Re: [PATCH] profiles: Generate GHC's package database cache.

[Federico Beffa <beffa@ieee.org>]

On Sun, Apr 5, 2015 at 10:33 PM, Federico Beffa <beffa@ieee.org> wrote:
> On Sun, Apr 5, 2015 at 10:24 PM, Mark H Weaver <mhw@netris.org> wrote:
>>>
>>>   ;; Don't depend on GHC when there's nothing to do.
>>>   (if (any (cut string-prefix? "ghc" <>)
>>>            (map manifest-entry-name (manifest-entries manifest)))
>>>       (gexp->derivation "ghc-package-cache" build
>>>                         #:modules '((guix build utils))
>>>                         #:local-build? #t)
>>>       (gexp->derivation "ghc-package-cache" #~(mkdir #$output))))
>>
>> Sure, this would be fine, although I wonder if we could replace the
>> 'string-prefix?' with 'string=?'.  If so, the conditional could be
>
> I used 'string-prefix?' to catch any GHC library (that we are
> prefixing with 'ghc-...'). However, to compile such a library we need
> GHC, so I think that 'string=?' should do.


Thinking again about this: In principle a user can install a 'ghc-...'
library without having GHC in his profile. I'm not sure how practical
this would be, but I don't see a good reason to not support this by
not creating the cache.  For this reason I would prefer to keep the
'(any ...)' variant.

Regards,
Fede