Suspense emits `fallback` but does not displays the slot when using a transition

[posva]

Version

3.1.1

Reproduction link

SFC Playground

Steps to reproduce

1. Click on toggle

What is expected?

The fallback content should be displayed

What is actually happening?

It's not

---

• The fallback event seems to be correctly emitted

[posva]

As a workaround it's possible to add a v-else case:

<Suspense>
      <template #default>
        <component v-if="Component" :is="Component" />
        <span v-else></span>
      </template>
      <template #fallback>
        <p>Loading...</p>
      </template>
    </Suspense>

[edison1105]

      if (delayEnter) {
+       suspense.isInFallback = true
        activeBranch!.transition!.afterLeave = mountFallback
      }
      // unmount current active branch
      unmount(
        activeBranch!,
        parentComponent,
        null, // no suspense so unmount hooks fire now
        true // shouldRemove
      )

will works fine.