Version

3.2.29

Reproduction link

sfc.vuejs.org/

Steps to reproduce

The above demo can show

What is expected?

1.attr should not be automatically passed from parent component to child component 2.Under the above premise, if attr and prop have the same name, attr should not overwrite prop 3.When a custom component is used as a root, it should behave as if it were wrapped in a div

What is actually happening?

1.attr(a) on Comp is automatically passed to CompChild, but not on CompA 2.attr (name) in comP is passed to props (name) of CompChild

That's working as intended and also worked like this in Vue 2 already.

I'll reopen this to re-evaluate one specific thing: attrs from parent overrwriting explicit props in the child, like this: Playground

That doesn't seem to be exactly desirable and would have worked differently in Vue 2 I_think_

one can also disable attributes inheritance

inheritAttrs:false

and manually pass attributes to the next child

// age is passthrough
// name is override  
<CompChild name="Set by comp" v-bind:age=$attrs.age></CompChild>

SFC Playground

I'll reopen this to re-evaluate one specific thing: attrs from parent overrwriting explicit props in the child

I don't think the fact it's is a prop or an attribute matters.

Since name is merged from App.vue template into Comp.vue, it makes sense for it to override the attribute/prop (going top down).

Yeah from that perspective I have to agree.

It's an edge-case, but a breaking change that we so far haven't documented.

https://jsfiddle.net/Linusborg/qoxj71f8/6/

App.vue > Comp.vue > Inner.vue

there is importance for name being attribute in Comp.vue attributes are expected to be applied to the root element,

which is then applied to <inner> root element, overriding the explicit prop/attribute

documented https://v3.vuejs.org/guide/component-attrs.html#attribute-inheritance

props don't fall through for root elements.

In the context of Comp.vue, name is a non-prop attribute - Comp.vue doesn't have a prop named name defined.

So the behavior matches the docs. it's just a subtle breaking change compared to Vue 2 that we so fare haven't documented.

I would say this is the more "correct" and expected behavior compared to Vue 2. name is not declared by Comp so it gets passed on to CompChild, and because it's from higher-up, it has higher priority.

Also considering that changing this would technically constitute a breaking change in Vue 3, I think this is a wontfix.