fix(runtime-core): in operator returning false for built-in insta…

…nce properties in `exposeProxy` (vuejs#6138)

fix vuejs#6137

packages/runtime-core/__tests__/apiExpose.spec.ts

@@ -203,7 +203,9 @@ describe('api: expose', () => {
         return h('div')
       },
       setup(_, { expose }) {
-        expose()
+        expose({
+          foo: 42
+        })
         return () => h(GrandChild, { ref: grandChildRef })
       }
     })
@@ -216,7 +218,10 @@ describe('api: expose', () => {
     }
     const root = nodeOps.createElement('div')
     render(h(Parent), root)
+    expect('$el' in childRef.value).toBe(true)
     expect(childRef.value.$el.tag).toBe('div')
+    expect('foo' in childRef.value).toBe(true)
+    expect('$parent' in grandChildRef.value).toBe(true)
     expect(grandChildRef.value.$parent).toBe(childRef.value)
     expect(grandChildRef.value.$parent.$parent).toBe(grandChildRef.value.$root)
   })

packages/runtime-core/src/component.ts

@@ -945,6 +945,9 @@ export function getExposeProxy(instance: ComponentInternalInstance) {
           } else if (key in publicPropertiesMap) {
             return publicPropertiesMap[key](instance)
           }
+        },
+        has(target, key: string) {
+          return key in target || key in publicPropertiesMap
         }
       }))
     )