Re: [Haskell-cafe] Listing native package requirements based on cabal information

I would imagine that the people working on Stackage may have already done some work in this area. https://github.com/fpco/stackage -- Dan Burton On Tue, Mar 18, 2014 at 2:54 PM, Tobias Dammers wrote:

On Wed, Mar 19, 2014 at 10:15:08AM +1300, Chris Wong wrote:

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On Wed, Mar 19, 2014 at 9:47 AM, Tobias Dammers wrote:

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Hmm, but then, not all package managers/repositories use the same names for packages. So even if there were a way to extract the required libraries from cabal, feeding that information to the package manager isn't going to be trivial at all.

It's not trivial, but I don't think it's difficult.

For example, Debian Haskell packages all take the form libghc-NAME-dev. Fedora uses haskell-NAME. Sure, there's a bit of hard coding involved, but the set of prominent distributions is finite.

I think installing *haskell* packages is not the problem; cabal already does a decent job at that. The problem we're facing is that cabal can *only* install haskell packages, but not any of the native libraries they depend on (usually through FFI, but other examples exist, such as the pg_config tool from PostgreSQL).

Besides naming convention issues (which could be compensated for with lookup dictionaries; a brute-force solution, sure, but better than nothing), a bigger problem is that sometimes packages don't match 1:1 between distros, so one distro might just provide one monolithic foobar-dev package, while another might split it up into foobar-client-dev and foobar-server-dev, while yet another might provide more than one alternative.

TL;DR: I think if we could just get a list of required native packages, we'd be a long way.

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One problem, though, would be versions. I know we often ask for the latest and greatest packages, which may conflict with what the distribution supplies. So the benefits may not be as high as they seem.

By the way -- has anyone looked into 0install? It hashes things, similarly to Nix, but also tries to integrate with the existing package manager. For example, if the user wishes to install GHC 7.6, but the Debian repositories already supply it, it will invoke apt-get instead of installing on its own.

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(And frankly, looking at build systems for other languages, I've never seen anything that does this - even autotools doesn't really do a lot more than check whether a library is available).

That said, even if we could just get a list of required libraries out

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cabal, in a somewhat human and machine readable format, that would be a huge win in itself.

On Tue, Mar 18, 2014 at 11:48:33AM -0700, David Thomas wrote:

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One option that just occurred to me would be to allow passing a

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cabal that could be passed the extra-libraries (if any), and could install if it knew the relevant OS packages (or NIX packages), or abort with a cleaner error message.

Actually, wrapping ghc might be sufficient (though not ideal).

On Tue, Mar 18, 2014 at 11:29 AM, Michal Antkiewicz < mantkiew@gsd.uwaterloo.ca> wrote:

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This is not an immediate solution but I can imagine listing NIX

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as dependencies inside a cabal file, then NIX would create a sandbox with these dependencies and cabal would build in that sandbox. The advantages are that you're not messing around with the underlying operating system's packages, NIX handles all dependencies transitively, and everything is specified declaratively. Sounds like a nice GSoC project :-) You could also do cross GHC version's builds as GHC itself can be sandboxed. Quite intriguing.

Michal

On Tue, Mar 18, 2014 at 2:16 PM, Michal Antkiewicz < mantkiew@gsd.uwaterloo.ca> wrote:

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Certainly NIX is an interesting approach. It already comes with a large base of dependencies, a format for specifying them. NIX can be installed in any Linux distro and serve as an environment for building

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might provide a cross-distribution solution to the native dependency problem.

See, a nice post by Oliver Charles

http://ocharles.org.uk/blog/posts/2014-02-04-how-i-develop-with-nixos.html

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Michal

On Tue, Mar 18, 2014 at 1:59 PM, David Thomas <

davidleothomas@gmail.com>wrote:

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> Ok, well, if that's the case I'd like to see about remedying that. > Anyone have any thoughts as to how to best go about this? I'm

not clear on

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> exactly what info lives where, especially across systems. Entirely manual > population would be a (barely) acceptable fallback. > > > On Tue, Mar 18, 2014 at 9:36 AM, Dan Burton < danburton.email@gmail.com>wrote: > >> I have wished for this on multiple occasions. I don't believe such a >> thing exists as of yet. >> >> -- Dan Burton >> >> >> On Tue, Mar 18, 2014 at 9:26 AM, David Thomas < davidleothomas@gmail.com >> > wrote: >> >>> Is there a way to extract this? I'm looking to make it easier for >>> newcomers to my project to get things building across different

of script to packages packages. That linux

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