Conditional import/export based on locus in Meteor with typings

index.ts

// these imports exist only in typescript-land (just importing types)
import * as _serverExports from './index.server'
import * as _clientExports from './index.client'

// Meteor for isClient / isServer
import { Meteor } from 'meteor/meteor'

// isomorphic imports
import { findByEmail } from './findByEmail'

// define vars with the same name as the client / server exports
// more importantly, copy over the original functions' typedefs
// so even though these vars are `undefined` at runtime, TS will
// tell you that they're `(blah, blah, blah) => something` (or w/e)
let {runCreationHooks, registerAccountCreationHook} = {} as typeof _serverExports
let {findByQuery, findByUsername} = {} as typeof _clientExports

if (Meteor.isServer) {
  // here's the sexy bit, import the _actual_ server exports (note how we're nested here)
  const serverExports: typeof _serverExports = require('./index.server')

  // overwrite the `undefined` values with the real things
  runCreationHooks = serverExports.runCreationHooks
  registerAccountCreationHook = serverExports.registerAccountCreationHook
  // ...
}

if (Meteor.isClient) {
  // same thing for client-only exports
  const clientExports: typeof _clientExports = require('./index.client')
  findByQuery = clientExports.findByQuery
  findByUsername = clientExports.findByUsername
  // ...
}

// export everything - important because TS and IDEs don't handle
// nested imports/exports *or* conditional imports/exports well.
// note that some of these values will be `undefined` depending on
// the current environment
export {
  findByEmail,
  runCreationHooks,
  registerAccountCreationHook,
  findByQuery,
  findByUsername
}