Self-Referential Relationships

By default, Bevy rejects relationship components that point to the entity they live on. If you insert one, Bevy will log a warning and remove it. This default exists for good reason: structural relationships like ChildOf form hierarchies that Bevy traverses recursively — a self-referential ChildOf would produce an infinite loop.

That being said, many relationships are not hierarchical. Likes(self), EmployedBy(self), Healing(self) — these are not meant for traversal, and self-reference is perfectly valid. You can now opt in with allow_self_referential:

#[derive(Component)]
#[relationship(relationship_target = PeopleILike, allow_self_referential)]
pub struct LikedBy(pub Entity);

#[derive(Component)]
#[relationship_target(relationship = LikedBy)]
pub struct PeopleILike(Vec<Entity>);

With the attribute set, inserting a self-referential relationship is accepted without warning. Of course, if you traverse these relationships yourself, you have to guard against infinite loops.