bug#61684: can't compose 'with-patch' with 'with-source'

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hi Ludovic,

Ludovic Courtès <ludo@gnu.org> writes:

> Hi Maxim,
>
> Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis:
>
>> Given 'with-source' discards any patch from the original source, I thought
>> I could at least add them back via 'with-patch', but it appears this
>> does not work:
>>
>> scheme@(gnu packages jami)> (options->transformation 
>>                              `((with-source . "libjami@20230220.0=/home/maxim/src/jami/jami-20230220.0.tar.gz")
>>                                (with-patch . ,(string-append 
>>                                                "libjami=" (search-patch 
>>                                                            "jami-disable-integration-tests.patch")))))
>> $6 = #<procedure 7f2cd01a97e0 at guix/transformations.scm:1010:2 (obj)>
>> scheme@(gnu packages jami)> ($6 libjami)
>> $7 = #<package libjami@20230220.0 guix/transformations.scm:1002 7f2ccc8386e0>
>> scheme@(gnu packages jami)> (package-source $7)
>> $8 = #<<downloaded-file> uri: "/home/maxim/src/jami/jami-20230220.0.tar.gz" recursive?: #t>
>> scheme@(gnu packages jami)>
>>
>> The downloaded-file resulting package source has lost the patch, and no
>> error got produced, leaving the user to discover this limitation by
>> themselves.
>
> The order of options matters; in this case, you need to do it the other
> way around:
>
> scheme@(guile-user)> (options->transformation '((with-patch . "jami=/tmp/t.patch")
> 						(with-source . "jami=http://example.org/foo.tar.gz")))
> $18 = #<procedure 7f7e6b1fd0c0 at guix/transformations.scm:1010:2 (obj)>
> scheme@(guile-user)> ($18 jami)
> $19 = #<package jami@20230206.0 guix/transformations.scm:1002 7f7e6b1602c0>
> scheme@(guile-user)> (package-source $19)
> $20 = #<<computed-file> name: "jami-20230206.0-source" gexp: #<gexp  guix/transformations.scm:688:19 7f7e6b6c8d50> guile: #f options: (#:local-build? #t)>
>
> The <computed-file> bit comes from the ‘with-patch’ transformation, to
> apply the patch to the <downloaded-file>.
>
> If you do it the other way around, the effect of ‘with-patch’ is
> canceled by that of ‘with-source’, which does not preserve patches.  So
> strictly speaking, both options had an effect, but they were
> contradictory.

Hm.  That seems sub-optimal; it seems to me that ideally, the
transformations would be additive, so that users would not need to care
about the ordering.  Or perhaps, alternatively, we could enforce such
ordering at the implementation level (sorting the transformations in the
order that is required).

> Note that ordering is “specified”, notably with the test added in
> 0f024554e63a49e20c2a7a67e928073c266bf5c5 (this is crucial for our HPC
> users, who routinely combine a whole bunch of options; you have no idea
> how far they go once you give them the tool :-)).  I don’t think the
> manual explicitly states it though.

It doesn't seem to be, indeed.  But I wish we wouldn't need to (see my
above suggestions/ideas).

-- 
Thanks,
Maxim