check-npm-client

npm and yarn are both npm clients used to manage node.js project dependencies. They are somehow different in some behavior, and thus can affect project running.

This package provides ready-to-use functionality to check current npm client. When used as pre commands in npm scripts, it will check if the script is executed by specific npm client (yarn or npm). If it is restricted, then the script execution will be aborted early.

Usage Scenario

yarn uses yarn.lock to ensure versions of dependencies, but npm use package-lock.json to do that instead. If you use yarn to install dependencies in a project which is actually managed by npm and package-lock.json, the actually installed dependencies in node_modules might be different due to semver behavior, and this could lead to some un-expected exception while code running.

This is common when working with others because people tends to use yarn or npm as their wishes.

Installation

$ npm install check-npm-client

or alternatively, with yarn:

$ yarn add check-npm-client

Example

This package provide a command line tool to invoke checking functionality:

# the user must use `npm` to execute the script
$ check-npm-client --npm-only

# the user must use `yarn` to execute the script
$ check-npm-client --yarn-only

# automatically check according to current working directory lock files if exists
$ check-npm-client

Besides, you can use it programmatically:

const { checkNpmClient } = require('check-npm-client');
console.log(checkNpmClient('yarn'));  // true/false

Ensure before installation

Add the script in your package.json to ensure that user must install dependencies with yarn:

{
  "scripts": {
    "preinstall": "npx check-npm-client --yarn-only"
  }
}

Note #1: npx is required to execute checking because before your project installation, the command check-npm-client won't be available.

Note #2: yarn and npm treat preinstall script a little differently. npm execute it only before npm install (not before npm install <module>), but yarn always run it before any installation. See issue here. So if specified as --yarn-only and user use npm to install another dependency, the preinstall will not be invoked (so the ensurance will fail).

Ensure before any other script

Add the script in your package.json to ensure that user must use npm to run the script my-task:

{
  "scripts": {
    "premy-task": "check-npm-client --npm-only",
    "my-task": "node my-task.js"
  }
}

References

• https://github.com/npm/cli/issues/481
• https://stackoverflow.com/questions/46725374/how-to-run-a-script-before-installing-any-npm-module
• https://github.com/yarnpkg/yarn/issues/5063
• https://docs.npmjs.com/cli/run-script#description