Query callback is called twice for the same entity about donburi

[bradbeam]

I think I'm running into something similar, but for my use case it is only around modifications ( namely transform.SetWorldPosition(card, localPosition) and transform.AppendChild(stack, card, false).
So far I'm suspecting it's related to the archetypes and how they get generated when the entity changes. In my case, calling transform.AppendChild calls child.AddComponent(parentComponent) which causes a new archetype to be created.

We discover and iterate through the archetypes via our calls to Each.
So in the first run, the only archetype that World knows about is PositionData.
After the add of DoActionData, the world knows about two archetypes, PositionData and one for PositionData, DoActionData. So in the second run, the query matches both archetypes and you wind up with seemingly duplicate entries.

Here's a modification of your example to highlight it ~ https://go.dev/play/p/F0vrtZdKLol
(note, you can ignore the move of query outside of the receive player input; in playing around I came across the note here https://pkg.go.dev/github.com/yohamta/[email protected]/query#Query and was curious if it was related, but don't believe it is )

Thoughts?

some refs:

• donburi/query.go

  Line 71 in db59a18

  result := q.evaluateQuery(w, &accessor)

  when the query is evaluated and archetypes identified

• donburi/internal/storage/iterator.go

  Line 28 in db59a18

  return it.archetypes[archetypeIndex].Entities()

  where the entries for each archetype are returned via iter.Next() call

[yohamta]

Thanks a lot for submitting the issue with such details, that's really helpful. In donburi, for performance reasons, a SwapRemove is performed internally on a slice. Therefore, when Remove is executed, the last element is inserted at the index of the removed element. This might be causing the behavior you're observing 🤔 I think we might have to investigate deeper to identify the cause.