# Contributing to Nixpkgs packages

This document is for people wanting to contribute specifically to the package collection in Nixpkgs.
See the [CONTRIBUTING.md](../CONTRIBUTING.md) document for more general information.

## Overview

- [`top-level`](./top-level): Entrypoints, package set aggregations
  - [`impure.nix`](./top-level/impure.nix), [`default.nix`](./top-level/default.nix), [`config.nix`](./top-level/config.nix): Definitions for the evaluation entry point of `import <nixpkgs>`
  - [`stage.nix`](./top-level/stage.nix), [`all-packages.nix`](./top-level/all-packages.nix), [`by-name-overlay.nix`](./top-level/by-name-overlay.nix), [`splice.nix`](./top-level/splice.nix): Definitions for the top-level attribute set made available through `import <nixpkgs> {…}`
  - `*-packages.nix`, [`linux-kernels.nix`](./top-level/linux-kernels.nix), [`unixtools.nix`](./top-level/unixtools.nix): Aggregations of nested package sets defined in `development`
  - [`aliases.nix`](./top-level/aliases.nix), [`python-aliases.nix`](./top-level/python-aliases.nix): Aliases for package definitions that have been renamed or removed
  - `release*.nix`, [`make-tarball.nix`](./top-level/make-tarball.nix), [`packages-config.nix`](./top-level/packages-config.nix), [`metrics.nix`](./top-level/metrics.nix), [`nixpkgs-basic-release-checks.nix`](./top-level/nixpkgs-basic-release-checks.nix): Entry-points and utilities used by Hydra for continuous integration
- [`development`](./development)
  - `*-modules`, `*-packages`, `*-pkgs`: Package definitions for nested package sets
  - All other directories loosely categorise top-level package definitions, see [category hierarchy][categories]
- [`build-support`](./build-support): [Builders](https://nixos.org/manual/nixpkgs/stable/#part-builders)
  - `fetch*`: [Fetchers](https://nixos.org/manual/nixpkgs/stable/#chap-pkgs-fetchers)
- [`stdenv`](./stdenv): [Standard environment](https://nixos.org/manual/nixpkgs/stable/#part-stdenv)
- [`pkgs-lib`](./pkgs-lib): Definitions for utilities that need packages but are not needed for packages
- [`test`](./test): Tests not directly associated with any specific packages
- [`by-name`](./by-name): Top-level packages organised by name ([docs](./by-name/README.md))
- All other directories loosely categorise top-level packages definitions, see [category hierarchy][categories]

## Quick Start to Adding a Package

We welcome new contributors of new packages to Nixpkgs, arguably the greatest software database known. However, each new package comes with a cost for the maintainers, Continuous Integration, caching servers and users downloading Nixpkgs.

Before adding a new package, please consider the following questions:

* Is the package ready for general use? We don't want to include projects that are too immature or are going to be abandoned immediately. In case of doubt, check with upstream.
* Does the project have a clear license statement? Remember that software is unfree by default (all rights reserved), and merely providing access to the source code does not imply its redistribution. In case of doubt, ask upstream.
* How realistic is it that it will be used by other people? It's good that nixpkgs caters to various niches, but if it's a niche of 5 people it's probably too small. A good estimate is checking upstream issues and pull requests, or other software repositories. Library packages should have at least one dependent.
* Is the software actively maintained upstream? Especially packages that are security-critical, rely on fast-moving dependencies, or affect data integrity should see regular maintenance.
* Are you willing to maintain the package? You should care enough about the package to be willing to keep it up and running for at least one complete Nixpkgs' release life-cycle.
  * In case you are not able to maintain the package you wrote, you can seek someone to fill that role, effectively adopting the package.

If any of these questions' answer is no, then you should probably not add the package.