niv

Painless dependencies for Nix projects. Read more in the use case section section below.

Install

$ nix-env -iA niv -f https://github.com/nmattia/niv/tarball/master

Build

Inside the provided nix shell:

$ repl

Run the test suite with this command:

$ ./script/test

Usage

niv simplifies adding and updating dependencies in Nix projects. It uses a single file, nix/sources.json, where it stores the data necessary for fetching and updating the packages.

• Add: inserts a package in nix/sources.json.
• Update: updates one or all packages in nix/sources.json.
• Drop: deletes a package from nix/sources.json.

niv has two more utility functions:

• Init: bootstraps a Nix project, in particular creates a nix/sources.json file containing niv and nixpkgs as well as a nix/sources.nix file that returns the sources as a Nix object.
• Show: shows the packages' information.

The next two sections cover common use cases and full command description.

Use cases

This section covers common use cases:

• Bootstrapping a Nix project.
• Tracking a different nixpkgs branch.
• Importing packages from GitHub.
• Fetching packages from custom URLs.

Bootstrapping a Nix project

There is an init command that is useful when starting a new Nix project or when porting an existing Nix project to the niv versioning:

$ niv init
...
$ tree
.
├── default.nix
├── nix
│   ├── default.nix
│   ├── packages.nix
│   ├── sources.json
│   └── sources.nix
└── shell.nix

1 directory, 6 files

The file nix/sources.json is the file used by niv to store versions and is initialized with niv and nixpkgs:

{
    "nixpkgs": {
        "url": "https://github.com/NixOS/nixpkgs-channels/archive/109a28ab954a0ad129f7621d468f829981b8b96c.tar.gz",
        "owner": "NixOS",
        "branch": "nixos-18.09",
        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
        "repo": "nixpkgs-channels",
        "sha256": "12wnxla7ld4cgpdndaipdh3j4zdalifk287ihxhnmrzrghjahs3q",
        "description": "Nixpkgs/NixOS branches that track the Nixpkgs/NixOS channels",
        "rev": "109a28ab954a0ad129f7621d468f829981b8b96c"
    },
    "niv": {
        "homepage": "https://github.com/nmattia/niv",
        "url": "https://github.com/nmattia/niv/archive/72e77204544527279e8f1e2d982d29503482b8f4.tar.gz",
        "owner": "nmattia",
        "branch": "master",
        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
        "repo": "niv",
        "sha256": "1zjcyzxhq9iwxh58j5d7sx1vz5s3r1f6gpmnfgj2a3rxmclwvn3c",
        "description": "Easy dependency management for Nix projects",
        "rev": "72e77204544527279e8f1e2d982d29503482b8f4"
    }
}

The content of this file can be used from Nix by importing nix/sources.nix as done in the generated nix/default.nix file:

{ sources ? import ./sources.nix }:
with
  { overlay = _: pkgs:
      { inherit (import sources.niv {}) niv;
        packages = pkgs.callPackages ./packages.nix {};
      };
  };
import sources.nixpkgs
  { overlays = [ overlay ] ; config = {}; }

The files default.nix, shell.nix and nix/packages.nix are placeholders for your project.

Tracking a nixpkgs branch

The init command sets the nix/sources.json file to track the latest commit present on nixpkgs 18.09 when the command was run. Run this commit to track update to the latest commit:

$ niv update nixpkgs

To change the branch being tracked run this command:

$ niv update nixpkgs -b nixos-19.03     # equivalent to --branch nixos-19.03

Importing packages from GitHub

The add command will infer information about the package being added, when possible. This works very well for GitHub repositories. Run this command to add jq to your project:

$ niv add stedolan/jq

The following data was added in nix/sources.json for jq:

{
  "homepage": "http://stedolan.github.io/jq/",
  "url": "https://github.com/stedolan/jq/archive/9fa2e51099c55af56e3e541dc4b399f11de74abe.tar.gz",
  "owner": "stedolan",
  "branch": "master",
  "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
  "repo": "jq",
  "sha256": "0819rvk8057qgcqvgn7fpldvly2pfdw9fxcjrlqa8gr59p8a1cic",
  "description": "Command-line JSON processor",
  "rev": "9fa2e51099c55af56e3e541dc4b399f11de74abe"
}

Alternatively, the GitHub add sub-command could have been used:

$ niv add github stedolan/jq

Using custom URLs

It is possible to use niv to fetch packages from custom URLs. Run this command to add the Haskell compiler GHC to your nix/sources.json:

$ niv add file \
     ghc       \
    'https://downloads.haskell.org/~ghc/<version>/ghc-<version>-i386-deb8-linux.tar.xz' \
    -v 8.4.3   \

The option -v sets the "version" attribute to 8.4.3. The second argument sets a template that can be reused by niv when fetching a new URL (see the documentation for add and update).

For updating the version of GHC used run this command:

$ niv update ghc -v 8.6.2

Commands

NIV - Version manager for Nix projects

Usage: niv COMMAND

Available options:
  -h,--help                Show this help text

Available commands:
  init                     Initialize a Nix project. Existing files won't be
                           modified.
  add                      Add dependency
  show                     
  update                   Update dependencies
  drop                     Drop dependency

Add

Usage: niv add (COMMAND | PACKAGE)
  Add dependency

Available options:
  -h,--help                Show this help text

Available commands:
  github                   Add GitHub dependency
  file                     Add file dependency
  <owner>/<repo>           Add GitHub dependency

Add a GitHub dependency

Examples:

  niv add github stedolan/jq
  niv add github NixOS/nixpkgs-channels -n nixpkgs -b nixos-18.09

Usage: niv add github [-n|--name NAME] PACKAGE [-a|--attribute KEY=VAL]
                      ([-b|--branch BRANCH] | [-o|--owner OWNER] |
                      [-r|--repo REPO] | [-v|--version VERSION] |
                      [-t|--template URL])
  Add GitHub dependency

Available options:
  -n,--name NAME           Set the package name to <NAME>
  -a,--attribute KEY=VAL   Set the package spec attribute <KEY> to <VAL>
  -b,--branch BRANCH       Equivalent to --attribute branch=<BRANCH>
  -o,--owner OWNER         Equivalent to --attribute owner=<OWNER>
  -r,--repo REPO           Equivalent to --attribute repo=<REPO>
  -v,--version VERSION     Equivalent to --attribute version=<VERSION>
  -t,--template URL        Used during 'update' when building URL. Occurrences
                           of <foo> are replaced with attribute 'foo'.
  -h,--help                Show this help text

Add a file dependency

Examples:

  niv add file my-package http://example.com/archive/<version>.zip -v alpha-0.1

Usage: niv add file [-n|--name NAME] PACKAGE URL-TEMPLATE
                    [-a|--attribute KEY=VAL] [-T|--type TYPE]
  Add file dependency

Available options:
  -n,--name NAME           Set the package name to <NAME>
  -a,--attribute KEY=VAL   Set the package spec attribute <KEY> to <VAL>
  -T,--type TYPE           The type of the URL target. The value can be either
                           'file' or 'tarball'. If not set, the value is
                           inferred from the suffix of the URL.
  -h,--help                Show this help text

Update

Examples:

  niv update
  niv update nixpkgs
  niv update my-package -v beta-0.2

Usage: niv update [PACKAGE] [-a|--attribute KEY=VAL]
  Update dependencies

Available options:
  -a,--attribute KEY=VAL   Set the package spec attribute <KEY> to <VAL>
  -h,--help                Show this help text

Drop

Examples:

  niv drop jq
  niv drop my-package version

Usage: niv drop PACKAGE [ATTRIBUTE]
  Drop dependency

Available options:
  -h,--help                Show this help text

Init

Usage: niv init 
  Initialize a Nix project. Existing files won't be modified.

Available options:
  -h,--help                Show this help text

show

Usage: niv show 

Available options:
  -h,--help                Show this help text

Related

• nix-flakes: niv support a subset of the Nix flakes. In particular it does not perform any kind of dependency resolution.
• nix-path: niv and nix-path share a similar goal and ideas tend to flow back and forth freely.