docs: add some docs for hackage2nix

1 files changed, 13 insertions, 0 deletions

diff --git a/doc/languages-frameworks/haskell.section.md b/doc/languages-frameworks/haskell.section.md
index c0dc741eabc..7677c366191 100644
--- a/doc/languages-frameworks/haskell.section.md
+++ b/doc/languages-frameworks/haskell.section.md
@@ -1047,6 +1047,19 @@ As you can see, `packunused` finds out that although the testsuite component has
 no redundant dependencies the library component of `scientific-0.3.5.1` depends
 on `ghc-prim` which is unused in the library.
 
+### Using hackage2nix with nixpkgs
+
+Hackage package derivations are found in the
+[`hackage-packages.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/hackage-packages.nix)
+file within `nixpkgs` and are used as the initial package set for
+`haskellPackages`. The `hackage-packages.nix` file is not meant to be edited
+by hand, but rather autogenerated by [`hackage2nix`](https://github.com/NixOS/cabal2nix/tree/master/hackage2nix),
+which by default uses the [`configuration-hackage2nix.yaml`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/configuration-hackage2nix.yaml)
+file to generate all the derivations.
+
+To modify the contents `configuration-hackage2nix.yaml`, follow the
+instructions on [`hackage2nix`](https://github.com/NixOS/cabal2nix/tree/master/hackage2nix).
+
 ## Other resources
 
   - The Youtube video [Nix Loves Haskell](https://www.youtube.com/watch?v=BsBhi_r-OeE)