Make `nix build` work and enable using output in other nix derivations

[niteria]

It would be really nice to be able to use the output of this project in another nix derivation, so you could combine it with a backend and package it as a NixOS module.

I gave it a shot here:
https://github.com/niteria/purescript-halogen-realworld/tree/mkSpagoDerivation

Both nix build and nix develop work fine. Maybe it can be a good starting point for anyone wanting to do something similar.

The tricky part was the FFI - I had to use node2nix to get that working properly.

I’m not opening a PR because I basically replaced your flake.nix with the default one from https://github.com/jeslie0/mkSpagoDerivation/tree/main. Since you’re the author of https://github.com/thomashoneyman/purescript-overlay, you probably have a cleaner way to do this.

[thomashoneyman]

Cool! I haven’t been doing anything with PureScript and Nix for a while (other work obligations, alas) so I don’t have anything better to suggest on the PureScript side. I do find node2nix requires far too many generated files for my liking — in the registry we use a different utility I wrote which should be sufficient for this use case:

https://github.com/thomashoneyman/slimlock

I’m happy to explore your suggestion and switch to mkSpagoDerivation, but I’d like to avoid node2nix.

[niteria]

Thank you for the quick response and this project!

I've replaced node2nix with slimlock and it's much cleaner.

I think for a good PR, I'd have to update the README.md as well.
I will probably do that in the future.