export default nix-validation

name	nix-validation
description	Comprehensive Nix validation: treefmt-nix integration, statix/deadnix linting, flake checks, khanelinix-specific patterns. Use when validating Nix code or setting up linting infrastructure.

Nix Validation & Linting

Tool Overview

Tool	Purpose	Speed
nix-instantiate --parse	Syntax check only	Instant
nixfmt	Official formatter (RFC-style)	Fast
statix	Linter for anti-patterns	Fast
deadnix	Find unused code	Fast
nix flake check	Full evaluation + checks	Slow

treefmt-nix Integration

The recommended way to combine all tools:

# flake.nix
{
  inputs.treefmt-nix.url = "github:numtide/treefmt-nix";

  outputs = { self, nixpkgs, treefmt-nix, ... }:
    let
      system = "x86_64-linux";
      pkgs = nixpkgs.legacyPackages.''${system};
      treefmtEval = treefmt-nix.lib.evalModule pkgs {
        projectRootFile = "flake.nix";
        programs = {
          nixfmt.enable = true;  # or nixfmt-rfc-style
          deadnix.enable = true;
          statix.enable = true;
        };
      };
    in {
      formatter.''${system} = treefmtEval.config.build.wrapper;
      checks.''${system}.formatting = treefmtEval.config.build.check self;
    };
}

Statix Lints (Anti-Patterns)

Lint	Issue	Fix
bool_comparison	x == true	Just use x
empty_let_in	let in expr	Remove let-in
eta_reduction	x: f x	Just use f
manual_inherit	x = x;	Use inherit x;
manual_inherit_from	x = a.x;	Use inherit (a) x;
legacy_let_syntax	let { x = 1; body = x; }	Use let x = 1; in x
unquoted_uri	https://...	Quote the URI
useless_parens	(expr) when not needed	Remove parens

# Check for anti-patterns
statix check .

# Auto-fix what's possible
statix fix .

# Ignore specific lint
# Add to file: # statix: ignore manual_inherit

Deadnix (Unused Code)

# Find unused bindings
deadnix .

# Auto-remove unused code
deadnix -e .

# Check specific patterns
deadnix --no-lambda-arg .  # Keep unused lambda args
deadnix --no-lambda-pattern-names .  # Keep pattern names

Common False Positives:

• self in flake outputs (hide with ...)
• _ prefixed variables (intentionally unused)
• Module arguments used in imports

khanelinix-Specific Validation

# Validate module options follow namespace
nix eval .#nixosModules.default --apply 'm: builtins.attrNames (m {} { lib = (import <nixpkgs> {}).lib; config = {}; pkgs = {}; }).options.khanelinix or {}'

# Check home-manager module
nix build .#homeConfigurations.khaneliman.activationPackage --dry-run

# Verify darwin configuration
nix build .#darwinConfigurations.khaneliman.system --dry-run

# Test specific host
nix build .#nixosConfigurations.khanelinux.config.system.build.toplevel --dry-run

Module Validation Patterns

# Check option types are correct
nix eval --expr '
  let
    pkgs = import <nixpkgs> {};
    module = import ./modules/mymodule.nix;
    result = pkgs.lib.evalModules {
      modules = [ module ];
    };
  in result.options
'

# Verify module doesn't have evaluation errors
nix eval --expr '
  let
    pkgs = import <nixpkgs> {};
    lib = pkgs.lib;
  in import ./path/to/module.nix { inherit lib pkgs; config = {}; }
'

Common Nix Errors & Fixes

Error	Cause	Fix
syntax error, unexpected ';'	Missing value before ;	Check previous line for missing =
undefined variable 'lib'	Not in scope	Add { lib, ... }: to function args
infinite recursion encountered	Self-reference in rec	Use let bindings or self pattern
attribute 'x' missing	Wrong path or typo	Check attr names, use or default
cannot coerce set to string	Using attrset as string	Use specific attr or builtins.toJSON
function expects 1 arguments	Missing argument	Check function signature
called with unexpected argument	Extra arg in call	Check function accepts arg

Flake Check Integration

# Add custom checks to flake
checks.''${system} = {
  # Formatting check
  formatting = treefmtEval.config.build.check self;

  # Module evaluation check
  module-eval = pkgs.runCommand "check-modules" {} '''
    ''${pkgs.nix}/bin/nix-instantiate --eval --strict \
      ''${self}/modules/test.nix
    touch $out
  ''';

  # Pre-commit hooks
  pre-commit = pre-commit-hooks.lib.''${system}.run {
    src = ./.;
    hooks = {
      nixfmt.enable = true;
      statix.enable = true;
      deadnix.enable = true;
    };
  };
};

Quick Validation Commands

# Fastest: syntax only
nix-instantiate --parse file.nix > /dev/null

# Fast: format + lint
nixfmt --check . && statix check . && deadnix .

# Project formatter (treefmt)
nix fmt

# Full check (slow but thorough)
nix flake check

# Git-aware (staged only)
git diff --cached --name-only | grep '\.nix$' | xargs -r nixfmt --check

Pre-Commit Hook (Nix)

# In devShell
devShells.default = pkgs.mkShell {
  packages = with pkgs; [ nixfmt statix deadnix ];
  shellHook = '''
    # Git pre-commit hook
    cat > .git/hooks/pre-commit << 'EOF'
    #!/bin/sh
    files=$(git diff --cached --name-only | grep '\.nix$')
    [ -z "$files" ] && exit 0
    echo "$files" | xargs nixfmt --check || exit 1
    echo "$files" | xargs statix check || exit 1
    echo "$files" | xargs deadnix || exit 1
    EOF
    chmod +x .git/hooks/pre-commit
  '