Tech Note: Cannot delete MaterialFunction assets from the Content Browser in 4.26.0

Jan 7, 2021.Knowledge

Description: Version 4.26.0 contains a bug that can prevent MaterialFunction assets (the uasset file) from being deleted through the Content Browser. The problem is linked to an optimization that improves the reference gathering time.

Potential Impact: Upon deletion, the MaterialFunction asset will disappear from the Content Browser but it will come back when the editor is relaunched as the file is still present on disk. This will also prevent the creation of a new asset using the same name.

Solution: Editor.UseLegacyGetReferencersForDeletion is a CVar that, when set, will revert to the old reference gathering code. Set to 1 either from the console or by adding the following section in DefaultEngine.ini:

[SystemSettings] Editor.UseLegacyGetReferencersForDeletion=1

Version 4.26.1 is expected to have a permanent fix. Make sure to remove the section above from your ini after upgrading to 4.26.1 to benefit from the improved deletion times.