Commit Graph

135 Commits

Author SHA1 Message Date
Testare
da83232fa8
Let Component::map_entities defer to MapEntities (#19414)
# Objective

The objective of this PR is to enable Components to use their
`MapEntities` implementation for `Component::map_entities`.

With the improvements to the entity mapping system, there is definitely
a huge reduction in boilerplate. However, especially since
`(Entity)HashMap<..>` doesn't implement `MapEntities` (I presume because
the lack of specialization in rust makes `HashMap<Entity|X, Entity|X>`
complicated), when somebody has types that contain these hashmaps they
can't use this approach.

More so, we can't even depend on the previous implementation, since
`Component::map_entities` is used instead of
`MapEntities::map_entities`. Outside of implementing `Component `and
`Component::map_entities` on these types directly, the only path forward
is to create a custom type to wrap the hashmaps and implement map
entities on that, or split these components into a wrapper type that
implement `Component`, and an inner type that implements `MapEntities`.

## Current Solution
The solution was to allow adding `#[component(map_entities)]` on the
component. By default this will defer to the `MapEntities`
implementation.

```rust
#[derive(Component)]
#[component(map_entities)]
struct Inventory {
    items: HashMap<Entity, usize>
}

impl MapEntities for Inventory {
    fn map_entities<M: EntityMapper>(&mut self, entity_mapper: &mut M) {
        self.items = self.items
           .drain()
           .map(|(id, count)|(entity_mapper.get_mapped(id), count))
           .collect();
    }
}

```

You can use `#[component(map_entities = <function path>)]` instead to
substitute other code in for components. This function can also include
generics, but sso far I haven't been able to find a case where they are
needed.

```rust
#[derive(Component)]
#[component(map_entities = map_the_map)]
// Also works #[component(map_entities = map_the_map::<T,_>)]
struct Inventory<T> {
    items: HashMap<Entity, T>
}

fn map_the_map<T, M: EntityMapper>(inv: &mut Inventory<T>, entity_mapper: &mut M) {
    inv.items = inv.items
       .drain()
       .map(|(id, count)|(entity_mapper.get_mapped(id), count))
       .collect();
}

```

The idea is that with the previous changes to MapEntities, MapEntities
is implemented more for entity collections than for Components. If you
have a component that makes sense as both, `#[component(map_entities)]`
would work great, while otherwise a component can use
`#[component(map_entities = <function>)]` to change the behavior of
`Component::map_entities` without opening up the component type to be
included in other components.


## (Original Solution if you want to follow the PR)

The solution was to allow adding `#[component(entities)]` on the
component itself to defer to the `MapEntities` implementation

```rust
#[derive(Component)]
#[component(entities)]
struct Inventory {
    items: HashMap<Entity, usize>
}

impl MapEntities for Inventory {
    fn map_entities<M: EntityMapper>(&mut self, entity_mapper: &mut M) {
        self.items = self.items
           .drain()
           .map(|(id, count)|(entity_mapper.get_mapped(id), count))
           .collect();
    }
}

```

## Testing

I tested this by patching my local changes into my own bevy project. I
had a system that loads a scene file and executes some logic with a
Component that contains a `HashMap<Entity, UVec2>`, and it panics when
Entity is not found from another query. Since the 0.16 update this
system has reliably panicked upon attempting to the load the scene.

After patching my code in, I added `#[component(entities)]` to this
component, and I was able to successfully load the scene.

Additionally, I wrote a doc test.

## Call-outs
### Relationships
This overrules the default mapping of relationship fields. Anything else
seemed more problematic, as you'd have inconsistent behavior between
`MapEntities` and `Component`.
2025-06-23 21:05:04 +00:00
theotherphil
7645ce91ed
Add newlines before impl blocks (#19746)
# Objective

Fix https://github.com/bevyengine/bevy/issues/19617 

# Solution

Add newlines before all impl blocks.

I suspect that at least some of these will be objectionable! If there's
a desired Bevy style for this then I'll update the PR. If not then we
can just close it - it's the work of a single find and replace.
2025-06-22 23:07:02 +00:00
François Mockers
4e694aea53
ECS: put strings only used for debug behind a feature (#19558)
# Objective

- Many strings in bevy_ecs are created but only used for debug: system
name, component name, ...
- Those strings make a significant part of the final binary and are no
use in a released game

## Solution

- Use [`strings`](https://linux.die.net/man/1/strings) to find ...
strings in a binary
- Try to find where they come from
- Many are made from `type_name::<T>()` and only used in error / debug
messages
- Add a new structure `DebugName` that holds no value if `debug` feature
is disabled
- Replace `core::any::type_name::<T>()` by `DebugName::type_name::<T>()`

## Testing

Measurements were taken without the new feature being enabled by
default, to help with commands

### File Size

I tried building the `breakout` example with `cargo run --release
--example breakout`

|`debug` enabled|`debug` disabled|
|-|-|
|81621776 B|77735728B|
|77.84MB|74.13MB|

### Compilation time

`hyperfine --min-runs 15 --prepare "cargo clean && sleep 5"
'RUSTC_WRAPPER="" cargo build --release --example breakout'
'RUSTC_WRAPPER="" cargo build --release --example breakout --features
debug'`

```
breakout' 'RUSTC_WRAPPER="" cargo build --release --example breakout --features debug'
Benchmark 1: RUSTC_WRAPPER="" cargo build --release --example breakout
  Time (mean ± σ):     84.856 s ±  3.565 s    [User: 1093.817 s, System: 32.547 s]
  Range (min … max):   78.038 s … 89.214 s    15 runs

Benchmark 2: RUSTC_WRAPPER="" cargo build --release --example breakout --features debug
  Time (mean ± σ):     92.303 s ±  2.466 s    [User: 1193.443 s, System: 33.803 s]
  Range (min … max):   90.619 s … 99.684 s    15 runs

Summary
  RUSTC_WRAPPER="" cargo build --release --example breakout ran
    1.09 ± 0.05 times faster than RUSTC_WRAPPER="" cargo build --release --example breakout --features debug
```
2025-06-18 20:15:25 +00:00
urben1680
a292ac539e
System::check_change_tick and similar methods take CheckChangeTicks (#19600)
Follow-up of #19274.

Make the `check_change_tick` methods, of which some are now public, take
`CheckChangeTicks` to make it obvious where this tick comes from, see
other PR.

This also affects the `System` trait, hence the many changed files.

---------

Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2025-06-13 19:24:27 +00:00
Joona Aalto
e5dc177b4b
Rename Trigger to On (#19596)
# Objective

Currently, the observer API looks like this:

```rust
app.add_observer(|trigger: Trigger<Explode>| {
    info!("Entity {} exploded!", trigger.target());
});
```

Future plans for observers also include "multi-event observers" with a
trigger that looks like this (see [Cart's
example](https://github.com/bevyengine/bevy/issues/14649#issuecomment-2960402508)):

```rust
trigger: Trigger<(
    OnAdd<Pressed>,
    OnRemove<Pressed>,
    OnAdd<InteractionDisabled>,
    OnRemove<InteractionDisabled>,
    OnInsert<Hovered>,
)>,
```

In scenarios like this, there is a lot of repetition of `On`. These are
expected to be very high-traffic APIs especially in UI contexts, so
ergonomics and readability are critical.

By renaming `Trigger` to `On`, we can make these APIs read more cleanly
and get rid of the repetition:

```rust
app.add_observer(|trigger: On<Explode>| {
    info!("Entity {} exploded!", trigger.target());
});
```

```rust
trigger: On<(
    Add<Pressed>,
    Remove<Pressed>,
    Add<InteractionDisabled>,
    Remove<InteractionDisabled>,
    Insert<Hovered>,
)>,
```

Names like `On<Add<Pressed>>` emphasize the actual event listener nature
more than `Trigger<OnAdd<Pressed>>`, and look cleaner. This *also* frees
up the `Trigger` name if we want to use it for the observer event type,
splitting them out from buffered events (bikeshedding this is out of
scope for this PR though).

For prior art:
[`bevy_eventlistener`](https://github.com/aevyrie/bevy_eventlistener)
used
[`On`](https://docs.rs/bevy_eventlistener/latest/bevy_eventlistener/event_listener/struct.On.html)
for its event listener type. Though in our case, the observer is the
event listener, and `On` is just a type containing information about the
triggered event.

## Solution

Steal from `bevy_event_listener` by @aevyrie and use `On`.

- Rename `Trigger` to `On`
- Rename `OnAdd` to `Add`
- Rename `OnInsert` to `Insert`
- Rename `OnReplace` to `Replace`
- Rename `OnRemove` to `Remove`
- Rename `OnDespawn` to `Despawn`

## Discussion

### Naming Conflicts??

Using a name like `Add` might initially feel like a very bad idea, since
it risks conflict with `core::ops::Add`. However, I don't expect this to
be a big problem in practice.

- You rarely need to actually implement the `Add` trait, especially in
modules that would use the Bevy ECS.
- In the rare cases where you *do* get a conflict, it is very easy to
fix by just disambiguating, for example using `ops::Add`.
- The `Add` event is a struct while the `Add` trait is a trait (duh), so
the compiler error should be very obvious.

For the record, renaming `OnAdd` to `Add`, I got exactly *zero* errors
or conflicts within Bevy itself. But this is of course not entirely
representative of actual projects *using* Bevy.

You might then wonder, why not use `Added`? This would conflict with the
`Added` query filter, so it wouldn't work. Additionally, the current
naming convention for observer events does not use past tense.

### Documentation

This does make documentation slightly more awkward when referring to
`On` or its methods. Previous docs often referred to `Trigger::target`
or "sends a `Trigger`" (which is... a bit strange anyway), which would
now be `On::target` and "sends an observer `Event`".

You can see the diff in this PR to see some of the effects. I think it
should be fine though, we may just need to reword more documentation to
read better.
2025-06-12 18:22:33 +00:00
Alice Cecile
6ddd0f16a8
Component lifecycle reorganization and documentation (#19543)
# Objective

I set out with one simple goal: clearly document the differences between
each of the component lifecycle events via module docs.

Unfortunately, no such module existed: the various lifecycle code was
scattered to the wind.
Without a unified module, it's very hard to discover the related types,
and there's nowhere good to put my shiny new documentation.

## Solution

1. Unify the assorted types into a single
`bevy_ecs::component_lifecycle` module.
2. Write docs.
3. Write a migration guide.

## Testing

Thanks CI!

## Follow-up

1. The lifecycle event names are pretty confusing, especially
`OnReplace`. We should consider renaming those. No bikeshedding in my PR
though!
2. Observers need real module docs too :(
3. Any additional functional changes should be done elsewhere; this is a
simple docs and re-org PR.

---------

Co-authored-by: theotherphil <phil.j.ellison@gmail.com>
2025-06-10 00:59:16 +00:00
Lucas Franca
f5f092f2f3
Fix new typos (#19562)
# Objective

Fix new typos found on new version of `typos` (#19551)

## Solution

Fix typos
2025-06-09 22:55:14 +00:00
urben1680
1294b71e35
Introduce CheckChangeTicks event that is triggered by World::check_change_ticks (#19274)
# Objective

In the past I had custom data structures containing `Tick`s. I learned
that these need to be regularly checked to clamp them. But there was no
way to hook into that logic so I abandoned storing ticks since then.

Another motivation to open this up some more is to be more able to do a
correct implementation of `System::check_ticks`.

## Solution

Add `CheckChangeTicks` and trigger it in `World::check_change_ticks`.
Make `Tick::check_tick` public.

This event makes it possible to store ticks in components or resources
and have them checked.

I also made `Schedules::check_change_ticks` public so users can store
schedules in custom resources/components for whatever reasons.

## Testing

The logic boils down to a single `World::trigger` call and I don't think
this needs more tests.

## Alternatives

Making this obsolete like with #15683.

---

## Showcase

From the added docs:

```rs
use bevy_ecs::prelude::*;
use bevy_ecs::component::CheckChangeTicks;

#[derive(Resource)]
struct CustomSchedule(Schedule);

let mut world = World::new();
world.add_observer(|tick: Trigger<CheckChangeTicks>, mut schedule: ResMut<CustomSchedule>| {
    schedule.0.check_change_ticks(tick.get());
});
```

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-06-09 20:44:49 +00:00
Eagster
8ad7118443
Only get valid component ids (#19510)
# Objective

- #19504 showed a 11x regression in getting component values for
unregistered components. This pr should fix that and improve others a
little too.
- This is some cleanup work from #18173 .

## Solution

- Whenever we expect a component value to exist, we only care about
fully registered components, not queued to be registered components
since, for the value to exist, it must be registered.
- So we can use the faster `get_valid_*` instead of `get_*` in a lot of
places.
- Also found a bug where `valid_*` did not forward to `get_valid_*`
properly. That's fixed.

## Testing

CI
2025-06-06 20:59:57 +00:00
atlv
d4985af7cb
refactor(utils): move SyncCell and SyncUnsafeCell to bevy_platform (#19305)
# Objective

- move SyncCell and SyncUnsafeCell to bevy_platform

## Solution

- move SyncCell and SyncUnsafeCell to bevy_platform

## Testing

- cargo clippy works
2025-05-27 04:57:26 +00:00
Zachary Harrold
63e78fe489
Deprecated Begone! 0.16 Cleanup (#19108)
# Objective

A fair few items were deprecated in 0.16. Let's delete them now that
we're in the 0.17 development cycle!

## Solution

- Deleted items marked deprecated in 0.16.

## Testing

- CI

---

## Notes

I'm making the assumption that _everything_ deprecated in 0.16 should be
removed in 0.17. That may be a false assumption in certain cases. Please
check the items to be removed to see if there are any exceptions we
should keep around for another cycle!
2025-05-07 18:17:41 +00:00
Han Kruiger
b8724c21ce
implement MapEntities for higher-order types (#19071)
# Objective

With the current `MapEntities` `impl`s, it is not possible to derive
things like this:

```rust
#[derive(Component)]
pub struct Inventory {
  #[entities]
  slots: Vec<Option<Entity>>,
}
```

This is because `MapEntities` is only implemented for `Vec<Entity>` &
`Option<Entity>`, and not arbitrary combinations of those.

It would be nice to also support those types.

## Solution

I replaced the `impl`s of the following types

- `Option<Entity>`: replaced with `Option<T>` 
- `Vec<Entity>`: replaced with `Vec<T>`
- `HashSet<Entity, S>`: replaced with `HashSet<T, S>`
- `T` also had to be `Eq + core:#️⃣:Hash` here. **Not sure if this is
too restrictive?**
- `IndexSet<Entity, S>`: replaced with `IndexSet <T, S>`
- `T` also had to be `Eq + core:#️⃣:Hash` here. **Not sure if this is
too restrictive?**
- `BTreeSet<Entity>`: replaced with `BTreeSet<T>`
- `VecDeque<Entity>`: replaced with `VecDeque<T>`
- `SmallVec<A: smallvec::Array<Item = Entity>>`: replaced with
`SmallVec<A: smallvec::Array<Item = T>>`

(in all of the above, `T` is a generic type that implements
`MapEntities` (`Entity` being one of them).)

## Testing

I did not test any of this, but extended the `Component::map_entities`
doctest with an example usage of the newly supported types.

---

## Showcase

With these changes, this is now possible:

```rust
#[derive(Component)]
pub struct Inventory {
  #[entities]
  slots: Vec<Option<Entity>>,
}
```
2025-05-06 05:24:37 +00:00
Tim Overbeek
60cdefd128
Derive clone_behavior for Components (#18811)
Allow Derive(Component) to specify a clone_behavior

```rust
#[derive(Component)]
#[component(clone_behavior = Ignore)]
MyComponent;
```
2025-05-06 00:32:59 +00:00
Greeble
b516e78317
Bump crate-ci/typos from 1.31.1 to 1.32.0 (#19072)
Adopted #19066. Bumps
[crate-ci/typos](https://github.com/crate-ci/typos) from 1.31.1 to
1.32.0.

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
2025-05-05 17:27:36 +00:00
Carter Anderson
e9a0ef49f9
Rename bevy_platform_support to bevy_platform (#18813)
# Objective

The goal of `bevy_platform_support` is to provide a set of platform
agnostic APIs, alongside platform-specific functionality. This is a high
traffic crate (providing things like HashMap and Instant). Especially in
light of https://github.com/bevyengine/bevy/discussions/18799, it
deserves a friendlier / shorter name.

Given that it hasn't had a full release yet, getting this change in
before Bevy 0.16 makes sense.

## Solution

- Rename `bevy_platform_support` to `bevy_platform`.
2025-04-11 23:13:28 +00:00
Eagster
5db67f35e4
Get names of queued components (#18451)
# Objective

#18173 allows components to be queued without being fully registered.
But much of bevy's debug logging contained
`components.get_name(id).unwrap()`. However, this panics when the id is
queued. This PR fixes this, allowing names to be retrieved for debugging
purposes, etc, even while they're still queued.

## Solution

We change `ComponentInfo::descriptor` to be `Arc<ComponentDescriptor>`
instead of not arc'd. This lets us pass the descriptor around (as a name
or otherwise) as needed. The alternative would require some form of
`MappedRwLockReadGuard`, which is unstable, and would be terribly
blocking. Putting it in an arc also signifies that it doesn't change,
which is a nice signal to users. This does mean there's an extra pointer
dereference, but I don't think that's an issue here, as almost all paths
that use this are for debugging purposes or one-time set ups.

## Testing

Existing tests.

## Migration Guide

`Components::get_name` now returns `Option<Cow<'_, str>` instead of
`Option<&str>`. This is because it now returns results for queued
components. If that behavior is not desired, or you know the component
is not queued, you can use
`components.get_info().map(ComponentInfo::name)` instead.

Similarly, `ScheduleGraph::conflicts_to_string` now returns `impl
Iterator<Item = (String, String, Vec<Cow<str>>)>` instead of `impl
Iterator<Item = (String, String, Vec<&str>)>`. Because `Cow<str>` derefs
to `&str`, most use cases can remain unchanged.

---------

Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2025-03-31 23:22:33 +00:00
Carter Anderson
1ba9da0812
Required Components: pass through all tokens in {} and () syntax (#18578)
# Objective

#18555 added improved require syntax, but inline structs didn't support
`..Default::default()` syntax (for technical reasons we can't parse the
struct directly, so there is manual logic that missed this case).

## Solution

When a `{}` or `()` section is encountered for a required component,
rather than trying to parse the fields directly, just pass _all_ of the
tokens through. This ensures no tokens are dropped, protects us against
any future syntax changes, and optimizes our parsing logic (as we're
dropping the field parsing logic entirely).
2025-03-27 21:20:08 +00:00
Carter Anderson
538afe2330
Improved Require Syntax (#18555)
# Objective

Requires are currently more verbose than they need to be. People would
like to define inline component values. Additionally, the current
`#[require(Foo(custom_constructor))]` and `#[require(Foo(|| Foo(10))]`
syntax doesn't really make sense within the context of the Rust type
system. #18309 was an attempt to improve ergonomics for some cases, but
it came at the cost of even more weirdness / unintuitive behavior. Our
approach as a whole needs a rethink.

## Solution

Rework the `#[require()]` syntax to make more sense. This is a breaking
change, but I think it will make the system easier to learn, while also
improving ergonomics substantially:

```rust
#[derive(Component)]
#[require(
    A, // this will use A::default()
    B(1), // inline tuple-struct value
    C { value: 1 }, // inline named-struct value
    D::Variant, // inline enum variant
    E::SOME_CONST, // inline associated const
    F::new(1), // inline constructor
    G = returns_g(), // an expression that returns G
    H = SomethingElse::new(), // expression returns SomethingElse, where SomethingElse: Into<H> 
)]
struct Foo;
```

## Migration Guide

Custom-constructor requires should use the new expression-style syntax:

```rust
// before
#[derive(Component)]
#[require(A(returns_a))]
struct Foo;

// after
#[derive(Component)]
#[require(A = returns_a())]
struct Foo;
```

Inline-closure-constructor requires should use the inline value syntax
where possible:

```rust
// before
#[derive(Component)]
#[require(A(|| A(10))]
struct Foo;

// after
#[derive(Component)]
#[require(A(10)]
struct Foo;
```

In cases where that is not possible, use the expression-style syntax:

```rust
// before
#[derive(Component)]
#[require(A(|| A(10))]
struct Foo;

// after
#[derive(Component)]
#[require(A = A(10)]
struct Foo;
```

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François Mockers <mockersf@gmail.com>
2025-03-26 17:48:27 +00:00
Carter Anderson
a033f1b206
Replace VisitEntities with MapEntities (#18432)
# Objective

There are currently too many disparate ways to handle entity mapping,
especially after #17687. We now have MapEntities, VisitEntities,
VisitEntitiesMut, Component::visit_entities,
Component::visit_entities_mut.

Our only known use case at the moment for these is entity mapping. This
means we have significant consolidation potential.

Additionally, VisitEntitiesMut cannot be implemented for map-style
collections like HashSets, as you cant "just" mutate a `&mut Entity`.
Our current approach to Component mapping requires VisitEntitiesMut,
meaning this category of entity collection isn't mappable. `MapEntities`
is more generally applicable. Additionally, the _existence_ of the
blanket From impl on VisitEntitiesMut blocks us from implementing
MapEntities for HashSets (or any types we don't own), because the owner
could always add a conflicting impl in the future.

## Solution

Use `MapEntities` everywhere and remove all "visit entities" usages.

* Add `Component::map_entities`
* Remove `Component::visit_entities`, `Component::visit_entities_mut`,
`VisitEntities`, and `VisitEntitiesMut`
* Support deriving `Component::map_entities` in `#[derive(Coomponent)]`
* Add `#[derive(MapEntities)]`, and share logic with the
`Component::map_entities` derive.
* Add `ComponentCloneCtx::queue_deferred`, which is command-like logic
that runs immediately after normal clones. Reframe `FromWorld` fallback
logic in the "reflect clone" impl to use it. This cuts out a lot of
unnecessary work and I think justifies the existence of a pseudo-command
interface (given how niche, yet performance sensitive this is).

Note that we no longer auto-impl entity mapping for ` IntoIterator<Item
= &'a Entity>` types, as this would block our ability to implement cases
like `HashMap`. This means the onus is on us (or type authors) to add
explicit support for types that should be mappable.

Also note that the Component-related changes do not require a migration
guide as there hasn't been a release with them yet.

## Migration Guide

If you were previously implementing `VisitEntities` or
`VisitEntitiesMut` (likely via a derive), instead use `MapEntities`.
Those were almost certainly used in the context of Bevy Scenes or
reflection via `ReflectMapEntities`. If you have a case that uses
`VisitEntities` or `VisitEntitiesMut` directly, where `MapEntities` is
not a viable replacement, please let us know!

```rust
// before
#[derive(VisitEntities, VisitEntitiesMut)]
struct Inventory {
  items: Vec<Entity>,
  #[visit_entities(ignore)]
  label: String,
}

// after
#[derive(MapEntities)]
struct Inventory {
  #[entities]
  items: Vec<Entity>,
  label: String,
}
```
2025-03-21 00:18:10 +00:00
Wuketuke
55fd10502c
Required components accept const values (#16720) (#18309)
# Objective

Const values should be more ergonomic to insert, since this is too
verbose
``` rust
#[derive(Component)]
#[require(
    LockedAxes(||LockedAxes::ROTATION_LOCKED),
)]
pub struct CharacterController;
```
instead, users can now abbreviate that nonsense like this
``` rust
#[derive(Component)]
#[require(
    LockedAxes = ROTATION_LOCKED),
)]
pub struct CharacterController;
```
it also works for enum labels.
I chose to omit the type, since were trying to reduce typing here. The
alternative would have been this:
```rust
#[require(
    LockedAxes = LockedAxes::ROTATION_LOCKED),
)]
```
This of course has its disadvantages, since the const has to be
associated, but the old closure method is still possible, so I dont
think its a problem.
- Fixes #16720

## Testing

I added one new test in the docs, which also explain the new change. I
also saw that the docs for the required components on line 165 was
missing an assertion, so I added it back in

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-03-21 00:02:10 +00:00
Carter Anderson
6d6054116a
Support skipping Relationship on_replace hooks (#18378)
# Objective

Fixes #18357

## Solution

Generalize `RelationshipInsertHookMode` to `RelationshipHookMode`, wire
it up to on_replace execution, and use it in the
`Relationship::on_replace` hook.
2025-03-18 01:24:07 +00:00
Gino Valente
9b32e09551
bevy_reflect: Add clone registrations project-wide (#18307)
# Objective

Now that #13432 has been merged, it's important we update our reflected
types to properly opt into this feature. If we do not, then this could
cause issues for users downstream who want to make use of
reflection-based cloning.

## Solution

This PR is broken into 4 commits:

1. Add `#[reflect(Clone)]` on all types marked `#[reflect(opaque)]` that
are also `Clone`. This is mandatory as these types would otherwise cause
the cloning operation to fail for any type that contains it at any
depth.
2. Update the reflection example to suggest adding `#[reflect(Clone)]`
on opaque types.
3. Add `#[reflect(clone)]` attributes on all fields marked
`#[reflect(ignore)]` that are also `Clone`. This prevents the ignored
field from causing the cloning operation to fail.
   
Note that some of the types that contain these fields are also `Clone`,
and thus can be marked `#[reflect(Clone)]`. This makes the
`#[reflect(clone)]` attribute redundant. However, I think it's safer to
keep it marked in the case that the `Clone` impl/derive is ever removed.
I'm open to removing them, though, if people disagree.
4. Finally, I added `#[reflect(Clone)]` on all types that are also
`Clone`. While not strictly necessary, it enables us to reduce the
generated output since we can just call `Clone::clone` directly instead
of calling `PartialReflect::reflect_clone` on each variant/field. It
also means we benefit from any optimizations or customizations made in
the `Clone` impl, including directly dereferencing `Copy` values and
increasing reference counters.

Along with that change I also took the liberty of adding any missing
registrations that I saw could be applied to the type as well, such as
`Default`, `PartialEq`, and `Hash`. There were hundreds of these to
edit, though, so it's possible I missed quite a few.

That last commit is **_massive_**. There were nearly 700 types to
update. So it's recommended to review the first three before moving onto
that last one.

Additionally, I can break the last commit off into its own PR or into
smaller PRs, but I figured this would be the easiest way of doing it
(and in a timely manner since I unfortunately don't have as much time as
I used to for code contributions).

## Testing

You can test locally with a `cargo check`:

```
cargo check --workspace --all-features
```
2025-03-17 18:32:35 +00:00
Gino Valente
c2854a2a05
bevy_reflect: Deprecate PartialReflect::clone_value (#18284)
# Objective

#13432 added proper reflection-based cloning. This is a better method
than cloning via `clone_value` for reasons detailed in the description
of that PR. However, it may not be immediately apparent to users why one
should be used over the other, and what the gotchas of `clone_value`
are.

## Solution

This PR marks `PartialReflect::clone_value` as deprecated, with the
deprecation notice pointing users to `PartialReflect::reflect_clone`.
However, it also suggests using a new method introduced in this PR:
`PartialReflect::to_dynamic`.

`PartialReflect::to_dynamic` is essentially a renaming of
`PartialReflect::clone_value`. By naming it `to_dynamic`, we make it
very obvious that what's returned is a dynamic type. The one caveat to
this is that opaque types still use `reflect_clone` as they have no
corresponding dynamic type.

Along with changing the name, the method is now optional, and comes with
a default implementation that calls out to the respective reflection
subtrait method. This was done because there was really no reason to
require manual implementors provide a method that almost always calls
out to a known set of methods.

Lastly, to make this default implementation work, this PR also did a
similar thing with the `clone_dynamic ` methods on the reflection
subtraits. For example, `Struct::clone_dynamic` has been marked
deprecated and is superseded by `Struct::to_dynamic_struct`. This was
necessary to avoid the "multiple names in scope" issue.

### Open Questions

This PR maintains the original signature of `clone_value` on
`to_dynamic`. That is, it takes `&self` and returns `Box<dyn
PartialReflect>`.

However, in order for this to work, it introduces a panic if the value
is opaque and doesn't override the default `reflect_clone`
implementation.

One thing we could do to avoid the panic would be to make the conversion
fallible, either returning `Option<Box<dyn PartialReflect>>` or
`Result<Box<dyn PartialReflect>, ReflectCloneError>`.

This makes using the method a little more involved (i.e. users have to
either unwrap or handle the rare possibility of an error), but it would
set us up for a world where opaque types don't strictly need to be
`Clone`. Right now this bound is sort of implied by the fact that
`clone_value` is a required trait method, and the default behavior of
the macro is to use `Clone` for opaque types.

Alternatively, we could keep the signature but make the method required.
This maintains that implied bound where manual implementors must provide
some way of cloning the value (or YOLO it and just panic), but also
makes the API simpler to use.

Finally, we could just leave it with the panic. It's unlikely this would
occur in practice since our macro still requires `Clone` for opaque
types, and thus this would only ever be an issue if someone were to
manually implement `PartialReflect` without a valid `to_dynamic` or
`reflect_clone` method.

## Testing

You can test locally using the following command:

```
cargo test --package bevy_reflect --all-features
```

---

## Migration Guide

`PartialReflect::clone_value` is being deprecated. Instead, use
`PartialReflect::to_dynamic` if wanting to create a new dynamic instance
of the reflected value. Alternatively, use
`PartialReflect::reflect_clone` to attempt to create a true clone of the
underlying value.

Similarly, the following methods have been deprecated and should be
replaced with these alternatives:
- `Array::clone_dynamic` → `Array::to_dynamic_array`
- `Enum::clone_dynamic` → `Enum::to_dynamic_enum`
- `List::clone_dynamic` → `List::to_dynamic_list`
- `Map::clone_dynamic` → `Map::to_dynamic_map`
- `Set::clone_dynamic` → `Set::to_dynamic_set`
- `Struct::clone_dynamic` → `Struct::to_dynamic_struct`
- `Tuple::clone_dynamic` → `Tuple::to_dynamic_tuple`
- `TupleStruct::clone_dynamic` → `TupleStruct::to_dynamic_tuple_struct`
2025-03-14 19:33:57 +00:00
Eagster
21f003f13f
Improve component registration performance (#18180)
# Objective

Make component registration faster. This is a tinny, almost petty PR,
but it led to roughly 10% faster registration, according to my
benchmarks in #17871.

Up to y'all if we do this or not. It is completely unnecessary, but its
such low hanging fruit that I wanted to put it out there.

## Solution

Instead of cloning a `HashSet`, collect it into a `SmallVec`. Since this
is empty for many components, this saves a lot of allocation and hashing
work.

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-03-10 21:49:07 +00:00
Eagster
246ce590e5
Queued component registration (#18173)
# Objective

This is an alternative to #17871 and #17701 for tracking issue #18155.
This thanks to @maniwani for help with this design.

The goal is to enable component ids to be reserved from multiple threads
concurrently and with only `&World`. This contributes to assets as
entities, read-only query and system parameter initialization, etc.

## What's wrong with #17871 ?

In #17871, I used my proposed staging utilities to allow *fully*
registering components from any thread concurrently with only
`&Components`. However, if we want to pursue components as entities
(which is desirable for a great many reasons. See
[here](https://discord.com/channels/691052431525675048/692572690833473578/1346499196655505534)
on discord), this staging isn't going to work. After all, if registering
a component requires spawning an entity, and spawning an entity requires
`&mut World`, it is impossible to register a component fully with only
`&World`.

## Solution

But what if we don't have to register it all the way? What if it's
enough to just know the `ComponentId` it will have once it is registered
and to queue it to be registered at a later time? Spoiler alert: That is
all we need for these features.

Here's the basic design:

Queue a registration:

1. Check if it has already been registered.
2. Check if it has already been queued.
3. Reserve a `ComponentId`.
4. Queue the registration at that id.

Direct (normal) registration:

1. Check if this registration has been queued.
2. If it has, use the queued registration instead.
3. Otherwise, proceed like normal.

Appllying the queue:

1. Pop queued items off one by one.
2. Register them directly.

One other change:

The whole point of this design over #17871 is to facilitate coupling
component registration with the World. To ensure that this would fully
work with that, I went ahead and moved the `ComponentId` generator onto
the world itself. That stemmed a couple of minor organizational changes
(see migration guide). As we do components as entities, we will replace
this generator with `Entities`, which lives on `World` too. Doing this
move early let me verify the design and will reduce migration headaches
in the future. If components as entities is as close as I think it is, I
don't think splitting this up into different PRs is worth it. If it is
not as close as it is, it might make sense to still do #17871 in the
meantime (see the risks section). I'll leave it up to y'all what we end
up doing though.

## Risks and Testing

The biggest downside of this compared to #17871 is that now we have to
deal with correct but invalid `ComponentId`s. They are invalid because
the component still isn't registered, but they are correct because, once
registered, the component will have exactly that id.

However, the only time this becomes a problem is if some code violates
safety rules by queuing a registration and using the returned id as if
it was valid. As this is a new feature though, nothing in Bevy does
this, so no new tests were added for it. When we do use it, I left
detailed docs to help mitigate issues here, and we can test those
usages. Ex: we will want some tests on using queries initialized from
queued registrations.

## Migration Guide

Component registration can now be queued with only `&World`. To
facilitate this, a few APIs needed to be moved around.

The following functions have moved from `Components` to
`ComponentsRegistrator`:

- `register_component`
- `register_component_with_descriptor`
- `register_resource_with_descriptor`
- `register_non_send`
- `register_resource`
- `register_required_components_manual`

Accordingly, functions in `Bundle` and `Component` now take
`ComponentsRegistrator` instead of `Components`.
You can obtain `ComponentsRegistrator` from the new
`World::components_registrator`.
You can obtain `ComponentsQueuedRegistrator` from the new
`World::components_queue`, and use it to stage component registration if
desired.

# Open Question

Can we verify that it is enough to queue registration with `&World`? I
don't think it would be too difficult to package this up into a
`Arc<MyComponentsManager>` type thing if we need to, but keeping this on
`&World` certainly simplifies things. If we do need the `Arc`, we'll
need to look into partitioning `Entities` for components as entities, so
we can keep most of the allocation fast on `World` and only keep a
smaller partition in the `Arc`. I'd love an SME on assets as entities to
shed some light on this.

---------

Co-authored-by: andriyDev <andriydzikh@gmail.com>
2025-03-10 21:46:27 +00:00
Eagster
79e7f8ae0c
Use register_dynamic for merging (#18028)
# Objective

I found a bug while working on #17871. When required components are
registered, ones that are more specific (smaller inheritance depth) are
preferred to others. So, if a ComponentA is already required, but it is
registered as required again, it will be updated if and only if the new
requirement has a smaller inheritance depth (is more specific). However,
this logic was not reflected in merging `RequriedComponents`s together.
Hence, for complicated requirement trees, the wrong initializer could be
used.

## Solution

Re-write merging to work by extending the collection via
`require_dynamic` instead of blindly combining the inner storage.

## Testing

I created this test to ensure this bug doesn't creep back in. This test
fails on main, but passes on this branch.

```rs
    #[test]
    fn required_components_inheritance_depth_bias() {
        #[derive(Component, PartialEq, Eq, Clone, Copy, Debug)]
        struct MyRequired(bool);

        #[derive(Component, Default)]
        #[require(MyRequired(|| MyRequired(false)))]
        struct MiddleMan;

        #[derive(Component, Default)]
        #[require(MiddleMan)]
        struct ConflictingRequire;

        #[derive(Component, Default)]
        #[require(MyRequired(|| MyRequired(true)))]
        struct MyComponent;

        let mut world = World::new();
        let order_a = world
            .spawn((ConflictingRequire, MyComponent))
            .get::<MyRequired>()
            .cloned();
        let order_b = world
            .spawn((MyComponent, ConflictingRequire))
            .get::<MyRequired>()
            .cloned();

        assert_eq!(order_a, Some(MyRequired(true)));
        assert_eq!(order_b, Some(MyRequired(true)));
    }
```
Note that when the inheritance depth is 0 (Like if there were no middle
man above), the order of the components in the bundle still matters.

## Migration Guide

`RequiredComponents::register_dynamic` has been changed to
`RequiredComponents::register_dynamic_with`.

Old:
```rust
required_components.register_dynamic(
      component_id,
      component_constructor.clone(),
      requirement_inheritance_depth,
);
```

New:
```rust
required_components.register_dynamic_with(
      component_id,
      requirement_inheritance_depth,
      || component_constructor.clone(),
);
```

This can prevent unnecessary cloning.

---------

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: Joona Aalto <jondolf.dev@gmail.com>
2025-03-10 21:35:55 +00:00
krunchington
ab38b61001
Update Component docs to point to Relationship trait (#18179)
also updates Relationship docs terminology

# Objective

- Contributes to #18111 

## Solution

Updates Component docs with a new section linking to Relationship. Also
updates some Relationship terminology as I understand it.

## Testing

- Did you test these changes? If so, how?
  - opened Docs, verified link
- Are there any parts that need more testing?
  - I don't think so
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- run `cargo doc --open` and check out Component and Relationship docs,
verify their correctness
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
  - I think this is n/a but I ran the doc command on Ubuntu 24.04.2 LTS

---

## Showcase


![image](https://github.com/user-attachments/assets/241eecb2-dd98-43ab-875a-1a3ec1176a79)


## Migration Guide

n/a
2025-03-07 23:32:43 +00:00
RobWalt
a85a3a2a15
allow Call and Closure expressions in hook macro attributes (#18017)
# Objective

This PR adds:

- function call hook attributes `#[component(on_add = func(42))]`
  - main feature of this commit
- closure hook attributes `#[component(on_add = |w, ctx| { /* ... */
})]`
  - maybe too verbose
  - but was easy to add
  - was suggested on discord

This allows to reuse common functionality without replicating a lot of
boilerplate. A small example is a hook which just adds different default
sprites. The sprite loading code would be the same for every component.
Unfortunately we can't use the required components feature, since we
need at least an `AssetServer` or other `Resource`s or `Component`s to
load the sprite.

```rs
fn load_sprite(path: &str) -> impl Fn(DeferredWorld, HookContext) {
  |mut world, ctx| {
    // ... use world to load sprite
  }
}

#[derive(Component)]
#[component(on_add = load_sprite("knight.png"))]
struct Knight;

#[derive(Component)]
#[component(on_add = load_sprite("monster.png"))]
struct Monster;
```

---

The commit also reorders the logic of the derive macro a bit. It's
probably a bit less lazy now, but the functionality shouldn't be
performance critical and is executed at compile time anyways.

## Solution

- Introduce `HookKind` enum in the component proc macro module
- extend parsing to allow more cases of expressions

## Testing

I have some code laying around. I'm not sure where to put it yet though.
Also is there a way to check compilation failures? Anyways, here it is:

```rs
use bevy::prelude::*;

#[derive(Component)]
#[component(
    on_add = fooing_and_baring,
    on_insert = fooing_and_baring,
    on_replace = fooing_and_baring,
    on_despawn = fooing_and_baring,
    on_remove = fooing_and_baring
)]
pub struct FooPath;

fn fooing_and_baring(
    world: bevy::ecs::world::DeferredWorld,
    ctx: bevy::ecs::component::HookContext,
) {
}

#[derive(Component)]
#[component(
    on_add = baring_and_bazzing("foo"),
    on_insert = baring_and_bazzing("foo"),
    on_replace = baring_and_bazzing("foo"),
    on_despawn = baring_and_bazzing("foo"),
    on_remove = baring_and_bazzing("foo")
)]
pub struct FooCall;

fn baring_and_bazzing(
    path: &str,
) -> impl Fn(bevy::ecs::world::DeferredWorld, bevy::ecs::component::HookContext) {
    |world, ctx| {}
}

#[derive(Component)]
#[component(
    on_add = |w,ctx| {},
    on_insert = |w,ctx| {},
    on_replace = |w,ctx| {},
    on_despawn = |w,ctx| {},
    on_remove = |w,ctx| {}
)]
pub struct FooClosure;

#[derive(Component, Debug)]
#[relationship(relationship_target = FooTargets)]
#[component(
    on_add = baring_and_bazzing("foo"),
    // on_insert = baring_and_bazzing("foo"),
    // on_replace = baring_and_bazzing("foo"),
    on_despawn = baring_and_bazzing("foo"),
    on_remove = baring_and_bazzing("foo")
)]
pub struct FooTargetOf(Entity);

#[derive(Component, Debug)]
#[relationship_target(relationship = FooTargetOf)]
#[component(
    on_add = |w,ctx| {},
    on_insert = |w,ctx| {},
    // on_replace = |w,ctx| {},
    // on_despawn = |w,ctx| {},
    on_remove = |w,ctx| {}
)]
pub struct FooTargets(Vec<Entity>);

// MSG:  mismatched types  expected fn pointer `for<'w> fn(bevy::bevy_ecs::world::DeferredWorld<'w>, bevy::bevy_ecs::component::HookContext)`    found struct `Bar`
//
// pub struct Bar;
// #[derive(Component)]
// #[component(
//     on_add = Bar,
// )]
// pub struct FooWrongPath;

// MSG: this function takes 1 argument but 2 arguements were supplied
//
// #[derive(Component)]
// #[component(
//     on_add = wrong_bazzing("foo"),
// )]
// pub struct FooWrongCall;
//
// fn wrong_bazzing(path: &str) -> impl Fn(bevy::ecs::world::DeferredWorld) {
//     |world| {}
// }

// MSG: expected 1 argument, found 2
//
// #[derive(Component)]
// #[component(
//     on_add = |w| {},
// )]
// pub struct FooWrongCall;
```

---

## Showcase

I'll try to continue to work on this to have a small section in the
release notes.
2025-03-06 16:39:11 +00:00
Carter Anderson
06cb5c5fd9
Fix Component require() IDE integration (#18165)
# Objective

Component `require()` IDE integration is fully broken, as of #16575.

## Solution

This reverts us back to the previous "put the docs on Component trait"
impl. This _does_ reduce the accessibility of the required components in
rust docs, but the complete erasure of "required component IDE
experience" is not worth the price of slightly increased prominence of
requires in docs.

Additionally, Rust Analyzer has recently started including derive
attributes in suggestions, so we aren't losing that benefit of the
proc_macro attribute impl.
2025-03-06 02:44:47 +00:00
Carter Anderson
a530c07bc5
Preserve spawned RelationshipTarget order and other improvements (#17858)
Fixes #17720

## Objective

Spawning RelationshipTargets from scenes currently fails to preserve
RelationshipTarget ordering (ex: `Children` has an arbitrary order).
This is because it uses the normal hook flow to set up the collection,
which means we are pushing onto the collection in _spawn order_ (which
is currently in archetype order, which will often produce mismatched
orderings).

We need to preserve the ordering in the original RelationshipTarget
collection. Ideally without expensive checking / fixups.

## Solution

One solution would be to spawn in hierarchy-order. However this gets
complicated as there can be multiple hierarchies, and it also means we
can't spawn in more cache-friendly orders (ex: the current per-archetype
spawning, or future even-smarter per-table spawning). Additionally,
same-world cloning has _slightly_ more nuanced needs (ex: recursively
clone linked relationships, while maintaining _original_ relationships
outside of the tree via normal hooks).

The preferred approach is to directly spawn the remapped
RelationshipTarget collection, as this trivially preserves the ordering.
Unfortunately we can't _just_ do that, as when we spawn the children
with their Relationships (ex: `ChildOf`), that will insert a duplicate.

We could "fixup" the collection retroactively by just removing the back
half of duplicates, but this requires another pass / more lookups /
allocating twice as much space. Additionally, it becomes complicated
because observers could insert additional children, making it harder
(aka more expensive) to determine which children are dupes and which are
not.

The path I chose is to support "opting out" of the relationship target
hook in the contexts that need that, as this allows us to just cheaply
clone the mapped collection. The relationship hook can look for this
configuration when it runs and skip its logic when that happens. A
"simple" / small-amount-of-code way to do this would be to add a "skip
relationship spawn" flag to World. Sadly, any hook / observer that runs
_as the result of an insert_ would also read this flag. We really need a
way to scope this setting to a _specific_ insert.

Therefore I opted to add a new `RelationshipInsertHookMode` enum and an
`entity.insert_with_relationship_insert_hook_mode` variant. Obviously
this is verbose and ugly. And nobody wants _more_ insert variants. But
sadly this was the best I could come up with from a performance and
capability perspective. If you have alternatives let me know!

There are three variants:

1. `RelationshipInsertHookMode::Run`: always run relationship insert
hooks (this is the default)
2. `RelationshipInsertHookMode::Skip`: do not run any relationship
insert hooks for this insert (this is used by spawner code)
3. `RelationshipInsertHookMode::RunIfNotLinked`: only run hooks for
_unlinked_ relationships (this is used in same-world recursive entity
cloning to preserve relationships outside of the deep-cloned tree)

Note that I have intentionally only added "insert with relationship hook
mode" variants to the cases we absolutely need (everything else uses the
default `Run` mode), just to keep the code size in check. I do not think
we should add more without real _very necessary_ use cases.

I also made some other minor tweaks:

1. I split out `SourceComponent` from `ComponentCloneCtx`. Reading the
source component no longer needlessly blocks mutable access to
`ComponentCloneCtx`.
2. Thanks to (1), I've removed the `RefCell` wrapper over the cloned
component queue.
3. (1) also allowed me to write to the EntityMapper while queuing up
clones, meaning we can reserve entities during the component clone and
write them to the mapper _before_ inserting the component, meaning
cloned collections can be mapped on insert.
4. I've removed the closure from `write_target_component_ptr` to
simplify the API / make it compatible with the split `SourceComponent`
approach.
5. I've renamed `EntityCloner::recursive` to
`EntityCloner::linked_cloning` to connect that feature more directly
with `RelationshipTarget::LINKED_SPAWN`
6. I've removed `EntityCloneBehavior::RelationshipTarget`. This was
always intended to be temporary, and this new behavior removes the need
for it.

---------

Co-authored-by: Viktor Gustavsson <villor94@gmail.com>
2025-03-05 22:18:57 +00:00
Sou1gh0st
f2b37c733e
Deduplicate register_inherited_required_components (#16519)
# Objective
- Fixes #16416 

## Solution
- Add a intermediate temporary mutable `RequiredComponents` to get avoid
of the borrowing issues.

## Testing

- I have run `cargo test --package bevy_ecs -- --exact --show-output`
and past all the tests.
2025-02-25 23:59:58 +00:00
Zachary Harrold
76e9bf9c99
Automatically enable portable-atomic when required (#17570)
# Objective

- Contributes to #15460
- Reduce quantity and complexity of feature gates across Bevy

## Solution

- Used `target_has_atomic` configuration variable to automatically
detect impartial atomic support and automatically switch to
`portable-atomic` over the standard library on an as-required basis.

## Testing

- CI

## Notes

To explain the technique employed here, consider getting `Arc` either
from `alloc::sync` _or_ `portable-atomic-util`. First, we can inspect
the `alloc` crate to see that you only have access to `Arc` _if_
`target_has_atomic = "ptr"`. We add a target dependency for this
particular configuration _inverted_:

```toml
[target.'cfg(not(target_has_atomic = "ptr"))'.dependencies]
portable-atomic-util = { version = "0.2.4", default-features = false }
```

This ensures we only have the dependency when it is needed, and it is
entirely excluded from the dependency graph when it is not. Next, we
adjust our configuration flags to instead of checking for `feature =
"portable-atomic"` to instead check for `target_has_atomic = "ptr"`:

```rust
// `alloc` feature flag hidden for brevity

#[cfg(not(target_has_atomic = "ptr"))]
use portable_atomic_util as arc;

#[cfg(target_has_atomic = "ptr")]
use alloc::sync as arc;

pub use arc::{Arc, Weak};
```

The benefits of this technique are three-fold:

1. For platforms without full atomic support, the functionality is
enabled automatically.
2. For platforms with atomic support, the dependency is never included,
even if a feature was enabled using `--all-features` (for example)
3. The `portable-atomic` feature no longer needs to virally spread to
all user-facing crates, it's instead something handled within
`bevy_platform_support` (with some extras where other dependencies also
need their features enabled).
2025-02-24 20:52:46 +00:00
Chris Russell
eee7fd5b3e
Encapsulate cfg(feature = "track_location") in a type. (#17602)
# Objective

Eliminate the need to write `cfg(feature = "track_location")` every time
one uses an API that may use location tracking. It's verbose, and a
little intimidating. And it requires code outside of `bevy_ecs` that
wants to use location tracking needs to either unconditionally enable
the feature, or include conditional compilation of its own. It would be
good for users to be able to log locations when they are available
without needing to add feature flags to their own crates.

Reduce the number of cases where code compiles with the `track_location`
feature enabled, but not with it disabled, or vice versa. It can be hard
to remember to test it both ways!

Remove the need to store a `None` in `HookContext` when the
`track_location` feature is disabled.

## Solution

Create an `MaybeLocation<T>` type that contains a `T` if the
`track_location` feature is enabled, and is a ZST if it is not. The
overall API is similar to `Option`, but whether the value is `Some` or
`None` is set at compile time and is the same for all values.

Default `T` to `&'static Location<'static>`, since that is the most
common case.

Remove all `cfg(feature = "track_location")` blocks outside of the
implementation of that type, and instead call methods on it.

When `track_location` is disabled, `MaybeLocation` is a ZST and all
methods are `#[inline]` and empty, so they should be entirely removed by
the compiler. But the code will still be visible to the compiler and
checked, so if it compiles with the feature disabled then it should also
compile with it enabled, and vice versa.

## Open Questions

Where should these types live? I put them in `change_detection` because
that's where the existing `MaybeLocation` types were, but we now use
these outside of change detection.

While I believe that the compiler should be able to remove all of these
calls, I have not actually tested anything. If we want to take this
approach, what testing is required to ensure it doesn't impact
performance?

## Migration Guide

Methods like `Ref::changed_by()` that return a `&'static
Location<'static>` will now be available even when the `track_location`
feature is disabled, but they will return a new `MaybeLocation` type.
`MaybeLocation` wraps a `&'static Location<'static>` when the feature is
enabled, and is a ZST when the feature is disabled.

Existing code that needs a `&Location` can call `into_option().unwrap()`
to recover it. Many trait impls are forwarded, so if you only need
`Display` then no changes will be necessary.

If that code was conditionally compiled, you may instead want to use the
methods on `MaybeLocation` to remove the need for conditional
compilation.

Code that constructs a `Ref`, `Mut`, `Res`, or `ResMut` will now need to
provide location information unconditionally. If you are creating them
from existing Bevy types, you can obtain a `MaybeLocation` from methods
like `Table::get_changed_by_slice_for()` or
`ComponentSparseSet::get_with_ticks`. Otherwise, you will need to store
a `MaybeLocation` next to your data and use methods like `as_ref()` or
`as_mut()` to obtain wrapped references.
2025-02-10 21:21:20 +00:00
raldone01
1b7db895b7
Harden proc macro path resolution and add integration tests. (#17330)
This pr uses the `extern crate self as` trick to make proc macros behave
the same way inside and outside bevy.

# Objective

- Removes noise introduced by `crate as` in the whole bevy repo.
- Fixes #17004.
- Hardens proc macro path resolution.

## TODO

- [x] `BevyManifest` needs cleanup.
- [x] Cleanup remaining `crate as`.
- [x] Add proper integration tests to the ci.

## Notes

- `cargo-manifest-proc-macros` is written by me and based/inspired by
the old `BevyManifest` implementation and
[`bkchr/proc-macro-crate`](https://github.com/bkchr/proc-macro-crate).
- What do you think about the new integration test machinery I added to
the `ci`?
  More and better integration tests can be added at a later stage.
The goal of these integration tests is to simulate an actual separate
crate that uses bevy. Ideally they would lightly touch all bevy crates.

## Testing

- Needs RA test
- Needs testing from other users
- Others need to run at least `cargo run -p ci integration-test` and
verify that they work.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-02-09 19:45:45 +00:00
Carter Anderson
3c8fae2390
Improved Entity Mapping and Cloning (#17687)
Fixes #17535

Bevy's approach to handling "entity mapping" during spawning and cloning
needs some work. The addition of
[Relations](https://github.com/bevyengine/bevy/pull/17398) both
[introduced a new "duplicate entities" bug when spawning scenes in the
scene system](#17535) and made the weaknesses of the current mapping
system exceedingly clear:

1. Entity mapping requires _a ton_ of boilerplate (implement or derive
VisitEntities and VisitEntitesMut, then register / reflect MapEntities).
Knowing the incantation is challenging and if you forget to do it in
part or in whole, spawning subtly breaks.
2. Entity mapping a spawned component in scenes incurs unnecessary
overhead: look up ReflectMapEntities, create a _brand new temporary
instance_ of the component using FromReflect, map the entities in that
instance, and then apply that on top of the actual component using
reflection. We can do much better.

Additionally, while our new [Entity cloning
system](https://github.com/bevyengine/bevy/pull/16132) is already pretty
great, it has some areas we can make better:

* It doesn't expose semantic info about the clone (ex: ignore or "clone
empty"), meaning we can't key off of that in places where it would be
useful, such as scene spawning. Rather than duplicating this info across
contexts, I think it makes more sense to add that info to the clone
system, especially given that we'd like to use cloning code in some of
our spawning scenarios.
* EntityCloner is currently built in a way that prioritizes a single
entity clone
* EntityCloner's recursive cloning is built to be done "inside out" in a
parallel context (queue commands that each have a clone of
EntityCloner). By making EntityCloner the orchestrator of the clone we
can remove internal arcs, improve the clarity of the code, make
EntityCloner mutable again, and simplify the builder code.
* EntityCloner does not currently take into account entity mapping. This
is necessary to do true "bullet proof" cloning, would allow us to unify
the per-component scene spawning and cloning UX, and ultimately would
allow us to use EntityCloner in place of raw reflection for scenes like
`Scene(World)` (which would give us a nice performance boost: fewer
archetype moves, less reflection overhead).

## Solution

### Improved Entity Mapping

First, components now have first-class "entity visiting and mapping"
behavior:

```rust
#[derive(Component, Reflect)]
#[reflect(Component)]
struct Inventory {
    size: usize,
    #[entities]
    items: Vec<Entity>,
}
```

Any field with the `#[entities]` annotation will be viewable and
mappable when cloning and spawning scenes.

Compare that to what was required before!

```rust
#[derive(Component, Reflect, VisitEntities, VisitEntitiesMut)]
#[reflect(Component, MapEntities)]
struct Inventory {
    #[visit_entities(ignore)]
    size: usize,
    items: Vec<Entity>,
}
```

Additionally, for relationships `#[entities]` is implied, meaning this
"just works" in scenes and cloning:

```rust
#[derive(Component, Reflect)]
#[relationship(relationship_target = Children)]
#[reflect(Component)]
struct ChildOf(pub Entity);
```

Note that Component _does not_ implement `VisitEntities` directly.
Instead, it has `Component::visit_entities` and
`Component::visit_entities_mut` methods. This is for a few reasons:

1. We cannot implement `VisitEntities for C: Component` because that
would conflict with our impl of VisitEntities for anything that
implements `IntoIterator<Item=Entity>`. Preserving that impl is more
important from a UX perspective.
2. We should not implement `Component: VisitEntities` VisitEntities in
the Component derive, as that would increase the burden of manual
Component trait implementors.
3. Making VisitEntitiesMut directly callable for components would make
it easy to invalidate invariants defined by a component author. By
putting it in the `Component` impl, we can make it harder to call
naturally / unavailable to autocomplete using `fn
visit_entities_mut(this: &mut Self, ...)`.

`ReflectComponent::apply_or_insert` is now
`ReflectComponent::apply_or_insert_mapped`. By moving mapping inside
this impl, we remove the need to go through the reflection system to do
entity mapping, meaning we no longer need to create a clone of the
target component, map the entities in that component, and patch those
values on top. This will make spawning mapped entities _much_ faster
(The default `Component::visit_entities_mut` impl is an inlined empty
function, so it will incur no overhead for unmapped entities).

### The Bug Fix

To solve #17535, spawning code now skips entities with the new
`ComponentCloneBehavior::Ignore` and
`ComponentCloneBehavior::RelationshipTarget` variants (note
RelationshipTarget is a temporary "workaround" variant that allows
scenes to skip these components. This is a temporary workaround that can
be removed as these cases should _really_ be using EntityCloner logic,
which should be done in a followup PR. When that is done,
`ComponentCloneBehavior::RelationshipTarget` can be merged into the
normal `ComponentCloneBehavior::Custom`).

### Improved Cloning

* `Option<ComponentCloneHandler>` has been replaced by
`ComponentCloneBehavior`, which encodes additional intent and context
(ex: `Default`, `Ignore`, `Custom`, `RelationshipTarget` (this last one
is temporary)).
* Global per-world entity cloning configuration has been removed. This
felt overly complicated, increased our API surface, and felt too
generic. Each clone context can have different requirements (ex: what a
user wants in a specific system, what a scene spawner wants, etc). I'd
prefer to see how far context-specific EntityCloners get us first.
* EntityCloner's internals have been reworked to remove Arcs and make it
mutable.
* EntityCloner is now directly stored on EntityClonerBuilder,
simplifying the code somewhat
* EntityCloner's "bundle scratch" pattern has been moved into the new
BundleScratch type, improving its usability and making it usable in
other contexts (such as future cross-world cloning code). Currently this
is still private, but with some higher level safe APIs it could be used
externally for making dynamic bundles
* EntityCloner's recursive cloning behavior has been "externalized". It
is now responsible for orchestrating recursive clones, meaning it no
longer needs to be sharable/clone-able across threads / read-only.
* EntityCloner now does entity mapping during clones, like scenes do.
This gives behavior parity and also makes it more generically useful.
* `RelatonshipTarget::RECURSIVE_SPAWN` is now
`RelationshipTarget::LINKED_SPAWN`, and this field is used when cloning
relationship targets to determine if cloning should happen recursively.
The new `LINKED_SPAWN` term was picked to make it more generically
applicable across spawning and cloning scenarios.

## Next Steps

* I think we should adapt EntityCloner to support cross world cloning. I
think this PR helps set the stage for that by making the internals
slightly more generalized. We could have a CrossWorldEntityCloner that
reuses a lot of this infrastructure.
* Once we support cross world cloning, we should use EntityCloner to
spawn `Scene(World)` scenes. This would yield significant performance
benefits (no archetype moves, less reflection overhead).

---------

Co-authored-by: eugineerd <70062110+eugineerd@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-02-06 22:13:41 +00:00
ElliottjPierce
1b2cf7d6cd
Isolate component registration (#17671)
# Objective

Progresses #17569. The end goal here is to synchronize component
registration. See the other PR for details for the motivation behind
that.

For this PR specifically, the objective is to decouple `Components` from
`Storages`. What components are registered etc should have nothing to do
with what Storages looks like. Storages should only care about what
entity archetypes have been spawned.

## Solution

Previously, this was used to create sparse sets for relevant components
when those components were registered. Now, we do that when the
component is inserted/spawned.

This PR proposes doing that in `BundleInfo::new`, but there may be a
better place.

## Testing

In theory, this shouldn't have changed any functionality, so no new
tests were created. I'm not aware of any examples that make heavy use of
sparse set components either.

## Migration Guide

- Remove storages from functions where it is no longer needed.
- Note that SparseSets are no longer present for all registered sparse
set components, only those that have been spawned.

---------

Co-authored-by: SpecificProtagonist <vincentjunge@posteo.net>
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2025-02-05 19:59:30 +00:00
Zachary Harrold
d0c0bad7b4
Split Component::register_component_hooks into individual methods (#17685)
# Objective

- Fixes #17411

## Solution

- Deprecated `Component::register_component_hooks`
- Added individual methods for each hook which return `None` if the hook
is unused.

## Testing

- CI

---

## Migration Guide

`Component::register_component_hooks` is now deprecated and will be
removed in a future release. When implementing `Component` manually,
also implement the respective hook methods on `Component`.

```rust
// Before
impl Component for Foo {
    // snip
    fn register_component_hooks(hooks: &mut ComponentHooks) {
            hooks.on_add(foo_on_add);
    }
}

// After
impl Component for Foo {
    // snip
    fn on_add() -> Option<ComponentHook> {
            Some(foo_on_add)
    }
}
```

## Notes

I've chosen to deprecate `Component::register_component_hooks` rather
than outright remove it to ease the migration guide. While it is in a
state of deprecation, it must be used by
`Components::register_component_internal` to ensure users who haven't
migrated to the new hook definition scheme aren't left behind. For users
of the new scheme, a default implementation of
`Component::register_component_hooks` is provided which forwards the new
individual hook implementations.

Personally, I think this is a cleaner API to work with, and would allow
the documentation for hooks to exist on the respective `Component`
methods (e.g., documentation for `OnAdd` can exist on
`Component::on_add`). Ideally, `Component::on_add` would be the hook
itself rather than a getter for the hook, but it is the only way to
early-out for a no-op hook, which is important for performance.

## Migration Guide

`Component::register_component_hooks` has been deprecated. If you are
manually implementing the `Component` trait and registering hooks there,
use the individual methods such as `on_add` instead for increased
clarity.
2025-02-05 19:33:05 +00:00
ElliottjPierce
361397fcac
Add a test for direct recursion in required components. (#17626)
I realized there wasn't a test for this yet and figured it would be
trivial to add. Why not? Unless there was a test for this, and I just
missed it?

I appreciate the unique error message it gives and wanted to make sure
it doesn't get broken at some point. Or worse, endlessly recurse.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-02-02 06:47:10 +00:00
Zachary Harrold
9bc0ae33c3
Move hashbrown and foldhash out of bevy_utils (#17460)
# Objective

- Contributes to #16877

## Solution

- Moved `hashbrown`, `foldhash`, and related types out of `bevy_utils`
and into `bevy_platform_support`
- Refactored the above to match the layout of these types in `std`.
- Updated crates as required.

## Testing

- CI

---

## Migration Guide

- The following items were moved out of `bevy_utils` and into
`bevy_platform_support::hash`:
  - `FixedState`
  - `DefaultHasher`
  - `RandomState`
  - `FixedHasher`
  - `Hashed`
  - `PassHash`
  - `PassHasher`
  - `NoOpHash`
- The following items were moved out of `bevy_utils` and into
`bevy_platform_support::collections`:
  - `HashMap`
  - `HashSet`
- `bevy_utils::hashbrown` has been removed. Instead, import from
`bevy_platform_support::collections` _or_ take a dependency on
`hashbrown` directly.
- `bevy_utils::Entry` has been removed. Instead, import from
`bevy_platform_support::collections::hash_map` or
`bevy_platform_support::collections::hash_set` as appropriate.
- All of the above equally apply to `bevy::utils` and
`bevy::platform_support`.

## Notes

- I left `PreHashMap`, `PreHashMapExt`, and `TypeIdMap` in `bevy_utils`
as they might be candidates for micro-crating. They can always be moved
into `bevy_platform_support` at a later date if desired.
2025-01-23 16:46:08 +00:00
Zachary Harrold
41e79ae826
Refactored ComponentHook Parameters into HookContext (#17503)
# Objective

- Make the function signature for `ComponentHook` less verbose

## Solution

- Refactored `Entity`, `ComponentId`, and `Option<&Location>` into a new
`HookContext` struct.

## Testing

- CI

---

## Migration Guide

Update the function signatures for your component hooks to only take 2
arguments, `world` and `context`. Note that because `HookContext` is
plain data with all members public, you can use de-structuring to
simplify migration.

```rust
// Before
fn my_hook(
    mut world: DeferredWorld,
    entity: Entity,
    component_id: ComponentId,
) { ... }

// After
fn my_hook(
    mut world: DeferredWorld,
    HookContext { entity, component_id, caller }: HookContext,
) { ... }
``` 

Likewise, if you were discarding certain parameters, you can use `..` in
the de-structuring:

```rust
// Before
fn my_hook(
    mut world: DeferredWorld,
    entity: Entity,
    _: ComponentId,
) { ... }

// After
fn my_hook(
    mut world: DeferredWorld,
    HookContext { entity, .. }: HookContext,
) { ... }
```
2025-01-23 02:45:24 +00:00
SpecificProtagonist
f32a6fb205
Track callsite for observers & hooks (#15607)
# Objective

Fixes #14708

Also fixes some commands not updating tracked location.


## Solution

`ObserverTrigger` has a new `caller` field with the
`track_change_detection` feature;
hooks take an additional caller parameter (which is `Some(…)` or `None`
depending on the feature).

## Testing

See the new tests in `src/observer/mod.rs`

---

## Showcase

Observers now know from where they were triggered (if
`track_change_detection` is enabled):
```rust
world.observe(move |trigger: Trigger<OnAdd, Foo>| {
    println!("Added Foo from {}", trigger.caller());
});
```

## Migration

- hooks now take an additional `Option<&'static Location>` argument

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-01-22 20:02:39 +00:00
Alice Cecile
44ad3bf62b
Move Resource trait to its own file (#17469)
# Objective

`bevy_ecs`'s `system` module is something of a grab bag, and *very*
large. This is particularly true for the `system_param` module, which is
more than 2k lines long!

While it could be defensible to put `Res` and `ResMut` there (lol no
they're in change_detection.rs, obviously), it doesn't make any sense to
put the `Resource` trait there. This is confusing to navigate (and
painful to work on and review).

## Solution

- Create a root level `bevy_ecs/resource.rs` module to mirror
`bevy_ecs/component.rs`
- move the `Resource` trait to that module
- move the `Resource` derive macro to that module as well (Rust really
likes when you pun on the names of the derive macro and trait and put
them in the same path)
- fix all of the imports

## Notes to reviewers

- We could probably move more stuff into here, but I wanted to keep this
PR as small as possible given the absurd level of import changes.
- This PR is ground work for my upcoming attempts to store resource data
on components (resources-as-entities). Splitting this code out will make
the work and review a bit easier, and is the sort of overdue refactor
that's good to do as part of more meaningful work.

## Testing

cargo build works!

## Migration Guide

`bevy_ecs::system::Resource` has been moved to
`bevy_ecs::resource::Resource`.
2025-01-21 19:47:08 +00:00
Zachary Harrold
a64446b77e
Create bevy_platform_support Crate (#17250)
# Objective

- Contributes to #16877

## Solution

- Initial creation of `bevy_platform_support` crate.
- Moved `bevy_utils::Instant` into new `bevy_platform_support` crate.
- Moved `portable-atomic`, `portable-atomic-util`, and
`critical-section` into new `bevy_platform_support` crate.

## Testing

- CI

---

## Showcase

Instead of needing code like this to import an `Arc`:

```rust
#[cfg(feature = "portable-atomic")]
use portable_atomic_util::Arc;

#[cfg(not(feature = "portable-atomic"))]
use alloc::sync::Arc;
```

We can now use:

```rust
use bevy_platform_support::sync::Arc;
```

This applies to many other types, but the goal is overall the same:
allowing crates to use `std`-like types without the boilerplate of
conditional compilation and platform-dependencies.

## Migration Guide

- Replace imports of `bevy_utils::Instant` with
`bevy_platform_support::time::Instant`
- Replace imports of `bevy::utils::Instant` with
`bevy::platform_support::time::Instant`

## Notes

- `bevy_platform_support` hasn't been reserved on `crates.io`
- ~~`bevy_platform_support` is not re-exported from `bevy` at this time.
It may be worthwhile exporting this crate, but I am unsure of a
reasonable name to export it under (`platform_support` may be a bit
wordy for user-facing).~~
- I've included an implementation of `Instant` which is suitable for
`no_std` platforms that are not Wasm for the sake of eliminating feature
gates around its use. It may be a controversial inclusion, so I'm happy
to remove it if required.
- There are many other items (`spin`, `bevy_utils::Sync(Unsafe)Cell`,
etc.) which should be added to this crate. I have kept the initial scope
small to demonstrate utility without making this too unwieldy.

---------

Co-authored-by: TimJentzsch <TimJentzsch@users.noreply.github.com>
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>
2025-01-20 20:45:30 +00:00
Carter Anderson
21f1e3045c
Relationships (non-fragmenting, one-to-many) (#17398)
This adds support for one-to-many non-fragmenting relationships (with
planned paths for fragmenting and non-fragmenting many-to-many
relationships). "Non-fragmenting" means that entities with the same
relationship type, but different relationship targets, are not forced
into separate tables (which would cause "table fragmentation").

Functionally, this fills a similar niche as the current Parent/Children
system. The biggest differences are:

1. Relationships have simpler internals and significantly improved
performance and UX. Commands and specialized APIs are no longer
necessary to keep everything in sync. Just spawn entities with the
relationship components you want and everything "just works".
2. Relationships are generalized. Bevy can provide additional built in
relationships, and users can define their own.

**REQUEST TO REVIEWERS**: _please don't leave top level comments and
instead comment on specific lines of code. That way we can take
advantage of threaded discussions. Also dont leave comments simply
pointing out CI failures as I can read those just fine._

## Built on top of what we have

Relationships are implemented on top of the Bevy ECS features we already
have: components, immutability, and hooks. This makes them immediately
compatible with all of our existing (and future) APIs for querying,
spawning, removing, scenes, reflection, etc. The fewer specialized APIs
we need to build, maintain, and teach, the better.

## Why focus on one-to-many non-fragmenting first?

1. This allows us to improve Parent/Children relationships immediately,
in a way that is reasonably uncontroversial. Switching our hierarchy to
fragmenting relationships would have significant performance
implications. ~~Flecs is heavily considering a switch to non-fragmenting
relations after careful considerations of the performance tradeoffs.~~
_(Correction from @SanderMertens: Flecs is implementing non-fragmenting
storage specialized for asset hierarchies, where asset hierarchies are
many instances of small trees that have a well defined structure)_
2. Adding generalized one-to-many relationships is currently a priority
for the [Next Generation Scene / UI
effort](https://github.com/bevyengine/bevy/discussions/14437).
Specifically, we're interested in building reactions and observers on
top.

## The changes

This PR does the following:

1. Adds a generic one-to-many Relationship system
3. Ports the existing Parent/Children system to Relationships, which now
lives in `bevy_ecs::hierarchy`. The old `bevy_hierarchy` crate has been
removed.
4. Adds on_despawn component hooks
5. Relationships can opt-in to "despawn descendants" behavior, meaning
that the entire relationship hierarchy is despawned when
`entity.despawn()` is called. The built in Parent/Children hierarchies
enable this behavior, and `entity.despawn_recursive()` has been removed.
6. `world.spawn` now applies commands after spawning. This ensures that
relationship bookkeeping happens immediately and removes the need to
manually flush. This is in line with the equivalent behaviors recently
added to the other APIs (ex: insert).
7. Removes the ValidParentCheckPlugin (system-driven / poll based) in
favor of a `validate_parent_has_component` hook.

## Using Relationships

The `Relationship` trait looks like this:

```rust
pub trait Relationship: Component + Sized {
    type RelationshipSources: RelationshipSources<Relationship = Self>;
    fn get(&self) -> Entity;
    fn from(entity: Entity) -> Self;
}
```

A relationship is a component that:

1. Is a simple wrapper over a "target" Entity.
2. Has a corresponding `RelationshipSources` component, which is a
simple wrapper over a collection of entities. Every "target entity"
targeted by a "source entity" with a `Relationship` has a
`RelationshipSources` component, which contains every "source entity"
that targets it.

For example, the `Parent` component (as it currently exists in Bevy) is
the `Relationship` component and the entity containing the Parent is the
"source entity". The entity _inside_ the `Parent(Entity)` component is
the "target entity". And that target entity has a `Children` component
(which implements `RelationshipSources`).

In practice, the Parent/Children relationship looks like this:

```rust
#[derive(Relationship)]
#[relationship(relationship_sources = Children)]
pub struct Parent(pub Entity);

#[derive(RelationshipSources)]
#[relationship_sources(relationship = Parent)]
pub struct Children(Vec<Entity>);
```

The Relationship and RelationshipSources derives automatically implement
Component with the relevant configuration (namely, the hooks necessary
to keep everything in sync).

The most direct way to add relationships is to spawn entities with
relationship components:

```rust
let a = world.spawn_empty().id();
let b = world.spawn(Parent(a)).id();

assert_eq!(world.entity(a).get::<Children>().unwrap(), &[b]);
```

There are also convenience APIs for spawning more than one entity with
the same relationship:

```rust
world.spawn_empty().with_related::<Children>(|s| {
    s.spawn_empty();
    s.spawn_empty();
})
```

The existing `with_children` API is now a simpler wrapper over
`with_related`. This makes this change largely non-breaking for existing
spawn patterns.

```rust
world.spawn_empty().with_children(|s| {
    s.spawn_empty();
    s.spawn_empty();
})
```

There are also other relationship APIs, such as `add_related` and
`despawn_related`.

## Automatic recursive despawn via the new on_despawn hook

`RelationshipSources` can opt-in to "despawn descendants" behavior,
which will despawn all related entities in the relationship hierarchy:

```rust
#[derive(RelationshipSources)]
#[relationship_sources(relationship = Parent, despawn_descendants)]
pub struct Children(Vec<Entity>);
```

This means that `entity.despawn_recursive()` is no longer required.
Instead, just use `entity.despawn()` and the relevant related entities
will also be despawned.

To despawn an entity _without_ despawning its parent/child descendants,
you should remove the `Children` component first, which will also remove
the related `Parent` components:

```rust
entity
    .remove::<Children>()
    .despawn()
```

This builds on the on_despawn hook introduced in this PR, which is fired
when an entity is despawned (before other hooks).

## Relationships are the source of truth

`Relationship` is the _single_ source of truth component.
`RelationshipSources` is merely a reflection of what all the
`Relationship` components say. By embracing this, we are able to
significantly improve the performance of the system as a whole. We can
rely on component lifecycles to protect us against duplicates, rather
than needing to scan at runtime to ensure entities don't already exist
(which results in quadratic runtime). A single source of truth gives us
constant-time inserts. This does mean that we cannot directly spawn
populated `Children` components (or directly add or remove entities from
those components). I personally think this is a worthwhile tradeoff,
both because it makes the performance much better _and_ because it means
theres exactly one way to do things (which is a philosophy we try to
employ for Bevy APIs).

As an aside: treating both sides of the relationship as "equivalent
source of truth relations" does enable building simple and flexible
many-to-many relationships. But this introduces an _inherent_ need to
scan (or hash) to protect against duplicates.
[`evergreen_relations`](https://github.com/EvergreenNest/evergreen_relations)
has a very nice implementation of the "symmetrical many-to-many"
approach. Unfortunately I think the performance issues inherent to that
approach make it a poor choice for Bevy's default relationship system.

## Followup Work

* Discuss renaming `Parent` to `ChildOf`. I refrained from doing that in
this PR to keep the diff reasonable, but I'm personally biased toward
this change (and using that naming pattern generally for relationships).
* [Improved spawning
ergonomics](https://github.com/bevyengine/bevy/discussions/16920)
* Consider adding relationship observers/triggers for "relationship
targets" whenever a source is added or removed. This would replace the
current "hierarchy events" system, which is unused upstream but may have
existing users downstream. I think triggers are the better fit for this
than a buffered event queue, and would prefer not to add that back.
* Fragmenting relations: My current idea hinges on the introduction of
"value components" (aka: components whose type _and_ value determines
their ComponentId, via something like Hashing / PartialEq). By labeling
a Relationship component such as `ChildOf(Entity)` as a "value
component", `ChildOf(e1)` and `ChildOf(e2)` would be considered
"different components". This makes the transition between fragmenting
and non-fragmenting a single flag, and everything else continues to work
as expected.
* Many-to-many support
* Non-fragmenting: We can expand Relationship to be a list of entities
instead of a single entity. I have largely already written the code for
this.
* Fragmenting: With the "value component" impl mentioned above, we get
many-to-many support "for free", as it would allow inserting multiple
copies of a Relationship component with different target entities.

Fixes #3742 (If this PR is merged, I think we should open more targeted
followup issues for the work above, with a fresh tracking issue free of
the large amount of less-directed historical context)
Fixes #17301
Fixes #12235 
Fixes #15299
Fixes #15308 

## Migration Guide

* Replace `ChildBuilder` with `ChildSpawnerCommands`.
* Replace calls to `.set_parent(parent_id)` with
`.insert(Parent(parent_id))`.
* Replace calls to `.replace_children()` with `.remove::<Children>()`
followed by `.add_children()`. Note that you'll need to manually despawn
any children that are not carried over.
* Replace calls to `.despawn_recursive()` with `.despawn()`.
* Replace calls to `.despawn_descendants()` with
`.despawn_related::<Children>()`.
* If you have any calls to `.despawn()` which depend on the children
being preserved, you'll need to remove the `Children` component first.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-01-18 22:20:30 +00:00
Sean Kim
294e0db719
Rename track_change_detection flag to track_location (#17075)
# Objective

- As stated in the related issue, this PR is to better align the feature
flag name with what it actually does and the plans for the future.
- Fixes #16852 

## Solution

- Simple find / replace

## Testing

- Local run of `cargo run -p ci`

## Migration Guide

The `track_change_detection` feature flag has been renamed to
`track_location` to better reflect its extended capabilities.
2025-01-01 18:43:47 +00:00
eugineerd
20049d4c34
Faster entity cloning (#16717)
# Objective

#16132 introduced entity cloning functionality, and while it works and
is useful, it can be made faster. This is the promised follow-up to
improve performance.

## Solution

**PREFACE**: This is my first time writing `unsafe` in rust and I have
only vague idea about what I'm doing. I would encourage reviewers to
scrutinize `unsafe` parts in particular.

The solution is to clone component data to an intermediate buffer and
use `EntityWorldMut::insert_by_ids` to insert components without
additional archetype moves.

To facilitate this, `EntityCloner::clone_entity` now reads all
components of the source entity and provides clone handlers with the
ability to read component data straight from component storage using
`read_source_component` and write to an intermediate buffer using
`write_target_component`. `ComponentId` is used to check that requested
type corresponds to the type available on source entity.

Reflect-based handler is a little trickier to pull of: we only have
`&dyn Reflect` and no direct access to the underlying data.
`ReflectFromPtr` can be used to get `&dyn Reflect` from concrete
component data, but to write it we need to create a clone of the
underlying data using `Reflect`. For this reason only components that
have `ReflectDefault` or `ReflectFromReflect` or `ReflectFromWorld` can
be cloned, all other components will be skipped. The good news is that
this is actually only a temporary limitation: once #13432 lands we will
be able to clone component without requiring one of these `type data`s.

This PR also introduces `entity_cloning` benchmark to better compare
changes between the PR and main, you can see the results in the
**showcase** section.

## Testing

- All previous tests passing
- Added test for fast reflect clone path (temporary, will be removed
after reflection-based cloning lands)
- Ran miri

## Showcase
Here's a table demonstrating the improvement:

| **benchmark** | **main, avg** | **PR, avg** | **change, avg** |
| ----------------------- | ------------- | ----------- |
--------------- |
| many components reflect | 18.505 µs | 2.1351 µs | -89.095% |
| hierarchy wide reflect* | 22.778 ms | 4.1875 ms | -81.616% |
| hierarchy tall reflect* | 107.24 µs | 26.322 µs | -77.141% |
| hierarchy many reflect | 78.533 ms | 9.7415 ms | -87.596% |
| many components clone | 1.3633 µs | 758.17 ns | -45.937% |
| hierarchy wide clone* | 2.7716 ms | 3.3411 ms | +20.546% |
| hierarchy tall clone* | 17.646 µs | 20.190 µs | +17.379% |
| hierarchy many clone | 5.8779 ms | 4.2650 ms | -27.439% |

*: these benchmarks have entities with only 1 component

## Considerations
Once #10154 is resolved a large part of the functionality in this PR
will probably become obsolete. It might still be a little bit faster
than using command batching, but the complexity might not be worth it.

## Migration Guide
- `&EntityCloner` in component clone handlers is changed to `&mut
ComponentCloneCtx` to better separate data.
- Changed `EntityCloneHandler` from enum to struct and added convenience
functions to add default clone and reflect handler more easily.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2024-12-18 20:03:39 +00:00
Zachary Harrold
1f2d0e6308
Add no_std support to bevy_ecs (#16758)
# Objective

- Contributes to #15460

## Solution

- Added the following features:
  - `std` (default)
  - `async_executor` (default)
  - `edge_executor`
  - `critical-section`
  - `portable-atomic`
- Gated `tracing` in `bevy_utils` to allow compilation on certain
platforms
- Switched from `tracing` to `log` for simple message logging within
`bevy_ecs`. Note that `tracing` supports capturing from `log` so this
should be an uncontroversial change.
- Fixed imports and added feature gates as required 
- Made `bevy_tasks` optional within `bevy_ecs`. Turns out it's only
needed for parallel operations which are already gated behind
`multi_threaded` anyway.

## Testing

- Added to `compile-check-no-std` CI command
- `cargo check -p bevy_ecs --no-default-features --features
edge_executor,critical-section,portable-atomic --target
thumbv6m-none-eabi`
- `cargo check -p bevy_ecs --no-default-features --features
edge_executor,critical-section`
- `cargo check -p bevy_ecs --no-default-features`

## Draft Release Notes

Bevy's core ECS now supports `no_std` platforms.

In prior versions of Bevy, it was not possible to work with embedded or
niche platforms due to our reliance on the standard library, `std`. This
has blocked a number of novel use-cases for Bevy, such as an embedded
database for IoT devices, or for creating games on retro consoles.

With this release, `bevy_ecs` no longer requires `std`. To use Bevy on a
`no_std` platform, you must disable default features and enable the new
`edge_executor` and `critical-section` features. You may also need to
enable `portable-atomic` and `critical-section` if your platform does
not natively support all atomic types and operations used by Bevy.

```toml
[dependencies]
bevy_ecs = { version = "0.16", default-features = false, features = [
  # Required for platforms with incomplete atomics (e.g., Raspberry Pi Pico)
  "portable-atomic",
  "critical-section",

  # Optional
  "bevy_reflect",
  "serialize",
  "bevy_debug_stepping",
  "edge_executor"
] }
```

Currently, this has been tested on bare-metal x86 and the Raspberry Pi
Pico. If you have trouble using `bevy_ecs` on a particular platform,
please reach out either through a GitHub issue or in the `no_std`
working group on the Bevy Discord server.

Keep an eye out for future `no_std` updates as we continue to improve
the parity between `std` and `no_std`. We look forward to seeing what
kinds of applications are now possible with Bevy!

## Notes

- Creating PR in draft to ensure CI is passing before requesting
reviews.
- This implementation has no support for multithreading in `no_std`,
especially due to `NonSend` being unsound if allowed in multithreading.
The reason is we cannot check the `ThreadId` in `no_std`, so we have no
mechanism to at-runtime determine if access is sound.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Vic <59878206+Victoronz@users.noreply.github.com>
2024-12-17 21:40:36 +00:00
SpecificProtagonist
5f1e114209
Descriptive error message for circular required components recursion (#16648)
# Objective

Fixes #16645

## Solution

Keep track of components in callstack when registering required
components.

## Testing

Added a test checking that the error fires.

---

## Showcase

```rust
#[derive(Component, Default)]
#[require(B)]
struct A;

#[derive(Component, Default)]
#[require(A)]
struct B;
World::new().spawn(A);
```

```
thread 'main' panicked at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/component.rs:415:13:
Recursive required components detected: A → B → A
```

---------

Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2024-12-11 01:26:35 +00:00
Zachary Harrold
a6adced9ed
Deny derive_more error feature and replace it with thiserror (#16684)
# Objective

- Remove `derive_more`'s error derivation and replace it with
`thiserror`

## Solution

- Added `derive_more`'s `error` feature to `deny.toml` to prevent it
sneaking back in.
- Reverted to `thiserror` error derivation

## Notes

Merge conflicts were too numerous to revert the individual changes, so
this reversion was done manually. Please scrutinise carefully during
review.
2024-12-06 17:03:55 +00:00
Zachary Harrold
a35811d088
Add Immutable Component Support (#16372)
# Objective

- Fixes #16208

## Solution

- Added an associated type to `Component`, `Mutability`, which flags
whether a component is mutable, or immutable. If `Mutability= Mutable`,
the component is mutable. If `Mutability= Immutable`, the component is
immutable.
- Updated `derive_component` to default to mutable unless an
`#[component(immutable)]` attribute is added.
- Updated `ReflectComponent` to check if a component is mutable and, if
not, panic when attempting to mutate.

## Testing

- CI
- `immutable_components` example.

---

## Showcase

Users can now mark a component as `#[component(immutable)]` to prevent
safe mutation of a component while it is attached to an entity:

```rust
#[derive(Component)]
#[component(immutable)]
struct Foo {
    // ...
}
```

This prevents creating an exclusive reference to the component while it
is attached to an entity. This is particularly powerful when combined
with component hooks, as you can now fully track a component's value,
ensuring whatever invariants you desire are upheld. Before this would be
done my making a component private, and manually creating a `QueryData`
implementation which only permitted read access.

<details>
  <summary>Using immutable components as an index</summary>
  
```rust
/// This is an example of a component like [`Name`](bevy::prelude::Name), but immutable.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Component)]
#[component(
    immutable,
    on_insert = on_insert_name,
    on_replace = on_replace_name,
)]
pub struct Name(pub &'static str);

/// This index allows for O(1) lookups of an [`Entity`] by its [`Name`].
#[derive(Resource, Default)]
struct NameIndex {
    name_to_entity: HashMap<Name, Entity>,
}

impl NameIndex {
    fn get_entity(&self, name: &'static str) -> Option<Entity> {
        self.name_to_entity.get(&Name(name)).copied()
    }
}

fn on_insert_name(mut world: DeferredWorld<'_>, entity: Entity, _component: ComponentId) {
    let Some(&name) = world.entity(entity).get::<Name>() else {
        unreachable!()
    };
    let Some(mut index) = world.get_resource_mut::<NameIndex>() else {
        return;
    };

    index.name_to_entity.insert(name, entity);
}

fn on_replace_name(mut world: DeferredWorld<'_>, entity: Entity, _component: ComponentId) {
    let Some(&name) = world.entity(entity).get::<Name>() else {
        unreachable!()
    };
    let Some(mut index) = world.get_resource_mut::<NameIndex>() else {
        return;
    };

    index.name_to_entity.remove(&name);
}

// Setup our name index
world.init_resource::<NameIndex>();

// Spawn some entities!
let alyssa = world.spawn(Name("Alyssa")).id();
let javier = world.spawn(Name("Javier")).id();

// Check our index
let index = world.resource::<NameIndex>();

assert_eq!(index.get_entity("Alyssa"), Some(alyssa));
assert_eq!(index.get_entity("Javier"), Some(javier));

// Changing the name of an entity is also fully capture by our index
world.entity_mut(javier).insert(Name("Steven"));

// Javier changed their name to Steven
let steven = javier;

// Check our index
let index = world.resource::<NameIndex>();

assert_eq!(index.get_entity("Javier"), None);
assert_eq!(index.get_entity("Steven"), Some(steven));
```
  
</details>

Additionally, users can use `Component<Mutability = ...>` in trait
bounds to enforce that a component _is_ mutable or _is_ immutable. When
using `Component` as a trait bound without specifying `Mutability`, any
component is applicable. However, methods which only work on mutable or
immutable components are unavailable, since the compiler must be
pessimistic about the type.

## Migration Guide

- When implementing `Component` manually, you must now provide a type
for `Mutability`. The type `Mutable` provides equivalent behaviour to
earlier versions of `Component`:
```rust
impl Component for Foo {
    type Mutability = Mutable;
    // ...
}
```
- When working with generic components, you may need to specify that
your generic parameter implements `Component<Mutability = Mutable>`
rather than `Component` if you require mutable access to said component.
- The entity entry API has had to have some changes made to minimise
friction when working with immutable components. Methods which
previously returned a `Mut<T>` will now typically return an
`OccupiedEntry<T>` instead, requiring you to add an `into_mut()` to get
the `Mut<T>` item again.

## Draft Release Notes

Components can now be made immutable while stored within the ECS.

Components are the fundamental unit of data within an ECS, and Bevy
provides a number of ways to work with them that align with Rust's rules
around ownership and borrowing. One part of this is hooks, which allow
for defining custom behavior at key points in a component's lifecycle,
such as addition and removal. However, there is currently no way to
respond to _mutation_ of a component using hooks. The reasons for this
are quite technical, but to summarize, their addition poses a
significant challenge to Bevy's core promises around performance.
Without mutation hooks, it's relatively trivial to modify a component in
such a way that breaks invariants it intends to uphold. For example, you
can use `core::mem::swap` to swap the components of two entities,
bypassing the insertion and removal hooks.

This means the only way to react to this modification is via change
detection in a system, which then begs the question of what happens
_between_ that alteration and the next run of that system?
Alternatively, you could make your component private to prevent
mutation, but now you need to provide commands and a custom `QueryData`
implementation to allow users to interact with your component at all.

Immutable components solve this problem by preventing the creation of an
exclusive reference to the component entirely. Without an exclusive
reference, the only way to modify an immutable component is via removal
or replacement, which is fully captured by component hooks. To make a
component immutable, simply add `#[component(immutable)]`:

```rust
#[derive(Component)]
#[component(immutable)]
struct Foo {
    // ...
}
```

When implementing `Component` manually, there is an associated type
`Mutability` which controls this behavior:

```rust
impl Component for Foo {
    type Mutability = Mutable;
    // ...
}
```

Note that this means when working with generic components, you may need
to specify that a component is mutable to gain access to certain
methods:

```rust
// Before
fn bar<C: Component>() {
    // ...
}

// After
fn bar<C: Component<Mutability = Mutable>>() {
    // ...
}
```

With this new tool, creating index components, or caching data on an
entity should be more user friendly, allowing libraries to provide APIs
relying on components and hooks to uphold their invariants.

## Notes

- ~~I've done my best to implement this feature, but I'm not happy with
how reflection has turned out. If any reflection SMEs know a way to
improve this situation I'd greatly appreciate it.~~ There is an
outstanding issue around the fallibility of mutable methods on
`ReflectComponent`, but the DX is largely unchanged from `main` now.
- I've attempted to prevent all safe mutable access to a component that
does not implement `Component<Mutability = Mutable>`, but there may
still be some methods I have missed. Please indicate so and I will
address them, as they are bugs.
- Unsafe is an escape hatch I am _not_ attempting to prevent. Whatever
you do with unsafe is between you and your compiler.
- I am marking this PR as ready, but I suspect it will undergo fairly
major revisions based on SME feedback.
- I've marked this PR as _Uncontroversial_ based on the feature, not the
implementation.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Benjamin Brienen <benjamin.brienen@outlook.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
Co-authored-by: Nuutti Kotivuori <naked@iki.fi>
2024-12-05 14:27:48 +00:00