What problem does this feature solve?

When I design a general purpose component, I want the component to have a basic default behavior without any properties or events, meaning that you can even give the component no properties or events and it will work. It would be nice to pass a property or event to a component when you think it needs to modify a part of its behavior, and then override the default behavior of its corresponding part. Unfortunately when I was designing this component I found that once I defined the list of events held by the current component via defineEmits, I couldn't get the event function passed by the parent in the current component, which made my attempt to override the default behavior of the events impossible

Of course I knew there had been offers early on, but I checked them back and forth and saw that this feature was not taken seriously, so I was hoping to show off my own scenarios with a new feature suggestion and hope vue would consider opening up useListeners to give developers more room to play

What does the proposed API look like?

<style lang="scss">
.bo-dialog {
}
</style>

<template>
    <el-dialog
        v-model="state.vis"
        :close-on-click-modal="false"
        class="bo-dialog"
        title="Tips"
        :align-center="true"
        :draggable="true"
        v-bind="$attrs"
        :style="{minWidth: props.minWidth, maxWidth: props.maxWidth}"
        width="30%"
    >
        <template #header="slot_props_header">
            <slot name="header" v-bind="slot_props_header"></slot>
        </template>

        <template #default="slot_props_default">
            <slot name="default" v-bind="slot_props_default">
                <span>This is a message</span>
            </slot>
        </template>

        <template #footer="slot_props_footer" v-if="!props.hiddenFooter">
            <slot name="footer" v-bind="slot_props_footer">
                <div class="dialog-footer">
                    <el-button @click="methods.cancel_handle">{{ props.btnCancelText }}</el-button>
                    <el-button type="primary" @click="methods.confirm_handle">
                        {{ props.btnConfirmText }}
                    </el-button>
                </div>
            </slot>
        </template>

    </el-dialog>
</template>
<script lang="ts" setup>

const emit = defineEmits(["confirm","cancel"]);
//
const listeners = useListeners();

const methods = {
    cancel_handle ()
    {
        emit("cancel")
        !listeners.onCancel && dialog_close(); // The default behavior is provided here

    },
    confirm_handle ()
    {
        emit( "confirm" );
        !listeners.onConfirm && dialog_confirm(); // The default behavior is provided here
    },
};

</script>

All listeners are actually props with on prefix. For example, @click listener becomes onClick prop. You can use such props even without using defineEmits.

In that case you can do something like this:

const props = defineProps<{
  onConfirm: () => void
}>()

const handleConfirm = () => {
  if (props.onConfirm) {
    props.onConfirm()
  } else {
    // do some default actions
  }
}

You can even pass async listeners and use them as awaitable hooks, which can't be achieved with emit (as far as I know).

All listeners are actually props with on prefix. For example, @click listener becomes onClick prop. You can use such props even without using defineEmits.↳

In that case you can do something like this:↳

const props = defineProps<{
  onConfirm: () => void
}>()

const handleConfirm = () => {
  if (props.onConfirm) {
    props.onConfirm()
  } else {
    // do some default actions
  }
}

You can even pass async listeners and use them as awaitable hooks, which can't be achieved with emit (as far as I know).↳

I know this method can get around this issue but I don't want to use it because it's not a uniform use of events and if I have to use this method to do my own stuff then I really need official support for useListeners. In fact due to the lack of this api, I've given up on 0 configuration design for components for now

Agree！ In vue2，users can get all registered events functions from parent by _events. But now I have to declare v-bind="attrs" in parent component, for that child component can get access to events name called onXXX. It makes complex to use component

Is it possible for useListener to be supported @yyx990803

You can do this

<script lang="ts" setup>
import { useAttrs } from 'vue'
// const emit = defineEmits(["confirm","cancel"]);
const attrs = useAttrs();

const methods = {
    cancel_handle ()
    {
        
        (attrs.onCancel || dialog_close)()
    },
    confirm_handle ()
    {
        (attrs.onConfirm || dialog_confirm)()
    },
};

</script>

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