fallow

Fallow

Fallow is a static analysis tool for TypeScript/JavaScript installed as a devDependency. It finds unused code, duplication, complexity hotspots, and refactoring targets. Run it via pnpm fallow scripts — never npx.

Quick reference

pnpm fallow                # full analysis: dead code + dupes + health
pnpm fallow:audit          # changed-file audit (PR gate)
pnpm fallow:health         # complexity, hotspots, refactoring targets
pnpm fallow:dead-code      # unused files, exports, types, deps
pnpm fallow:dupes          # duplicated code blocks

JSON output for programmatic use

Always invoke via pnpm --silent fallow … --format json --quiet 2>/dev/null and append || true. The --silent is load-bearing: fallow exits 1 when issues are found (normal), and without --silent pnpm appends [ELIFECYCLE] Command failed with exit code 1. to stdout after the JSON — json.load then fails with "Extra data", and 2>/dev/null does not strip it. Only exit code 2 is a real error.

pnpm --silent fallow dead-code --format json --quiet 2>/dev/null || true
pnpm --silent fallow health --score --targets --format json --quiet 2>/dev/null || true

Useful flags

Flag	Purpose
--unused-exports	Filter to only unused exports
--unused-files	Filter to only unused files
--changed-since main	Only files changed since a ref
--score	Show health score (0–100)
--hotspots	Riskiest files by churn × complexity
--targets	Ranked refactoring recommendations
--mode semantic	Duplication: catch renamed-variable clones

Configuration

Config lives at .fallowrc.json in the repo root. This is a single package, so the config declares one entry point manually — the Pi extension entry ["src/index.ts"] — since fallow does not know that convention. Rules use "error" (fail CI), "warn" (report only), or "off" (skip).

Suppressing findings

// fallow-ignore-next-line unused-export
export const keepThis = 1;

// fallow-ignore-next-line unused-type
export type KeepThisType = string;

// fallow-ignore-file