Alejandra 💅
The Uncompromising Nix Code Formatter
Try it on your browser! here
Features
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✔️ Fast
It's written in Rust and formats Nixpkgs in just a few seconds. 1
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✔️ Powerful
We define a comprehensive style for all possible combinations of the Nix expression language.
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✔️ Reliable
High coverage, battle tested.
From Nix's eyes, code is just the same. 2
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✔️ Beautiful
Beauty is subjective, right?
We started from the wisdom of the crowd, which comes in big part from the 2.3 million lines of code of Nixpkgs. Then we applied the feedback of developers who have used Nix on a day to day basis for several years.
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✔️ Transparent
You won't notice the formatter after a while.
Humans care about the content, machines about the style!
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✔️ Native
We integrate with common code editors:
Getting started
On the web editor
Please visit: kamadorueda.github.io/alejandra
Prebuilt binaries
You can download a binary for your platform from the releases section, make it executable and have fun!
Alternatively there is an automated method. It needs: curl, sh and chmod:
-
On any x86_64 Linux:
$ curl https://raw.githubusercontent.com/kamadorueda/alejandra/main/installers/x86_64-linux.sh | sh
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On any AArch64/ARM64 Linux:
$ curl https://raw.githubusercontent.com/kamadorueda/alejandra/main/installers/aarch64-linux.sh | sh
Then run Alejandra with:
$ ./alejandra --help
or:
$ /path/to/alejandra --help
Nix installation
-
Nix with Flakes:
$ nix profile install github:kamadorueda/alejandra
-
Nix stable:
Pick one depending on your platform:
$ nix-env -ivA aarch64-darwin -f https://github.com/kamadorueda/alejandra/tarball/main $ nix-env -ivA aarch64-linux -f https://github.com/kamadorueda/alejandra/tarball/main $ nix-env -ivA x86_64-darwin -f https://github.com/kamadorueda/alejandra/tarball/main $ nix-env -ivA x86_64-linux -f https://github.com/kamadorueda/alejandra/tarball/main
Then run Alejandra with:
$ alejandra --help
Do I need to configure anything?
- No.
Discussion
Cool libraries
Alternatives
See why Alejandra was created and a comparison between alternatives here.
Versioning
We use semver to version Alejandra.
Our public API consists of:
- The formatting rules (a.k.a. the style).
- The CLI tool (
$ alejandra
), command line flags, positional arguments, and stdout.
Changelog
Please see: CHANGELOG.md.
Footnotes
Footnotes
-
Running on a machine with:
- CPU: 8 physical x Intel(R) Core(TM) i7-10700K, 16 logical
- MHz: 3800.00
- BogoMips: 7599.80
- Cache Size: 16384 KB
Results:
Logical Cores Seconds 1 45 2 22 4 14 8 10 16 11 -
The methodology to claim this is:
-
Checkout Nixpkgs and run:
$ nix-env -qaP --json --drv-path > before
-
Now format with Alejandra and run:
$ nix-env -qaP --json --drv-path > after
As of 2022-02-08, there are 47 differences in a set of 36278 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:
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