psychomb / iohk-nix

nix scripts shared across projects

IOHK Common Nix Code

This repo contains build code and tools shared between IOHK projects.

1. Pinned versions of input-output-hk/nixpkgs.
2. Haskell.nix and nix-tools, plus package overlays and patches for cross-compiling to Windows.
3. Scripts for regenerating code with nix-tools.
4. Util functions such as source filtering.
5. Nix builds of development tools such as HLint, ShellCheck, Stylish Haskell, SHC, cache-s3.
6. Nix packages and overlay for the rust-cardano projects.
7. A skeleton project demonstrating how to use iohk-nix and set up CI.

How to use in your project

See Starting a new project.

How to update the iohk-nix revision.

niv update iohk-nix

Some things may have changed which could break your build, so refer to the ChangeLog.

How to use Haskell.nix and stack-to-nix

Look in the "User Guide" section of the Haskell.nix Documentation.

After updating your Stackage LTS

If you have updated your project's Stackage LTS version, then you may need to update the iohk-nix revision in your project. The error message you may see is:

error: This version of stackage.nix does not know
  about the Stackage resolver X.Y.

  You may need to update haskell.nix to one
  that includes a newer stackage.nix.

If updating the LTS, the compiler version may also have been increased. Note that we maintain a patched GHC for cross-compiling to Windows. The GHC version that you use needs to be supported by iohk-nix. The error message in this case will be:

error: This version of Nixpkgs does not contain GHC x.y.z

In both of these cases, update the iohk-nix revision to the latest available using the instructions above.

Adding new GHC versions

To add support for a new GHC version in iohk-nix, first update its Nixpkgs version to one that provides that compiler, then work on adding the version to nix-tools-iohk-extras.nix.

Nix Gotchas

The docs folder contains a list of typical Nix errors encountered while developing with Haskell and Nix. The hope is developers will add Nix related problems they've encountered and solved to this folder.

• Gotcha 1 - attribute unbuildable missing (win32/unix dependency issues)
• Gotcha 2 - more help with build problems
• Gotcha 3 - filtering sources
• Gotcha 4 - overriding version pins
• Gotcha 5 - ghci
• Gotcha 6 - how to get longer error messages from nix build

When making changes to iohk-nix

Please document any change that might affect project builds in the ChangeLog. For example:

• Bumping nixpkgs to a different branch.
• Changing API (renaming attributes, changing function parameters, etc).
• Bumping the haskell.nix version.

Also update the skeleton project if necessary.