Extend Environment Variables to get build format at build time

[abarke]

I would like to know what build.lib.format is at build time

Use case: usage information (we log which build our clients are using at runtime).

This would also be useful for anyone who would like to change some values for different builds e.g. es, cjs and esm.

Current workaround: Assuming I define process.env.VITE_LIB_TYPE=umd in vite.config.js I can use import.meta.env in the code and at build it will be replaced.

// app.js

function buildType() {
  return import.meta.env.VITE_LIB_TYPE || "empty"
}

// dist/app.js

function buildType() {
  return "umd"
}

However this solution means I need to have two vite.config.js files. One for each build format e.g. es and umd. Or is there a way to define an array of configs?

Ideally there should be an environment variable set in import.meta.env for the build format e.g.

{ 
  "BASE_URL": "/", 
  "MODE": "production", 
  "DEV": false, 
  "PROD": true, 
  "BUILD": "umd" // <----- Additional environment variable for library format
}

This way I only need one configuration and I think this is a much more elegant solution.

[abarke]

What do you think @antfu ? Feedback most appreciated 😃

[abarke]

Created Issue #6954