Version

3.2.4

Reproduction link

https://codepen.io/pawel-golubew/pen/OJmeLvV

Steps to reproduce

1. Define component

const ShowPhoneNumber = Vue.defineCustomElement({
    props: {
        phone: String
    },
    template: `<div>Phone number is: {{phone}}</div>`,
});

customElements.define('show-phone-number', ShowPhoneNumber);

2. Use component

<show-phone-number phone="8-909-952-45-93"></show-phone-number>

3. Show in console

[Vue warn]: Invalid prop: type check failed for prop "phone". Expected String with value "8", got Number with value 8. 
  at <App phone=8 > warn$1 @ vue@next:8290

What is expected?

Show number 8-909-952-45-93 as string

What is actually happening?

Show only first char string

There are some bugs here: https://github.com/vuejs/vue-next/blob/872b3f7ec5e1a41c60018bb1f64d841c309b8939/packages/runtime-dom/src/apiCustomElement.ts#L248-L250 Will convert attribute to number.

Any update on this?