Support bevy 0.13

• Fix missing RelationCommands impl for EntityCommands
• Fix missing trait impls for RelationId conversion.
• Add set & scope examples to API tour.
• Add basic examples.
• Add change detection filter for edges.
• Tidy up scope docs.

• Use only required deps to better support projects that only use a subset of bevy crates.

• Update to bevy 0.12.
• Add missing docs for Scope.
• Scope now works with Commands and does not require a &mut World.
• Added partial bevy_hierarchy compatibility. All of the query APIs can be used to perform operations with bevy_hierarchy edges.

fn sys(
    query: Query<(&C, Relations<Hierarchy>)>,
    roots: Query<Entity, (With<Children>, Without<Parent>)>
) {
    query.traverse::<Hierarchy>(roots.iter()).for_each(|c, _| {
        // ..
    })
}

• New filters for relations: Abstains, Branch, Leaf.
• Internals completely reworked for better performance & memory footprint (SmallVecs like bevy_hierarchy now).
• New Track API to track the last seen item from a query when traversing an edge.

  fn sys(
      mut foos: Query<&mut Foo>,
      tree: Query<(Option<&Bar>, Relations<R>)>,
      roots: Query<Entity, Root<R>>
  ) {
      tree.traverse::<R>(roots.iter()).track(&mut foos).for_each(|foo, bar, _| {
          // ..
      });
  }
  

• Derive macro can handle generic types now.
• Fold breadth API for multi pass algorithms.

  fn sys(
      tree: Query<(Foo, Relations<R>)>,
      roots: Query<Entity, Root<R>>
  ) {
      tree.traverse::<R>(roots.iter())
          .track_self()
          .fold_breadth(|foo, _| /*init*/, |accum, foo, _| /*fold*/)
          .for_each(|accum, parent_foo,  _, child_foo, _| {
              // ..
          });
  }
  

Breaking:

• Yeet cursed option hack for relation commands + scope APIs.
• Completely reworked Scope API to be more declarative. Not all previous functionality will be possible.

  world.spawn(bundle).scope::<ChildOf>(|scope| {
      // x, y, z are implicitly `ChildOf` the last spawned entity 
      scope.add(x)
           .add(y)
           .add(z)
           .scope::<ChildOf>(|scope| {
                // a, b are implicitly `ChildOf` the last spawned entity (z) 
               scope.add(a)
                    .add(b);
           });
  });
  

• Improved macro hygiene. All property overrides are done through the aery attribute.
  • Available attributes: Counted, Recursive, Total, Poly (previously multi), Symmetric.

  #[derive(Relation)]
  #[aery(Recursive)]
  struct R;
  

• Edge direction changes for all operations is now done through the Up modifier. All opereations use hosts by default. To use targets use Up.

  fn sys(foos: Query<(&Foo, Relation<R>)>, starts: Query<Entity, Root<R>>) {
      // descent
      foos.traverse::<R>(starts.iter()).for_each(|foo, _| {
          // ..
      });
      
      // ascent
      foos.traverse::<Up<R>>(starts.iter()).for_each(|foo, _| {
          // ..
      });
  }
  

• Traversal are reworked to make sense with new operations. By default traversal visits each node & to get the old 2 arity ancestor descendant permutations use .track_self().
• Rework how Joins work for consistent defaults + better composability:
  • Join on hosts not targets by default which is more common and makes for a consistent edge default direction. Use Up for targets.
  • Separate Joins from Traversals. Joins must be done through the Relations<R> world query Item. This adds some rightward drift but significantly reduces API complexity & allows joins to work on tracked query items.
  • Split ControlFlow into JCF and TCF.

Doc fix

Bevy version

• Bump to bevy 0.11

New in 0.3

This is decently sized release with quite a few new things.

• New ControlFlow variant: Probe.
• ZSTs for relations are now enforced at compile time.

  ---- src/lib.rs - (line 20) stdout ----
  error[E0080]: evaluation of `<Likes as aery::relation::ZstOrPanic>::ZST_OR_PANIC` failed
     --> /home/yogii/Repos/aery/src/relation.rs:142:13
      |
  142 |             panic!("Not a ZST")
      |             ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'Not a ZST', /home/yogii/Repos/aery/src/relation.rs:142:13
      |
      = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
  
  note: erroneous constant used
    --> src/lib.rs:47:10
     |
  29 | #[derive(Relation)]
     |          ^^^^^^^^
     |
  

• New Scope API to spawn and manipulate hierarchies.

  wrld.spawn(A)
      .scope::<R>(|_, mut ent| {
          ent.insert(B);
          ent.scope::<R>(|_, mut ent| {
              ent.insert(C);
          });
      });
  

• Symmetric Relations.

  #[derive(Relation)]
  #[symmetric]
  struct R;
  

• Relation events for target changes and entity cleanup.

  fn sys(mut events: EventReader<TargetEvent>) {
      for e in events.iter() {
          // Did some entity set an `R` to some other entity?
          if e.matches(Wc, TargetOp::Set, R, Wc) {
              // ..
          }
      }
  }
  

• Hierarchy ascent is now supported along side the existing descent.

  fn sys(query: Query<(A, Relations<R>)>, roots: Query<Entity, Root<R>>) {
      query.ops().traverse_targets::<R>().for_each(|a, a_ancestor| {
          // ..
      })
  }
  

Breaking

• Module restructures if you're not using prelude.
• .breadth_first::<R>(roots) -> .traverse::<R>(roots)
• Recursive cleanup no longer triggers when unsetting. This never made sense.
• RelationCommands reworked and no longer implemented for Commands and World. New implementation is for EntityMut<'_> with a new API.

Misc

• Many doc improvements & with illustrations in documentation with aquamarine.
  

New in 0.2

• Logging for Set command.
• Derive macros for Relation.

// Change cleanup behavior
#[derive(Relation)]
#[cleanup(policy = "Recursive")]
struct R;

// Change arity
#[derive(Relation)]
#[multi]
struct R;

• Ancestors now provided when traversing a hierarchy.

fn sys(a: Query<(&A, Relations<R>)>, roots: Query<Entity, Root<R>>) {
    q.ops().breadth_first::<R>(roots.iter()).for_each(|a_ancestor, a| {
        // ..
    })
}

• UnsetAll command to remove all relation targets of a given type from an entity.
• Withdraw command for entities to remove themselves as targets from relations of a given type.
• More granular ControlFlow options
  • ControlFlow::FastForward(n): Advance the nth join to the next valid permutation skipping any permutations in between.
  • ControlFlow::Walk: Walk to the next entity in a traversal, skipping any remaining permutations to iterate for the current entity.

Breaking changes

• For each arity changes.
• Various type and module name changes.

Other

• License is now dual MIT + Apache 2.0.
• Various doc improvements.