feat(reactivity): proxyRefs method and ShallowUnwrapRefs type (#1682)

* feat(reactivity): `proxyRefs` method and `ShallowUnwrapRefs` type

BREAKING CHANGE: template auto ref unwrapping are now applied shallowly,
i.e. only at the root level. See https://github.com/vuejs/vue-next/pull/1682 for
more details.

packages/reactivity/src/index.ts

@@ -1,15 +1,17 @@
 export {
   ref,
-  unref,
   shallowRef,
   isRef,
   toRef,
   toRefs,
+  unref,
+  proxyRefs,
   customRef,
   triggerRef,
   Ref,
-  UnwrapRef,
   ToRefs,
+  UnwrapRef,
+  ShallowUnwrapRef,
   RefUnwrapBailTypes
 } from './ref'
 export {

packages/reactivity/src/ref.ts

@@ -1,7 +1,7 @@
 import { track, trigger } from './effect'
 import { TrackOpTypes, TriggerOpTypes } from './operations'
 import { isObject, hasChanged } from '@vue/shared'
-import { reactive, isProxy, toRaw } from './reactive'
+import { reactive, isProxy, toRaw, isReactive } from './reactive'
 import { CollectionTypes } from './collectionHandlers'
 
 declare const RefSymbol: unique symbol
@@ -71,6 +71,27 @@ export function unref<T>(ref: T): T extends Ref<infer V> ? V : T {
   return isRef(ref) ? (ref.value as any) : ref
 }
 
+const shallowUnwrapHandlers: ProxyHandler<any> = {
+  get: (target, key, receiver) => unref(Reflect.get(target, key, receiver)),
+  set: (target, key, value, receiver) => {
+    const oldValue = target[key]
+    if (isRef(oldValue) && !isRef(value)) {
+      oldValue.value = value
+      return true
+    } else {
+      return Reflect.set(target, key, value, receiver)
+    }
+  }
+}
+
+export function proxyRefs<T extends object>(
+  objectWithRefs: T
+): ShallowUnwrapRef<T> {
+  return isReactive(objectWithRefs)
+    ? objectWithRefs
+    : new Proxy(objectWithRefs, shallowUnwrapHandlers)
+}
+
 export type CustomRefFactory<T> = (
   track: () => void,
   trigger: () => void
@@ -146,6 +167,10 @@ type BaseTypes = string | number | boolean
  */
 export interface RefUnwrapBailTypes {}
 
+export type ShallowUnwrapRef<T> = {
+  [K in keyof T]: T[K] extends Ref<infer V> ? V : T[K]
+}
+
 export type UnwrapRef<T> = T extends Ref<infer V>
   ? UnwrapRefSimple<V>
   : UnwrapRefSimple<T>