unison/docs/nix.md

(Todo: it might be nice to have a gentle and concise introduction into why Unison does anything with Nix and what cachix is.)

We can push any nix store path into our cachix cache. This is typically done with cachix push unison <STORE_PATH>.

Some ways to come up with a store path:

1. If you build something you get a symlink to the store path of the built thing, named result by default.
2. With nix path-info

So, you could push the unison executable with the cache with

nix build -o my-little-unison-store-path
cachix push unison my-little-unison-store-path

or

nix build | cachix push unison

We want to cache the [immediate] build dependencies of our build products, because those are the only ones actually needed to build our build products.

nix-store --query --references $(nix path-info --derivation) | xargs nix-store --realize | cachix push unison

Breaking down the above:

nix path-info --derivation

gets the store path of the derivation of the unison executable

nix-store --query --references $(nix path-info --derivation)

gets the store paths of the derivations of immediate dependencies of the unison executable derivation.

nix-store --query --references $(nix path-info --derivation) | xargs nix-store --realize

builds the above derivations if necessary and writes the resulting store paths to stdout

These paths are then fed to cachix with | cachix push unison.

Development environments are defined in the flake under the devShells key. There are a number of different development environments, and they can be entered by giving a different argument to nix develop. If you want to push a development environment you could do so with something like:

nix build --no-link '.#devShells.x86_64-linux.default' | cachix push unison

and you could push the build dependencies of the default shell with something like

nix-store --query --references $(nix path-info --derivation '.#devShells.x86_64-linux.default') | xargs nix-store --realize | cachix push unison

nix-store --query --references $(nix path-info --derivation '.#devShells.aarch64-darwin.default') | xargs nix-store --realize | cachix push unison