perf(reactivity): add existing index or non-integer prop on Array should not trigger length dependency (#1969)

packages/reactivity/src/effect.ts

@@ -1,5 +1,5 @@
 import { TrackOpTypes, TriggerOpTypes } from './operations'
-import { EMPTY_OBJ, isArray } from '@vue/shared'
+import { EMPTY_OBJ, isArray, isIntegerKey } from '@vue/shared'
 
 // The main WeakMap that stores {target -> key -> dep} connections.
 // Conceptually, it's easier to think of a dependency as a Dep class
@@ -202,16 +202,17 @@ export function trigger(
       add(depsMap.get(key))
     }
     // also run for iteration key on ADD | DELETE | Map.SET
-    const isAddOrDelete =
-      type === TriggerOpTypes.ADD ||
+    const shouldTriggerIteration =
+      (type === TriggerOpTypes.ADD &&
+        (!isArray(target) || isIntegerKey(key))) ||
       (type === TriggerOpTypes.DELETE && !isArray(target))
     if (
-      isAddOrDelete ||
+      shouldTriggerIteration ||
       (type === TriggerOpTypes.SET && target instanceof Map)
     ) {
       add(depsMap.get(isArray(target) ? 'length' : ITERATE_KEY))
     }
-    if (isAddOrDelete && target instanceof Map) {
+    if (shouldTriggerIteration && target instanceof Map) {
       add(depsMap.get(MAP_KEY_ITERATE_KEY))
     }
   }