Pin exact dependencies

Recipe: prevent ^ / ~ in dependencies and devDependencies.

Detect package manager

Prefer in order:

1. packageManager field in package.json (e.g. bun@…, pnpm@…, npm@…)
2. Lockfile: bun.lock / bun.lockb → bun; pnpm-lock.yaml → pnpm; yarn.lock → yarn; package-lock.json → npm
3. Default: bun

Use that PM for all install / script commands below. Map:

save-exact=true in .npmrc is respected by bun, npm, pnpm, yarn.

Steps

1. .npmrc — write exact on install

# Pin exact versions in package.json (no ^ / ~ ranges) when adding deps
save-exact=true

Prevents new ranges from package-manager add/install. Does not rewrite existing entries.

2. Fix existing ranges

Strip ^ / ~ from every dep in package.json, then refresh lockfile with the project PM. Lint fails until clean.

3. npm-package-json-lint — enforce

# bun (default):
bun add -d npm-package-json-lint
# pnpm: pnpm add -D npm-package-json-lint
# npm:  npm i -D npm-package-json-lint
# yarn: yarn add -D npm-package-json-lint

.npmpackagejsonlintrc.json:

{
  "rules": {
    "prefer-absolute-version-dependencies": "error",
    "prefer-absolute-version-devDependencies": "error"
  }
}

package.json scripts:

"lint:package": "npmPkgJsonLint ."

4. Wire git hooks (if present)

Detect before wiring:

• Husky: .husky/ and/or husky in devDependencies / prepare script
• Lefthook: lefthook.yml / lefthook.yaml and/or lefthook in devDependencies

Husky + lint-staged (common)

If lint-staged exists, add (run before generic *.json prettier if both match):

"package.json": ["npmPkgJsonLint", "prettier --write"]

Ensure pre-commit already runs lint-staged (e.g. .husky/pre-commit → bun run lint-staged / pnpm exec lint-staged / npx lint-staged).

If husky without lint-staged: add npmPkgJsonLint . (or $PM run lint:package) to .husky/pre-commit.

Lefthook

In lefthook.yml (or .yaml), under pre-commit:

pre-commit:
  commands:
    lint-package:
      glob: "package.json"
      run: npmPkgJsonLint {staged_files}
      # or: <pm> run lint:package

Match existing lefthook style (parallel vs serial, root, etc.). Prefer glob-scoped run when other package.json-only checks exist.

Neither husky nor lefthook

Skip hooks. Rely on CI + manual lint:package. Do not add a hook tool unless the user asks.

5. Wire CI

After install, with other lints (substitute project PM):

- name: Lint package.json
  run: bun run lint:package
  # pnpm run lint:package | npm run lint:package | yarn lint:package

6. Verify

bun run lint:package   # or pnpm/npm/yarn equivalent

Must exit 0. Introduce a ^ temporarily only to confirm it fails, then revert.

Notes

• Exact pins in package.json ≠ locked tree — lockfile still owns transitive versions.
• save-exact = prevent; lint = catch hand-edits / leftovers.
• Skip syncpack unless monorepo with many package.jsons.