Justfile Authoring

Guidance for writing maintainable, correct Justfiles. just is a command runner — not a build system. It saves and runs project-specific commands without Make's complexity.

Based on the Just Programmer's Manual and patterns from production codebases.

1. Design Philosophy

A Justfile is the project's command palette. Every developer interaction with the project should go through just.

• One canonical way — for any operation (build, test, lint, deploy), there should be exactly one recipe. Never leave developers guessing which command to run
• Composites at the top — high-level recipes (dev, build, test, check) sit at the top of the file, composed from lower-level recipes
• Self-documenting — just (no arguments) shows all recipes with descriptions. Every recipe should have a comment explaining what it does
• Idempotent where possible — running a recipe twice should produce the same result. Guard against re-running setup steps unnecessarily
• Fail fast — recipes should fail on the first error, not silently continue