Re: How to remove output from inherited package?

[宋文武]

Bodertz <bodertz@gmail.com> writes:

> 宋文武 via "Development of GNU Guix and the GNU System distribution."
> <guix-devel@gnu.org> writes:
>
>> I think you should not reuse phases from transmisison, the error came
>> from '#$phases', which has reference to 'gui' output.  so:
>>
>>   ...
>>   (inherit transmission)
>>   (name "transmission-qt")
>>   (outputs '("out")
>>   (arguments
>>     (list ...))   ; instead of 'substitute-keyword-arguments'
>>   ...
>
> Hmm, you appear to be right, but I don't understand why, as I removed
> the tests that referenced the :gui output: 'move-gui, 'glib-or-gtk-wrap,
> and 'wrap-program.
>
> Do you understand it?  Did I miss one?

As described in the manual (8.12 G-Expressions), gexp is used to embed
"build code" into "host code".  In:

         (substitute-keyword-arguments (package-arguments transmission)
           ((#:phases phases)
            #~(modify-phases #$phases
                (delete 'move-gui)
                (delete 'glib-or-gtk-wrap)
                (delete 'wrap-program)))))


'substitute-keywoard-arguments', 'package-arguments' and 'transmission'
will be executed by the host guile, while 'modify-phases' will be
executed by the builder of 'transmission-qt'.  So in this case, the phases
have "gui" was deleted too late, if we managed to delete them before the
builder:

         (substitute-keyword-arguments (package-arguments transmission)
           ((#:phases phases)
            (modify-phases/xxx phases
                (delete 'move-gui)
                (delete 'glib-or-gtk-wrap)
                (delete 'wrap-program)))))

That could work.  But since phases of 'transmission' is a gexp object,
not a alist suitable for 'modify-phases', it not reusable now...