`setup`'s parameter `expose` is not documented

[wenfangdu]

Couldn't find expose anywhere in the document, please correct me if I'm mistaken.

Taken from https://github.com/vuejs/vue-next/blob/f7c54caeb1dac69a26b79c98409e9633a7fe4bd3/packages/runtime-core/src/component.ts#L179:

export declare interface SetupContext<E = EmitsOptions> {
  attrs: Data
  slots: Slots
  emit: EmitFn<E>
  expose: (exposed: Record<string, any>) => void
}

It's the savior for this type of issues: https://stackoverflow.com/q/67659374/7881859

[skirtles-code]

This is still at the RFC stage and is considered experimental:

vuejs/rfcs#210

It is related to another experimental feature, <script setup>:

vuejs/rfcs#227

In that scenario the context object is accessed using useContext(), allowing access to attrs, slots, emit and expose.

Experimental features are typically not included in the documentation as they are still subject to change.