Re: Using symlinks in 'local-file'

[Alex Kost]

Ludovic Courtès (2015-06-15 23:44 +0300) wrote:

> Alex Kost <address@hidden> skribis:
>
>> If one uses a relative symlink in 'local-file', it will lead to a broken
>> symlink in the store as illustrated in the attached example.  So I think
>> it either:
>>
>> - should be documented explicitly that 'local-file' adds a specified
>>   file to the store blindly, which may lead to the problem with a broken
>>   symlink.
>>
>> - or 'local-file' (or a deeper procedure) should take care of that case
>>   and dereference a symlink if needed.
>>
>> WDYT?
>
> Actually, this only happens with #:recursive? #t, which is currently the
> default.
>
> With #:recursive? #f, you get an error:
>
>
> scheme@(guile-user)> ,enter-store-monad
> store-monad@(guile-user) [1]> (gexp->derivation "foo" #~(symlink 
> #$(local-file "/tmp/symlink1" #:recursive? #f) #$output))
> guix/store.scm:604:22: In procedure add-to-store:
> guix/store.scm:604:22: Throw to key `srfi-34' with args `(#<condition 
> &nix-protocol-error [message: "regular file expected" status: 1] 30c5ab0>)'.
>
> So I think we should first make #:recursive? default to #f, since that’s
> what we want by default, and optionally have the <local-file> gexp
> expander resolve symlinks.
>
> WDYT?

I agree, getting an error is better than a broken link, so I'm for
making (#:recursive? #f) a default.  And resolving symlinks would
probably be even better.

>> (define (call-derivation drv)
>>   (apply system*
>>          (cons (derivation-builder drv)
>>                (derivation-builder-arguments drv))))
>
> This is quite original.  ;-)

I suppose that's a polite version of "That's not how it should be done".
I just don't know what the proper way to "call" derivation is :-)

-- 
Alex