Cargo Shear ✂️ 🐑

Detect and remove unused dependencies from Cargo.toml in Rust projects.

Does not work with transitive dependencies from macros (need to manually ignore).

Installation

cargo binstall cargo-shear
# OR
cargo install cargo-shear

Usage

cargo shear --fix

CI

- name: Install cargo-binstall
  uses: cargo-bins/cargo-binstall@main

- name: Install cargo-shear
  run: cargo binstall --no-confirm cargo-shear

- run: cargo shear

Exit Code (for CI)

The exit code gives an indication whether unused dependencies have been found:

• 0 if found no unused dependencies,
• 1 if it found at least one unused dependency,
• 2 if there was an error during processing (in which case there's no indication whether any unused dependency was found or not).

Ignore

Add to package's Cargo.toml

[package.metadata.cargo-shear]
ignored = ["crate"]

Technique

1. use the cargo_metadata crate to list all dependencies specified in [workspace.dependencies] and [dependencies]
2. iterate through all package targets to locate all Rust files
3. use syn to parse these Rust files and extract imports
4. identify the difference between the imports and the package dependencies

Prior Arts

• https://github.com/est31/cargo-udeps
• https://github.com/bnjbvr/cargo-machete

Trophy Cases

• -7 lines from oxc
• -59 lines from rspack
• -39 lines from rolldown
• -12 lines ast-grep commit1 commit2
• -66 lines biome

TODO

• make the reporting more granular for [dependencies], [dev-dependencies] and [build-dependencies]
• add tests
• print things nicely