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PERF001-bundle-size

Dimension: performance Default severity: Low Languages: JavaScript / TypeScript (npm) Kind: ProjectLevel CWE: (none)

What it detects​

Fires when the dist/ directory's total byte size recursively exceeds 1 MiB (1,048,576 bytes).

A large unminified bundle suggests the package has not been tree-shaken or split into smaller chunks. Consumers who install the package will download and parse all of it, increasing page-load and startup latency.

Detection algorithm​

Recursively sums the byte sizes of every regular file under <project_root>/dist/. If the total exceeds 1 MiB, one PERF001-bundle-size Low finding is emitted pointing at the dist/ directory. If dist/ does not exist the rule is skipped silently.

Example — flagged​

A dist/ directory containing large, unminified files totalling more than 1 MiB:

dist/
  index.js        (800 KiB — unminified)
  helpers.js      (400 KiB — unminified)

Example — not flagged​

dist/
  index.min.js    (120 KiB — minified and tree-shaken)
  helpers.min.js   (40 KiB — minified)

How to fix​

  • Enable minification in your bundler (Rollup, webpack, esbuild, Vite).
  • Enable tree-shaking by using ES module (import/export) syntax and setting "sideEffects": false in package.json.
  • Split large entry points into smaller chunks using code-splitting.
  • Audit and remove unused dependencies.
# Check current bundle size
du -sh dist/

# Analyse what is contributing to bundle size (example with source-map-explorer)
npx source-map-explorer dist/index.js

Configuration​

There is no configuration knob in v1 — the 1 MiB threshold is fixed. A configurable threshold will be available when Config gains a [javascript.perf] section.

Suppression​

[ignore]
rules = ["PERF001-bundle-size"]

References​