fix(setup): setup props should pass isReactive check

close #12561

src/core/instance/state.ts

@@ -30,7 +30,7 @@ import {
   isFunction
 } from '../util/index'
 import type { Component } from 'types/component'
-import { TrackOpTypes } from '../../v3'
+import { shallowReactive, TrackOpTypes } from 'v3'
 
 const sharedPropertyDefinition = {
   enumerable: true,
@@ -71,7 +71,7 @@ export function initState(vm: Component) {
 
 function initProps(vm: Component, propsOptions: Object) {
   const propsData = vm.$options.propsData || {}
-  const props = (vm._props = {})
+  const props = (vm._props = shallowReactive({}))
   // cache prop keys so that future props updates can iterate using Array
   // instead of dynamic object key enumeration.
   const keys: string[] = (vm.$options._propKeys = [])

src/v3/apiSetup.ts

@@ -1,5 +1,6 @@
 import { Component } from 'types/component'
 import { PropOptions } from 'types/options'
+import { toggleObserving } from '../core/observer'
 import { def, invokeWithErrorHandling, isReserved, warn } from '../core/util'
 import VNode from '../core/vdom/vnode'
 import {
@@ -10,6 +11,7 @@ import {
   isObject
 } from '../shared/util'
 import { currentInstance, setCurrentInstance } from './currentInstance'
+import { shallowReactive } from './reactivity/reactive'
 import { isRef } from './reactivity/ref'
 
 /**
@@ -29,13 +31,15 @@ export function initSetup(vm: Component) {
     const ctx = (vm._setupContext = createSetupContext(vm))
 
     setCurrentInstance(vm)
+    toggleObserving(false)
     const setupResult = invokeWithErrorHandling(
       setup,
       null,
-      [vm._props, ctx],
+      [vm._props || shallowReactive({}), ctx],
       vm,
       `setup`
     )
+    toggleObserving(true)
     setCurrentInstance()
 
     if (isFunction(setupResult)) {

test/unit/features/v3/apiSetup.spec.ts

@@ -1,4 +1,4 @@
-import { h, ref, reactive } from 'v3'
+import { h, ref, reactive, isReactive, toRef, isRef } from 'v3'
 import { nextTick } from 'core/util'
 import { effect } from 'v3/reactivity/effect'
 import Vue from 'vue'
@@ -247,4 +247,24 @@ describe('api: setup context', () => {
     }).$mount()
     expect(spy).toHaveBeenCalled()
   })
+
+  // #12561
+  it.only('setup props should be reactive', () => {
+    const msg = ref('hi')
+
+    const Child = {
+      props: ['msg'],
+      setup: props => {
+        expect(isReactive(props)).toBe(true)
+        expect(isRef(toRef(props, 'foo'))).toBe(true)
+        return () => {}
+      }
+    }
+
+    new Vue({
+      setup() {
+        return h => h(Child, { props: { msg } })
+      }
+    }).$mount()
+  })
 })