Organize a Rust CLI app with clap

Use when designing or refactoring the structure of a Rust CLI application built with clap.

Mental model

• Treat the CLI surface as an interface layer over application logic, not as the place where all behavior lives.
• Keep argument parsing, command dispatch, and business logic separate so the CLI remains readable and testable.
• Design for growth: a simple one-command binary can live in one file, but subcommands and shared config should move into clear modules before the crate becomes hard to navigate.

Project shape

• Keep main.rs small: startup, tracing/logging init, command parsing, and top-level error handling only.
• Put the clap parser definitions in a dedicated cli module once the binary has more than a few flags or subcommands.
• Put command execution in per-command modules so adding a subcommand does not turn one file into a giant match block.
• Keep domain logic in library-style modules that do not depend on clap types directly.

clap structure