Vue: key attribute set by `v-bind="obj"` is ignored by transition-group

[nirazul]

Version

2.3.4

Reproduction link

https://codepen.io/Nirazul/pen/RgGRjm

Steps to reproduce

1. Click on the trigger button
2. There is only one list visible instead of two

What is expected?

According to the documentation I was expecting that I can use the v-bind object notation to set the key attribute.

What is actually happening?

The list is not rendered when the key attribute is not directly present on the element.

---

I'm aware that key is a special attribute and that there may be some sort of "hen and egg" problem at work when rendering items in a transition-group.
If the behaviour is intentional, there's maybe some space for improvement in the documentation.

[yyx990803]

Yeah, we should improve the docs regarding the special case for key. In fact all reserved attributes cannot be bound using v-bind object syntax.

/cc @chrisvfritz

[gebilaoxiong]

... I'm fixing it

ping @yyx990803

https://github.com/vuejs/vue/blob/dev/src/core/instance/render-helpers/bind-object-props.js#L27

Can I add an error warn here?

[yyx990803]

@gebilaoxiong ah, I realized it should indeed be fixable. Just check for the special keys in https://github.com/vuejs/vue/blob/dev/src/core/instance/render-helpers/bind-object-props.js

[gebilaoxiong]

@yyx990803

OK, boss