bug#35387: unpack phase in the gnu-build-system is sometimes non-deterministic

bug#35387: unpack phase in the gnu-build-system is sometimes non-deterministic

[Christopher Baines]

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I believe that the direnv package has encountered an issue with the
gnu-build-system [1].

1: https://issues.guix.info/issue/35386

Due to the combination of the 'setup-go-environment phase from the
go-build-system, and the 'unpack phase of the gnu-build-system, there
are two directories to be considered by first-subdirectory when called
from the unpack phase.

It seems from direnv that this either consistently, with the package
working on one machine, or failing consistently on another.

To avoid issues like this in the future, I think it would be good to
have first-subdirectory raise an error if it's behaviour could be
non-deterministic.

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bug#35387: unpack phase in the gnu-build-system is sometimes non-deterministic

[Ludovic Courtès]

Hi Chris,

Christopher Baines <mail@cbaines.net> skribis:

> I believe that the direnv package has encountered an issue with the
> gnu-build-system [1].
>
> 1: https://issues.guix.info/issue/35386
>
> Due to the combination of the 'setup-go-environment phase from the
> go-build-system, and the 'unpack phase of the gnu-build-system, there
> are two directories to be considered by first-subdirectory when called
> from the unpack phase.
>
> It seems from direnv that this either consistently, with the package
> working on one machine, or failing consistently on another.
>
> To avoid issues like this in the future, I think it would be good to
> have first-subdirectory raise an error if it's behaviour could be
> non-deterministic.

‘file-system-fold’ is just a wrapper around ‘readdir’ so the order in
which it sees directory entries is non-deterministic.

What about writing it like this:

  (define (first-subdirectory directory)
    "Return the file name of the first sub-directory of DIRECTORY."
    (match (scandir directory
                    (lambda (file)
                      (and (not (member file '("." "..")))
                           (file-is-directory? (string-append directory "/"
                                                              file)))))
      ((first . _) first)))

The result will be deterministic since ‘scandir’ sorts entries.

Thanks,
Ludo’.

bug#35387: unpack phase in the gnu-build-system is sometimes non-deterministic

[Christopher Baines]

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Ludovic Courtès <ludo@gnu.org> writes:

> Hi Chris,
>
> Christopher Baines <mail@cbaines.net> skribis:
>
>> I believe that the direnv package has encountered an issue with the
>> gnu-build-system [1].
>>
>> 1: https://issues.guix.info/issue/35386
>>
>> Due to the combination of the 'setup-go-environment phase from the
>> go-build-system, and the 'unpack phase of the gnu-build-system, there
>> are two directories to be considered by first-subdirectory when called
>> from the unpack phase.
>>
>> It seems from direnv that this either consistently, with the package
>> working on one machine, or failing consistently on another.
>>
>> To avoid issues like this in the future, I think it would be good to
>> have first-subdirectory raise an error if it's behaviour could be
>> non-deterministic.
>
> ‘file-system-fold’ is just a wrapper around ‘readdir’ so the order in
> which it sees directory entries is non-deterministic.
>
> What about writing it like this:
>
>   (define (first-subdirectory directory)
>     "Return the file name of the first sub-directory of DIRECTORY."
>     (match (scandir directory
>                     (lambda (file)
>                       (and (not (member file '("." "..")))
>                            (file-is-directory? (string-append directory "/"
>                                                               file)))))
>       ((first . _) first)))
>
> The result will be deterministic since ‘scandir’ sorts entries.

That sounds great :)

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bug#35387: unpack phase in the gnu-build-system is sometimes non-deterministic

[Ludovic Courtès]

Ludovic Courtès <ludo@gnu.org> skribis:

> What about writing it like this:
>
>   (define (first-subdirectory directory)
>     "Return the file name of the first sub-directory of DIRECTORY."
>     (match (scandir directory
>                     (lambda (file)
>                       (and (not (member file '("." "..")))
>                            (file-is-directory? (string-append directory "/"
>                                                               file)))))
>       ((first . _) first)))
>
> The result will be deterministic since ‘scandir’ sorts entries.

Pushed as cfd4e4d06e3cda0f3eed8d6b9277ce53e55404b8 on ‘core-updates’.

Thanks,
Ludo’.