On Tue, Jun 29 2021, Ludovic Courtès wrote:

> Hi,
>
> Xinglu Chen <public@yoctocell.xyz> skribis:
>
>> When developing a Haskell package it is often useful to have a Guix package
>> definition for that package, previously one would have to write that package
>> definition by hand, and if the .cabal file changed one would manually update
>> the Guix package definition.
>>
>> This commit allows one to specify a custom source for their package, meaning
>> that one could programatically generate a Guix package definition for their
>> local Haskell package.  If the .cabal file changes, the generated package
>> definition will also change accordingly.  One could for instance write the
>> following in a guix.scm file:
>>
>>   (define-values (ghc-haskeme deps)
>>     (call-with-input-file "haskeme.cabal"
>>       (lambda (port)
>>         (hackage->guix-package
>>          "haskeme"
>>          #:port port
>>          #:source (local-file "." "haskeme-checkout"
>>                               #:recursive? #t
>>                               #:select? hg-predicate)))))
>>
>>   ghc-haskeme
>>
>> Invoking ‘guix build -f guix.scm’ would then always build an up-to-date
>> version of the package.
>>
>> * guix/import/hackage.scm (hackage-module->sexp): Add optional keyword
>> argument ‘source’
>> (hackage->guix-package): Likewise.
>> * tests/hackage.scm (eval-test-with-cabal): Likewise.
>> ("hackage->guix-package local source"): New test.
>
> Looks like a nice improvement.
>
> What I don’t get is that this functionality doesn’t seem to be available
> from the CLI, which the patch doesn’t change.  Or am I missing
> something?

No, I don’t think this functionality is available from the CLI since
‘hackage->guix-package’ is not called with the #:source keyword
argument.  Once all the other importers (or those where it makes sense
to do this) get this functionality,  it would be a good idea to add an
option for reading a .cabal/setup.py/whatever file and generating a
package definition from that.