when using mixins in component, the mixin's data will overwrite component's data; 数据对象在合并时，以mixins优先，而不是以组件数据优先

[zhuxindaba]

Version

3.0.0-beta.10

Reproduction link

https://codepen.io/zhuxin/pen/yLYxKpv

Steps to reproduce

      data() {
        return {
          a: 1
        }
      }
    }
    const Comp = {
      mixins: [mixinA],
      data() {
        return {
          a: 3
        }
      },
      render(this: any) {
        return `${this.a}`
      }
    }
    expect(renderToString(h(Comp))).toBe(`3`);

What is expected?

3

What is actually happening?

1

---

      data() {
        return {
          a: 1
        }
      }
    }
    const Comp = {
      mixins: [mixinA],
      data() {
        return {
          a: 3
        }
      },
      render(this: any) {
        return `${this.a}`
      }
    }
    expect(renderToString(h(Comp))).toBe(`3`);

[Kagashino]

Could you please spent some time to read the Document first?

[zhuxindaba]

Could you please spent some time to read the Document first?

I read the document again, but vue3 is actually different from vue2. Is a breaking change?

[Kagashino]

Well, I found the relative rfcs, it may help you.

There is no more defaultStrat in 3.0. Users must now always provide their own merge strategy functions instead of reusing built-in strategies(in Vue2.0):

/**
 * Default strategy.
 */
var defaultStrat = function (parentVal, childVal) {
  return childVal === undefined
    ? parentVal
    : childVal
};

[zhuxindaba]

Well, I found the relative rfcs, it may help you.

There is no more defaultStrat in 3.0. Users must now always provide their own merge strategy functions instead of reusing built-in strategies(in Vue2.0):

/**
 * Default strategy.
 */
var defaultStrat = function (parentVal, childVal) {
  return childVal === undefined
    ? parentVal
    : childVal
};

thx~

[zhuxindaba]

not a bug