WaitGameplayTagQuery does not adhere to its Query rules if there are no tags on the Actor

Hello,

I posted a bug submission some days ago on [Link Removed], however I received a mail asking me to repost it here instead. So here I go, even if it's not a question per say.

 

Description: The WaitGameplayTagQuery node doesn't work with EGameplayTagQueryExprType::NoTagsMatch because of the UAbilityAsync_WaitGameplayTagQuery::EvaluateTagQuery implementation. Indeed, to test if the query matches, the line "const bool bMatchesQuery = !TargetTags.IsEmpty() && TagQuery.Matches(TargetTags);" is executed. However, it is incorrect, since with EGameplayTagQueryExprType::NoTagsMatch (and presumably EGameplayTagQueryExprType::NoExprMatch), the correct line would be "const bool bMatchesQuery = TargetTags.IsEmpty() || TagQuery.Matches(TargetTags);". Indeed, if the target tags array is empty, the query matches.

UDN Case:  00535139

• Create a gameplay tag for testing purpose, e.g. "Gameplay_Locked".
• Add the WaitGameplayTagQuery node in a BP with the expression type to "No Tags Match", and add in the query tags the "Gameplay_Locked" tag.
• Branch any BP node on the "Trigger" out exec pin from the WaitGameplayTagQuery node.
• Make sure that the "Gameplay_Locked" tag is added on the tested Actor.
• Make sure that the "Gameplay_Locked" tag is removed from the tested Actor after the WaitGameplayTagQuery has been reached.
• Start the game.

Expected:

The WaitGameplayTagQuery node should resolve when the tested Actor loses the "Gameplay_Locked" tag.

 

Results:

The WaitGameplayTagQuery node will never resolve, thus the "Trigger" exec pin will never be reached.

 

Thank you,

—

I found it easiest to just create a Gameplay Ability that adds and removes loose tags while waiting for the GameplayTagQuery to succeed.  That way all the logic is together.
Baptiste