fix(watch): watching multiple sources: computed

vuejs/core#3066

Author: yangmingshan

packages/wechat/__tests__/watch.spec.ts

@@ -558,6 +558,30 @@ describe('watch', () => {
     expect(spy).toHaveBeenCalledTimes(1)
   })
 
+  test('watching sources: ref<any[]>', async () => {
+    const foo = ref([1])
+    const spy = jest.fn()
+    watch(foo, () => {
+      spy()
+    })
+    foo.value = [...foo.value]
+    await nextTick()
+    expect(spy).toBeCalledTimes(1)
+  })
+
+  test('watching multiple sources: computed', async () => {
+    let count = 0
+    const value = ref('1')
+    const plus = computed(() => Boolean(value.value))
+    watch([plus], () => {
+      count++
+    })
+    value.value = '2'
+    await nextTick()
+    expect(plus.value).toBe(true)
+    expect(count).toBe(0)
+  })
+
   /** Dividing line, the above tests is directly copy from vue.js **/
 
   it('warn when using old simple watch api', async () => {

packages/wechat/src/watch.ts

@@ -160,6 +160,8 @@ function doWatch(
 
   let getter: () => any
   let forceTrigger = false
+  let isMultiSource = false
+
   if (isRef(source)) {
     getter = () => (source as Ref).value
     // @ts-expect-error
@@ -168,6 +170,8 @@ function doWatch(
     getter = () => source
     deep = true
   } else if (isArray(source)) {
+    isMultiSource = true
+    forceTrigger = source.some((s) => isReactive(s))
     getter = () =>
       source.map((s) => {
         if (isRef(s)) {
@@ -225,7 +229,7 @@ function doWatch(
     }
   }
 
-  let oldValue = isArray(source) ? [] : INITIAL_WATCHER_VALUE
+  let oldValue = isMultiSource ? [] : INITIAL_WATCHER_VALUE
   const job: SchedulerJob = () => {
     if (!runner.active) {
       return
@@ -234,7 +238,15 @@ function doWatch(
     if (cb) {
       // Watch(source, cb)
       const newValue = runner()
-      if (deep || forceTrigger || hasChanged(newValue, oldValue)) {
+      if (
+        deep ||
+        forceTrigger ||
+        (isMultiSource
+          ? (newValue as any[]).some((v, i) =>
+              hasChanged(v, (oldValue as any[])[i])
+            )
+          : hasChanged(newValue, oldValue))
+      ) {
         // Cleanup before running cb again
         if (cleanup) {
           cleanup()