Re: [PATCH RFC 0/4] Getting rid of input labels?

["Ludovic Courtès" <ludo@gnu.org>]

Hi Maxime,

Maxime Devos <maximedevos@telenet.be> skribis:

> Ludovic Courtès schreef op do 20-05-2021 om 16:58 [+0200]:
>> Hello Guix!
>> 
>> Here’s a proposal for a soft revolution: getting rid of input labels
>> in package definitions.  Instead of writing: [...]
>>    
>> one can write:
>> 
>>     (native-inputs (list autoconf automake pkg-config guile-3.0))
>> [...]
>
> This concept LGTM (but I haven't looked closely at the patches), but
> as noted on #guix, some issues with eliminating labels completely:
>
> A package definition of P may require both Q@1.0 and Q@2.0 as inputs,
> in which case a ‘label collision’ would be created if we generate
> labels package-name. More specifically, I'm thinking of packaging
> go-ipfs-migrations (or what's its name ...). It would be a good idea
> to add an (additional?) test to actually try to migrate from
> go-ipfs@first-version to go-ipfs@another-version.

Keep in mind that labels exist to make it easier to refer to a specific
input from the build side—in a phase, configure flag, etc.

In many cases, you don’t need the ability to refer to a specific input;
you just need all the inputs to contribute to search path environment
variables, and that’s enough.  A “label collision” does not matter at
all in this case.

In some cases, you do need to refer to a specific input, as in:

  #:configure-flags (list (string-append "--with-gmp-prefix="
                                         (assoc-ref %build-inputs "gmp")))

In this case, there are now two options:

  1. Arrange so that label is unique among your inputs, as is already
     the case.

  2. Use a gexp instead (possible on ‘core-updates’) like so:

       #:configure-flags #~(list (string-append "--with-gmp-prefix=" #$gmp))

     or, to allow for inheritance:

       #:configure-flags #~(list (string-append "--with-gmp-prefix="
                                                #$@(assoc-ref
                                                    (package-inputs this-package)
                                                    "gmp")))

     The second variant is ugly, but we could provide helpers to make it
     prettier.

Do you think there are unaddressed issues with go-ipfs-migrations?

Thanks for your feedback!

Ludo’.