\.so")
>     ...
>
> looks faulty to me as tk always expands to an outputs path.

It can also be #f in the case of python-minimal.

HTH!

Ludo=E2=80=99.