Warning / "Attribute not supported" Notification after adding "on" event

If these attributes are not good practice or a security issue, then please warn the user instead of deleting their code without telling them the code was removed.

It is very confusing to debug this issue, adding the attribute in BSS and seeing it in the attributes section, then exporting, to find it doesn't work. Then going through all the code to realise it was not added.

I checked in BSS and added again in case I mistyped. I wasn't sure about the problem.

It's very odd behaviour to remove a user's code without a notification that the code is not supported and therefore was removed.

To clarify, I was adding oninput attribute

Thank you for the suggestion! We will look into allowing on attributes in our upcoming releases. Thanks to some work we did recently I think we can do it without security risks (this is the reason on* attributes aren't permitted).