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

[Mark H Weaver <mhw@netris.org>]

Federico Beffa <beffa@ieee.org> writes:

> 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.

Is the package database cache used by anything other than GHC?  If the
user doesn't have GHC installed, what would consult the GHC package
database cache?

      Mark