Nisp

Statically-checked Lisp for Nix. A Racket #lang that compiles to Nix, paired with a checker that catches unknown option paths, type mismatches, and enum violations at file:line:col — before nix-build runs.

$ nisp validate
modules/printing/default.rkt:6:7: unknown option services.pipwire.alsa.enable
  did you mean: services.pipewire.alsa.enable?
modules/net/default.rkt:10:47: unknown package networkmanagers in pkgs set
  did you mean: networkmanager, networkmanager-ssh or networkmanager-sstp?
hosts/laptop/configuration.rkt:11:47: type mismatch at boot.loader.systemd-boot.consoleMode:
  "atuo" not in enum {"0", "1", "2", "auto", "max", "keep"} — did you mean "auto"?
modules/foo/default.rkt:8:9: duplicate assignment to networking.hostName (first set at line 5)

NixOS already validates option paths and types, but only at module evaluation time — errors point at the force site, not the typo. nisp compiles from an eager language to a lazy one, which means there's a walkable AST before anything gets emitted. The validator runs there, checking against the options schema NixOS publishes and a cached index of 25K+ nixpkgs attribute names.

Is this really statically typed? It checks NixOS's options schema, not a type system defined inside the language — closer to TypeScript over JavaScript than to ML. The practical result: errors before runtime, at the source line, with did-you-mean suggestions.

A taste

#lang nisp

(raw-file
  (att
    (services.openssh.enable #t)
    (networking.firewall.allowedTCPPorts (lst 80 443))
    (users.users.tom (att (isNormalUser #t)
                          (shell pkgs.zsh)
                          (extraGroups (lst "wheel" "docker"))))))

→

{
  services.openssh.enable = true;
  networking.firewall.allowedTCPPorts = [ 80 443 ];
  users.users.tom = {
    isNormalUser = true;
    shell = pkgs.zsh;
    extraGroups = [ "wheel" "docker" ];
  };
}

Both .rkt and the emitted .nix are committed; the flake reads ordinary Nix. You're not trapped — drop down to raw Nix anytime, or stop using nisp entirely by deleting the .rkt files.

Install

Requires Racket 8.x, Nix (for schema extraction), and Cargo (one-time build of the import parser shim).

git clone https://github.com/tompassarelli/nisp
cd nisp
raco pkg install --link --auto
cd nix-parser && cargo build --release && cd ..
export PATH="$PWD/bin:$PATH"

Usage

nisp extract-schema           # cache the options schema for your host
nisp validate                 # check every .rkt in the cwd's flake
nisp import some-config.nix   # convert existing Nix to nisp

The toolchain is a single nisp dispatcher. Run nisp <cmd> --help for full options on any subcommand.

command	what it does
validate	check .rkt sources for unknown option paths, type mismatches, invalid package names, and duplicate assignments. --auto-fix rewrites unambiguous typos.
extract-schema	dump an options tree into .nisp-cache/schema.json. Works with NixOS, home-manager, nix-darwin — anything evalModules-shaped. Re-run after nix flake update.
extract-packages	dump nixpkgs attribute names into .nisp-cache/packages.json for package-name validation.
import [file]	translate .nix → .rkt. Comments preserved. 100% pass rate on all 2,332 nixpkgs/nixos modules.
schema <path>	query the cached schema: --children, --search (fuzzy), --json.
rename <old> <new>	rename an option path across every .rkt in the flake. --dry-run to preview.
edit <op> <file>	source-preserving edits: set/unset, enable-add/enable-remove.

nisp-lsp is a separate binary (so editors can spawn it by name) providing diagnostics, hover, completion, code actions, and goto-definition. See editor setup for configuration.

Further reading

• Language reference — surface forms, module-shape wrappers, mk* helpers, type helpers
• Editor setup — LSP configuration for Doom Emacs, Helix, Neovim
• API — using nisp as a Racket library
• AGENTS.md — repo internals, contributor guide, release process

Ecosystem

firnos is a NixOS configuration framework built on nisp — modules, bundles, host configs, scaffolding, the firn CLI. If you want "Doom Emacs for NixOS config", that's the one.

A nisp-based repo typically commits both the .rkt and the generated .nix side by side. The flake reads the .nix, but it's a build artifact — always edit the .rkt. If you're an AI agent reaching in from another working directory, note that you won't auto-load this repo's instructions; add a CLAUDE.md / AGENTS.md to your config repo to make the convention explicit.

Status

v0.13.0. Full Nix surface coverage, 77 tests.

Validates a real-world 211-file config in ~5 seconds. nisp import handles 100% of nixpkgs (2,332 modules). The LSP covers diagnostics, hover, completion, code actions, and goto-definition.

API may shift before v1.0 based on usage feedback.

Tests

raco test tests/

License

MIT