[Nix-dev] Proper way of adding custom nix expressions

[Richard Wallace]

On Thu, Nov 1, 2012 at 12:14 AM, Andres Loeh <ksnix at andres-loeh.de> wrote:
> Hi Richard.
>
> What Peter says is true. And ultimately, you should be motivated to
> just submit your new packages as a pull request to nixpkgs.
>
> However, I'd like to point out that there's also a somewhat less
> invasive way to test your own Haskell packages.
>
> There's a nixpkgs configuration file at ~/.nixpkgs/config.nix (it
> might not exist yet). In this config file you can specify a
> configuration option called packageOverrides that modifies the package
> set from nixpkgs in any way you like. In particular, you can add
> packages. Now, adding something to the set of Haskell packages is a
> little bit tricky, because they're all defined in a sub-attribute
> depending on the compiler version, and you have to ensure that
> dependencies are picked up correctly from that set.
>
> So here's what you'd do to add the "boomerang" Haskell package.
>
> (1) Call cabal2nix to produce a Nix expression for boomerang and put
> it in a suitable location. I'm assuming
> ~/.nixpkgs/haskell/boomerang.nix.
>
> (2) Edit your ~/.nixpkgs/config.nix so that it has the following structure:
>
>> pkgs : {
>>   packageOverrides = pkgs : rec {
>>     myHaskellPackages =
>>       let callPackage = pkgs.lib.callPackageWith myHaskellPackages; in
>>         pkgs.recurseIntoAttrs (pkgs.haskellPackages.override {
>>           extraPrefs = self : {
>>             boomerang = callPackage ./haskell/boomerang.nix {};
>>           };
>>         });
>>   };
>> }
>
> Instead of pkgs.haskellPackages.override, you can select another set
> of haskellPackages from all-packages.nix, one that's specific to your
> compiler version, if you prefer. The pkgs.recurseIntoAttrs call is
> optional, but it ensures that you can view your own new Haskell
> packages in nix-env -q calls.
>

Using this I'm getting the error

error: attribute `recurseIntoAttrs' missing

Not sure what's up.  I tried taking out `recurseIntoAttrs` so I end up with

pkgs : {
  packageOverrides = self : rec {
    myHaskellPackages =
      let callPackage = pkgs.lib.callPackageWith myHaskellPackages; in
        pkgs.haskellPackages.override {
          extraPrefs = self : {
            boomerang = callPackage ./haskell/boomerang.nix {};
          };
        };
  };
}

Then I get

error: attribute `haskellPackages.override' missing

Any ideas what I'm missing?

Thanks,
Rich

> (3) You can now install boomerang via path
> (nixos.pkgs.myHaskellPackages.boomerang) or you can use
> myHaskellPackages.ghcWithPackages to build a set of specific packages
> for this version of GHC.
>
> Cheers,
>   Andres
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