data method not called with `this` as argument when using mixins with data option

[coolzjy]

Version

2.5.9

Reproduction link

https://codepen.io/cool_zjy/pen/KyLpve

Steps to reproduce

1. run the reproduction
2. VueComponent logged in console
3. uncomment // mixins: [mixin],
4. run the reproduction again

What is expected?

VueComponent logged in console

What is actually happening?

undefined logged in console

[Akryum]

Please use this to access component instance in hooks and other methods.
https://codepen.io/Akryum/pen/OOYywd

[sqal]

@Akryum Why? Since 2.5 data function receives vm instance as the first argument #6760

[Akryum]

I'm on a PR.

[posva]

I think the fix is adding this as the second arg on call in the mergeDataOrFn function