when watch a reactive data, the old value is equal new value. if watch a ref, it's right.

[huangfengya]

Version

3.0.0-beta.15

Reproduction link

https://codesandbox.io/s/cool-lovelace-kw6hp?file=/src/App.vue

Steps to reproduce

import { reactive, watch } from 'vue'

export default {
mounted() {
},
setup() {
const msg1 = reactive({
val: 1
});
watch(msg1, (val, oldVal) => {
console.log(val === oldVal); // true?
console.log(new val: ${val.val}, old val: ${oldVal.val});
});
const changeMsg1 = () => {
msg1.val = 1;
};

    return {
        msg1,
        changeMsg1
    };
}

};

What is expected?

"val == oldVal" is false
"val.val === oldVal.val" is false

What is actually happening?

"val === oldVal" is true
"val.val === oldVal.val" is true

---

this app is use vue-cli3 create，then use "vue add vue-next" change version vue2 to vue3。

[HcySunYang]

This is consistent with the behavior of Vue2, because the old and new values have the same reference.

[yyx990803]

^

This is expected behavior.

[haishengXie0712]

@huangfengya

watch(
  () => msg1.val,
  (val, oldVal) => {
    msg1.isOldEqualNew = val.val === oldVal.val
    console.log(val === oldVal) // true?
    console.log(`new val: ${val}, old val: ${oldVal}`)
  }
)

[yaquawa]

no workaround for this?