[Feature] Add support for package.json script variables

• I’d be willing to implement a fix

Describe the bug

When using “yarn pack” in Yarn v1, package.json variables (such as npm_package_version) are honoured. This seems to not be th case in yarn v2.

To Reproduce

I have a package.json which defines a “pack” script like so:

  "scripts": {
    "pack": "yarn pack --filename my-file-v$npm_package_version.tar.gz",
  }

The error when I run “yarn run pack” is Internal Error: Unbound variable "npm_package_version"

The minimal information needed to reproduce your issue (ideally a package.json with a single dep). Note that bugs without minimal reproductions might be closed.

Environment if relevant (please complete the following information):

• OS: Linux
• Node version 10.22.0
• Yarn version 2.1.1

[lucasfeliciano]

Other use case is when it’s used on .env files for example:

PORT=7000
REACT_APP_VERSION=$npm_package_version

With yarn2 this is not possible and it is quite surprising that it doesn’t work by design

[Ayc0]

👋 I’m a bit late to the party but I also needed the yarn classic var envs, so I created a plugin for that: https://github.com/Ayc0/yarn-plugin-envs

@jheaff1 it should fit your needs