[2.6.13] Node after v-if node inside named slot is not shown anymore

[caugner]

Version

2.6.13

Reproduction link

https://codesandbox.io/s/recursing-dream-0zdf5?file=/src/App.vue

Steps to reproduce

<template>
  <ComponentWithSlot>
    <template #slot-name>
      <span v-if="false">...</span>
      <span>This is shown in 2.6.12, but not in 2.6.13.</span>
    </template>
  </ComponentWithSlot>
</template>

What is expected?

The text after the v-if node should be shown.

What is actually happening?

It was shown in 2.6.12, but isn't shown in 2.6.13 anymore.

[caugner]

A workaround is to wrap all nodes (inside the slot template) in one node (like a <div> or a <span>), but the Slots documentation doesn't mention this limitation.

[gilles-crealp]

Another workaround is to put an empty node first.

<template>
  <ComponentWithSlot>
    <template #slot-name>
      <div /> <!-- HERE -->
      <span v-if="false">...</span>
      <span>This is shown in 2.6.12, but not in 2.6.13.</span>
    </template>
  </ComponentWithSlot>
</template>

[JaviIG]

The issue seems to be with the normalizeScopedSlot function, which is only taking into account the first vnode of the scoped slot for checking it is a comment but not a placeholder.

Something like this does the trick, but I'm not familiar with this part of the source code.

    return res && (
      res.every(vNode => vNode.isComment && !isAsyncPlaceholder(vNode)) // #9658, #10391
    ) ? undefined
      :  res

[caugner]

The issue seems to be with the normalizeScopedSlot function

Good catch, this would suggest the regression is caused by #11963.

/cc @pi0

edit: My guess would be that this is the solution:

     return res && (
       !vnode ||
-      (vnode.isComment && !isAsyncPlaceholder(vnode)) // #9658, #10391
+      (res.length === 1 && vnode.isComment && !isAsyncPlaceholder(vnode)) // #9658, #10391
     ) ? undefined
      : res