Installing idris2-pack on NixOS

This post acts as a simple note-to-self on how to install Pack, the primary package manager for Idris 2, on NixOS.

The Idris community currently doesn’t overlap much with the Nix community. Ignoring a basic nixpkgs entry for the compiler itself, and editor plugins for Vim and Emacs, there is nothing packaged for Idris 2 at all.

The primary package manager that has arisen is Stefan Hoeck’s Pack. It follows a Stack-like model, but the main thing that we care about is it’s what the community has settled on. Most libraries that have been written for Idris 2 can be installed through Pack, and it can even manage the version of the Idris 2 compiler¹ itself!

So Pack is a pretty indispensible tool for the Idris 2 programmer. How can we use it on NixOS?

The Pack repo offers a simple command to install it to the current user’s home directory on a standard Linux system.

bash -c "$(curl -fsSL https://raw.githubusercontent.com/stefan-hoeck/idris2-pack/main/install.bash)"

But NixOS is no standard Linux system.

The first hurdle is the shebang at the start of the file. Trying to run this command as-is can return:

bash: line 1: #!/usr/bin/env: No such file or directory

This can be fixed by downloading the file and running it directly with bash install.bash.

Then, the script may complain about missing dependencies such as git or make². These can simply be installed system-wide, or you can enter a shell that provides them.

Finally, when trying to compile the RefC backend, the script may complain about not being able to access the C headers for GMP. This can’t be solved by installing the gmp package globally, due to the nature of NixOS. The quickest way around this is to enter a Nix shell that exposes the package to the linker:

nix-shell -p bash gcc gmp gnumake

The above command will expose all the needed dependencies. From here, you should be able to install Pack as normal.

Ideally, a nixpkgs derivation would be made that does all of this, but I’m not experienced enough with writing Nix packages to do this myself. Maybe some day in the future.