NPM Install add custom warning message

Question

How should I got about adding a warning message when a user tries to install a given version of a library?

For example, when you install babel-preset-es2015 you get the following warning:

🙌 Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update!

By inspecting their code I saw they add a deprecated entry in their package.json as follows:

"deprecated": "🙌  Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update! ",

I can easily add that, but I'm not actually deprecating anything. I just want to warn users that they are installing an alpha version and there may be changes in the API.

Question

Is there a similar entry to deprecated that can do the job?

Answer 1

There's not necessarily a way you can do that, or not with given fields like "deprecated"

What you can do, which is a little bit of a workaround, is adding a post-install script, that outputs a string to the console if you mark a version as alpha.

// package.json
{
  "version": "1.2.3-alpha.2",
  "scripts": {
    "postinstall": "node postinstall.js"
  }
}

// postinstall.js
const package = require('./package.json')

if (package.version.includes('alpha')) {
  console.log('You are using an alpha version. Beware!')
}

Answer 2

Please check out belows:

• https://docs.npmjs.com/cli/deprecate
• https://docs.npmjs.com/deprecating-and-undeprecating-packages-or-package-versions

$ npm deprecate <pkg>[@<version>] <message>

Example:

$ npm deprecate some-lib@"< 1.0.0" "🙌 Thanks for using it. we recommend using new version, 1.x.x. Please check out https://example.com"

then,

$ yarn
yarn install v1.16.0
info No lockfile found.
[1/4] 🔍  Resolving packages...
warning [email protected]: 🙌 Thanks for using it. we recommend using new version, 1.x.x. Please check out https://example.com
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 🔨  Building fresh packages...
success Saved lockfile.
✨  Done in 5.25s.
Time: 0h:00m:06s