Readonly reference to an array is not honored when inside v-for

[ahmadshahwan]

Vue version

3.5.13

Link to minimal reproduction

https://play.vuejs.org/#eNp9kdFPwjAQxv+VS1+ABIcEfcFBooYHfVCjvlljlu0Gxa1t2m6OLPvfvXYBITG89e779bvv2pbdah3VFbI5i21qhHZg0VV6yaUotTIOWjCYZEoWO+ggN6qEAfGDmxMgP9G45DJV0jpIld7B4uAwJHL40UIzhyl0n6MRuXAZT/rJNJMKh6UuEodUAcSZqKG+yJVZcFaCkMGRs2XbQhk1ZH0JXRdPCOv5zdRLYazvU+n9jzzZmDlL4XKxjrZWSVq89Tc5S1WpRYHmWTtB4TmbQ1C8lhSF+nkMPWcqHO/76QbT73/6W9v4HmcvBi2aGjk7aC4xa3S9vHp7wobOB7FUWVUQfUZ8RauKymfssbtKZhT7iAtpH8LvCLl+t6vGobT7pXxQT3aB54x+7P7M6n9xZ9FVuMdlR6/4VaPxnvSAs+g6ms5Y9wtIl8Jq

Steps to reproduce

Create a readonly reference to a reference of an array of objects.

const copy = readonly(ref([{ x: 1 }]));

In the template, iterate over the reference array using v-for, while attempting to modify the current element, for instance, inside a child component setup function or directly in the template as follows.

<div v-for="m in copy">{{ m.x = 0 }}</div>

What is expected?

Modification should be disallowed as the reference is a readonly one.

What is actually happening?

Modification is permitted. Data is mutated. No error or waring issued.

System Info

System:
    OS: Linux 5.15 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat)
    CPU: (22) x64 Intel(R) Core(TM) Ultra 9 185H
    Memory: 10.22 GB / 15.43 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 23.10.0 - /usr/local/bin/node
    npm: 10.9.2 - /usr/local/bin/npm

Any additional comments?

This observation only occurs when readonly() is passed a reference. It doesn't happend if the array is passed directly to readonly().

[edison1105]

a side note: In v3.4, it works as expected, and the console will have warnings.