crap4ts

A small CRAP score analyzer for TypeScript and TSX, powered by Rust and Oxc.

CRAP = complexity² × (1 - coverage)³ + complexity

crap4ts reads TypeScript source code and an Istanbul coverage-final.json, then reports cyclomatic complexity, statement coverage, and a CRAP score for each function.

Status

This is an intentionally small MVP. It supports:

• .ts and .tsx source files;
• functions, arrow functions, and class methods;
• Istanbul JSON produced by Vitest, Jest, or c8;
• human-readable and JSON output;
• an optional threshold for CI gates.

Install

Rust 1.97 or newer is currently required:

cargo install --path .

Usage

Generate Istanbul coverage with your test runner first, then run:

crap4ts src --coverage coverage/coverage-final.json

Use JSON for automation:

crap4ts src \
  --coverage coverage/coverage-final.json \
  --format json

Use a threshold as a CI gate:

crap4ts src \
  --coverage coverage/coverage-final.json \
  --threshold 30

Exit codes:

• 0: analysis or gate passed;
• 1: at least one function exceeded the threshold;
• 2: invalid input, coverage, or source code.

If a scanned source file is absent from the coverage report, analysis fails instead of silently treating it as covered or uncovered. Configure your test runner to include all files that you want to gate.

Complexity profile

Each function starts at complexity 1. The MVP adds one for each if, loop, catch, ternary, non-default case, logical expression, logical assignment, default value, and optional chain. Nested functions are measured separately.

Coverage statements are assigned to the innermost containing function, so a nested function does not change its parent's coverage percentage.

Development

cargo fmt --check
cargo clippy --all-targets -- -D warnings
cargo test

Not in the MVP

Native V8 coverage, baselines, SARIF, HTML reports, and npm binary packaging are deliberately deferred until the core behavior has been exercised on real TypeScript projects.

License

MIT