fix(runtime-core): when using the deep mode of watch, watchCallBack will be triggered even if the value does not change (fix #7160)

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

@@ -1150,4 +1150,26 @@ describe('api: watch', () => {
     // own update effect
     expect(instance!.scope.effects.length).toBe(1)
   })
+
+  // #7160
+  test('when using the deep mode of watch, watchCallBack wont be triggered if the value does not change', async () => {
+    const msg = ref('hi')
+    const msgTrim = computed(() => msg.value.trim())
+
+    let changeCounter = 0
+    let deepChangeCounter = 0
+
+    watch(msgTrim, () => ++changeCounter)
+    watch(msgTrim, () => ++deepChangeCounter, { deep: true })
+
+    msg.value = 'hi!'
+    await nextTick()
+    expect(changeCounter).toBe(1)
+    expect(deepChangeCounter).toBe(1)
+
+    msg.value = 'hi! '
+    await nextTick()
+    expect(changeCounter).toBe(1)
+    expect(deepChangeCounter).toBe(1)
+  })
 })

packages/runtime-core/src/apiWatch.ts

@@ -311,13 +311,13 @@ function doWatch(
       // watch(source, cb)
       const newValue = effect.run()
       if (
-        deep ||
         forceTrigger ||
         (isMultiSource
-          ? (newValue as any[]).some((v, i) =>
-              hasChanged(v, (oldValue as any[])[i])
+          ? (newValue as any[]).some(
+              (v, i) =>
+                (deep && isObject(v)) || hasChanged(v, (oldValue as any[])[i])
             )
-          : hasChanged(newValue, oldValue)) ||
+          : (deep && isObject(newValue)) || hasChanged(newValue, oldValue)) ||
         (__COMPAT__ &&
           isArray(newValue) &&
           isCompatEnabled(DeprecationTypes.WATCH_ARRAY, instance))
@@ -329,11 +329,11 @@ function doWatch(
         callWithAsyncErrorHandling(cb, instance, ErrorCodes.WATCH_CALLBACK, [
           newValue,
           // pass undefined as the old value when it's changed for the first time
-          oldValue === INITIAL_WATCHER_VALUE 
+          oldValue === INITIAL_WATCHER_VALUE
             ? undefined
-            : (isMultiSource && oldValue[0] === INITIAL_WATCHER_VALUE)
-              ? []
-              : oldValue,
+            : isMultiSource && oldValue[0] === INITIAL_WATCHER_VALUE
+            ? []
+            : oldValue,
           onCleanup
         ])
         oldValue = newValue