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Handle TriggerTargets that are combinations for components/entities #14563

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cBournhonesque
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@cBournhonesque cBournhonesque commented Jul 31, 2024

Objective

Solution

  • We can now use ((A, B), (entity_1, entity_2)) as a trigger target, as well as the reverse

Testing

  • Added a unit test.
    The triggering rules for observers are quite confusing:
  • triggers once per entity target
  • for each entity target, an observer system triggers if any of its components matches the trigger target components (but it triggers at most once, since we use an internal counter to make sure that an observer can run at most once per entity target)

@cBournhonesque cBournhonesque added A-ECS Entities, components, systems, and events C-Usability A targeted quality-of-life change that makes Bevy easier to use labels Jul 31, 2024
@cBournhonesque cBournhonesque added this to the 0.15 milestone Jul 31, 2024
@cBournhonesque cBournhonesque added S-Needs-Review Needs reviewer attention (from anyone!) to move forward D-Straightforward Simple bug fixes and API improvements, docs, test and examples labels Jul 31, 2024
@cBournhonesque cBournhonesque requested a review from NthTensor July 31, 2024 21:31
@alice-i-cecile
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The triggering rules for observers are quite confusing:

I'd like to see more docs explicitly explaining this.

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@jrobsonchase jrobsonchase left a comment

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I had a similar change in the works that added impls for various combinations of (<entities>, <components>), but this is more general!

Comment on lines 102 to 108
pub trait TriggerTargets {
/// The components the trigger should target.
fn components(&self) -> &[ComponentId];
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone;

/// The entities the trigger should target.
fn entities(&self) -> &[Entity];
fn entities(&self) -> impl Iterator<Item = Entity>;
}
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Worth noting that this effectively reverts the change to this trait from #13991 which made it object-safe. I don't see any discussion for that original change, but if it's being changed back, it probably warrants some. At the very least, we should probably go back to the original impl ExactSizeIterator<...> return types if possible to keep it consistent with 0.14.0 and minimize potential for breakage.

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Yes I was hoping to see more discussions on the consequences of this change; I wasn't sure why the change was made in the first place.

Note that impl ExactSizeIterator is unfortunately not possible because calling chain on 2 ExactSizeIterator does not return an ExactSizeIterator

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We could also just provide our own Iterator type to make this object safe

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After digging into #14775, returning Iterators would simplify its implementation. So I'm in favor of this change.

@alice-i-cecile alice-i-cecile added D-Modest A "normal" level of difficulty; suitable for simple features or challenging fixes and removed D-Straightforward Simple bug fixes and API improvements, docs, test and examples labels Aug 1, 2024
@cBournhonesque
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The triggering rules for observers are quite confusing:

I'd like to see more docs explicitly explaining this.

This should be independent from this PR I think, right?
Here i'm just adding the possibility to have more flexible trigger targets

@alice-i-cecile alice-i-cecile added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it and removed S-Needs-Review Needs reviewer attention (from anyone!) to move forward labels Oct 8, 2024
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Kind of wondering if we shouldn't cut this from 0.15 for stability.

@alice-i-cecile alice-i-cecile modified the milestones: 0.15, 0.16 Oct 8, 2024
@cBournhonesque cBournhonesque added the S-Adopt-Me The original PR author has no intent to complete this work. Pick me up! label Oct 8, 2024
@alice-i-cecile alice-i-cecile removed the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Oct 14, 2024
@BenjaminBrienen
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Adopted in #16326

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A-ECS Entities, components, systems, and events C-Usability A targeted quality-of-life change that makes Bevy easier to use D-Modest A "normal" level of difficulty; suitable for simple features or challenging fixes S-Adopt-Me The original PR author has no intent to complete this work. Pick me up!
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Observers missing API for triggers targetting components on a given Entity
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