The Uncompromising Nix Code Formatter
The Uncompromising Nix Code Formatter
Try it on your browser! here
✔️ Fast
It's written in Rust and formats Nixpkgs in just a few seconds. [^benchmark-specs]
✔️ Powerful
We define a comprehensive style for all possible combinations of the Nix expression language.
✔️ Reliable
High coverage, battle tested.
From Nix's eyes, code is just the same. [^semantic-changes]
✔️ Beautiful
Beauty is subjective, right?
We started from the original style of Nixpkgs, and then we applied the feedback of developers who have used Nix at scale for several years, producing a very well-grounded style guide.
✔️ Transparent
You won't notice the formatter after a while.
Humans care about the content, machines about the style!
✔️ Native
We integrate with common code editors and workflows:
Please visit: kamadorueda.github.io/alejandra.
You can download a binary for your platform:
Make it executable ($ chmod +x
)
and run Alejandra with:
$ ./alejandra --help
or:
$ /path/to/alejandra --help
Please visit: search.nixos.org/packages?query=alejandra.
Nix stable:
$ nix-env -ivf https://github.com/kamadorueda/alejandra/tarball/3.0.0
Nix with Flakes:
$ nix profile install github:kamadorueda/alejandra/3.0.0
Then run Alejandra with:
$ alejandra --help
Nix stable:
let
alejandra =
(import (builtins.fetchTarball {
url = "https://github.com/kamadorueda/alejandra/tarball/3.0.0";
sha256 = "0000000000000000000000000000000000000000000000000000";
}) {})
.outPath;
in {
environment.systemPackages = [alejandra];
}
Nix with Flakes:
{
inputs = {
nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
alejandra.url = "github:kamadorueda/alejandra/3.0.0";
alejandra.inputs.nixpkgs.follows = "nixpkgs";
};
outputs = {alejandra, nixpkgs, ...}: {
nixosConfigurations = {
example = nixpkgs.lib.nixosSystem rec {
# We support: aarch64-darwin, aarch64-linux, i686-linux, x86_64-darwin, x86_64-linux
system = "x86_64-linux";
modules = [
{
environment.systemPackages = [alejandra.defaultPackage.${system}];
}
# Import your other modules here
# ./path/to/my/module.nix
# ...
];
};
};
};
}
See why Alejandra was created and a comparison between alternatives here.
Alternatively, checkout the code examples of the different formatters here.
We use semver to version Alejandra.
Our public API consists of:
$ alejandra
),
command line flags,
positional arguments,
exit codes,
and stdout.Please read: CHANGELOG.
The following people have helped improving Alejandra.
Thank you ❤️
[^benchmark-specs]: Running on a machine with:
- CPU: 4 physical, 4 logical, 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
- MHz: from 400 to 4700 MHz
- BogoMips: 5606.40
- Cache L3: 12 MiB
Using:
```bash
# x86_64-unknown-linux-gnu
$ time alejandra --threads $threads /path/to/nixpkgs
```
Results:
| $threads | Seconds |
| :------: | :-----: |
| 1 | 45 |
| 2 | 25 |
| 4 | 14 |
[^semantic-changes]: The methodology to claim this is:
1. Checkout [Nixpkgs](https://github.com/nixos/nixpkgs) and run:
```bash
$ nix-env -qaf . --drv-path --xml > before
```
1. Now format with Alejandra and run:
```bash
$ nix-env -qaf . --drv-path --xml > after
```
As of 2022-06-22,
there are 41 differences in a set of 38109 derivations
because of things like this:
```
goDeps = ./deps.nix;
```
Since `./deps.nix` was also formatted
you get a semantical difference.
This is something that should be solved on Nixpkgs
and not a bug in Alejandra.
For example:
- https://github.com/NixOS/nixpkgs/pull/178378
- https://github.com/NixOS/nixpkgs/pull/157760