Re: Apply a patch to a given package definition

[Ian Eure <ian@retrospec.tv>]

Hi Christoph,

Christoph Buck <dev@icepic.de> writes:

> Hi!
>
> How do i define a new package which is just a variation of a 
> given
> package defined in guix?
>
> In my concrete example i try to add a new board definition file 
> via a
> patch to the u-boot bootloader. What i come up with, looks like 
> this:
>
> ```
> ;; Defines a package ub which will compile u-boot for the
> ;; `new-cool-board` description file
>
> (define ub (make-u-boot-package "new-cool-board" 
> "arm-linux-gnueabihf"))
>
> (define-public u-boot-new-cool-board-arm
>   (package
>     (inherit ub)
>     (version "2024.01")
>     (source (origin
>               (patches 
>               '("0001-Add-board-description-for-new-cool-board.patch"))
>               (method url-fetch)
>               (uri (string-append
>                     "https://ftp.denx.de/pub/u-boot/"
>                     "u-boot-" version ".tar.bz2"))
>               (sha256
>                (base32
>                 "1czmpszalc6b8cj9j7q6cxcy19lnijv3916w3dag6yr3xpqi35mr"))))))
>
> ```
>
> I create a u-boot variant for my "new-cool-board" using the 
> build in
> `make-u-boot-package` function, then i define a new package and 
> inherit
> from the package variant created with the `make-u-boot-package`
> function. Then i overwrite `source` entry with an entry which 
> also
> applies my patch file. This works, however the original u-boot 
> package
> also apply some patches, which are now lost and must manually 
> added by
> me again. This seems rather error prone. Is there a better 
> solution?
>

You can have your source inherit from the original package’s, but 
with modifications -- just like the package itself.  This might 
not be exaxtly right, but should give you the right idea:

    (define-public u-boot-new-cool-board-arm
      (package
        (inherit ub)
        (version "2024.01")
        (source
         (origin
           (inherit (package-source ub))
           (patches (append (origin-patches (package-source ub))
                            '("0001-Add-board-description-for-new-cool-board.patch")))))))

Any fields you don’t want to modify will be inherited, so you may 
be able to eliminate the version field as well.

  — Ian