Cabal2nix
=========
[](http://hackage.haskell.org/package/cabal2nix)
[](http://stackage.org/lts/package/cabal2nix)
[](http://stackage.org/nightly/package/cabal2nix)
`cabal2nix` converts a single Cabal file into a single Nix build expression.
For example:
$ cabal2nix cabal://mtl
{ mkDerivation, base, lib, transformers }:
mkDerivation {
pname = "mtl";
version = "2.2.1";
sha256 = "1icdbj2rshzn0m1zz5wa7v3xvkf6qw811p4s7jgqwvx1ydwrvrfa";
libraryHaskellDepends = [ base transformers ];
homepage = "http://github.com/ekmett/mtl";
description = "Monad classes, using functional dependencies";
license = lib.licenses.bsd3;
}
Cabal files can be referred to using the magic URL `cabal://NAME-VERSION`,
which will automatically download the file from Hackage. Alternatively, a
direct `http://host/path/pkg.cabal` URL can be provided, as well as a
`file:///local/path/pkg.cabal` URI that doesn't depend on network access.
However, if the source hash is not already in `cabal2nix`'s cache or provided
using the `--sha256` option, `cabal2nix` still needs to download the source
code to compute the hash, which still causes network traffic. Run the utility
with `--help` to see the complete list of supported command-line flags.
Detailed instructions on how to use those generated files with Nix can be found at
https://haskell4nix.readthedocs.io/nixpkgs-users-guide.html#how-to-create-nix-builds-for-your-own-private-haskell-packages.
`cabal2nix` can also build derivations for projects from other sources than
Hackage. You only need to provide a URI that points to a cabal project. The
most common use-case for this is probably to generate a derivation for a
project on the local file system:
$ cabal get mtl-2.2.1 && cd mtl-2.2.1
$ cabal2nix .
{ mkDerivation, base, lib, transformers }:
mkDerivation {
pname = "mtl";
version = "2.2.1";
src = ./.;
libraryHaskellDepends = [ base transformers ];
homepage = "http://github.com/ekmett/mtl";
description = "Monad classes, using functional dependencies";
license = lib.licenses.bsd3;
}
This derivation will not fetch from hackage, but instead use the directory which
contains the derivation as the source repository.
`cabal2nix` currently supports the following repository types:
* directory
* source archive (zip, tar.gz, ...) from http or https URL or local file.
* git, mercurial, svn or bazaar repository
## `hackage2nix`
This repository also contains, in the [`hackage2nix/`](./hackage2nix) directory,
the tool to update the Haskell packages in
[nixpkgs](https://github.com/NixOS/nixpkgs). It has its own README there.
## Building
For ease of contribution, we support these methods to build `cabal2nix`:
* `stack build` if you have [_Stack_](http://haskellstack.org/)
* The Stack build can use system dependencies from a pinned nixpkgs
version for increased reproducibility (see [`stack.yaml`](./stack.yaml)).
On NixOS this happens automatically.
On non-NixOS, use `stack --nix build` for that.
* `cabal install` if you have [_cabal-install_](https://www.haskell.org/cabal/)
installed
* TODO: Add a build method that requires only `nix` preinstalled,
also pins nixpkgs, and is thus fully reproducible.
When making changes, please ensure that all these methods continue to work.