[Nix-dev] Will Haskell-ng and hackage2nix allow building *any* versions of deps?

[Anthony Cowley]

This almost certainly isn't ready for release, but I'd like to avoid
duplicating efforts if other people want to work on it...

Here is cabbage https://github.com/acowley/cabbage

It is a tool for doing the obvious thing: use the cabal solver to find
a build plan, then build the specific version of each package, and
then link them into the sandbox in the current directory.

As I said, this script has every warning tape and flashing light
imaginable attached to it. I've used it to install ghc-mod, pandoc,
hakyll, a bunch of web things like amazonka, and my Frames package
with all its demos (involving Chart, diagrams, JuicyPixels, and who
knows what else).

There are missing pieces outlined in the Tasks list at the end of the
Org file that is the source code for the script. I would more than
welcome contributions as this is how I would like to use Nix with
Cabal, and getting help from like-minded folks would be a big boost!

Anthony


On Tue, Feb 24, 2015 at 5:38 PM, Mateusz Kowalczyk
<fuuzetsu at fuuzetsu.co.uk> wrote:
> On 02/22/2015 12:04 PM, Peter Simons wrote:
>> Hi Cody,
>>
>>  > haskellngPackages doesn't seem to have all versions of all dependencies...
>>
>> I'm not sure what you mean by "all versions of all dependencies". Dependencies
>> of what exactly? The way I understand the term, "dependency" has meaning only
>> as a relationship between two packages, i.e. "transformers" is a dependency of
>> "mtl". I'm not sure how to apply that interpretation to your question?
>>
>> If you're asking why hackage-packages.nix doesn't contain every single version
>> of every package registered on Hackage, then the answer is because that would
>> be a database containing well over 50,000 packages, the vast majority of which
>> no-one will ever care about (nor will they ever compile). So it seems pointless
>> to distribute all that stuff as part of Nixpkgs.
>>
>> Best regards,
>> Peter
>>
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>>
>
> A related question: is there a way to generate a package list containing
> exactly the versions of dependencies we require?
>
> Say we have a package with cabal file
>
> A == 1.0
> B > 2.0
> C < 0.5
>
> but the latest Hackage has versions lower and higher &c and that's what
> is in nixpkgs. I found myself wishing that there was an easy to just say
> ‘give me a set of packages that's valid from cabal's point of view’
> rather than what we currently tend to do which is ‘include latest
> versions of everything, jailbreak and hope it works’ which is fine for
> nixpkgs but subpar if we just want that one project working but it
> requires specific versions of dependencies.
>
> --
> Mateusz K.
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