Regression for slots and functional components

[blake-newman]

Version

2.5.16

Reproduction link

https://codesandbox.io/s/816m7v3rq9

Steps to reproduce

Create a nested set of functional components, then change the slot definition in the child component. In 2.5.15 the slots are correctly rendered, but in 2.5.16 this is not happening. This is because the slot names are being persisted, so not correctly passed down the chain.

This is a common pattern when creating reusable AHOC components, such as a dropdown with predefined content, but using a lower level component as a structural component.

https://codesandbox.io/s/j44nj82483 (Version 2.5.15)

https://codesandbox.io/s/816m7v3rq9 (Version 2.5.16)

What is expected?

Slots to render in there correct position

What is actually happening?

Slots are not correctly assigned to there correct possition

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This is introduced by this ticket: #7710

[TheCommunistCow]

Just an FYI for anyone that runs into this problem in Vue 2.6, this seems to be fixed by switching to the new slot syntax like:
<template v-slot:name></template>