feat(reactivity): add triggerRef API

Also make shallowRef assignment behavior consistent with normal ref

packages/reactivity/src/index.ts

@@ -6,6 +6,7 @@ export {
   toRef,
   toRefs,
   customRef,
+  triggerRef,
   Ref,
   UnwrapRef
 } from './ref'

packages/reactivity/src/ref.ts

@@ -55,7 +55,7 @@ function createRef(rawValue: unknown, shallow = false) {
       return value
     },
     set value(newVal) {
-      if (shallow || hasChanged(toRaw(newVal), rawValue)) {
+      if (hasChanged(toRaw(newVal), rawValue)) {
         rawValue = newVal
         value = shallow ? newVal : convert(newVal)
         trigger(
@@ -70,6 +70,15 @@ function createRef(rawValue: unknown, shallow = false) {
   return r
 }
 
+export function triggerRef(ref: Ref) {
+  trigger(
+    ref,
+    TriggerOpTypes.SET,
+    'value',
+    __DEV__ ? { newValue: ref.value } : void 0
+  )
+}
+
 export function unref<T>(ref: T): T extends Ref<infer V> ? V : T {
   return isRef(ref) ? (ref.value as any) : ref
 }