Version

3.2.19

Reproduction link

https://codesandbox.io/s/solitary-fast-4fgmx?file=/src/App.vue

Steps to reproduce

1. Create a keyed looped template with 2 child elements.
2. Wrap this template with transition-group.

What is expected?

No [Vue warn]: children must be keyed. Because the key is given to template tag.

What is actually happening?

[Vue warn]: children must be keyed. Transition of the 2 elements also seems to be breaking.

This was not an issue in Vue2 as we were able to manually specify key for child elements inside template.