Inputs

Inputs allow you to refer to Nix code outside of your project, while preserving reproducibility.

Think of inputs as dependency management of your developer environment.

If you omit devenv.yaml, it defaults to:

devenv.yaml

inputs:
  nixpkgs:
    url: github:NixOS/nixpkgs/nixpkgs-unstable
  pre-commit-hooks:
    url: github:cachix/pre-commit-hooks.nix

Input names like nixpkgs and pre-commit-hooks are identifiers for what is passsed in the first line of the function:

devenv.nix

{ pkgs, lib, nixpkgs, pre-commit-hooks, config, ... }:

{
}

See basics for more about devenv.nix.

There are a few special inputs passed into devenv.nix:

• pkgs is a nixpkgs input containing all of the available packages for your system.
• lib is a collection of functions for working with Nix data structures.
• config is the resolved configuration for your developer environment, which you can use to reference any other options set in devenv.nix.
• pre-commit-hooks can be used to set up git hooks.

Note

... is a catch-all pattern for any additional inputs, so you can safely omit the inputs you're not using.

See devenv.yaml reference for all supported inputs.

Locking and updating inputs

When you run any of the commands, devenv resolves inputs like github:NixOS/nixpkgs/nixpkgs-unstable into a commit revision and writes it to devenv.lock. This ensures that your environment is reproducible.

To update an input to a newer commit, run devenv update or read devenv.yaml reference to learn how to pin down the revision/branch at the input level.