[bug#55248] [PATCH 2/7] gnu: racket: Fix out-of-source build.

[Philip McGrath <philip@philipmcgrath.com>]

Hi,

On 5/4/22 05:29, Maxime Devos wrote:
> Philip McGrath schreef op di 03-05-2022 om 14:33 [-0400]:
>> -       ;; help with debugging, but it confuses `install-license-files`.
> [...]
>> +             ;; workaround for install-license-files
>> +             (lambda* (#:key out-of-source? #:allow-other-keys)
>> +               (when out-of-source?
>> +                 (with-directory-excursion ".."
>> +                   (symlink "src"
>> +                            (package-name->name+version
>> +                             (strip-store-file-name #$output))))))))))
> 
> Surely we could fix this bug/limitation of install-license-files
> upstream (in this case, upstream=Guix)?
> 

I'd certainly be in favor of that! I've never edited '(guix build 
gnu-build-system)' but I assume that would be a 'core-updates' change. 
I'm also not sure what the best solution would be in general.

In Racket's specific case, the source directory for the Racket VM is 
(relative to the repository root), "racket/src/", where other notable 
directories present include "racket/collects/" and "pkgs/". An 
out-of-source build ends up happening in "racket/build/". The license 
files are in the source directory, which is what install-license-files 
expects, but the find-source-directory helper function fails to guess 
the location of the source directory:

>   (define (find-source-directory package)
>     ;; For an out-of-source build, guess the source directory location
>     ;; relative to the current directory.  Return #f on failure.
>     (match (scandir ".."
>                     (lambda (file)
>                       (and (not (member file '("." ".." "build")))
>                            (file-is-directory?
>                             (string-append "../" file)))))
>       (()                                         ;hmm, no source
>        #f)
>       ((source)                                   ;only one other file
>        (string-append "../" source))
>       ((directories ...)                          ;pick the most likely one
>        ;; This happens for example with libstdc++, which lives within the GCC
>        ;; source tree.
>        (any (lambda (directory)
>               (and (string-prefix? package directory)
>                    (string-append "../" directory)))
>             directories))))

Some possibilities I can imagine:

   * We could add a case to find-source-directory specifically for "src".

   * We could change configure to communicate the location of the source
     directory, e.g. via an environment variable, rather than trying to
     guess.

   * We could change install-license-files to do more searching in
     general, e.g. trying multiple directories or preferring a directory
     that contains at least one match for #:license-file-regexp. We'd
     have to consider the potential for false positives, too (e.g.
     sibling directories with projects under different licenses.)

   * We could add an argument to install-license-files to specify the
     directory explicitly, as a complement to #:license-file-regexp.

Another scenario that might be worth considering is projects that follow 
the REUSE specification[1], which I don't think would be handled by the 
current install-license-files.

But actually, for Racket, I forgot that a patch I'd sent upstream to 
handle this in `make install` should be in 8.5, so we may not need this 
patch at all: I'll confirm before I send v2.

-Philip

[1]: https://reuse.software/
[2]: https://github.com/racket/racket/pull/4127