[Nix-dev] nix-shell for a custom haskell library

[Dmitry Malikov]

> I'm not sure what you mean. Pre-Haskell-NG packages had no support for
> nix-shell at all, and the behavior in Haskell NG has never been different
> from what it is now. mkDerivation builds and installs the library, of
> course, but the while point of nix-shell is that the code which does this
> is not executed automatically so that you can run your own commands
> instead.

The way I've used nix-shell for some haskell packages before was something
like that:
nix-shell -p '(haskellPackages.callPackage ./default.nix { })' --command
'builtExecutable'

And here is an example of one of that old-way-haskell-packages expressions:

{ pkgs ? (import <nixpkgs> {}) }:

let biegunka = import ./biegunka.nix {}; in

pkgs.haskellPackages.cabal.mkDerivation (self: {
  pname = "dotfiles";
  version = "9999";
  src = builtins.filterSource (_: type: type != "unknown") ./biegunka/.;
  isLibrary = false;
  isExecutable = true;
  buildDepends = with pkgs.haskellPackages; [
    biegunka dataDefault lens optparseApplicative regexPcreBuiltin
  ];
  meta = {
    license = self.stdenv.lib.licenses.mit;
    platforms = self.ghc.meta.platforms;
  };
})

Nowadays, there is no more `haskellPackages.cabal.mkDerivation`/

> > How to configure `shell.nix` to get `cabal configure && cabal build`
> > done after entering the nix-shell?
> nix-shell --command "cabal configure && cabal build".

Yeah, but the problem with this approach is some kind of lack of an
isolation, since the path where the packages are being installed into
is shared:

/Users/m/.ghc/x86_64-darwin-7.10.1/package.conf.d
   engine-io-1.2.6

Thus, for now I see now way how can I migrate the flow that I've used
in old-way-haskell-packages to the new infrastructure.

I hope I just didn't get something right and there is such way.


On 31 May 2015 at 12:48, Peter Simons <simons at cryp.to> wrote:

> Hi Dmitry,
>
>  >> The "env" attribute of engine-io (which is what nix-shell enters
>  >> here) gives you an environment in which engine-io can be compiled.
>  >
>  > If I remember correctly, old `haskellPackages.mkDerivation` was
>  > producing an environment with compiled sources and installed
>  > libraries.
>
> I'm not sure what you mean. Pre-Haskell-NG packages had no support for
> nix-shell at all, and the behavior in Haskell NG has never been different
> from what it is now. mkDerivation builds and installs the library, of
> course, but the while point of nix-shell is that the code which does this
> is not executed automatically so that you can run your own commands
> instead.
>
>
>  > How to configure `shell.nix` to get `cabal configure && cabal build`
>  > done after entering the nix-shell?
>
> nix-shell --command "cabal configure && cabal build".
>
>
>  > What was the reason to move this step out of nix-shell routine?
>
> No such code ever existed in the nix-shell environment for Haskell
> packages.
>
> Best regards,
> Peter
>
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