is-dev-dependency

This library helps us identify whether a Node package is used exclusive as a direct or indirect dev dependency in a Node library project. If a Node package is an exclusive dev dependency, we can safely add/remove/upgrade this dependency without modifying the Node project's behavior as an library.

For instance, is-dev-dependency uses jest to run tests. jest is its dev dependency. Adding/removing/upgrading jest may affect is-dev-dependency's developer experience but it won't affect anyone using is-dev-dependency as a library. (When adding is-dev-dependency as a dependency to another Node project it won't bring jest into that project as an indirect dependency. Modifying jest won't change is-dev-dependency as a library.)

Usage

The Node project directory we target needs to include a package.json file and a lock file (either package-lock.json or yarn.lock). We use the directory's relative or absolute path and a Node package name to find out if this particular package is exclusively a dev dependency.

import { isExclusiveDevDependency } from 'is-dev-dependency';

// `is-dev-dependency` uses `jest` as a dev dependency.
console.log(isExclusiveDevDependency('./', 'jest')); // true

// `is-dev-dependency` uses `snyk-nodejs-lockfile-parser` as a dependency.
// Both `snyk-nodejs-lockfile-parser` and `jest` use '@types/node' as a dependency so it's a mixed dependency.
console.log(isExclusiveDevDependency('./', '@types/node')); // false

console.log(isExclusiveDevDependency('./', 'snyk-nodejs-lockfile-parser')); // false