rot

rot is a Rust-only LOC, complexity measuring tool, primarily to guide agents in refactoring goals.

Prompt

Give a prompt like below to get rid of slop, DTOs, ceremony in your project:

refactor the repo. identify increasingly larger pieces for simplification and reuse (but dont reuse for the sake of it) and act on it. after each round of simplification, repeat the same exercise. use native codex subagents whenever needed. the goal is reducing code base prod LOC by 30% and complexity by 20%, use rot CLI to measure it.

Features

• Counts physical, code, comment, documentation, and blank Rust lines.
• Classifies source by Cargo role: production, tests, benches, examples, build, conditional, inactive, or orphan.
• Evaluates Cargo features, common cfg forms, module edges, and literal include! paths.
• Reports lexical, authored cyclomatic, and authored cognitive complexity.
• Counts explicit unrestricted pub declarations.
• Emits deterministic human tables or versioned JSON, with project and per-file detail.
• Compares a committed Git baseline with the live working tree.
• Includes optional compiler-backed visibility analysis for aggressive refactoring.

Install

# macOS
brew install daulet/tap/rot

# Cargo (installs the `rot` executable)
cargo install rot-metrics

Prebuilt macOS and Linux archives and Debian packages are available from GitHub Releases. Install rot-audit with cargo install rot-metrics --features audit; it also requires the matching driver described below.

Quick start

Run rot against any Rust package or workspace.

Common workflows:

# Project summary
rot .

# Include every file row
rot . --files

# Compact JSON for automation
rot . --format json --summary-only

# Compare a commit with staged, unstaged, and untracked Rust
rot . --baseline HEAD~1
rot . --baseline origin/main --format json --summary-only

# Select a Cargo/configuration profile
rot . --features serde,cli
rot . --all-features --exclude-feature unstable
rot . --target aarch64-unknown-linux-gnu --release

Positional PATH arguments select input; --files only changes table detail. Each selected directory is its own ignore boundary. Use --hidden or --no-ignore to broaden discovery. JSON goes to stdout and diagnostics go to stderr.

Run rot --help for the complete option list and profile controls.

Deeper compiler analysis

rot-audit runs a real Cargo/rustc build to find public declarations that must remain public, can be narrowed, or are dead. It can also compare public API topology with a Git revision and explain a definition's compiled consumers.

Use rot for routine source metrics and revision diffs. Use rot-audit when you need compiler evidence before narrowing, deleting, or reexporting code across a workspace.

rot-audit . --locked --offline --driver PATH
rot-audit . --baseline origin/main --locked --offline --driver PATH
rot-audit . --explain 'my-package:module::item' --driver PATH

Building the required driver needs a Git checkout. It must match the selected rustc release, commit, and host, and must be rebuilt for each rustc patch.

Evidence is closed-world: selected targets and feature profile only, excluding doctests and unknown external consumers. See Compiler-backed audit for full setup.