Cargo Shear ✂️ 🐑

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

Installation

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

Usage

cargo shear --fix

Limitation

Important

cargo shear cannot detect "hidden" imports from macro expansions. This is because cargo shear uses syn to parse files and does not expand macros.

Ignore false positives

False positives can be ignored by adding them to the package's Cargo.toml:

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

or in workspace's Cargo.toml:

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

Otherwise please report the issue as a bug.

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).

Technique

1. use the cargo_metadata crate to list all dependencies specified in [workspace.dependencies] and [dependencies]
2. iterate through all package targets (lib, bin, example, test and bench) to locate all Rust files
3. use syn to parse these Rust files and extract imports
4. find the difference between the imports and the package dependencies

Prior Arts

• est31/cargo-udeps
  • it collects dependency usage by compiling your project and find them from the target/ directory
  • does not seem to work anymore with the latest versions of cargo
  • does not work with cargo workspaces
• bnjbvr/cargo-machete
  • it collects dependency usage by running regex patterns on source code
  • does not detect all usages of a dependency
  • does not remove unused dependencies from the workspace root
• cargo and clippy
  • There was intention to add similar features to cargo or clippy, but the progress is currently stagnant
  • See rust-lang/rust#57274 and rust-lang/rust-clippy#4341

Trophy Cases

• -7 lines from oxc
• -59 lines from rspack
• -39 lines from rolldown
• -12 lines ast-grep commit1 commit2
• -66 lines biome
• -164 lines astral-sh/uv
• -86 lines reqsign

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