[bug#48999] [PATCH] import: hackage: Accept local source for package.

[Ludovic Courtès]

Hi,

Xinglu Chen <public@yoctocell.xyz> skribis:

> 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.

IOW, this functionality is not accessible, unless you use the Scheme API
as in the example above, right?

> 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.

‘guix import hackage’ could support it even if other importers don’t
have equivalent functionality, no?

Thanks,
Ludo’.