# `mix deps.nix`
[🔗](https://github.com/code-supply/deps_nix/blob/main/lib/mix/tasks/deps.nix.ex#L1)

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
```

## Git dependencies

`deps_nix` supports git dependencies.

For open-source GitHub dependencies, `pkgs.fetchFromGitHub` is used. Hashes
are prefetched using [Mint](https://hexdocs.pm/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](https://discourse.nixos.org/t/fetchgit-vs-fetchgit/23325).

---

*Consult [api-reference.md](api-reference.md) for complete listing*