Nu-Lint

Linter for the innovative Nu shell.

Learning to use a new shell is a radical change that can use some assistance. This project is aimed at helping new users of the Nu shell. Nu shell has a lot of interesting and useful features and this program will give you hints to use all the features of Nu.

For example, the rule prefer_pipeline_input in this program recommends to use pipelines instead of positional arguments (to use lazy instead of eager list processing):

def filter-positive [numbers] { 
    $numbers | where $it > 0 
}

def filter-positive [] { 
    where $it > 0 
}

All rules are optional and can be disabled with a configuration file. The rule definitions are designed to be compatible with:

• The standard Nu parser nu-check.
• The standard Nu formatter topiary-nushell.

Installation

Cross-platform

From crates.io:

cargo install nu-lint

Source

Build from source:

cargo install --path .
cargo install --git "$THIS_GIT_URL"

Nix

To install in Nix or NixOS, add to configuration.nix:

let
  nu-lint = pkgs.callPackage (pkgs.fetchFromGitHub {
    owner = "wvhulle";
    repo = "nu-lint";
    rev = "COMMIT_HASH";
    sha256 = ""; # nix will tell you the correct hash
  }) {};
in
{
  environment.systemPackages = [
    nu-lint
  ];
}

Editor extension

VS Code extension

Available at VS Code Marketplace.

Helix

Add to your ~/.config/helix/languages.toml:

[language-server.nu-lint]
command = "nu-lint"
args = ["lsp"]

[[language]]
name = "nu"
language-servers = ["nu-lint"]

CLI usage

Basic:

nu-lint                               # Lint working directory
nu-lint script.nu                     # Lint a file
nu-lint directory/                    # Lint directory
'let x =' | nu-lint                   # Pipe in over stdin

Apply fixes (also works with STDIN):

nu-lint --fix --dry-run   # Test
nu-lint --fix             # Apply

Output formats:

nu-lint script.nu --format text           # Human-readable (default)
nu-lint script.nu --format json-vscode    # JSON 

Configuration

Show all rules:

nu-lint list-rules                         

Show all rule sets:

nu-lint list-sets

Create .nu-lint.toml in your project root (or any parent directory):

# Simple format - just list rules and sets with their levels
systemd_journal_prefix = "warn"
snake_case_variables = "deny"
naming = "deny"  # Apply deny level to all rules in the "naming" set

# Or use the structured format for more complex configs
[lints.sets]
performance = "warn"
type-safety = "deny"

[lints.rules]
prefer_pipeline_input = "deny"
max_function_body_length = "allow"

Available lint levels: allow, warn, deny.

The linter will automatically find and use this config file when you run it. Otherwise:

nu-lint --config custom.toml script.nu  

Rules

You can add, remove or change rules by forking this repo and opening a PR (see ./CONTRIBUTING.md).

License

MIT