Version

3.0.0-rc.9

Reproduction link

https://jsfiddle.net/ef6o4rLd/2/

Steps to reproduce

1. see the console

What is expected?

properties defined in the component should have a higher priority than properties from extends and mixin

What is actually happening?

mixin and extends properties override those defined in the component

vue2 works well : https://jsfiddle.net/whv3dLzq/6/

sorry I just find that it's a duplicate issue with #1978 😂