Duplicate keys detected not warned

[dejour]

Version

2.5.17

Reproduction link

https://codesandbox.io/s/zwm20ozlym

Steps to reproduce

check reproduction url

What is expected?

Duplicate keys detected to be warned

What is actually happening?

Duplicate keys detected not warned

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when addVnodes is called, vnodes with same key are not warned

[DanielSanRocha]

Hi, may I try to make this improvement my first contribution? I have already had some situations with duplicated keys in which a warning would have helped.

[posva]

of course, nobody is working on this 🙂

[DanielSanRocha]

Added a pull request (#8881) with a new test case and a solution.