Commit Graph

67 Commits

Author SHA1 Message Date
Carter Anderson
a033f1b206
Replace VisitEntities with MapEntities (#18432)
# Objective

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

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

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

## Solution

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

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

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

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

## Migration Guide

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

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

// after
#[derive(MapEntities)]
struct Inventory {
  #[entities]
  items: Vec<Entity>,
  label: String,
}
```
2025-03-21 00:18:10 +00:00
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
Eagster
246ce590e5
Queued component registration (#18173)
# Objective

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

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

## What's wrong with #17871 ?

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

## Solution

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

Here's the basic design:

Queue a registration:

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

Direct (normal) registration:

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

Appllying the queue:

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

One other change:

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

## Risks and Testing

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

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

## Migration Guide

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

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

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

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

# Open Question

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

---------

Co-authored-by: andriyDev <andriydzikh@gmail.com>
2025-03-10 21:46:27 +00:00
Tim Overbeek
664000f848
Improve derive(Event) and simplify macro code (#18083)
# Objective

simplify some code and improve Event macro

Closes https://github.com/bevyengine/bevy/issues/14336,


# Showcase

you can now write derive Events like so
```rust
#[derive(event)]
#[event(auto_propagate, traversal = MyType)]
struct MyEvent;
```
2025-03-07 02:01:23 +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
Carter Anderson
a530c07bc5
Preserve spawned RelationshipTarget order and other improvements (#17858)
Fixes #17720

## Objective

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

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

## Solution

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

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

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

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

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

There are three variants:

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

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

I also made some other minor tweaks:

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

---------

Co-authored-by: Viktor Gustavsson <villor94@gmail.com>
2025-03-05 22:18:57 +00:00
Zachary Harrold
20813aed64
Handle TriggerTargets that are combinations for components/entities (#18024)
# Objective

* Fixes https://github.com/bevyengine/bevy/issues/14074
* Applies CI fixes for #16326

It is currently not possible to issues a trigger that targets a specific
list of components AND a specific list of entities

## Solution

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

## Testing

Added a unit test.

The triggering rules for observers are quite confusing:

Triggers once per entity target

For each entity target, an observer system triggers if any of its
components matches the trigger target components (but it triggers at
most once, since we use an internal counter to make sure that an
observer can run at most once per entity target)

(copied from #14563)
(copied from #16326)

## Notes

All credit to @BenjaminBrienen and @cBournhonesque! Just applying a
small fix to this PR so it can be merged.

---------

Co-authored-by: Benjamin Brienen <Benjamin.Brienen@outlook.com>
Co-authored-by: Christian Hughes <xdotdash@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-02-24 23:57:34 +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
Jean Mertz
7d8504f30e
feat(ecs): implement fallible observer systems (#17731)
This commit builds on top of the work done in #16589 and #17051, by
adding support for fallible observer systems.

As with the previous work, the actual results of the observer system are
suppressed for now, but the intention is to provide a way to handle
errors in a global way.

Until then, you can use a `PipeSystem` to manually handle results.

---------

Signed-off-by: Jean Mertz <git@jeanmertz.com>
2025-02-11 22:15:43 +00:00
Chris Russell
eee7fd5b3e
Encapsulate cfg(feature = "track_location") in a type. (#17602)
# Objective

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

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

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

## Solution

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

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

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

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

## Open Questions

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

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

## Migration Guide

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

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

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

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

# Objective

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

## TODO

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

## Notes

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

## Testing

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

---------

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

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

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

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

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

## Solution

### Improved Entity Mapping

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

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

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

Compare that to what was required before!

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

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

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

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

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

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

### The Bug Fix

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

### Improved Cloning

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

## Next Steps

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

---------

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

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

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

## Solution

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

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

## Testing

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

## Migration Guide

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

---------

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

- Fixes #17411

## Solution

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

## Testing

- CI

---

## Migration Guide

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

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

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

## Notes

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

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

## Migration Guide

`Component::register_component_hooks` has been deprecated. If you are
manually implementing the `Component` trait and registering hooks there,
use the individual methods such as `on_add` instead for increased
clarity.
2025-02-05 19:33:05 +00:00
Periwink
75e8e8c0f6
Expose ObserverDescriptor fields (#17623)
# Objective

Expose accessor functions to the `ObserverDescriptor`, so that users can
use the `Observer` component to inspect what the observer is watching.
This would be useful for me, I don't think there's any reason to hide
these.
2025-02-02 20:10:37 +00:00
Zachary Harrold
9bc0ae33c3
Move hashbrown and foldhash out of bevy_utils (#17460)
# Objective

- Contributes to #16877

## Solution

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

## Testing

- CI

---

## Migration Guide

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

## Notes

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

- Make the function signature for `ComponentHook` less verbose

## Solution

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

## Testing

- CI

---

## Migration Guide

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

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

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

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

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

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

Fixes #14708

Also fixes some commands not updating tracked location.


## Solution

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

## Testing

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

---

## Showcase

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

## Migration

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

---------

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

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

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

## Solution

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

## Notes to reviewers

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

## Testing

cargo build works!

## Migration Guide

`bevy_ecs::system::Resource` has been moved to
`bevy_ecs::resource::Resource`.
2025-01-21 19:47:08 +00:00
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
Alice Cecile
5a9bc28502
Support non-Vec data structures in relations (#17447)
# Objective

The existing `RelationshipSourceCollection` uses `Vec` as the only
possible backing for our relationships. While a reasonable choice,
benchmarking use cases might reveal that a different data type is better
or faster.

For example:

- Not all relationships require a stable ordering between the
relationship sources (i.e. children). In cases where we a) have many
such relations and b) don't care about the ordering between them, a hash
set is likely a better datastructure than a `Vec`.
- The number of children-like entities may be small on average, and a
`smallvec` may be faster

## Solution

- Implement `RelationshipSourceCollection` for `EntityHashSet`, our
custom entity-optimized `HashSet`.
-~~Implement `DoubleEndedIterator` for `EntityHashSet` to make things
compile.~~
   -  This implementation was cursed and very surprising.
- Instead, by moving the iterator type on `RelationshipSourceCollection`
from an erased RPTIT to an explicit associated type we can add a trait
bound on the offending methods!
- Implement `RelationshipSourceCollection` for `SmallVec`

## Testing

I've added a pair of new tests to make sure this pattern compiles
successfully in practice!

## Migration Guide

`EntityHashSet` and `EntityHashMap` are no longer re-exported in
`bevy_ecs::entity` directly. If you were not using `bevy_ecs` / `bevy`'s
`prelude`, you can access them through their now-public modules,
`hash_set` and `hash_map` instead.

## Notes to reviewers

The `EntityHashSet::Iter` type needs to be public for this impl to be
allowed. I initially renamed it to something that wasn't ambiguous and
re-exported it, but as @Victoronz pointed out, that was somewhat
unidiomatic.

In
1a8564898f,
I instead made the `entity_hash_set` public (and its `entity_hash_set`)
sister public, and removed the re-export. I prefer this design (give me
module docs please), but it leads to a lot of churn in this PR.

Let me know which you'd prefer, and if you'd like me to split that
change out into its own micro PR.
2025-01-20 21:26:08 +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
Alice Cecile
237c6b207e
Remove Event: Component trait bound using a wrapper type which impls Component (#17380)
# Objective

As raised in https://github.com/bevyengine/bevy/pull/17317, the `Event:
Component` trait bound is confusing to users.

In general, a type `E` (like `AppExit`) which implements `Event` should
not:

- be stored as a component on an entity
- be a valid option for `Query<&AppExit>`
- require the storage type and other component metadata to be specified

Events are not components (even if they one day use some of the same
internal mechanisms), and this trait bound is confusing to users.

We're also automatically generating `Component` impls with our derive
macro, which should be avoided when possible to improve explicitness and
avoid conflicts with user impls.

Closes #17317, closes #17333

## Solution

- We only care that each unique event type gets a unique `ComponentId`
- dynamic events need their own tools for getting identifiers anyways
- This avoids complicating the internals of `ComponentId` generation.
- Clearly document why this cludge-y solution exists.

In the medium term, I think that either a) properly generalizing
`ComponentId` (and moving it into `bevy_reflect?) or b) using a
new-typed `Entity` as the key for events is more correct. This change is
stupid simple though, and removes the offending trait bound in a way
that doesn't introduce complex tech debt and does not risk changes to
the internals.

This change does not:

- restrict our ability to implement dynamic buffered events (the main
improvement over #17317)
- there's still a fair bit of work to do, but this is a step in the
right direction
- limit our ability to store event metadata on entities in the future
- make it harder for users to work with types that are both events and
components (just add the derive / trait bound)

## Migration Guide

The `Event` trait no longer requires the `Component` trait. If you were
relying on this behavior, change your trait bounds from `Event` to
`Event + Component`. If you also want your `Event` type to implement
`Component`, add a derive.

---------

Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
2025-01-15 18:42:47 +00:00
Adrian Kortyczko
dcff8f3ecb
Make ObservedBy public (#17297)
# Objective
- Currently, the `ObservedBy`-component is only public within the
`bevy_ecs` crate. Sometimes it is desirable to refer to this component
in the "game-code". Two examples that come in mind:
- Clearing all components in an entity, but intending to keep the
existing observers: Making `ObservedBy` public allows us to use
`commands.entity(entity).retain::<ObservedBy>();`, which clears all
other components, but keeps `ObservedBy`, which prevents the Observers
from despawning.
- The opposite of the above, clearing all of entities' Observers:
`commands.entity(entity).remove::<ObservedBy>` will despawn all
associated Observers. Admittedly, a cleaner solution would be something
like `commands.entity(entity).clear_observers()`, but this is
sufficient.

## Solution

- Removed `(crate)` "rule" and added `ObservedBy` to the prelude-module

## Testing

- Linked `bevy_ecs` locally with another project to see if `ObservedBy`
could be referenced.
2025-01-14 21:53:42 +00:00
Rob Parrett
651b22f31f
Update typos (#17126)
# Objective

Use the latest version of `typos` and fix the typos that it now detects

# Additional Info

By the way, `typos` has a "low priority typo suggestions issue" where we
can throw typos we find that `typos` doesn't catch.

(This link may go stale) https://github.com/crate-ci/typos/issues/1200
2025-01-03 17:44:26 +00:00
Zachary Harrold
0403948aa2
Remove Implicit std Prelude from no_std Crates (#17086)
# Background

In `no_std` compatible crates, there is often an `std` feature which
will allow access to the standard library. Currently, with the `std`
feature _enabled_, the
[`std::prelude`](https://doc.rust-lang.org/std/prelude/index.html) is
implicitly imported in all modules. With the feature _disabled_, instead
the [`core::prelude`](https://doc.rust-lang.org/core/prelude/index.html)
is implicitly imported. This creates a subtle and pervasive issue where
`alloc` items _may_ be implicitly included (if `std` is enabled), or
must be explicitly included (if `std` is not enabled).

# Objective

- Make the implicit imports for `no_std` crates consistent regardless of
what features are/not enabled.

## Solution

- Replace the `cfg_attr` "double negative" `no_std` attribute with
conditional compilation to _include_ `std` as an external crate.
```rust
// Before
#![cfg_attr(not(feature = "std"), no_std)]

// After
#![no_std]

#[cfg(feature = "std")]
extern crate std;
```
- Fix imports that are currently broken but are only now visible with
the above fix.

## Testing

- CI

## Notes

I had previously used the "double negative" version of `no_std` based on
general consensus that it was "cleaner" within the Rust embedded
community. However, this implicit prelude issue likely was considered
when forming this consensus. I believe the reason why is the items most
affected by this issue are provided by the `alloc` crate, which is
rarely used within embedded but extensively used within Bevy.
2025-01-03 01:58:43 +00:00
JaySpruce
0f2b2de333
Move some structs that impl Command to methods on World and EntityWorldMut (#16999)
## Objective

Commands were previously limited to structs that implemented `Command`.
Now there are blanket implementations for closures, which (in my
opinion) are generally preferable.

Internal commands within `commands/mod.rs` have been switched from
structs to closures, but there are a number of internal commands in
other areas of the engine that still use structs. I'd like to tidy these
up by moving their implementations to methods on
`World`/`EntityWorldMut` and changing `Commands` to use those methods
through closures.

This PR handles the following:
- `TriggerEvent` and `EmitDynamicTrigger` double as commands and helper
structs, and can just be moved to `World` methods.
- Four structs that enabled insertion/removal of components via
reflection. This functionality shouldn't be exclusive to commands, and
can be added to `EntityWorldMut`.
- Five structs that mostly just wrapped `World` methods, and can be
replaced with closures that do the same thing.

## Solution

- __Observer Triggers__ (`observer/trigger_event.rs` and
`observer/mod.rs`)
- Moved the internals of `TriggerEvent` to the `World` methods that used
it.
  - Replaced `EmitDynamicTrigger` with two `World` methods:
    - `trigger_targets_dynamic`
    - `trigger_targets_dynamic_ref`
- `TriggerTargets` was now the only thing in
`observer/trigger_event.rs`, so it's been moved to `observer/mod.rs` and
`trigger_event.rs` was deleted.
- __Reflection Insert/Remove__ (`reflect/entity_commands.rs`)
- Replaced the following `Command` impls with equivalent methods on
`EntityWorldMut`:
    - `InsertReflect` -> `insert_reflect`
    - `InsertReflectWithRegistry` -> `insert_reflect_with_registry`
    - `RemoveReflect` -> `remove_reflect`
    - `RemoveReflectWithRegistry` -> `remove_reflect_with_registry`
- __System Registration__ (`system/system_registry.rs`)
- The following `Command` impls just wrapped a `World` method and have
been replaced with closures:
    - `RunSystemWith`
    - `UnregisterSystem`
    - `RunSystemCachedWith`
    - `UnregisterSystemCached`
- `RegisterSystem` called a helper function that basically worked as a
constructor for `RegisteredSystem` and made sure it came with a marker
component. That helper function has been replaced with
`RegisteredSystem::new` and a `#[require]`.

## Possible Addition

The extension trait that adds the reflection commands,
`ReflectCommandExt`, isn't strictly necessary; we could just `impl
EntityCommands`. We could even move them to the same files as the main
impls and put it behind a `#[cfg]`.

The PR that added it [had a similar
conversation](https://github.com/bevyengine/bevy/pull/8895#discussion_r1234713671)
and decided to stick with the trait, but we could revisit it here if so
desired.
2024-12-29 22:18:53 +00:00
Benjamin Brienen
64efd08e13
Prefer Display over Debug (#16112)
# Objective

Fixes #16104

## Solution

I removed all instances of `:?` and put them back one by one where it
caused an error.

I removed some bevy_utils helper functions that were only used in 2
places and don't add value. See: #11478

## Testing

CI should catch the mistakes

## Migration Guide

`bevy::utils::{dbg,info,warn,error}` were removed. Use
`bevy::utils::tracing::{debug,info,warn,error}` instead.

---------

Co-authored-by: SpecificProtagonist <vincentjunge@posteo.net>
2024-12-27 00:40:06 +00:00
eugineerd
20049d4c34
Faster entity cloning (#16717)
# Objective

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

## Solution

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

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

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

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

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

## Testing

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

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

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

*: these benchmarks have entities with only 1 component

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

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

---------

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

- Contributes to #15460

## Solution

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

## Testing

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

## Draft Release Notes

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

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

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

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

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

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

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

## Notes

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

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Vic <59878206+Victoronz@users.noreply.github.com>
2024-12-17 21:40:36 +00:00
Aevyrie
61b98ec80f
Rename trigger.entity() to trigger.target() (#16716)
# Objective

- A `Trigger` has multiple associated `Entity`s - the entity observing
the event, and the entity that was targeted by the event.
- The field `entity: Entity` encodes no semantic information about what
the entity is used for, you can already tell that it's an `Entity` by
the type signature!

## Solution

- Rename `trigger.entity()` to `trigger.target()`

---

## Changelog

- `Trigger`s are associated with multiple entities. `Trigger::entity()`
has been renamed to `Trigger::target()` to reflect the semantics of the
entity being returned.

## Migration Guide

- Rename `Trigger::entity()` to `Trigger::target()`.
- Rename `ObserverTrigger::entity` to `ObserverTrigger::target`
2024-12-08 21:55:09 +00:00
Miles Silberling-Cook
09b0b5df91
Window picking (#16103)
# Objective

On the web, it's common to attach observers to windows. As @viridia has
discovered, this can be quite a nice paradigm in bevy as well when
applied to observers. The changes here are intended to make this
possible.
+ Adds a new default picking back-end as part to the core picking plugin
(which can be disabled) that causes pointers on windows to treat the
window entity as the final hit, behind everything else. This means
clicking empty space now dispatches normal picking events to the window,
and is especially nice for drag-and-drop functionality.
+ Adds a new traversal type, specific to picking events, that causes
them to bubble up to the window entity after they reach the root of the
hierarchy.

## Solution

The window picking back-end is extremely simple, but the bubbling
changes are much more complex, since they require doing a different
traversal depending on the picking event.

To achieve this, `Traversal` has been made generic over an associated
sized data type `D`. Observer bounds have been changed such that
`Event::Traversal<D>` is required for `Trigger<D>`. A blanket
implementation has been added for `()` and `Parent` that preserves the
existing functionality. A new `PointerTraversal` traversal has been
implemented, with a blanket implementation for `Traversal<Pointer<E>>`.

It is still possible to use `Parent` as the traversal for any event,
because of the blanket implementation. It is now possible for users to
add other custom traversals, which read event data during traversal.

## Testing

I tested these changes locally on some picking UI prototypes I have been
playing with. I also tested them on the picking examples.

---------

Co-authored-by: Martín Maita <47983254+mnmaita@users.noreply.github.com>
2024-12-05 21:14:39 +00:00
Zachary Harrold
a35811d088
Add Immutable Component Support (#16372)
# Objective

- Fixes #16208

## Solution

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

## Testing

- CI
- `immutable_components` example.

---

## Showcase

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

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

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

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

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

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

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

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

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

    index.name_to_entity.remove(&name);
}

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

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

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

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

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

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

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

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

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

## Migration Guide

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

## Draft Release Notes

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

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

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

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

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

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

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

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

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

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

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

## Notes

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

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Benjamin Brienen <benjamin.brienen@outlook.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
Co-authored-by: Nuutti Kotivuori <naked@iki.fi>
2024-12-05 14:27:48 +00:00
eugineerd
2e267bba5a
Entity cloning (#16132)
## Objective

Fixes #1515 

This PR implements a flexible entity cloning system. The primary use
case for it is to clone dynamically-generated entities.

Example:
```rs
#[derive(Component, Clone)]
pub struct Projectile;

#[derive(Component, Clone)]
pub struct Damage {
    value: f32,
}

fn player_input(
    mut commands: Commands,
    projectiles: Query<Entity, With<Projectile>>,
    input: Res<ButtonInput<KeyCode>>,
) {
    // Fire a projectile
    if input.just_pressed(KeyCode::KeyF) {
        commands.spawn((Projectile, Damage { value: 10.0 }));
    }

    // Triplicate all active projectiles
    if input.just_pressed(KeyCode::KeyT) {
        for projectile in projectiles.iter() {
            // To triplicate a projectile we need to create 2 more clones
            for _ in 0..2{
                commands.clone_entity(projectile)
            }
        }
    }
}
```

## Solution

### Commands
Add a `clone_entity` command to create a clone of an entity with all
components that can be cloned. Components that can't be cloned will be
ignored.
```rs
commands.clone_entity(entity)
```
If there is a need to configure the cloning process (like set to clone
recursively), there is a second command:
```rs
commands.clone_entity_with(entity, |builder| {
    builder.recursive(true)
});
```
Both of these commands return `EntityCommands` of the cloned entity, so
the copy can be modified afterwards.

### Builder
All these commands use `EntityCloneBuilder` internally. If there is a
need to clone an entity using `World` instead, it is also possible:
```rs
let entity = world.spawn(Component).id();
let entity_clone = world.spawn_empty().id();
EntityCloneBuilder::new(&mut world).clone_entity(entity, entity_clone);
```

Builder has methods to `allow` or `deny` certain components during
cloning if required and can be extended by implementing traits on it.
This PR includes two `EntityCloneBuilder` extensions:
`CloneEntityWithObserversExt` to configure adding cloned entity to
observers of the original entity, and `CloneEntityRecursiveExt` to
configure cloning an entity recursively.

### Clone implementations
By default, all components that implement either `Clone` or `Reflect`
will be cloned (with `Clone`-based implementation preferred in case
component implements both).

This can be overriden on a per-component basis:
```rs
impl Component for SomeComponent {
    const STORAGE_TYPE: StorageType = StorageType::Table;

    fn get_component_clone_handler() -> ComponentCloneHandler {
        // Don't clone this component
        ComponentCloneHandler::Ignore
    }
}
```

### `ComponentCloneHandlers`
Clone implementation specified in `get_component_clone_handler` will get
registered in `ComponentCloneHandlers` (stored in
`bevy_ecs::component::Components`) at component registration time.

The clone handler implementation provided by a component can be
overriden after registration like so:
```rs
let component_id = world.components().component_id::<Component>().unwrap()
world.get_component_clone_handlers_mut()
     .set_component_handler(component_id, ComponentCloneHandler::Custom(component_clone_custom))
```
The default clone handler for all components that do not explicitly
define one (or don't derive `Component`) is
`component_clone_via_reflect` if `bevy_reflect` feature is enabled, and
`component_clone_ignore` (noop) otherwise.
Default handler can be overriden using
`ComponentCloneHandlers::set_default_handler`

### Handlers
Component clone handlers can be used to modify component cloning
behavior. The general signature for a handler that can be used in
`ComponentCloneHandler::Custom` is as follows:
```rs
pub fn component_clone_custom(
    world: &mut DeferredWorld,
    entity_cloner: &EntityCloner,
) {
    // implementation
}
```
The `EntityCloner` implementation (used internally by
`EntityCloneBuilder`) assumes that after calling this custom handler,
the `target` entity has the desired version of the component from the
`source` entity.

### Builder handler overrides
Besides component-defined and world-overriden handlers,
`EntityCloneBuilder` also has a way to override handlers locally. It is
mainly used to allow configuration methods like `recursive` and
`add_observers`.
```rs
// From observer clone handler implementation
impl CloneEntityWithObserversExt for EntityCloneBuilder<'_> {
    fn add_observers(&mut self, add_observers: bool) -> &mut Self {
        if add_observers {
            self.override_component_clone_handler::<ObservedBy>(ComponentCloneHandler::Custom(
                component_clone_observed_by,
            ))
        } else {
            self.remove_component_clone_handler_override::<ObservedBy>()
        }
    }
}
```

## Testing
Includes some basic functionality tests and doctests.

Performance-wise this feature is the same as calling `clone` followed by
`insert` for every entity component. There is also some inherent
overhead due to every component clone handler having to access component
data through `World`, but this can be reduced without breaking current
public API in a later PR.
2024-12-03 17:38:10 +00:00
Rob Parrett
30d84519a2
Use en-us locale for typos (#16037)
# Objective

Bevy seems to want to standardize on "American English" spellings. Not
sure if this is laid out anywhere in writing, but see also #15947.

While perusing the docs for `typos`, I noticed that it has a `locale`
config option and tried it out.

## Solution

Switch to `en-us` locale in the `typos` config and run `typos -w`

## Migration Guide

The following methods or fields have been renamed from `*dependants*` to
`*dependents*`.

- `ProcessorAssetInfo::dependants`
- `ProcessorAssetInfos::add_dependant`
- `ProcessorAssetInfos::non_existent_dependants`
- `AssetInfo::dependants_waiting_on_load`
- `AssetInfo::dependants_waiting_on_recursive_dep_load`
- `AssetInfos::loader_dependants`
- `AssetInfos::remove_dependants_and_labels`
2024-10-20 18:55:17 +00:00
Christian Hughes
345f935b1a
Add Trigger::components, which lists the component targets that were triggered (#15811)
# Objective

- Closes #14774 

## Solution

Added:

```rust
impl<'w, E, B: Bundle> Trigger<'w, E, B> {
    pub fn components(&self) -> &[ComponentId];
}
```

I went with storing it in the trigger as a `SmallVec<[Component; 1]>`
because a singular target component will be the most common case, and it
remains the same size as `Vec<ComponentId>`.

## Testing

Added a test.
2024-10-15 02:17:03 +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
Christian Hughes
584d14808a
Allow World::entity family of functions to take multiple entities and get multiple references back (#15614)
# Objective

Following the pattern established in #15593, we can reduce the API
surface of `World` by providing a single function to grab both a
singular entity reference, or multiple entity references.

## Solution

The following functions can now also take multiple entity IDs and will
return multiple entity references back:
- `World::entity`
- `World::get_entity`
- `World::entity_mut`
- `World::get_entity_mut`
- `DeferredWorld::entity_mut`
- `DeferredWorld::get_entity_mut`

If you pass in X, you receive Y:
- give a single `Entity`, receive a single `EntityRef`/`EntityWorldMut`
(matches current behavior)
- give a `[Entity; N]`/`&[Entity; N]` (array), receive an equally-sized
`[EntityRef; N]`/`[EntityMut; N]`
- give a `&[Entity]` (slice), receive a
`Vec<EntityRef>`/`Vec<EntityMut>`
- give a `&EntityHashSet`, receive a
`EntityHashMap<EntityRef>`/`EntityHashMap<EntityMut>`

Note that `EntityWorldMut` is only returned in the single-entity case,
because having multiple at the same time would lead to UB. Also,
`DeferredWorld` receives an `EntityMut` in the single-entity case
because it does not allow structural access.

## Testing

- Added doc-tests on `World::entity`, `World::entity_mut`, and
`DeferredWorld::entity_mut`
- Added tests for aliased mutability and entity existence

---

## Showcase

<details>
  <summary>Click to view showcase</summary>

The APIs for fetching `EntityRef`s and `EntityMut`s from the `World`
have been unified.

```rust
// This code will be referred to by subsequent code blocks.
let world = World::new();
let e1 = world.spawn_empty().id();
let e2 = world.spawn_empty().id();
let e3 = world.spawn_empty().id();
```

Querying for a single entity remains mostly the same:

```rust
// 0.14
let eref: EntityRef = world.entity(e1);
let emut: EntityWorldMut = world.entity_mut(e1);
let eref: Option<EntityRef> = world.get_entity(e1);
let emut: Option<EntityWorldMut> = world.get_entity_mut(e1);

// 0.15
let eref: EntityRef = world.entity(e1);
let emut: EntityWorldMut = world.entity_mut(e1);
let eref: Result<EntityRef, Entity> = world.get_entity(e1);
let emut: Result<EntityWorldMut, Entity> = world.get_entity_mut(e1);
```

Querying for multiple entities with an array has changed:

```rust
// 0.14
let erefs: [EntityRef; 2] = world.many_entities([e1, e2]);
let emuts: [EntityMut; 2] = world.many_entities_mut([e1, e2]);
let erefs: Result<[EntityRef; 2], Entity> = world.get_many_entities([e1, e2]);
let emuts: Result<[EntityMut; 2], QueryEntityError> = world.get_many_entities_mut([e1, e2]);

// 0.15
let erefs: [EntityRef; 2] = world.entity([e1, e2]);
let emuts: [EntityMut; 2] = world.entity_mut([e1, e2]);
let erefs: Result<[EntityRef; 2], Entity> = world.get_entity([e1, e2]);
let emuts: Result<[EntityMut; 2], EntityFetchError> = world.get_entity_mut([e1, e2]);
```

Querying for multiple entities with a slice has changed:

```rust
let ids = vec![e1, e2, e3]);

// 0.14
let erefs: Result<Vec<EntityRef>, Entity> = world.get_many_entities_dynamic(&ids[..]);
let emuts: Result<Vec<EntityMut>, QueryEntityError> = world.get_many_entities_dynamic_mut(&ids[..]);

// 0.15
let erefs: Result<Vec<EntityRef>, Entity> = world.get_entity(&ids[..]);
let emuts: Result<Vec<EntityMut>, EntityFetchError> = world.get_entity_mut(&ids[..]);
let erefs: Vec<EntityRef> = world.entity(&ids[..]); // Newly possible!
let emuts: Vec<EntityMut> = world.entity_mut(&ids[..]); // Newly possible!
```

Querying for multiple entities with an `EntityHashSet` has changed:

```rust
let set = EntityHashSet::from_iter([e1, e2, e3]);

// 0.14
let emuts: Result<Vec<EntityMut>, QueryEntityError> = world.get_many_entities_from_set_mut(&set);

// 0.15
let emuts: Result<EntityHashMap<EntityMut>, EntityFetchError> = world.get_entity_mut(&set);
let erefs: Result<EntityHashMap<EntityRef>, EntityFetchError> = world.get_entity(&set); // Newly possible!
let emuts: EntityHashMap<EntityMut> = world.entity_mut(&set); // Newly possible!
let erefs: EntityHashMap<EntityRef> = world.entity(&set); // Newly possible!
```

</details>

## Migration Guide

- `World::get_entity` now returns `Result<_, Entity>` instead of
`Option<_>`.
- Use `world.get_entity(..).ok()` to return to the previous behavior.
- `World::get_entity_mut` and `DeferredWorld::get_entity_mut` now return
`Result<_, EntityFetchError>` instead of `Option<_>`.
- Use `world.get_entity_mut(..).ok()` to return to the previous
behavior.
- Type inference for `World::entity`, `World::entity_mut`,
`World::get_entity`, `World::get_entity_mut`,
`DeferredWorld::entity_mut`, and `DeferredWorld::get_entity_mut` has
changed, and might now require the input argument's type to be
explicitly written when inside closures.
- The following functions have been deprecated, and should be replaced
as such:
    - `World::many_entities` -> `World::entity::<[Entity; N]>`
    - `World::many_entities_mut` -> `World::entity_mut::<[Entity; N]>`
    - `World::get_many_entities` -> `World::get_entity::<[Entity; N]>`
- `World::get_many_entities_dynamic` -> `World::get_entity::<&[Entity]>`
- `World::get_many_entities_mut` -> `World::get_entity_mut::<[Entity;
N]>`
- The equivalent return type has changed from `Result<_,
QueryEntityError>` to `Result<_, EntityFetchError>`
- `World::get_many_entities_dynamic_mut` ->
`World::get_entity_mut::<&[Entity]>1
- The equivalent return type has changed from `Result<_,
QueryEntityError>` to `Result<_, EntityFetchError>`
- `World::get_many_entities_from_set_mut` ->
`World::get_entity_mut::<&EntityHashSet>`
- The equivalent return type has changed from `Result<Vec<EntityMut>,
QueryEntityError>` to `Result<EntityHashMap<EntityMut>,
EntityFetchError>`. If necessary, you can still convert the
`EntityHashMap` into a `Vec`.
2024-10-07 15:21:40 +00:00
Kristoffer Søholm
336c23c1aa
Rename observe to observe_entity on EntityWorldMut (#15616)
# Objective

The current observers have some unfortunate footguns where you can end
up confused about what is actually being observed. For apps you can
chain observe like `app.observe(..).observe(..)` which works like you
would expect, but if you try the same with world the first `observe()`
will return the `EntityWorldMut` for the created observer, and the
second `observe()` will only observe on the observer entity. It took
several hours for multiple people on discord to figure this out, which
is not a great experience.

## Solution

Rename `observe` on entities to `observe_entity`. It's slightly more
verbose when you know you have an entity, but it feels right to me that
observers for specific things have more specific naming, and it prevents
this issue completely.

Another possible solution would be to unify `observe` on `App` and
`World` to have the same kind of return type, but I'm not sure exactly
what that would look like.

## Testing

Simple name change, so only concern is docs really.

---


## Migration Guide

The `observe()` method on entities has been renamed to
`observe_entity()` to prevent confusion about what is being observed in
some cases.
2024-10-03 17:05:26 +00:00
Matt Tracy
8fb55dbf59
Implement SystemParam::queue() method for blanket implementation of ParamSet (#15599)
# Objective

The `queue()` method is an optional trait method which is necessary for
deferred operations (such as command queues) to work properly in the
context of an observer.

This method was omitted from the proc_macro blanket implementation of
`ParamSet` for tuples; as a result, SystemParams with deferred
application (such as Commands) would not work in observers if they were
part of a ParamSet.

This appears to have been a simple omission, as `queue()` was already
implemented for the separate blanket implementation of `ParamSet` for
`Vec<T>`. In both cases, it is a simple pass-through to the component
SystemParams.

## Solution

Add the `queue()` method implementation to the `impl_param_set` proco
macro.

## Testing

Added a unit test which clearly demonstrates the issue. It fails before
the fix, and passes afterwards.

---
2024-10-02 19:46:50 +00:00
MiniaczQ
5289e18e0b
System param validation for observers, system registry and run once (#15526)
# Objective

Fixes #15394

## Solution

Observers now validate params.

System registry has a new error variant for when system running fails
due to invalid parameters.

Run once now returns a `Result<Out, RunOnceError>` instead of `Out`.
This is more inline with system registry, which also returns a result.

I'll address warning messages in #15500.

## Testing

Added one test for each case.

---

## Migration Guide

- `RunSystemOnce::run_system_once` and
`RunSystemOnce::run_system_once_with` now return a `Result<Out>` instead
of just `Out`

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Zachary Harrold <zac@harrold.com.au>
2024-09-30 01:00:39 +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
hshrimp
35d10866b8
Rename init_component & friends (#15454)
# Objective

- Fixes #15451 

## Migration Guide

- `World::init_component` has been renamed to `register_component`.
- `World::init_component_with_descriptor` has been renamed to
`register_component_with_descriptor`.
- `World::init_bundle` has been renamed to `register_bundle`.
- `Components::init_component` has been renamed to `register_component`.
- `Components::init_component_with_descriptor` has been renamed to
`register_component_with_descriptor`.
- `Components::init_resource` has been renamed to `register_resource`.
- `Components::init_non_send` had been renamed to `register_non_send`.
2024-09-26 22:47:28 +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
Josh Robson Chase
3d0f2409d5
bevy_ecs: flush entities after running observers and hooks in despawn (#15398)
# Objective

Fixes #14467

Observers and component lifecycle hooks are allowed to perform
operations that subsequently require `Entities` to be flushed, such as
reserving a new entity. If this occurs during an `on_remove` hook or an
`OnRemove` event trigger during an `EntityWorldMut::despawn`, a panic
will occur.

## Solution

Call `world.flush_entities()` after running `on_remove` hooks/observers
during `despawn`

## Testing

Added a new test that fails before the fix and succeeds afterward.
2024-09-24 01:08:10 +00:00
Benjamin Brienen
27bea6abf7
Bubbling observers traversal should use query data (#15385)
# Objective

Fixes #14331

## Solution

- Make `Traversal` a subtrait of `ReadOnlyQueryData`
- Update implementations and usages

## Testing

- Updated unit tests

## Migration Guide

Update implementations of `Traversal`.

---------

Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
2024-09-23 18:08:36 +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
Christian Hughes
4682f33e0c
Add World::trigger_ref and World::trigger_targets_ref (#14894)
# Objective

Closes #14888.

## Solution

Add non-consuming trigger functions:

```rust
impl World {
    pub fn trigger_ref(&mut self, event: &mut impl Event);
    pub fn trigger_targets_ref(&mut self, event: &mut impl Event, targets: impl TriggerTargets);
}
```

## Testing

- Added two new tests, `observer_trigger_ref` and
`observer_trigger_targets_ref`.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-09-23 16:31:44 +00:00
Benjamin Brienen
b45d83ebda
Rename Add to Queue for methods with deferred semantics (#15234)
# Objective

- Fixes #15106

## Solution

- Trivial refactor to rename the method. The duplicate method `push` was
removed as well. This will simpify the API and make the semantics more
clear. `Add` implies that the action happens immediately, whereas in
reality, the command is queued to be run eventually.
- `ChildBuilder::add_command` has similarly been renamed to
`queue_command`.

## Testing

Unit tests should suffice for this simple refactor.

---

## Migration Guide

- `Commands::add` and `Commands::push` have been replaced with
`Commnads::queue`.
- `ChildBuilder::add_command` has been renamed to
`ChildBuilder::queue_command`.
2024-09-17 00:17:49 +00:00
Wybe Westra
70808af776
Added ordering information to observer tests (#14332) (#15178)
Fixes #14332 by recording the order in which the events occur.
2024-09-14 14:08:49 +00:00