Commit Graph

223 Commits

Author SHA1 Message Date
mgi388
efd17f133d
Rename num_entities to entity_count (#19781)
As discussed in
https://github.com/bevyengine/bevy/pull/19780#issuecomment-2994554024.
2025-06-23 05:08:02 +00:00
Trashtalk217
6dbe3600ed
Add num_entities() to World (#19780)
# Objective

There is a lot of `world.entities().len()`, especially in tests. In
tests, usually, the assumption is made that empty worlds do not contain
any entities. This is about to change (#19711), and as such all of these
tests are failing for that PR.

## Solution

`num_entities` is a convenience method that returns the number of
entities inside a world. It can later be adapted to exclude 'unexpected'
entities, associated with internal data structures such as Resources,
Queries, Systems. In general I argue for a separation of concepts where
`World` ignores internal entities in methods such as `iter_entities()`
and `clear_entities()`, that discussion is, however, separate from this
PR.

## Testing

I replaced most occurrences of `world.entities().len()` with
`world.num_entities()` and the tests passed.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-06-22 22:48:35 +00:00
Joona Aalto
38c3423693
Event Split: Event, EntityEvent, and BufferedEvent (#19647)
# Objective

Closes #19564.

The current `Event` trait looks like this:

```rust
pub trait Event: Send + Sync + 'static {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
    
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}
```

The `Event` trait is used by both buffered events
(`EventReader`/`EventWriter`) and observer events. If they are observer
events, they can optionally be targeted at specific `Entity`s or
`ComponentId`s, and can even be propagated to other entities.

However, there has long been a desire to split the trait semantically
for a variety of reasons, see #14843, #14272, and #16031 for discussion.
Some reasons include:

- It's very uncommon to use a single event type as both a buffered event
and targeted observer event. They are used differently and tend to have
distinct semantics.
- A common footgun is using buffered events with observers or event
readers with observer events, as there is no type-level error that
prevents this kind of misuse.
- #19440 made `Trigger::target` return an `Option<Entity>`. This
*seriously* hurts ergonomics for the general case of entity observers,
as you need to `.unwrap()` each time. If we could statically determine
whether the event is expected to have an entity target, this would be
unnecessary.

There's really two main ways that we can categorize events: push vs.
pull (i.e. "observer event" vs. "buffered event") and global vs.
targeted:

|              | Push            | Pull                        |
| ------------ | --------------- | --------------------------- |
| **Global**   | Global observer | `EventReader`/`EventWriter` |
| **Targeted** | Entity observer | -                           |

There are many ways to approach this, each with their tradeoffs.
Ultimately, we kind of want to split events both ways:

- A type-level distinction between observer events and buffered events,
to prevent people from using the wrong kind of event in APIs
- A statically designated entity target for observer events to avoid
accidentally using untargeted events for targeted APIs

This PR achieves these goals by splitting event traits into `Event`,
`EntityEvent`, and `BufferedEvent`, with `Event` being the shared trait
implemented by all events.

## `Event`, `EntityEvent`, and `BufferedEvent`

`Event` is now a very simple trait shared by all events.

```rust
pub trait Event: Send + Sync + 'static {
    // Required for observer APIs
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}
```

You can call `trigger` for *any* event, and use a global observer for
listening to the event.

```rust
#[derive(Event)]
struct Speak {
    message: String,
}

// ...

app.add_observer(|trigger: On<Speak>| {
    println!("{}", trigger.message);
});

// ...

commands.trigger(Speak {
    message: "Y'all like these reworked events?".to_string(),
});
```

To allow an event to be targeted at entities and even propagated
further, you can additionally implement the `EntityEvent` trait:

```rust
pub trait EntityEvent: Event {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
}
```

This lets you call `trigger_targets`, and to use targeted observer APIs
like `EntityCommands::observe`:

```rust
#[derive(Event, EntityEvent)]
#[entity_event(traversal = &'static ChildOf, auto_propagate)]
struct Damage {
    amount: f32,
}

// ...

let enemy = commands.spawn((Enemy, Health(100.0))).id();

// Spawn some armor as a child of the enemy entity.
// When the armor takes damage, it will bubble the event up to the enemy.
let armor_piece = commands
    .spawn((ArmorPiece, Health(25.0), ChildOf(enemy)))
    .observe(|trigger: On<Damage>, mut query: Query<&mut Health>| {
        // Note: `On::target` only exists because this is an `EntityEvent`.
        let mut health = query.get(trigger.target()).unwrap();
        health.0 -= trigger.amount();
    });

commands.trigger_targets(Damage { amount: 10.0 }, armor_piece);
```

> [!NOTE]
> You *can* still also trigger an `EntityEvent` without targets using
`trigger`. We probably *could* make this an either-or thing, but I'm not
sure that's actually desirable.

To allow an event to be used with the buffered API, you can implement
`BufferedEvent`:

```rust
pub trait BufferedEvent: Event {}
```

The event can then be used with `EventReader`/`EventWriter`:

```rust
#[derive(Event, BufferedEvent)]
struct Message(String);

fn write_hello(mut writer: EventWriter<Message>) {
    writer.write(Message("I hope these examples are alright".to_string()));
}

fn read_messages(mut reader: EventReader<Message>) {
    // Process all buffered events of type `Message`.
    for Message(message) in reader.read() {
        println!("{message}");
    }
}
```

In summary:

- Need a basic event you can trigger and observe? Derive `Event`!
- Need the event to be targeted at an entity? Derive `EntityEvent`!
- Need the event to be buffered and support the
`EventReader`/`EventWriter` API? Derive `BufferedEvent`!

## Alternatives

I'll now cover some of the alternative approaches I have considered and
briefly explored. I made this section collapsible since it ended up
being quite long :P

<details>

<summary>Expand this to see alternatives</summary>

### 1. Unified `Event` Trait

One option is not to have *three* separate traits (`Event`,
`EntityEvent`, `BufferedEvent`), and to instead just use associated
constants on `Event` to determine whether an event supports targeting
and buffering or not:

```rust
pub trait Event: Send + Sync + 'static {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
    const TARGETED: bool = false;
    const BUFFERED: bool = false;
    
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}
```

Methods can then use bounds like `where E: Event<TARGETED = true>` or
`where E: Event<BUFFERED = true>` to limit APIs to specific kinds of
events.

This would keep everything under one `Event` trait, but I don't think
it's necessarily a good idea. It makes APIs harder to read, and docs
can't easily refer to specific types of events. You can also create
weird invariants: what if you specify `TARGETED = false`, but have
`Traversal` and/or `AUTO_PROPAGATE` enabled?

### 2. `Event` and `Trigger`

Another option is to only split the traits between buffered events and
observer events, since that is the main thing people have been asking
for, and they have the largest API difference.

If we did this, I think we would need to make the terms *clearly*
separate. We can't really use `Event` and `BufferedEvent` as the names,
since it would be strange that `BufferedEvent` doesn't implement
`Event`. Something like `ObserverEvent` and `BufferedEvent` could work,
but it'd be more verbose.

For this approach, I would instead keep `Event` for the current
`EventReader`/`EventWriter` API, and call the observer event a
`Trigger`, since the "trigger" terminology is already used in the
observer context within Bevy (both as a noun and a verb). This is also
what a long [bikeshed on
Discord](https://discord.com/channels/691052431525675048/749335865876021248/1298057661878898791)
seemed to land on at the end of last year.

```rust
// For `EventReader`/`EventWriter`
pub trait Event: Send + Sync + 'static {}

// For observers
pub trait Trigger: Send + Sync + 'static {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
    const TARGETED: bool = false;
    
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}
```

The problem is that "event" is just a really good term for something
that "happens". Observers are rapidly becoming the more prominent API,
so it'd be weird to give them the `Trigger` name and leave the good
`Event` name for the less common API.

So, even though a split like this seems neat on the surface, I think it
ultimately wouldn't really work. We want to keep the `Event` name for
observer events, and there is no good alternative for the buffered
variant. (`Message` was suggested, but saying stuff like "sends a
collision message" is weird.)

### 3. `GlobalEvent` + `TargetedEvent`

What if instead of focusing on the buffered vs. observed split, we
*only* make a distinction between global and targeted events?

```rust
// A shared event trait to allow global observers to work
pub trait Event: Send + Sync + 'static {
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}

// For buffered events and non-targeted observer events
pub trait GlobalEvent: Event {}

// For targeted observer events
pub trait TargetedEvent: Event {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
}
```

This is actually the first approach I implemented, and it has the neat
characteristic that you can only use non-targeted APIs like `trigger`
with a `GlobalEvent` and targeted APIs like `trigger_targets` with a
`TargetedEvent`. You have full control over whether the entity should or
should not have a target, as they are fully distinct at the type-level.

However, there's a few problems:

- There is no type-level indication of whether a `GlobalEvent` supports
buffered events or just non-targeted observer events
- An `Event` on its own does literally nothing, it's just a shared trait
required to make global observers accept both non-targeted and targeted
events
- If an event is both a `GlobalEvent` and `TargetedEvent`, global
observers again have ambiguity on whether an event has a target or not,
undermining some of the benefits
- The names are not ideal

### 4. `Event` and `EntityEvent`

We can fix some of the problems of Alternative 3 by accepting that
targeted events can also be used in non-targeted contexts, and simply
having the `Event` and `EntityEvent` traits:

```rust
// For buffered events and non-targeted observer events
pub trait Event: Send + Sync + 'static {
    fn register_component_id(world: &mut World) -> ComponentId { ... }
    fn component_id(world: &World) -> Option<ComponentId> { ... }
}

// For targeted observer events
pub trait EntityEvent: Event {
    type Traversal: Traversal<Self>;
    const AUTO_PROPAGATE: bool = false;
}
```

This is essentially identical to this PR, just without a dedicated
`BufferedEvent`. The remaining major "problem" is that there is still
zero type-level indication of whether an `Event` event *actually*
supports the buffered API. This leads us to the solution proposed in
this PR, using `Event`, `EntityEvent`, and `BufferedEvent`.

</details>

## Conclusion

The `Event` + `EntityEvent` + `BufferedEvent` split proposed in this PR
aims to solve all the common problems with Bevy's current event model
while keeping the "weirdness" factor minimal. It splits in terms of both
the push vs. pull *and* global vs. targeted aspects, while maintaining a
shared concept for an "event".

### Why I Like This

- The term "event" remains as a single concept for all the different
kinds of events in Bevy.
- Despite all event types being "events", they use fundamentally
different APIs. Instead of assuming that you can use an event type with
any pattern (when only one is typically supported), you explicitly opt
in to each one with dedicated traits.
- Using separate traits for each type of event helps with documentation
and clearer function signatures.
- I can safely make assumptions on expected usage.
- If I see that an event is an `EntityEvent`, I can assume that I can
use `observe` on it and get targeted events.
- If I see that an event is a `BufferedEvent`, I can assume that I can
use `EventReader` to read events.
- If I see both `EntityEvent` and `BufferedEvent`, I can assume that
both APIs are supported.

In summary: This allows for a unified concept for events, while limiting
the different ways to use them with opt-in traits. No more guess-work
involved when using APIs.

### Problems?

- Because `BufferedEvent` implements `Event` (for more consistent
semantics etc.), you can still use all buffered events for non-targeted
observers. I think this is fine/good. The important part is that if you
see that an event implements `BufferedEvent`, you know that the
`EventReader`/`EventWriter` API should be supported. Whether it *also*
supports other APIs is secondary.
- I currently only support `trigger_targets` for an `EntityEvent`.
However, you can technically target components too, without targeting
any entities. I consider that such a niche and advanced use case that
it's not a huge problem to only support it for `EntityEvent`s, but we
could also split `trigger_targets` into `trigger_entities` and
`trigger_components` if we wanted to (or implement components as
entities :P).
- You can still trigger an `EntityEvent` *without* targets. I consider
this correct, since `Event` implements the non-targeted behavior, and
it'd be weird if implementing another trait *removed* behavior. However,
it does mean that global observers for entity events can technically
return `Entity::PLACEHOLDER` again (since I got rid of the
`Option<Entity>` added in #19440 for ergonomics). I think that's enough
of an edge case that it's not a huge problem, but it is worth keeping in
mind.
- ~~Deriving both `EntityEvent` and `BufferedEvent` for the same type
currently duplicates the `Event` implementation, so you instead need to
manually implement one of them.~~ Changed to always requiring `Event` to
be derived.

## Related Work

There are plans to implement multi-event support for observers,
especially for UI contexts. [Cart's
example](https://github.com/bevyengine/bevy/issues/14649#issuecomment-2960402508)
API looked like this:

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

I believe this shouldn't be in conflict with this PR. If anything, this
PR might *help* achieve the multi-event pattern for entity observers
with fewer footguns: by statically enforcing that all of these events
are `EntityEvent`s in the context of `EntityCommands::observe`, we can
avoid misuse or weird cases where *some* events inside the trigger are
targeted while others are not.
2025-06-15 16:46:34 +00:00
Alice Cecile
58c276ab44
Make the ObservedBy component useful to public consumers (#19591)
# Objective

As raised by @Jondolf, this type is `pub`, and useful for various
consumers to ensure cleanup or debugging.

However, it doesn't offer any way to actually view the data.

## Solution

- Add a read-only view of the data.
- Don't add any (easy) way to mutate the data, as this presents a huge
footgun.
- Implement Reflect and register the component so you can see it in
inspectors nicely.
2025-06-12 20:07:11 +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
theotherphil
54c9f03021
Mention in .add_observer() docs that first parameter must be a Trigger (#19315)
# Objective

Fix https://github.com/bevyengine/bevy/issues/13860

## Solution

Add note in docs that Trigger must be the first parameter of observer
systems
2025-05-26 20:06:08 +00:00
SpecificProtagonist
e7e9973c80
Per world error handler (#18810)
# Objective

[see original
comment](https://github.com/bevyengine/bevy/pull/18801#issuecomment-2796981745)
> Alternately, could we store it on the World instead of a global? I
think we have a World nearby whenever we call default_error_handler().
That would avoid the need for atomics or locks, since we could do
ordinary reads and writes to the World.

Global error handlers don't actually need to be global – per world is
enough. This allows using different handlers for different worlds and
also removes the restrictions on changing the handler only once.

## Solution

Each `World` can now store its own error handler in a resource.

For convenience, you can also set the default error handler for an
`App`, which applies it to the worlds of all `SubApp`s. The old behavior
of only being able to set the error handler once is kept for apps.

We also don't need the `configurable_error_handler` feature anymore now.

## Testing

New/adjusted tests for failing schedule systems & observers.

---

## Showcase

```rust
App::new()
    .set_error_handler(info)
    …
```
2025-05-19 01:35:07 +00:00
Joona Aalto
7b1c9f192e
Adopt consistent FooSystems naming convention for system sets (#18900)
# Objective

Fixes a part of #14274.

Bevy has an incredibly inconsistent naming convention for its system
sets, both internally and across the ecosystem.

<img alt="System sets in Bevy"
src="https://github.com/user-attachments/assets/d16e2027-793f-4ba4-9cc9-e780b14a5a1b"
width="450" />

*Names of public system set types in Bevy*

Most Bevy types use a naming of `FooSystem` or just `Foo`, but there are
also a few `FooSystems` and `FooSet` types. In ecosystem crates on the
other hand, `FooSet` is perhaps the most commonly used name in general.
Conventions being so wildly inconsistent can make it harder for users to
pick names for their own types, to search for system sets on docs.rs, or
to even discern which types *are* system sets.

To reign in the inconsistency a bit and help unify the ecosystem, it
would be good to establish a common recommended naming convention for
system sets in Bevy itself, similar to how plugins are commonly suffixed
with `Plugin` (ex: `TimePlugin`). By adopting a consistent naming
convention in first-party Bevy, we can softly nudge ecosystem crates to
follow suit (for types where it makes sense to do so).

Choosing a naming convention is also relevant now, as the [`bevy_cli`
recently adopted
lints](https://github.com/TheBevyFlock/bevy_cli/pull/345) to enforce
naming for plugins and system sets, and the recommended naming used for
system sets is still a bit open.

## Which Name To Use?

Now the contentious part: what naming convention should we actually
adopt?

This was discussed on the Bevy Discord at the end of last year, starting
[here](<https://discord.com/channels/691052431525675048/692572690833473578/1310659954683936789>).
`FooSet` and `FooSystems` were the clear favorites, with `FooSet` very
narrowly winning an unofficial poll. However, it seems to me like the
consensus was broadly moving towards `FooSystems` at the end and after
the poll, with Cart
([source](https://discord.com/channels/691052431525675048/692572690833473578/1311140204974706708))
and later Alice
([source](https://discord.com/channels/691052431525675048/692572690833473578/1311092530732859533))
and also me being in favor of it.

Let's do a quick pros and cons list! Of course these are just what I
thought of, so take it with a grain of salt.

`FooSet`:

- Pro: Nice and short!
- Pro: Used by many ecosystem crates.
- Pro: The `Set` suffix comes directly from the trait name `SystemSet`.
- Pro: Pairs nicely with existing APIs like `in_set` and
`configure_sets`.
- Con: `Set` by itself doesn't actually indicate that it's related to
systems *at all*, apart from the implemented trait. A set of what?
- Con: Is `FooSet` a set of `Foo`s or a system set related to `Foo`? Ex:
`ContactSet`, `MeshSet`, `EnemySet`...

`FooSystems`:

- Pro: Very clearly indicates that the type represents a collection of
systems. The actual core concept, system(s), is in the name.
- Pro: Parallels nicely with `FooPlugins` for plugin groups.
- Pro: Low risk of conflicts with other names or misunderstandings about
what the type is.
- Pro: In most cases, reads *very* nicely and clearly. Ex:
`PhysicsSystems` and `AnimationSystems` as opposed to `PhysicsSet` and
`AnimationSet`.
- Pro: Easy to search for on docs.rs.
- Con: Usually results in longer names.
- Con: Not yet as widely used.

Really the big problem with `FooSet` is that it doesn't actually
describe what it is. It describes what *kind of thing* it is (a set of
something), but not *what it is a set of*, unless you know the type or
check its docs or implemented traits. `FooSystems` on the other hand is
much more self-descriptive in this regard, at the cost of being a bit
longer to type.

Ultimately, in some ways it comes down to preference and how you think
of system sets. Personally, I was originally in favor of `FooSet`, but
have been increasingly on the side of `FooSystems`, especially after
seeing what the new names would actually look like in Avian and now
Bevy. I prefer it because it usually reads better, is much more clearly
related to groups of systems than `FooSet`, and overall *feels* more
correct and natural to me in the long term.

For these reasons, and because Alice and Cart also seemed to share a
preference for it when it was previously being discussed, I propose that
we adopt a `FooSystems` naming convention where applicable.

## Solution

Rename Bevy's system set types to use a consistent `FooSet` naming where
applicable.

- `AccessibilitySystem` → `AccessibilitySystems`
- `GizmoRenderSystem` → `GizmoRenderSystems`
- `PickSet` → `PickingSystems`
- `RunFixedMainLoopSystem` → `RunFixedMainLoopSystems`
- `TransformSystem` → `TransformSystems`
- `RemoteSet` → `RemoteSystems`
- `RenderSet` → `RenderSystems`
- `SpriteSystem` → `SpriteSystems`
- `StateTransitionSteps` → `StateTransitionSystems`
- `RenderUiSystem` → `RenderUiSystems`
- `UiSystem` → `UiSystems`
- `Animation` → `AnimationSystems`
- `AssetEvents` → `AssetEventSystems`
- `TrackAssets` → `AssetTrackingSystems`
- `UpdateGizmoMeshes` → `GizmoMeshSystems`
- `InputSystem` → `InputSystems`
- `InputFocusSet` → `InputFocusSystems`
- `ExtractMaterialsSet` → `MaterialExtractionSystems`
- `ExtractMeshesSet` → `MeshExtractionSystems`
- `RumbleSystem` → `RumbleSystems`
- `CameraUpdateSystem` → `CameraUpdateSystems`
- `ExtractAssetsSet` → `AssetExtractionSystems`
- `Update2dText` → `Text2dUpdateSystems`
- `TimeSystem` → `TimeSystems`
- `AudioPlaySet` → `AudioPlaybackSystems`
- `SendEvents` → `EventSenderSystems`
- `EventUpdates` → `EventUpdateSystems`

A lot of the names got slightly longer, but they are also a lot more
consistent, and in my opinion the majority of them read much better. For
a few of the names I took the liberty of rewording things a bit;
definitely open to any further naming improvements.

There are still also cases where the `FooSystems` naming doesn't really
make sense, and those I left alone. This primarily includes system sets
like `Interned<dyn SystemSet>`, `EnterSchedules<S>`, `ExitSchedules<S>`,
or `TransitionSchedules<S>`, where the type has some special purpose and
semantics.

## Todo

- [x] Should I keep all the old names as deprecated type aliases? I can
do this, but to avoid wasting work I'd prefer to first reach consensus
on whether these renames are even desired.
- [x] Migration guide
- [x] Release notes
2025-05-06 15:18:03 +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
Alice Cecile
5d0505a85e
Unify and simplify command and system error handling (#18351)
# Objective

- ECS error handling is a lovely flagship feature for Bevy 0.16, all in
the name of reducing panics and encouraging better error handling
(#14275).
- Currently though, command and system error handling are completely
disjoint and use different mechanisms.
- Additionally, there's a number of distinct ways to set the
default/fallback/global error handler that have limited value. As far as
I can tell, this will be cfg flagged to toggle between dev and
production builds in 99.9% of cases, with no real value in more granular
settings or helpers.
- Fixes #17272

## Solution

- Standardize error handling on the OnceLock global error mechanisms
ironed out in https://github.com/bevyengine/bevy/pull/17215
- As discussed there, there are serious performance concerns there,
especially for commands
- I also think this is a better fit for the use cases, as it's truly
global
- Move from `SystemErrorContext` to a more general purpose
`ErrorContext`, which can handle observers and commands more clearly
- Cut the superfluous setter methods on `App` and `SubApp`
- Rename the limited (and unhelpful) `fallible_systems` example to
`error_handling`, and add an example of command error handling

## Testing

Ran the `error_handling` example.

## Notes for reviewers

- Do you see a clear way to allow commands to retain &mut World access
in the per-command custom error handlers? IMO that's a key feature here
(allowing the ad-hoc creation of custom commands), but I'm not sure how
to get there without exploding complexity.
- I've removed the feature gate on the default_error_handler: contrary
to @cart's opinion in #17215 I think that virtually all apps will want
to use this. Can you think of a category of app that a) is extremely
performance sensitive b) is fine with shipping to production with the
panic error handler? If so, I can try to gather performance numbers
and/or reintroduce the feature flag. UPDATE: see benches at the end of
this message.
- ~~`OnceLock` is in `std`: @bushrat011899 what should we do here?~~
- Do you have ideas for more automated tests for this collection of
features?

## Benchmarks

I checked the impact of the feature flag introduced: benchmarks might
show regressions. This bears more investigation. I'm still skeptical
that there are users who are well-served by a fast always panicking
approach, but I'm going to re-add the feature flag here to avoid
stalling this out.


![image](https://github.com/user-attachments/assets/237f644a-b36d-4332-9b45-76fd5cbff4d0)

---------

Co-authored-by: Zachary Harrold <zac@harrold.com.au>
2025-03-18 19:27:50 +00:00
Alice Cecile
ab0e3f8714
Small cleanup for ECS error handling (#18280)
# Objective

While poking at https://github.com/bevyengine/bevy/issues/17272, I
noticed a few small things to clean up.

## Solution

- Improve the docs
- ~~move `SystemErrorContext` out of the `handler.rs` module: it's not
an error handler~~
2025-03-13 00:13:02 +00:00
newclarityex
ecccd57417
Generic system config (#17962)
# Objective
Prevents duplicate implementation between IntoSystemConfigs and
IntoSystemSetConfigs using a generic, adds a NodeType trait for more
config flexibility (opening the door to implement
https://github.com/bevyengine/bevy/issues/14195?).

## Solution
Followed writeup by @ItsDoot:
https://hackmd.io/@doot/rJeefFHc1x

Removes IntoSystemConfigs and IntoSystemSetConfigs, instead using
IntoNodeConfigs with generics.

## Testing
Pending

---

## Showcase
N/A

## Migration Guide
SystemSetConfigs -> NodeConfigs<InternedSystemSet>
SystemConfigs -> NodeConfigs<ScheduleSystem>
IntoSystemSetConfigs -> IntoNodeConfigs<InternedSystemSet, M>
IntoSystemConfigs -> IntoNodeConfigs<ScheduleSystem, M>

---------

Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-03-12 00:12:30 +00:00
Zachary Harrold
c6204279eb
Support for non-browser wasm (#17499)
# Objective

- Contributes to #15460
- Supersedes #8520
- Fixes #4906

## Solution

- Added a new `web` feature to `bevy`, and several of its crates.
- Enabled new `web` feature automatically within crates without `no_std`
support.

## Testing

- `cargo build --no-default-features --target wasm32v1-none`

---

## Migration Guide

When using Bevy crates which _don't_ automatically enable the `web`
feature, please enable it when building for the browser.

## Notes

- I added [`cfg_if`](https://crates.io/crates/cfg-if) to help manage
some of the feature gate gore that this extra feature introduces. It's
still pretty ugly, but I think much easier to read.
- Certain `wasm` targets (e.g.,
[wasm32-wasip1](https://doc.rust-lang.org/nightly/rustc/platform-support/wasm32-wasip1.html#wasm32-wasip1))
provide an incomplete implementation for `std`. I have not tested these
platforms, but I suspect Bevy's liberal use of usually unsupported
features (e.g., threading) will cause these targets to fail. As such,
consider `wasm32-unknown-unknown` as the only `wasm` platform with
support from Bevy for `std`. All others likely will need to be treated
as `no_std` platforms.
2025-03-07 21:22:28 +00:00
Zachary Harrold
cc69fdd0c6
Add no_std support to bevy (#17955)
# Objective

- Fixes #15460 (will open new issues for further `no_std` efforts)
- Supersedes #17715

## Solution

- Threaded in new features as required
- Made certain crates optional but default enabled
- Removed `compile-check-no-std` from internal `ci` tool since GitHub CI
can now simply check `bevy` itself now
- Added CI task to check `bevy` on `thumbv6m-none-eabi` to ensure
`portable-atomic` support is still valid [^1]

[^1]: This may be controversial, since it could be interpreted as
implying Bevy will maintain support for `thumbv6m-none-eabi` going
forward. In reality, just like `x86_64-unknown-none`, this is a
[canary](https://en.wiktionary.org/wiki/canary_in_a_coal_mine) target to
make it clear when `portable-atomic` no longer works as intended (fixing
atomic support on atomically challenged platforms). If a PR comes
through and makes supporting this class of platforms impossible, then
this CI task can be removed. I however wager this won't be a problem.

## Testing

- CI

---

## Release Notes

Bevy now has support for `no_std` directly from the `bevy` crate.

Users can disable default features and enable a new `default_no_std`
feature instead, allowing `bevy` to be used in `no_std` applications and
libraries.

```toml
# Bevy for `no_std` platforms
bevy = { version = "0.16", default-features = false, features = ["default_no_std"] }
```

`default_no_std` enables certain required features, such as `libm` and
`critical-section`, and as many optional crates as possible (currently
just `bevy_state`). For atomically-challenged platforms such as the
Raspberry Pi Pico, `portable-atomic` will be used automatically.

For library authors, we recommend depending on `bevy` with
`default-features = false` to allow `std` and `no_std` users to both
depend on your crate. Here are some recommended features a library crate
may want to expose:

```toml
[features]
# Most users will be on a platform which has `std` and can use the more-powerful `async_executor`.
default = ["std", "async_executor"]

# Features for typical platforms.
std = ["bevy/std"]
async_executor = ["bevy/async_executor"]

# Features for `no_std` platforms.
libm = ["bevy/libm"]
critical-section = ["bevy/critical-section"]

[dependencies]
# We disable default features to ensure we don't accidentally enable `std` on `no_std` targets, for example. 
bevy = { version = "0.16", default-features = false }
```

While this is verbose, it gives the maximum control to end-users to
decide how they wish to use Bevy on their platform.

We encourage library authors to experiment with `no_std` support. For
libraries relying exclusively on `bevy` and no other dependencies, it
may be as simple as adding `#![no_std]` to your `lib.rs` and exposing
features as above! Bevy can also provide many `std` types, such as
`HashMap`, `Mutex`, and `Instant` on all platforms. See
`bevy::platform_support` for details on what's available out of the box!

## Migration Guide

- If you were previously relying on `bevy` with default features
disabled, you may need to enable the `std` and `async_executor`
features.
- `bevy_reflect` has had its `bevy` feature removed. If you were relying
on this feature, simply enable `smallvec` and `smol_str` instead.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-03-07 03:39:46 +00:00
Carter Anderson
cca5813472
BevyError: Bevy's new catch-all error type (#18144)
## Objective

Fixes #18092

Bevy's current error type is a simple type alias for `Box<dyn Error +
Send + Sync + 'static>`. This largely works as a catch-all error, but it
is missing a critical feature: the ability to capture a backtrace at the
point that the error occurs. The best way to do this is `anyhow`-style
error handling: a new error type that takes advantage of the fact that
the `?` `From` conversion happens "inline" to capture the backtrace at
the point of the error.

## Solution

This PR adds a new `BevyError` type (replacing our old
`std::error::Error` type alias), which uses the "from conversion
backtrace capture" approach:

```rust
fn oh_no() -> Result<(), BevyError> {
    // this fails with Rust's built in ParseIntError, which
    // is converted into the catch-all BevyError type
    let number: usize = "hi".parse()?;
    println!("parsed {number}");
    Ok(())
}
```

This also updates our exported `Result` type alias to default to
`BevyError`, meaning you can write this instead:

```rust
fn oh_no() -> Result {
    let number: usize = "hi".parse()?;
    println!("parsed {number}");
    Ok(())
}
```

When a BevyError is encountered in a system, it will use Bevy's default
system error handler (which panics by default). BevyError does custom
"backtrace filtering" by default, meaning we can cut out the _massive_
amount of "rust internals", "async executor internals", and "bevy system
scheduler internals" that show up in backtraces. It also trims out the
first generally-unnecssary `From` conversion backtrace lines that make
it harder to locate the real error location. The result is a blissfully
simple backtrace by default:


![image](https://github.com/user-attachments/assets/7a5f5c9b-ea70-4176-af3b-d231da31c967)

The full backtrace can be shown by setting the `BEVY_BACKTRACE=full`
environment variable. Non-BevyError panics still use the default Rust
backtrace behavior.

One issue that prevented the truly noise-free backtrace during panics
that you see above is that Rust's default panic handler will print the
unfiltered (and largely unhelpful real-panic-point) backtrace by
default, in _addition_ to our filtered BevyError backtrace (with the
helpful backtrace origin) that we capture and print. To resolve this, I
have extended Bevy's existing PanicHandlerPlugin to wrap the default
panic handler. If we panic from the result of a BevyError, we will skip
the default "print full backtrace" panic handler. This behavior can be
enabled and disabled using the new `error_panic_hook` cargo feature in
`bevy_app` (which is enabled by default).

One downside to _not_ using `Box<dyn Error>` directly is that we can no
longer take advantage of the built-in `Into` impl for strings to errors.
To resolve this, I have added the following:

```rust
// Before
Err("some error")?

// After
Err(BevyError::message("some error"))?
```

We can discuss adding shorthand methods or macros for this (similar to
anyhow's `anyhow!("some error")` macro), but I'd prefer to discuss that
later.

I have also added the following extension method:

```rust
// Before
some_option.ok_or("some error")?;

// After
some_option.ok_or_message("some error")?;
```

I've also moved all of our existing error infrastructure from
`bevy_ecs::result` to `bevy_ecs::error`, as I think that is the better
home for it

## Why not anyhow (or eyre)?

The biggest reason is that `anyhow` needs to be a "generically useful
error type", whereas Bevy is a much narrower scope. By using our own
error, we can be significantly more opinionated. For example, anyhow
doesn't do the extensive (and invasive) backtrace filtering that
BevyError does because it can't operate on Bevy-specific context, and
needs to be generically useful.

Bevy also has a lot of operational context (ex: system info) that could
be useful to attach to errors. If we have control over the error type,
we can add whatever context we want to in a structured way. This could
be increasingly useful as we add more visual / interactive error
handling tools and editor integrations.

Additionally, the core approach used is simple and requires almost no
code. anyhow clocks in at ~2500 lines of code, but the impl here uses
160. We are able to boil this down to exactly what we need, and by doing
so we improve our compile times and the understandability of our code.
2025-03-07 01:50:07 +00:00
Zachary Harrold
5241e09671
Upgrade to Rust Edition 2024 (#17967)
# Objective

- Fixes #17960

## Solution

- Followed the [edition upgrade
guide](https://doc.rust-lang.org/edition-guide/editions/transitioning-an-existing-project-to-a-new-edition.html)

## Testing

- CI

---

## Summary of Changes

### Documentation Indentation

When using lists in documentation, proper indentation is now linted for.
This means subsequent lines within the same list item must start at the
same indentation level as the item.

```rust
/* Valid */
/// - Item 1
///   Run-on sentence.
/// - Item 2
struct Foo;

/* Invalid */
/// - Item 1
///     Run-on sentence.
/// - Item 2
struct Foo;
```

### Implicit `!` to `()` Conversion

`!` (the never return type, returned by `panic!`, etc.) no longer
implicitly converts to `()`. This is particularly painful for systems
with `todo!` or `panic!` statements, as they will no longer be functions
returning `()` (or `Result<()>`), making them invalid systems for
functions like `add_systems`. The ideal fix would be to accept functions
returning `!` (or rather, _not_ returning), but this is blocked on the
[stabilisation of the `!` type
itself](https://doc.rust-lang.org/std/primitive.never.html), which is
not done.

The "simple" fix would be to add an explicit `-> ()` to system
signatures (e.g., `|| { todo!() }` becomes `|| -> () { todo!() }`).
However, this is _also_ banned, as there is an existing lint which (IMO,
incorrectly) marks this as an unnecessary annotation.

So, the "fix" (read: workaround) is to put these kinds of `|| -> ! { ...
}` closuers into variables and give the variable an explicit type (e.g.,
`fn()`).

```rust
// Valid
let system: fn() = || todo!("Not implemented yet!");
app.add_systems(..., system);

// Invalid
app.add_systems(..., || todo!("Not implemented yet!"));
```

### Temporary Variable Lifetimes

The order in which temporary variables are dropped has changed. The
simple fix here is _usually_ to just assign temporaries to a named
variable before use.

### `gen` is a keyword

We can no longer use the name `gen` as it is reserved for a future
generator syntax. This involved replacing uses of the name `gen` with
`r#gen` (the raw-identifier syntax).

### Formatting has changed

Use statements have had the order of imports changed, causing a
substantial +/-3,000 diff when applied. For now, I have opted-out of
this change by amending `rustfmt.toml`

```toml
style_edition = "2021"
```

This preserves the original formatting for now, reducing the size of
this PR. It would be a simple followup to update this to 2024 and run
`cargo fmt`.

### New `use<>` Opt-Out Syntax

Lifetimes are now implicitly included in RPIT types. There was a handful
of instances where it needed to be added to satisfy the borrow checker,
but there may be more cases where it _should_ be added to avoid
breakages in user code.

### `MyUnitStruct { .. }` is an invalid pattern

Previously, you could match against unit structs (and unit enum
variants) with a `{ .. }` destructuring. This is no longer valid.

### Pretty much every use of `ref` and `mut` are gone

Pattern binding has changed to the point where these terms are largely
unused now. They still serve a purpose, but it is far more niche now.

### `iter::repeat(...).take(...)` is bad

New lint recommends using the more explicit `iter::repeat_n(..., ...)`
instead.

## Migration Guide

The lifetimes of functions using return-position impl-trait (RPIT) are
likely _more_ conservative than they had been previously. If you
encounter lifetime issues with such a function, please create an issue
to investigate the addition of `+ use<...>`.

## Notes

- Check the individual commits for a clearer breakdown for what
_actually_ changed.

---------

Co-authored-by: François Mockers <francois.mockers@vleue.com>
2025-02-24 03:54:47 +00:00
AlephCubed
5f86668bbb
Renamed EventWriter::send methods to write. (#17977)
Fixes #17856.

## Migration Guide
- `EventWriter::send` has been renamed to `EventWriter::write`.
- `EventWriter::send_batch` has been renamed to
`EventWriter::write_batch`.
- `EventWriter::send_default` has been renamed to
`EventWriter::write_default`.

---------

Co-authored-by: François Mockers <mockersf@gmail.com>
2025-02-23 21:18:52 +00:00
Zachary Harrold
6bcb2b633b
Remove unused #[must_used] (#17959)
# Objective

- Fixed CI compilation failure on Rust Nightly 1.87 due to [this
PR](https://github.com/rust-lang/rust/pull/136923)

## Solution

- Removed unused `#[must_use]`

## Testing

- cargo +nightly check --target wasm32-unknown-unknown -Z
build-std=std,panic_abort
2025-02-21 05:39:16 +00:00
Jean Mertz
fd67ca7eb0
feat(ecs): configurable error handling for fallible systems (#17753)
You can now configure error handlers for fallible systems. These can be
configured on several levels:

- Globally via `App::set_systems_error_handler`
- Per-schedule via `Schedule::set_error_handler`
- Per-system via a piped system (this is existing functionality)

The default handler of panicking on error keeps the same behavior as
before this commit.

The "fallible_systems" example demonstrates the new functionality.

This builds on top of #17731, #16589, #17051.

---------

Signed-off-by: Jean Mertz <git@jeanmertz.com>
2025-02-11 18:36:08 +00:00
Alice Cecile
fcc77fe3d6
Allow users to register their own disabling components / default query filters (#17768)
# Objective

Currently, default query filters, as added in #13120 / #17514 are
hardcoded to only use a single query filter.

This is limiting, as multiple distinct disabling components can serve
important distinct roles. I ran into this limitation when experimenting
with a workflow for prefabs, which don't represent the same state as "an
entity which is temporarily nonfunctional".

## Solution

1. Change `DefaultQueryFilters` to store a SmallVec of ComponentId,
rather than an Option.
2. Expose methods on `DefaultQueryFilters`, `World` and `App` to
actually configure this.
3. While we're here, improve the docs, write some tests, make use of
FromWorld and make some method names more descriptive.

## Follow-up

I'm not convinced that supporting sparse set disabling components is
useful, given the hit to iteration performance and runtime checks
incurred. That's disjoint from this PR though, so I'm not doing it here.
The existing warnings are fine for now.

## Testing

I've added both a doc test and an mid-level unit test to verify that
this works!
2025-02-11 18:25:32 +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
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
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
Carter Anderson
ba5e71f53d
Parent -> ChildOf (#17427)
Fixes #17412

## Objective

`Parent` uses the "has a X" naming convention. There is increasing
sentiment that we should use the "is a X" naming convention for
relationships (following #17398). This leaves `Children` as-is because
there is prevailing sentiment that `Children` is clearer than `ParentOf`
in many cases (especially when treating it like a collection).

This renames `Parent` to `ChildOf`.

This is just the implementation PR. To discuss the path forward, do so
in #17412.

## Migration Guide

- The `Parent` component has been renamed to `ChildOf`.
2025-01-20 22:13:29 +00:00
SpecificProtagonist
a7051a4815
Diagnostics for label traits (#17441)
# Objective

Diagnostics for labels don't suggest how to best implement them.
```
error[E0277]: the trait bound `Label: ScheduleLabel` is not satisfied
   --> src/main.rs:15:35
    |
15  |     let mut sched = Schedule::new(Label);
    |                     ------------- ^^^^^ the trait `ScheduleLabel` is not implemented for `Label`
    |                     |
    |                     required by a bound introduced by this call
    |
    = help: the trait `ScheduleLabel` is implemented for `Interned<(dyn ScheduleLabel + 'static)>`
note: required by a bound in `bevy_ecs::schedule::Schedule::new`
   --> /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/schedule/schedule.rs:297:28
    |
297 |     pub fn new(label: impl ScheduleLabel) -> Self {
    |                            ^^^^^^^^^^^^^ required by this bound in `Schedule::new`
```

## Solution

`diagnostics::on_unimplemented` and `diagnostics::do_not_recommend`

## Showcase

New error message:
```
error[E0277]: the trait bound `Label: ScheduleLabel` is not satisfied
   --> src/main.rs:15:35
    |
15  |     let mut sched = Schedule::new(Label);
    |                     ------------- ^^^^^ the trait `ScheduleLabel` is not implemented for `Label`
    |                     |
    |                     required by a bound introduced by this call
    |
    = note: consider annotating `Label` with `#[derive(ScheduleLabel)]`
note: required by a bound in `bevy_ecs::schedule::Schedule::new`
   --> /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/schedule/schedule.rs:297:28
    |
297 |     pub fn new(label: impl ScheduleLabel) -> Self {
    |                            ^^^^^^^^^^^^^ required by this bound in `Schedule::new`
```
2025-01-20 21:51:26 +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
Rob Parrett
b77e3ef33a
Fix a few typos (#17292)
# Objective

Stumbled upon a `from <-> form` transposition while reviewing a PR,
thought it was interesting, and went down a bit of a rabbit hole.

## Solution

Fix em
2025-01-10 22:48:30 +00:00
Zachary Harrold
d60764908c
Update downcast-rs to version 2 (#17223)
# Objective & Solution

- Update `downcast-rs` to the latest version, 2.
- Disable (new) `sync` feature to improve compatibility with atomically
challenged platforms.
- Remove stub `downcast-rs` alternative code from `bevy_app`

## Testing

- CI

## Notes

The only change from version 1 to version 2 is the addition of a new
`sync` feature, which allows disabling the `DowncastSync` parts of
`downcast-rs`, which require access to `alloc::sync::Arc`, which is not
available on atomically challenged platforms. Since Bevy makes no use of
the functionality provided by the `sync` feature, I've disabled it in
all crates. Further details can be found
[here](https://github.com/marcianx/downcast-rs/pull/22).
2025-01-07 21:33:40 +00:00
MichiRecRoom
4a681c3f05
Expose access to SubApps within App (#16952)
# Objective
`SubApps` is visible within the documentation for `bevy_app`. However,
no way of accessing the `SubApps` field in `App` is currently available.

## Solution
Expose two new functions, `App::sub_apps()` and `App::sub_apps_mut()`,
which give immutable and mutable access to `SubApps` respectively.

The other solution is to hide `SubApps`, which I submitted as a PR at
<https://github.com/bevyengine/bevy/pull/16953>.

## Testing
Because of the simplicity of the changes, I only tested by compiling
`bevy_app` - which compiled successfully.

Note: `SubApps`, and its corresponding field on `App`, are not used
outside of `bevy_app` - which means that compiling the other crates is
not necessary.
2024-12-24 06:15:16 +00:00
Zachary Harrold
21786632c3
Remove bevy_core (#16897)
# Objective

- Fixes #16892

## Solution

- Removed `TypeRegistryPlugin` (`Name` is now automatically registered
with a default `App`)
- Moved `TaskPoolPlugin` to `bevy_app`
- Moved `FrameCountPlugin` to `bevy_diagnostic`
- Deleted now-empty `bevy_core`

## Testing

- CI

## Migration Guide

- `TypeRegistryPlugin` no longer exists. If you can't use a default
`App` but still need `Name` registered, do so manually with
`app.register_type::<Name>()`.
- References to `TaskPoolPlugin` and associated types will need to
import it from `bevy_app` instead of `bevy_core`
- References to `FrameCountPlugin` and associated types will need to
import it from `bevy_diagnostic` instead of `bevy_core`

## Notes

This strategy was agreed upon by Cart and several other members in
[Discord](https://discord.com/channels/691052431525675048/692572690833473578/1319137218312278077).
2024-12-19 18:36:51 +00:00
Zachary Harrold
f45e78e658
Add no_std support to bevy_app (#16874)
# Objective

- Contributes to #15460

## Solution

- Added the following features:
  - `std` (default)
  - `bevy_tasks` (default)
  - `downcast ` (default)
  - `portable-atomic`
  - `critical-section`
- `downcast` and `bevy_tasks` are now optional dependencies for
`bevy_app`.

## Testing

- CI
- Personal UEFI and Raspberry Pi Pico demo applications compile and run
against this branch

## Draft Release Notes

Bevy's application framework now supports `no_std` platforms.

Following up on `bevy_ecs` gaining `no_std` support, `bevy_app` extends
the functionality available on these targets to include the powerful
`App` and `Plugin` abstractions. With this, library authors now have the
option of making their plugins `no_std` compatible, or even offering
plugins specifically to improve Bevy on certain embedded platforms!

To start making a `no_std` compatible plugin, simply disable default
features when including `bevy_app`:

```toml
[dependencies]
bevy_app = { version = "0.16", default-features = false }
```

We encourage library authors to do this anyway, as it can also help with
compile times and binary size on all platforms.

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

- `downcast-rs` is optional as it isn't compatible with
`portable-atomic`. I will investigate making a PR upstream to add
support for this functionality, as it should be very straightforward.
- In line with the `bevy_ecs` no-std-ification, I've added documentation
to all features, and grouped them as well.
- ~~Creating this PR in draft while CI runs and so I can polish before
review.~~

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-12-18 22:04:45 +00:00
Clar Fon
711246aa34
Update hashbrown to 0.15 (#15801)
Updating dependencies; adopted version of #15696. (Supercedes #15696.)

Long answer: hashbrown is no longer using ahash by default, meaning that
we can't use the default-hasher methods with ahasher. So, we have to use
the longer-winded versions instead. This takes the opportunity to also
switch our default hasher as well, but without actually enabling the
default-hasher feature for hashbrown, meaning that we'll be able to
change our hasher more easily at the cost of all of these method calls
being obnoxious forever.

One large change from 0.15 is that `insert_unique_unchecked` is now
`unsafe`, and for cases where unsafe code was denied at the crate level,
I replaced it with `insert`.

## Migration Guide

`bevy_utils` has updated its version of `hashbrown` to 0.15 and now
defaults to `foldhash` instead of `ahash`. This means that if you've
hard-coded your hasher to `bevy_utils::AHasher` or separately used the
`ahash` crate in your code, you may need to switch to `foldhash` to
ensure that everything works like it does in Bevy.
2024-12-10 19:45:50 +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
MichiRecRoom
2a66bf0909
Clarify that bevy_app::App.world() (and mut variant) returns the main SubApp's World (#16527)
# Objective
The documentation for `bevy_app::App.world()` (and its mut variant)
could confuse some into thinking that this is the only World that the
App will contain.

## Solution
Clarify the documentation for `bevy_app::App.world()` (and its mut
variant), to say that it returns the main subapp's world. This helps
imply that Apps can contain more than one world (albeit, only one per
SubApp).

## Testing
This is a documentation change, with no changes to doctests. Thus,
testing is not necessary beyond ensuring the link syntax is correct.
2024-11-27 16:09:09 +00:00
Pablo Reinhardt
d96a9d15f6
Migrate from Query::single and friends to Single (#15872)
# Objective

- closes #15866

## Solution

- Simply migrate where possible.

## Testing

- Expect that CI will do most of the work. Examples is another way of
testing this, as most of the work is in that area.
---

## Notes
For now, this PR doesn't migrate `QueryState::single` and friends as for
now, this look like another issue. So for example, QueryBuilders that
used single or `World::query` that used single wasn't migrated. If there
is a easy way to migrate those, please let me know.

Most of the uses of `Query::single` were removed, the only other uses
that I found was related to tests of said methods, so will probably be
removed when we remove `Query::single`.
2024-10-13 20:32:06 +00:00
Christian Hughes
219b5930f1
Rename App/World::observe to add_observer, EntityWorldMut::observe_entity to observe. (#15754)
# Objective

- Closes #15752

Calling the functions `App::observe` and `World::observe` doesn't make
sense because you're not "observing" the `App` or `World`, you're adding
an observer that listens for an event that occurs *within* the `World`.
We should rename them to better fit this.

## Solution

Renames:
- `App::observe` -> `App::add_observer`
- `World::observe` -> `World::add_observer`
- `Commands::observe` -> `Commands::add_observer`
- `EntityWorldMut::observe_entity` -> `EntityWorldMut::observe`

(Note this isn't a breaking change as the original rename was introduced
earlier this cycle.)

## Testing

Reusing current tests.
2024-10-09 15:39:29 +00:00
Zachary Harrold
1be0ed33fc
Remove thiserror from bevy_app (#15779)
# Objective

- Contributes to #15460

## Solution

- Removed `thiserror` from `bevy_app`
2024-10-09 14:17:52 +00:00
Joona Aalto
f3e8ae03cd
Runtime required components (#15458)
# Objective

Fixes #15367.

Currently, required components can only be defined through the `require`
macro attribute. While this should be used in most cases, there are also
several instances where you may want to define requirements at runtime,
commonly in plugins.

Example use cases:

- Require components only if the relevant optional plugins are enabled.
For example, a `SleepTimer` component (for physics) is only relevant if
the `SleepPlugin` is enabled.
- Third party crates can define their own requirements for first party
types. For example, "each `Handle<Mesh>` should require my custom
rendering data components". This also gets around the orphan rule.
- Generic plugins that add marker components based on the existence of
other components, like a generic `ColliderPlugin<C: AnyCollider>` that
wants to add a `ColliderMarker` component for all types of colliders.
- This is currently relevant for the retained render world in #15320.
The `ExtractComponentPlugin<C>` should add `SyncToRenderWorld` to all
components that should be extracted. This is currently done with
observers, which is more expensive than required components, and causes
archetype moves.
- Replace some built-in components with custom versions. For example, if
`GlobalTransform` required `Transform` through `TransformPlugin`, but we
wanted to use a `CustomTransform` type, we could replace
`TransformPlugin` with our own plugin. (This specific example isn't
good, but there are likely better use cases where this may be useful)

See #15367 for more in-depth reasoning.

## Solution

Add `register_required_components::<T, R>` and
`register_required_components_with::<T, R>` methods for `Default` and
custom constructors respectively. These methods exist on `App` and
`World`.

```rust
struct BirdPlugin;

impl Plugin for BirdPlugin {
    fn plugin(app: &mut App) {
        // Make `Bird` require `Wings` with a `Default` constructor.
        app.register_required_components::<Bird, Wings>();

        // Make `Wings` require `FlapSpeed` with a custom constructor.
        // Fun fact: Some hummingbirds can flutter their wings 80 times per second!
        app.register_required_components_with::<Wings, FlapSpeed>(|| FlapSpeed::from_duration(1.0 / 80.0));
    }
}
```

The custom constructor is a function pointer to match the `require` API,
though it could take a raw value too.

Requirement inheritance works similarly as with the `require` attribute.
If `Bird` required `FlapSpeed` directly, it would take precedence over
indirectly requiring it through `Wings`. The same logic applies to all
levels of the inheritance tree.

Note that registering the same component requirement more than once will
panic, similarly to trying to add multiple component hooks of the same
type to the same component. This avoids constructor conflicts and
confusing ordering issues.

### Implementation

Runtime requirements have two additional challenges in comparison to the
`require` attribute.

1. The `require` attribute uses recursion and macros with clever
ordering to populate hash maps of required components for each component
type. The expected semantics are that "more specific" requirements
override ones deeper in the inheritance tree. However, at runtime, there
is no representation of how "specific" each requirement is.
2. If you first register the requirement `X -> Y`, and later register `Y
-> Z`, then `X` should also indirectly require `Z`. However, `Y` itself
doesn't know that it is required by `X`, so it's not aware that it
should update the list of required components for `X`.

My solutions to these problems are:

1. Store the depth in the inheritance tree for each entry of a given
component's `RequiredComponents`. This is used to determine how
"specific" each requirement is. For `require`-based registration, these
depths are computed as part of the recursion.
2. Store and maintain a `required_by` list in each component's
`ComponentInfo`, next to `required_components`. For `require`-based
registration, these are also added after each registration, as part of
the recursion.

When calling `register_required_components`, it works as follows:

1. Get the required components of `Foo`, and check that `Bar` isn't
already a *direct* requirement.
3. Register `Bar` as a required component for `Foo`, and add `Foo` to
the `required_by` list for `Bar`.
4. Find and register all indirect requirements inherited from `Bar`,
adding `Foo` to the `required_by` list for each component.
5. Iterate through components that require `Foo`, registering the new
inherited requires for them as indirect requirements.

The runtime registration is likely slightly more expensive than the
`require` version, but it is a one-time cost, and quite negligible in
practice, unless projects have hundreds or thousands of runtime
requirements. I have not benchmarked this however.

This does also add a small amount of extra cost to the `require`
attribute for updating `required_by` lists, but I expect it to be very
minor.

## Testing

I added some tests that are copies of the `require` versions, as well as
some tests that are more specific to the runtime implementation. I might
add a few more tests though.

## Discussion

- Is `register_required_components` a good name? Originally I went for
`register_component_requirement` to be consistent with
`register_component_hooks`, but the general feature is often referred to
as "required components", which is why I changed it to
`register_required_components`.
- Should we *not* panic for duplicate requirements? If so, should they
just be ignored, or should the latest registration overwrite earlier
ones?
- If we do want to panic for duplicate, conflicting registrations,
should we at least not panic if the registrations are *exactly* the
same, i.e. same component and same constructor? The current
implementation panics for all duplicate direct registrations regardless
of the constructor.

## Next Steps

- Allow `register_required_components` to take a `Bundle` instead of a
single required component.
    - I could also try to do it in this PR if that would be preferable.
- Not directly related, but archetype invariants?
2024-09-30 19:20:16 +00:00
Zachary Harrold
d70595b667
Add core and alloc over std Lints (#15281)
# Objective

- Fixes #6370
- Closes #6581

## Solution

- Added the following lints to the workspace:
  - `std_instead_of_core`
  - `std_instead_of_alloc`
  - `alloc_instead_of_core`
- Used `cargo +nightly fmt` with [item level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Item%5C%3A)
to split all `use` statements into single items.
- Used `cargo clippy --workspace --all-targets --all-features --fix
--allow-dirty` to _attempt_ to resolve the new linting issues, and
intervened where the lint was unable to resolve the issue automatically
(usually due to needing an `extern crate alloc;` statement in a crate
root).
- Manually removed certain uses of `std` where negative feature gating
prevented `--all-features` from finding the offending uses.
- Used `cargo +nightly fmt` with [crate level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Crate%5C%3A)
to re-merge all `use` statements matching Bevy's previous styling.
- Manually fixed cases where the `fmt` tool could not re-merge `use`
statements due to conditional compilation attributes.

## Testing

- Ran CI locally

## Migration Guide

The MSRV is now 1.81. Please update to this version or higher.

## Notes

- This is a _massive_ change to try and push through, which is why I've
outlined the semi-automatic steps I used to create this PR, in case this
fails and someone else tries again in the future.
- Making this change has no impact on user code, but does mean Bevy
contributors will be warned to use `core` and `alloc` instead of `std`
where possible.
- This lint is a critical first step towards investigating `no_std`
options for Bevy.

---------

Co-authored-by: François Mockers <francois.mockers@vleue.com>
2024-09-27 00:59:59 +00:00
Clar Fon
efda7f3f9c
Simpler lint fixes: makes ci lints work but disables a lint for now (#15376)
Takes the first two commits from #15375 and adds suggestions from this
comment:
https://github.com/bevyengine/bevy/pull/15375#issuecomment-2366968300

See #15375 for more reasoning/motivation.

## Rebasing (rerunning)

```rust
git switch simpler-lint-fixes
git reset --hard main
cargo fmt --all -- --unstable-features --config normalize_comments=true,imports_granularity=Crate
cargo fmt --all
git add --update
git commit --message "rustfmt"
cargo clippy --workspace --all-targets --all-features --fix
cargo fmt --all -- --unstable-features --config normalize_comments=true,imports_granularity=Crate
cargo fmt --all
git add --update
git commit --message "clippy"
git cherry-pick e6c0b94f6795222310fb812fa5c4512661fc7887
```
2024-09-24 11:42:59 +00:00
Christian Hughes
c7ec456e50
Support systems that take references as input (#15184)
# Objective

- Fixes #14924
- Closes #9584

## Solution

- We introduce a new trait, `SystemInput`, that serves as a type
function from the `'static` form of the input, to its lifetime'd
version, similarly to `SystemParam` or `WorldQuery`.
- System functions now take the lifetime'd wrapped version,
`SystemInput::Param<'_>`, which prevents the issue presented in #14924
(i.e. `InRef<T>`).
- Functions for running systems now take the lifetime'd unwrapped
version, `SystemInput::Inner<'_>` (i.e. `&T`).
- Due to the above change, system piping had to be re-implemented as a
standalone type, rather than `CombinatorSystem` as it was previously.
- Removes the `Trigger<'static, E, B>` transmute in observer runner
code.

## Testing

- All current tests pass.
- Added additional tests and doc-tests.

---

## Showcase

```rust
let mut world = World::new();

let mut value = 2;

// Currently possible:
fn square(In(input): In<usize>) -> usize {
    input * input
}
value = world.run_system_once_with(value, square);

// Now possible:
fn square_mut(InMut(input): InMut<usize>) {
    *input *= *input;
}
world.run_system_once_with(&mut value, square_mut);

// Or:
fn square_ref(InRef(input): InRef<usize>) -> usize {
    *input * *input
}
value = world.run_system_once_with(&value, square_ref);
```

## Migration Guide

- All current explicit usages of the following types must be changed in
the way specified:
    - `SystemId<I, O>` to `SystemId<In<I>, O>`
    - `System<In = T>` to `System<In = In<T>>`
    - `IntoSystem<I, O, M>` to `IntoSystem<In<I>, O, M>`
    - `Condition<M, T>` to `Condition<M, In<T>>`
- `In<Trigger<E, B>>` is no longer a valid input parameter type. Use
`Trigger<E, B>` directly, instead.

---------

Co-authored-by: Giacomo Stevanato <giaco.stevanato@gmail.com>
2024-09-23 17:37:29 +00:00
Rich Churcher
fd329c0426
Allow to expect (adopted) (#15301)
# Objective

> Rust 1.81 released the #[expect(...)] attribute, which works like
#[allow(...)] but throws a warning if the lint isn't raised. This is
preferred to #[allow(...)] because it tells us when it can be removed.

- Adopts the parts of #15118 that are complete, and updates the branch
so it can be merged.
- There were a few conflicts, let me know if I misjudged any of 'em.

Alice's
[recommendation](https://github.com/bevyengine/bevy/issues/15059#issuecomment-2349263900)
seems well-taken, let's do this crate by crate now that @BD103 has done
the lion's share of this!

(Relates to, but doesn't yet completely finish #15059.)

Crates this _doesn't_ cover:

- bevy_input
- bevy_gilrs
- bevy_window
- bevy_winit
- bevy_state
- bevy_render
- bevy_picking
- bevy_core_pipeline
- bevy_sprite
- bevy_text
- bevy_pbr
- bevy_ui
- bevy_gltf
- bevy_gizmos
- bevy_dev_tools
- bevy_internal
- bevy_dylib

---------

Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
Co-authored-by: Ben Frankel <ben.frankel7@gmail.com>
Co-authored-by: Antony <antony.m.3012@gmail.com>
2024-09-20 19:16:42 +00:00
Benjamin Brienen
1b8c1c1242
simplify std::mem references (#15315)
# Objective
- Fixes #15314

## Solution

- Remove unnecessary usings and simplify references to those functions.

## Testing

CI
2024-09-19 21:28:16 +00:00
Zachary Harrold
bc13161416
Migrated NonZero* to NonZero<*> (#14978)
# Objective

- Fixes #14974

## Solution

- Replace all* instances of `NonZero*` with `NonZero<*>`

## Testing

- CI passed locally.

---

## Notes

Within the `bevy_reflect` implementations for `std` types,
`impl_reflect_value!()` will continue to use the type aliases instead,
as it inappropriately parses the concrete type parameter as a generic
argument. If the `ZeroablePrimitive` trait was stable, or the macro
could be modified to accept a finite list of types, then we could fully
migrate.
2024-08-30 02:37:47 +00:00
Zachary Harrold
6250698b56
Added on_unimplemented Diagnostic for IntoObserverSystem (#14840)
# Objective

- Fixes #14658.

## Solution

- Added `on_unimplemented` Diagnostic for `IntoObserverSystem` calling
out argument ordering in a `note`
- Added an example to the documentation on `App::observe` to provide
some explanation to users.

## Testing

- Ran CI locally
- Deliberately introduced a parameter order error in the
`ecs/observers.rs` example as a test.

---

## Showcase

<details>
  <summary>Error Before</summary>

```
error[E0277]: the trait bound `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>` is not satisfied
   --> examples/ecs/observers.rs:19:13
    |
18  |           .observe(
    |            ------- required by a bound introduced by this call
19  | /             |mines: Query<&Mine>,
20  | |             trigger: Trigger<ExplodeMines>,
21  | |             index: Res<SpatialIndex>,
22  | |              mut commands: Commands| {
...   |
34  | |                 }
35  | |             },
    | |_____________^ the trait `bevy::prelude::IntoSystem<bevy::prelude::Trigger<'static, _, _>, (), _>` is not implemented for closure `{closure@examples/ecs/observers.rs:19:13: 22:37}`, which is required by `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>`
    |
    = note: required for `{closure@examples/ecs/observers.rs:19:13: 22:37}` to implement `IntoObserverSystem<_, _, _>`
note: required by a bound in `bevy::prelude::App::observe`
   --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:995:24
    |
993 |     pub fn observe<E: Event, B: Bundle, M>(
    |            ------- required by a bound in this associated function
994 |         &mut self,
995 |         observer: impl IntoObserverSystem<E, B, M>,
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::observe`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `bevy` (example "observers") due to 1 previous error
```

</details>

<details>
  <summary>Error After</summary>

```
error[E0277]: `{closure@examples/ecs/observers.rs:19:13: 22:37}` cannot become an `ObserverSystem`
    --> examples/ecs/observers.rs:19:13
     |
18   |           .observe(
     |            ------- required by a bound introduced by this call
19   | /             |mines: Query<&Mine>,
20   | |             trigger: Trigger<ExplodeMines>,
21   | |             index: Res<SpatialIndex>,
22   | |              mut commands: Commands| {
...    |
34   | |                 }
35   | |             },
     | |_____________^ the trait `IntoObserverSystem` is not implemented
     |
     = help: the trait `bevy::prelude::IntoSystem<bevy::prelude::Trigger<'static, _, _>, (), _>` is not implemented for closure `{closure@examples/ecs/observers.rs:19:13: 22:37}`, which is required by `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>`
     = note: for function `ObserverSystem`s, ensure the first argument is a `Trigger<T>` and any subsequent ones are `SystemParam`
     = note: required for `{closure@examples/ecs/observers.rs:19:13: 22:37}` to implement `IntoObserverSystem<_, _, _>`
note: required by a bound in `bevy::prelude::App::observe`
    --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:1025:24
     |
1023 |     pub fn observe<E: Event, B: Bundle, M>(
     |            ------- required by a bound in this associated function
1024 |         &mut self,
1025 |         observer: impl IntoObserverSystem<E, B, M>,
     |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::observe`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `bevy` (example "observers") due to 1 previous error
```

</details>
2024-08-25 14:15:49 +00:00
EdJoPaTo
938d810766
Apply unused_qualifications lint (#14828)
# Objective

Fixes #14782

## Solution

Enable the lint and fix all upcoming hints (`--fix`). Also tried to
figure out the false-positive (see review comment). Maybe split this PR
up into multiple parts where only the last one enables the lint, so some
can already be merged resulting in less many files touched / less
potential for merge conflicts?

Currently, there are some cases where it might be easier to read the
code with the qualifier, so perhaps remove the import of it and adapt
its cases? In the current stage it's just a plain adoption of the
suggestions in order to have a base to discuss.

## Testing

`cargo clippy` and `cargo run -p ci` are happy.
2024-08-21 12:29:33 +00:00
Gino Valente
2b4180ca8f
bevy_reflect: Function reflection terminology refactor (#14813)
# Objective

One of the changes in #14704 made `DynamicFunction` effectively the same
as `DynamicClosure<'static>`. This change meant that the de facto
function type would likely be `DynamicClosure<'static>` instead of the
intended `DynamicFunction`, since the former is much more flexible.

We _could_ explore ways of making `DynamicFunction` implement `Copy`
using some unsafe code, but it likely wouldn't be worth it. And users
would likely still reach for the convenience of
`DynamicClosure<'static>` over the copy-ability of `DynamicFunction`.

The goal of this PR is to fix this confusion between the two types.

## Solution

Firstly, the `DynamicFunction` type was removed. Again, it was no
different than `DynamicClosure<'static>` so it wasn't a huge deal to
remove.

Secondly, `DynamicClosure<'env>` and `DynamicClosureMut<'env>` were
renamed to `DynamicFunction<'env>` and `DynamicFunctionMut<'env>`,
respectively.

Yes, we still ultimately kept the naming of `DynamicFunction`, but
changed its behavior to that of `DynamicClosure<'env>`. We need a term
to refer to both functions and closures, and "function" was the best
option.


[Originally](https://discord.com/channels/691052431525675048/1002362493634629796/1274091992162242710),
I was going to go with "callable" as the replacement term to encompass
both functions and closures (e.g. `DynamciCallable<'env>`). However, it
was
[suggested](https://discord.com/channels/691052431525675048/1002362493634629796/1274653581777047625)
by @SkiFire13 that the simpler "function" term could be used instead.

While "callable" is perhaps the better umbrella term—being truly
ambiguous over functions and closures— "function" is more familiar, used
more often, easier to discover, and is subjectively just
"better-sounding".

## Testing

Most changes are purely swapping type names or updating documentation,
but you can verify everything still works by running the following
command:

```
cargo test --package bevy_reflect
```
2024-08-19 21:52:36 +00:00
Gino Valente
423285cf1c
bevy_reflect: Store functions as DynamicClosure<'static> in FunctionRegistry (#14704)
# Objective

#14098 added the `FunctionRegistry` for registering functions such that
they can be retrieved by name and used dynamically. One thing we chose
to leave out in that initial PR is support for closures.

Why support closures? Mainly, we don't want to prohibit users from
injecting environmental data into their registered functions. This
allows these functions to not leak their internals to the public API.

For example, let's say we're writing a library crate that allows users
to register callbacks for certain actions. We want to perform some
actions before invoking the user's callback so we can't just call it
directly. We need a closure for this:

```rust
registry.register("my_lib::onclick", move |event: ClickEvent| {
    // ...other work...

    user_onclick.call(event); // <-- Captured variable
});
```

We could have made our callback take a reference to the user's callback.
This would remove the need for the closure, but it would change our
desired API to place the burden of fetching the correct callback on the
caller.

## Solution

Modify the `FunctionRegistry` to store registered functions as
`DynamicClosure<'static>` instead of `DynamicFunction` (now using
`IntoClosure` instead of `IntoFunction`).

Due to limitations in Rust and how function reflection works,
`DynamicClosure<'static>` is functionally equivalent to
`DynamicFunction`. And a normal function is considered a subset of
closures (it's a closure that doesn't capture anything), so there
shouldn't be any difference in usage: all functions that satisfy
`IntoFunction` should satisfy `IntoClosure`.

This means that the registration API introduced in #14098 should require
little-to-no changes on anyone following `main`.

### Closures vs Functions

One consideration here is whether we should keep closures and functions
separate.

This PR unifies them into `DynamicClosure<'static>`, but we can consider
splitting them up. The reasons we might want to do so are:

- Simplifies mental model and terminology (users don't have to
understand that functions turn into closures)
- If Rust ever improves its function model, we may be able to add
additional guarantees to `DynamicFunction` that make it useful to
separate the two
- Adding support for generic functions may be less confusing for users
since closures in Rust technically can't be generic

The reasons behind this PR's unification approach are:

- Reduces the number of methods needed on `FunctionRegistry`
- Reduces the number of lookups a user may have to perform (i.e.
"`get_function` or else `get_closure`")
- Establishes `DynamicClosure<'static>` as the de facto dynamic callable
(similar to how most APIs in Rust code tend to prefer `impl Fn() ->
String` over `fn() -> String`)

I'd love to hear feedback on this matter, and whether we should continue
with this PR's approach or switch to a split model.

## Testing

You can test locally by running:

```
cargo test --package bevy_reflect
```

---

## Showcase

Closures can now be registered into the `FunctionRegistry`:

```rust
let punct = String::from("!!!");

registry.register_with_name("my_crate::punctuate", move |text: String| {
  format!("{}{}", text, punct)
});
```
2024-08-17 00:20:47 +00:00
Gino Valente
a0cc636ea3
bevy_reflect: Anonymous function parsing (#14641)
# Objective

### TL;DR

#14098 added the `FunctionRegistry` but had some last minute
complications due to anonymous functions. It ended up going with a
"required name" approach to ensure anonymous functions would always have
a name.

However, this approach isn't ideal for named functions since, by
definition, they will always have a name.

Therefore, this PR aims to modify function reflection such that we can
make function registration easier for named functions, while still
allowing anonymous functions to be registered as well.

### Context

Function registration (#14098) ran into a little problem: anonymous
functions.

Anonymous functions, including function pointers, have very non-unique
type names. For example, the anonymous function `|a: i32, b: i32| a + b`
has the type name of `fn(i32, i32) -> i32`. This obviously means we'd
conflict with another function like `|a: i32, b: i32| a - b`.

The solution that #14098 landed on was to always require a name during
function registration.

The downside with this is that named functions (e.g. `fn add(a: i32, b:
i32) -> i32 { a + b }`) had to redundantly provide a name. Additionally,
manually constructed `DynamicFunction`s also ran into this ergonomics
issue.

I don't entirely know how the function registry will be used, but I have
a strong suspicion that most of its registrations will either be named
functions or manually constructed `DynamicFunction`s, with anonymous
functions only being used here and there for quick prototyping or adding
small functionality.

Why then should the API prioritize the anonymous function use case by
always requiring a name during registration?

#### Telling Functions Apart

Rust doesn't provide a lot of out-of-the-box tools for reflecting
functions. One of the biggest hurdles in attempting to solve the problem
outlined above would be to somehow tell the different kinds of functions
apart.

Let's briefly recap on the categories of functions in Rust:

| Category           | Example                                   |
| ------------------ | ----------------------------------------- |
| Named function     | `fn add(a: i32, b: i32) -> i32 { a + b }` |
| Closure            | `\|a: i32\| a + captured_variable`          |
| Anonymous function | `\|a: i32, b: i32\| a + b`                  |
| Function pointer   | `fn(i32, i32) -> i32`                     |

My first thought was to try and differentiate these categories based on
their size. However, we can see that this doesn't quite work:

| Category           | `size_of` |
| ------------------ | --------- |
| Named function     | 0         |
| Closure            | 0+        |
| Anonymous function | 0         |
| Function pointer   | 8         |

Not only does this not tell anonymous functions from named ones, but it
struggles with pretty much all of them.

My second then was to differentiate based on type name:

| Category           | `type_name`             |
| ------------------ | ----------------------- |
| Named function     | `foo::bar::baz`         |
| Closure            | `foo::bar::{{closure}}` |
| Anonymous function | `fn() -> String`        |
| Function pointer   | `fn() -> String`        |

This is much better. While it can't distinguish between function
pointers and anonymous functions, this doesn't matter too much since we
only care about whether we can _name_ the function.

So why didn't we implement this in #14098?

#### Relying on `type_name`

While this solution was known about while working on #14098, it was left
out from that PR due to it being potentially controversial.

The [docs](https://doc.rust-lang.org/stable/std/any/fn.type_name.html)
for `std::any::type_name` state:

> The returned string must not be considered to be a unique identifier
of a type as multiple types may map to the same type name. Similarly,
there is no guarantee that all parts of a type will appear in the
returned string: for example, lifetime specifiers are currently not
included. In addition, the output may change between versions of the
compiler.

So that's it then? We can't use `type_name`?

Well, this statement isn't so much a rule as it is a guideline. And Bevy
is no stranger to bending the rules to make things work or to improve
ergonomics. Remember that before `TypePath`, Bevy's scene system was
entirely dependent on `type_name`. Not to mention that `type_name` is
being used as a key into both the `TypeRegistry` and the
`FunctionRegistry`.

Bevy's practices aside, can we reliably use `type_name` for this?

My answer would be "yes".

Anonymous functions are anonymous. They have no name. There's nothing
Rust could do to give them a name apart from generating a random string
of characters. But remember that this is a diagnostic tool, it doesn't
make sense to obfuscate the type by randomizing the output. So changing
it to be anything other than what it is now is very unlikely.

The only changes that I could potentially see happening are:

1. Closures replace `{{closure}}` with the name of their variable
2. Lifetimes are included in the output

I don't think the first is likely to happen, but if it does then it
actually works out in our favor: closures are now named!

The second point is probably the likeliest. However, adding lifetimes
doesn't mean we can't still rely on `type_name` to determine whether or
not a function is named. So we should be okay in this case as well.

## Solution

Parse the `type_name` of the function in the `TypedFunction` impl to
determine if the function is named or anonymous.

This once again makes `FunctionInfo::name` optional. For manual
constructions of `DynamicFunction`, `FunctionInfo::named` or
``FunctionInfo::anonymous` can be used.

The `FunctionRegistry` API has also been reworked to account for this
change.

`FunctionRegistry::register` no longer takes a name and instead takes it
from the supplied function, returning a
`FunctionRegistrationError::MissingName` error if the name is `None`.
This also doubles as a replacement for the old
`FunctionRegistry::register_dynamic` method, which has been removed.

To handle anonymous functions, a `FunctionRegistry::register_with_name`
method has been added. This works in the same way
`FunctionRegistry::register` used to work before this PR.

The overwriting methods have been updated in a similar manner, with
modifications to `FunctionRegistry::overwrite_registration`, the removal
of `FunctionRegistry::overwrite_registration_dynamic`, and the addition
of `FunctionRegistry::overwrite_registration_with_name`.

This PR also updates the methods on `App` in a similar way:
`App::register_function` no longer requires a name argument and
`App::register_function_with_name` has been added to handle anonymous
functions (and eventually closures).

## Testing

You can run the tests locally by running:

```
cargo test --package bevy_reflect --features functions
```

---

## Internal Migration Guide

> [!important]
> Function reflection was introduced as part of the 0.15 dev cycle. This
migration guide was written for developers relying on `main` during this
cycle, and is not a breaking change coming from 0.14.

> [!note]
> This list is not exhaustive. It only contains some of the most
important changes.

`FunctionRegistry::register` no longer requires a name string for named
functions. Anonymous functions, however, need to be registered using
`FunctionRegistry::register_with_name`.

```rust
// BEFORE
registry
  .register(std::any::type_name_of_val(&foo), foo)?
  .register("bar", || println!("Hello world!"));

// AFTER
registry
  .register(foo)?
  .register_with_name("bar", || println!("Hello world!"));
```

`FunctionInfo::name` is now optional. Anonymous functions and closures
will now have their name set to `None` by default. Additionally,
`FunctionInfo::new` has been renamed to `FunctionInfo::named`.
2024-08-07 03:11:08 +00:00