use-yarn

If running npm install instead of yarn, the process will exit with error code 1 and print an error message.

Note: this will not work if installing specific packages like npm install my-package.

Note: this will not work if used with npm install --save-dev --ignore-scripts.

Note: Use with >= yarn@1 requires >= use-yarn@2.

Install

Use

CLI

For example, in your package.json:

{
  "scripts": {
    "preinstall": "use-yarn || ( npm install --no-scripts --no-save use-yarn && use-yarn )"
  }
}

Or if you’re on npm >=5 or have npx, you can run it by passing $npm_execpath:

{
  "scripts": {
    "preinstall": "npx use-yarn $npm_execpath"
  }
}

You may provide a custom message via the -m flag:

{
  "scripts": {
    "preinstall": "npx use-yarn $npm_execpath -m 'Please use yarn!'"
  }
}

Or, you may also provide a custom message read from a file via the -f flag:

{
  "scripts": {
    "preinstall": "npx use-yarn $npm_execpath -f path/to/customMessage.txt"
  }
}

You may disable use-yarn by setting the DISABLE_USE_YARN environment variable to true.

API

var useYarn = require("use-yarn");

useYarn();

// or a custom message:
useYarn({ message: "We like npm!" });

Etc.

If you want to catch missed updates to yarn.lock on CI, try danger-yarn-lock.