This is now a proper compile-time constant.

import { IS_DEV, SOME_VALUE } from './other.constants'
if (SOME_VALUE === 'x') { // statically evaluates to `true`
  console.log('x')
}
if (IS_DEV) { // statically evaluates to `true`
  console.log('dev')
}

// other.constants.ts
export const SOME_VALUE = 'x'

const node_env = process.env.NODE_ENV
const development_ent = 'development'
export const IS_DEV = node_env === development_ent

You can use code to compute constants just fine, and use any existing constants such as process.env.NODE_ENV. But no imports, and it fails when exporting a value that isn't constant.

Currently, it silently fails when importing a missing export. But I'd expect that to be covered by typechecking anyway, and detecting this would complicate the implementation quite a bit.

Problems:

• how do we detect imports of constants modules. Right now, I just did request.includes(".constants")
• this is similar in behavior to process.env.SOME_VALUE, but not exactly, because it's only constant for conditionals-evaluation, but the values isn't actually inlined for e.g. console.log(SOME_VALUE);
• small: the error message for export is not a constant isn't very pretty