Since Nix does not officially support YAML yet (NixOS/nix#7340), I created this flake which runs yq for conversions between JSON and YAML.

Such a solution is not ideal to be merged to nixpkgs, as it's based on the concept of IFD.

In flake.nix:

{
  inputs = {
    # ...
    yaml.url = "github:jim3692/yaml.nix";
  };

  outputs = { yaml, ... }: {
    specialArgs = {
      lib = nixpkgs.lib.extend (
        final: prev: { yaml = yaml.lib; }
      );
      # ...
    };
    # ...
  };
}

lib.yaml.fromYaml :: path -> set

Description: It takes a YAML file path as parameter and returns the resulting attrSet

lib.yaml.toYaml :: set -> path

Description: It takes an attrSet as parameter and returns the path of the generated YAML file