nix-eval-js

nix interpreter in javascript

status

early draft

for a list of implemented features, see test/nix-eval.snapshots.txt

autocompletion

a very simple version of autocompletion is working

this is based on the last valid eval state

see the demo

demo

nix-eval-js demo

documentation

see docs/

install

git clone --recurse-submodules https://github.com/milahu/nix-eval-js
cd nix-eval-js
pnpm install

commands

./bin/nix-parse -e 1+1
./bin/nix-eval -e 1+1

./bin/nix-parse -f /etc/nixos/configuration.nix
./bin/nix-eval -f /etc/nixos/configuration.nix

./bin/nix-parse -f ~/src/nixpkgs/pkgs/top-level/all-packages.nix
./bin/nix-eval -f ~/src/nixpkgs/pkgs/top-level/all-packages.nix

offline demo

cd demo
pnpm install
npm run dev

goals

incremental evaluator

create a prototype for an incremental evaluator

example

__head [ 1 ]

this evaluates to the result 1

adding values to the list does not change the result

__head [ 1 2 ]

still evaluates to the result 1

only changing the first value changes the result

__head [ 3 ]

this evaluates to the result 3

intellisense

autocompletion

let
  pkgs = {
    hello = ''
      #! /bin/sh
      echo hello
    '';
  };
in
pkgs.
#    ^ cursor

at this cursor, i want the autocompletion hello

this should also work with callPackage and makeScope

Nix Interpreters

aka: Nix Evaluators

status = how much of "the perfect nix" is implemented

• nix - the original nix interpreter in C++. aka nix.cc. Status: 90%
• tour of nix - nix interpreter in javascript. aka nix.js.
  the original nix interpreter, compiled to asm.js. Status: nix-instantiate
  • https://nixcloud.io/tour/
  • https://lastlog.de/blog/posts/tour_of_nix.html
  • NixOS/nixpkgs#16208 - emscripten based toolchain for nix
• hnix - nix interpreter in haskell. aka nix.hs. Status: 50%
• rnix-lsp - nix interpreter in rust. error-tolerant interpreter for intellisense. based on the rnix-parser. aka nix.rs. Status: 20%
• Toros - Nix implementation in Rust. Based on the NixEL parser. aka nix.rs. Status: 10%
• nix-eval-js - Nix interpreter in pure JavaScript. Proof of concept. Based on the lezer-parser-nix parser. aka nix.js. Status: 5%

in a distant future, nickel can interpret nix tweag/nickel#93

see also nix-community/awesome-nix#133

related

• lezer-parser-nix - nix parser in javascript
• nixos-config-webui - old project
• nijs - Nix bindings for JavaScript

keywords

• nix evaluator in javascript
• eval nix code in javascript
• evaluate nix code in javascript