Copy and pasting Event bindings in UMG causes cook failures and UEFN crashes when trying to reopen offending Widget

General Issues and Bug Reporting
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1

Summary

This is a bug I experienced yesterday and didn’t think anything of it until I saw 2 other people reporting the same issue in the UEFN discord.

When copy and pasting existing view bindings (I tested it with the event bindings specifically, YMMV with other bindings) widgets compile correctly, but upon cooking the project fails with the error “[Compiler] Internal error: An event is invalid.”.

After trying to delete, remake and adjust these events inside the widget, UEFN crashed. I then experienced the same thing each time i tried to open the widget. I duplicated it and the same thing happened, I couldn’t open the widget anymore without crashing.

I had to delete it. I remade the same widget step by step, this time WITHOUT duplicating bindings, and I didn’t experience any crashes.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Stability

Steps to Reproduce

  1. create widget blueprint
  2. create an event binding (ie. OnHovered, OnUnhovered for a button with a custom verse event)
  3. compile widget to confirm it is valid and cook project, confirm no validation issues
  4. duplicate event binding and connect to different things (for example a buttons “On Hovered” event to a different verse event)
  5. compile widget to make sure it shows it’s valid
  6. try and push changes/load into a session (at this point you should get a cook error)
  7. try and edit the widget to fix the issue (remove the offending binding). It should STILL give a cook failure and [potentially crash while trying to edit the bindings
  8. (Optional) if editor didn’t crash while trying to fix the widget, close and open UEFN and try to open the widget again - I was never able to open the widget again at this point

Expected Result

duplicated binding passes cook stage and allows for correct functionality

Observed Result

duplicated binding corrupts the widget and any duplicate versions of it, causing editor crashes upon opening the widget, as well as quiet cook errors which the widget compiler doesn’t catch

Platform(s)

PC

2

FORT-1074412 has been created and its status is ‘Unconfirmed’. This is now in a queue to be reproduced and confirmed.