How to access `app.config.globalProperties` in a`<script setup lang="ts">`?

Question

how to access app.config.globalProperties withing <script setup lang="ts"> ?

I have looked around for several approaches: like this SO post, and tried to combine elements below:

\\ main.ts

import mitt from 'mitt'
const emitter = mitt()

declare module '@vue/runtime-core' {
  export interface ComponentCustomProperties {
    emitter: typeof mitt
  }
}

app.config.globalProperties.emitter = emitter

tried packaging for use in composition-api .. no luck either

\\ bus.ts

import { getCurrentInstance } from 'vue'

const app = getCurrentInstance()
const bus = app.appContext.config.globalProperties.emitter // app is undefined

export const useBus = () => ({ bus })

Answer 1

There are two problems:

1. You can use getCurrentInstance only in setup or lifecycle hooks of a Vue component
2. Properties added to app.config.globalProperties are exposed directly on component instances

So my preferred solution would be:

// bus.ts 

import mitt from 'mitt'

export const emitter = mitt()
export const useBus = () => ({ bus: emitter })

// main.ts

import { emitter } from `bus.ts`

declare module '@vue/runtime-core' {
  export interface ComponentCustomProperties {
    emitter: typeof emitter
  }
}

app.config.globalProperties.emitter = emitter

Now you can use this.emitter in Options API or in templates. And const { bus } = useBus() in setup

Although I would probably use just single name (either emitter or bus) :)