mix deps.nix (deps_nix v3.1.0)

Creates Nix derivations for Mix dependencies.

When run without arguments, generates deps.nix in the current directory, but only for :prod dependencies.

The resulting file contains a Nix function that can be called with an empty attribute set:

pkgs.callPackages ./deps.nix { }

That attribute set can optionally include overrides, which look like Nix overlays:

pkgs.callPackages ./deps.nix {
  overrides = (
    final: prev: {
      some_mix_dep = prev.some_mix_dep.override {
        mixEnv = "dev";
      };
    }
  );
}

Example with all options

This command creates derivations for everything in :prod, and only ex_doc and credo in :dev. It will include :path dependencies (this option is useful for repos with multiple Mix projects). It outputs the Nix expression to nix/deps.nix. It specifies appConfigPath to be ./my-app/config for all nix dependency derivations.

mix deps.nix --include-paths --env prod --env dev=ex_doc,credo --output nix/deps.nix --app-config-path ./my-app/config

Application config

By default, every buildMix derivation is given an appConfigPath pointing at your application's config directory, so that dependencies see your compile-time configuration. This means a change to any config file invalidates every dependency and forces a recompile.

Pass --no-app-config to omit appConfigPath entirely. Dependencies then build with an empty config and are no longer rebuilt when your config changes. Individual dependencies that need compile-time config can be given one back through the overrides argument of the generated file:

some_dep = prev.some_dep.override { appConfigPath = ./config; };

Git dependencies

deps_nix supports git dependencies.

For open-source GitHub dependencies, pkgs.fetchFromGitHub is used. Hashes are prefetched using Mint and hashed using nix hash path.

builtins.fetchGit is used for non-GitHub projects, which doesn't require any prefetching and relies on the git SHA as a unique identifier. However, it suffers from several disadvantages.