Just Config

Just Configuration Standards

Core Philosophy

Apply these principles in strict priority order:

1. Discoverability — just --list is the entry point. Every recipe is documented, grouped, and easy to find.
2. Idiomaticity — Follow just conventions. Use attributes, modules, and settings as the tool intends.
3. Modularity — Group related recipes into submodules. A flat file with 30 recipes is unmaintainable.
4. Simplicity — Recipes are thin wrappers. Complex logic belongs in scripts, not justfiles.

Hard Rules

These are non-negotiable. NEVER violate them.

Never use hyphens to namespace recipes

If two or more recipes share a prefix, they belong in a module. Hyphenated namespacing creates a flat, unsearchable list and defeats just's built-in module system.

# WRONG — hyphenated namespacing
docker-build:
    docker build -t app .

docker-run:
    docker run app

docker-push:
    docker push app

# RIGHT — use a submodule
mod docker

# docker.just
[doc('Build the container image')]
build:
    docker build -t app .

[doc('Run the container')]
run:
    docker run app

[doc('Push to registry')]
push:
    docker push app

Invocation becomes just docker build, just docker run — clear, grouped, and discoverable via just --list.

Always use attributes for organization

Every public recipe MUST have a [doc()] attribute. Group related recipes with [group()]. Hide helpers with [private].

[doc('Run the full test suite')]
[group('test')]
test:
    pytest

[doc('Run tests with coverage report')]
[group('test')]
coverage:
    pytest --cov

[private]
ensure-venv:
    [ -d .venv ] || python -m venv .venv

Always set shell for non-POSIX environments

If the project may run on Windows or needs a specific shell, declare it explicitly.

set shell := ["bash", "-euo", "pipefail", "-c"]

Use shebang recipes for multi-line logic

Each line in a normal recipe runs in a separate shell. For multi-line logic, use a shebang recipe or the [script] attribute.

[script]
[doc('Generate release notes from git log')]
release-notes version:
    #!/usr/bin/env bash
    set -euo pipefail
    tag="v{{version}}"
    git log --oneline "$(git describe --tags --abbrev=0)..$tag"

Module Organization

The mod keyword

Use mod to split a justfile into focused submodules. Each module gets its own namespace in just --list.

# justfile (root)
mod docker
mod db
mod ci

File layout

Two conventions — pick one per project:

# Flat: one file per module
justfile
docker.just
db.just
ci.just

# Nested: directory per module (for complex modules)
justfile
docker/
  mod.just
db/
  mod.just
  migrations.just    # sub-submodule

For nested modules, the entry point must be mod.just inside the directory.

Module comments

Add a doc comment above mod to describe the module in just --list:

# Docker container management
mod docker

# Database operations
mod db

Recipe Design

Parameters and defaults

[doc('Deploy to target environment')]
deploy env="staging":
    ./scripts/deploy.sh {{env}}

Variadic arguments

[doc('Run specific test files')]
test *files:
    pytest {{files}}

The + prefix requires at least one argument:

[doc('Install packages')]
install +packages:
    pip install {{packages}}

Dependencies

[doc('Build and run')]
run: build
    ./target/release/app

[doc('Compile the project')]
build:
    cargo build --release

Parameterized dependencies:

[doc('Push to production')]
push: (deploy "production")
    @echo 'Pushed to production'

Guard patterns

Use confirmation for destructive recipes:

[confirm('This will drop the database. Continue? (y/N)')]
[doc('Drop and recreate the database')]
[group('db')]
db-reset:
    dropdb myapp && createdb myapp

Settings

Place settings at the top of the justfile, before any recipes.

# Load .env file automatically
set dotenv-load

# Use bash with strict mode
set shell := ["bash", "-euo", "pipefail", "-c"]

# Suppress recipe echo by default
set quiet

# Export all variables as environment variables
set export

# Enable positional arguments ($1, $2 in shell)
set positional-arguments

Essential settings

Attributes

Anti-Patterns

Hyphenated namespacing

Already covered in Hard Rules. Use mod submodules instead.

Bare recipes without documentation

Every public recipe must have [doc()]. Without it, just --list shows recipe names with no context.

# Bad
build:
    cargo build

# Good
[doc('Build the project in release mode')]
build:
    cargo build --release

Missing settings

A justfile without set shell is fragile across platforms. A justfile without set dotenv-load forces users to manually source environment files.

Line-by-line shell pitfalls

Each line runs in a separate shell by default. Variables and cd don't carry across lines.

# BROKEN — cd has no effect on the next line
build:
    cd src
    make

# FIXED — single line or shebang
build:
    cd src && make

# BETTER — shebang for complex logic
[script]
build:
    #!/usr/bin/env bash
    set -euo pipefail
    cd src
    make

Overloaded root justfile

If your root justfile has more than ~10 recipes, split into modules. The root justfile should be a table of contents: settings, module declarations, and a handful of top-level convenience recipes.

Self-Review Checklist

Before finalizing any justfile, verify:

• No hyphenated namespacing — modules used instead
• All public recipes have [doc()] attributes
• Related recipes are grouped with [group()]
• Helper recipes are marked [private]
• set shell is declared if non-POSIX compatibility needed
• set dotenv-load is used if .env file exists
• Multi-line logic uses shebang or [script]
• Destructive recipes use [confirm()]
• Root justfile has fewer than ~10 direct recipes
• Module file layout is consistent (flat or nested)

For complete settings reference, built-in functions, and real-world examples, consult references/detailed-guide.md.