How to call an internal functions in a '<script setup>' components?

[LemoFire]

App.vue

<template>
    <Comp1 ref="RefComp1"/>     // General SFC with setup()
    <Comp2 ref="RefComp2"/>     // <script setup> 
</template>

<script>
import .....
export default {
    setup(){
        const RefComp1=ref(null)
        const RefComp2=ref(null)
        onMounted(() => {
            RefComp1.value.testFunction()      // call function successfully
            RefComp2.value.testFunction()      // can't call function with error "Maximum call stack size exceeded", and can't see any function(but variables can) in `console.log(RefComp2.value)`
            console.log(RefComp1.value.testFunction, RefComp2.value.testFunction); // ()=>{...} undefined
        }

        return {RefComp1,RefComp2}
    }
}

<script>

Comp1.vue // General SFC with setup()

<script>
export default {
  setup() {
    const testFunction = () => {
        console.log("WOW",test1)
    };
    return {
      testFunction,
    };
  },
};
</script>

Comp2.vue // <script setup>

<script setup>
const testFunction = () => {
    console.log("WOW",test1)
};
</script>

[leopiccionia]

I think it needs to use defineExpose, as documented here.

[LemoFire]

Hello, thanks for your help,I had try to use this doc's example in my project(use Vue 3.1.2),It doesn't work with an undefined error.

<script setup>
const testFunction = () => {
  console.log("WOW", test1);
};
defineExpose({
  testFunction,
});
</script>

<template><div>s</div></template>

q.vue:5 Uncaught ReferenceError: defineExpose is not defined
    at setup (q.vue:5)
    at callWithErrorHandling (runtime-core.esm-bundler.js:154)
    at setupStatefulComponent (runtime-core.esm-bundler.js:7131)
   ......

When I import it from vue import { defineExpose } from "vue";, I will get another error

The requested module '/node_modules/.vite/vue.js?v=078c2df7' does not provide an export named 'defineExpose'

I don't know if it is implemented in 3.1.2

[patak-dev]

This will be released in 3.1.3, check out Evan's comment in the RFC #227 (comment)

[LemoFire]

Thank you so much :) I will pay more attention to RFC‘s comments.