# Objective
There are several uninlined format args (seems to be in more formatting
macros and in more crates) that are not detected on stable, but are on
nightly.
## Solution
Fix them.
# Objective
#19047 added an `MaybeUninit` field to `EntityMeta`, but did not
guarantee that it will be initialized before access:
```rust
let mut world = World::new();
let id = world.entities().reserve_entity();
world.flush();
world.entity(id);
```
<details>
<summary>Miri Error</summary>
```
error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
--> /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1121:26
|
1121 | unsafe { meta.spawned_or_despawned.assume_init() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory
|
= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
= note: BACKTRACE:
= note: inside closure at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1121:26: 1121:65
= note: inside `std::option::Option::<&bevy_ecs::entity::EntityMeta>::map::<bevy_ecs::entity::SpawnedOrDespawned, {closure@bevy_ecs::entity::Entities::entity_get_spawned_or_despawned::{closure#1}}>` at /home/vj/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1144:29: 1144:33
= note: inside `bevy_ecs::entity::Entities::entity_get_spawned_or_despawned` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1112:9: 1122:15
= note: inside closure at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1094:13: 1094:57
= note: inside `bevy_ecs::change_detection::MaybeLocation::<std::option::Option<&std::panic::Location<'_>>>::new_with_flattened::<{closure@bevy_ecs::entity::Entities::entity_get_spawned_or_despawned_by::{closure#0}}>` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/change_detection.rs:1371:20: 1371:24
= note: inside `bevy_ecs::entity::Entities::entity_get_spawned_or_despawned_by` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1093:9: 1096:11
= note: inside `bevy_ecs::entity::Entities::entity_does_not_exist_error_details` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1163:23: 1163:70
= note: inside `bevy_ecs::entity::EntityDoesNotExistError::new` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1182:22: 1182:74
= note: inside `bevy_ecs::world::unsafe_world_cell::UnsafeWorldCell::<'_>::get_entity` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/unsafe_world_cell.rs:368:20: 368:73
= note: inside `<bevy_ecs::entity::Entity as bevy_ecs::world::WorldEntityFetch>::fetch_ref` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/entity_fetch.rs:207:21: 207:42
= note: inside `bevy_ecs::world::World::get_entity::<bevy_ecs::entity::Entity>` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/mod.rs:911:18: 911:42
note: inside `main`
--> src/main.rs:12:15
|
12 | world.entity(id);
|
```
</details>
## Solution
- remove the existing `MaybeUninit` in `EntityMeta.spawned_or_despawned`
- initialize during flush. This is not needed for soundness, but not
doing this means we can't return a sensible location/tick for flushed
entities.
## Testing
Test via the snippet above (also added equivalent test).
---------
Co-authored-by: urben1680 <55257931+urben1680@users.noreply.github.com>
# Objective
Remove `ArchetypeComponentId` and `archetype_component_access`.
Following #16885, they are no longer used by the engine, so we can stop
spending time calculating them or space storing them.
## Solution
Remove `ArchetypeComponentId` and everything that touches it.
The `System::update_archetype_component_access` method no longer needs
to update `archetype_component_access`. We do still need to update query
caches, but we no longer need to do so *before* running the system. We'd
have to touch every caller anyway if we gave the method a better name,
so just remove `System::update_archetype_component_access` and
`SystemParam::new_archetype` entirely, and update the query cache in
`Query::get_param`.
The `Single` and `Populated` params also need their query caches updated
in `SystemParam::validate_param`, so change `validate_param` to take
`&mut Self::State` instead of `&Self::State`.
# Objective
Since #18704 is done, we can track the length of unique entity row
collections with only a `u32` and identify an index within that
collection with only a `NonMaxU32`. This leaves an opportunity for
performance improvements.
## Solution
- Use `EntityRow` in sparse sets.
- Change table, entity, and query lengths to be `u32` instead of
`usize`.
- Keep `batching` module `usize` based since that is reused for events,
which may exceed `u32::MAX`.
- Change according `Range<usize>` to `Range<u32>`. This is more
efficient and helps justify safety.
- Change `ArchetypeRow` and `TableRow` to wrap `NonMaxU32` instead of
`u32`.
Justifying `NonMaxU32::new_unchecked` everywhere is predicated on this
safety comment in `Entities::set`: "`location` must be valid for the
entity at `index` or immediately made valid afterwards before handing
control to unknown code." This ensures no entity is in two table rows
for example. That fact is used to argue uniqueness of the entity rows in
each table, archetype, sparse set, query, etc. So if there's no
duplicates, and a maximum total entities of `u32::MAX` none of the
corresponding row ids / indexes can exceed `NonMaxU32`.
## Testing
CI
---------
Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
## Objective
Add documentation useful to users of `bevy_ecs` not also using `App`.
Fixes#19270.
## Solution
* Add explanation of labels to `Schedule` documentation.
* Add example of `derive(ScheduleLabel)` to `trait ScheduleLabel`.
* Add a third example to `Schedule` which demonstrates using a schedule
via label instead of owning it directly.
* Add further explanation and links to `World::add_schedule()`, and
`World::run_schedule()`.
## Testing
Reviewed generated documentation.
Please review this documentation carefully for correctness, as I have
little experience with `bevy_ecs` and I am adding this information
because it would have helped my own past confusion, but I may still be
wrong about how things should be done.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: theotherphil <phil.j.ellison@gmail.com>
# Objective
[see original
comment](https://github.com/bevyengine/bevy/pull/18801#issuecomment-2796981745)
> Alternately, could we store it on the World instead of a global? I
think we have a World nearby whenever we call default_error_handler().
That would avoid the need for atomics or locks, since we could do
ordinary reads and writes to the World.
Global error handlers don't actually need to be global – per world is
enough. This allows using different handlers for different worlds and
also removes the restrictions on changing the handler only once.
## Solution
Each `World` can now store its own error handler in a resource.
For convenience, you can also set the default error handler for an
`App`, which applies it to the worlds of all `SubApp`s. The old behavior
of only being able to set the error handler once is kept for apps.
We also don't need the `configurable_error_handler` feature anymore now.
## Testing
New/adjusted tests for failing schedule systems & observers.
---
## Showcase
```rust
App::new()
.set_error_handler(info)
…
```
# Objective
In my own project I was encountering the issue to find out which
entities were spawned after applying commands. I began maintaining a
vector of all entities with generational information before and after
applying the command and diffing it. This was awfully complicated though
and has no constant complexity but grows with the number of entities.
## Solution
Looking at `EntyMeta` it seemed obvious to me that struct can track the
tick just as it does with `MaybeLocation`, updated from the same call.
After that it became almost a given to also introduce query data
`SpawnDetails` which offers methods to get the spawn tick and location,
and query filter `Spawned` that filters entities out that were not
spawned since the last run.
## Testing
I expanded a few tests and added new ones, though maybe I forgot a group
of tests that should be extended too. I basically searched `bevy_ecs`
for mentions of `Changed` and `Added` to see where the tests and docs
are.
Benchmarks of spawn/despawn can be found
[here](https://github.com/bevyengine/bevy/pull/19047#issuecomment-2852181374).
---
## Showcase
From the added docs, systems with equal complexity since the filter is
not archetypal:
```rs
fn system1(q: Query<Entity, Spawned>) {
for entity in &q { /* entity spawned */ }
}
fn system2(query: Query<(Entity, SpawnDetails)>) {
for (entity, spawned) in &query {
if spawned.is_spawned() { /* entity spawned */ }
}
}
```
`SpawnedDetails` has a few more methods:
```rs
fn print_spawn_details(query: Query<(Entity, SpawnDetails)>) {
for (entity, spawn_details) in &query {
if spawn_details.is_spawned() {
print!("new ");
}
println!(
"entity {:?} spawned at {:?} by {:?}",
entity,
spawn_details.spawned_at(),
spawn_details.spawned_by()
);
}
}
```
## Changes
No public api was changed, I only added to it. That is why I added no
migration guide.
- query data `SpawnDetails`
- query filter `Spawned`
- method `Entities::entity_get_spawned_or_despawned_at`
- method `EntityRef::spawned_at`
- method `EntityMut::spawned_at`
- method `EntityWorldMut::spawned_at`
- method `UnsafeEntityCell::spawned_at`
- method `FilteredEntityRef::spawned_at`
- method `FilteredEntityMut::spawned_at`
- method `EntityRefExcept::spawned_at`
- method `EntityMutExcept::spawned_at`
---------
Co-authored-by: Eagster <79881080+ElliottjPierce@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fixes a subset of https://github.com/bevyengine/bevy/issues/13735 by
making `EntityRef`, `EntityMut` + similar WorldQueries use the system's
change ticks when being created from within a system.
In particular, this means that `entity_ref.get_ref::<T>()` will use the
correct change ticks (the ones from the system), which matches the
behaviour of querying for `Ref<T>` directly in the system parameters.
## Solution
- Implements the solution described by
https://github.com/bevyengine/bevy/issues/13735#issuecomment-2652482918
which is to add change ticks to the `UnsafeEntityCell`
## Testing
- Added a unit test that is close to what users would encounter: before
this PR the `Added`/`Changed` filters on `Ref`s created from `EntityRef`
are incorrect.
# Objective
A fair few items were deprecated in 0.16. Let's delete them now that
we're in the 0.17 development cycle!
## Solution
- Deleted items marked deprecated in 0.16.
## Testing
- CI
---
## Notes
I'm making the assumption that _everything_ deprecated in 0.16 should be
removed in 0.17. That may be a false assumption in certain cases. Please
check the items to be removed to see if there are any exceptions we
should keep around for another cycle!
# Objective
It has long been a todo item in the ecs to create a `BundleRemover`
alongside the inserter, spawner, etc.
This is an uncontroversial first step of #18514.
## Solution
Move existing code from complex helper functions to one generalized
`BundleRemover`.
## Testing
Existing tests.
# Objective
Let `FilteredEntityRef` and `FilteredEntityMut` receive access when
nested inside tuples or `#[derive(QueryData)]` types. Make sure to
exclude any access that would conflict with other subqueries!
Fixes#14349
## Solution
Replace `WorldQuery::set_access(state, access)` with a new method,
`QueryData::provide_extra_access(state, access, available_access)`, that
passes both the total available access and the currently used access.
This is called after `WorldQuery::update_component_access()`, so any
access used by ordinary subqueries will be known. `FilteredEntityRef`
and `FilteredEntityMut` can use the combination to determine how much
access they can safely take, while tuples can safely pass those
parameters directly to their subqueries.
This requires a new `Access::remove_conflicting_access()` method that
can be used to remove any access that would conflict with existing
access. Implementing this method was easier by first factoring some
common set manipulation code out of `Access::extend`. I can extract that
refactoring to a separate PR if desired.
Have `FilteredEntity(Ref|Mut)` store `Access` instead of
`FilteredAccess` because they do not need to keep track of the filter.
This was necessary in an early draft but no longer is. I left it in
because it's small and I'm touching that code anyway, but I can extract
it to a separate PR if desired.
# Objective
Based on and closes#18054, this PR builds on #18035 and #18147 to
remove:
- `Commands::insert_or_spawn_batch`
- `Entities::alloc_at_without_replacement`
- `Entities::alloc_at`
- `entity::AllocAtWithoutReplacement`
- `World::insert_or_spawn_batch`
- `World::insert_or_spawn_batch_with_caller`
## Testing
Just removing unused, deprecated code, so no new tests. Note that as of
writing, #18035 is still under testing and review.
## Future Work
Per
[this](https://github.com/bevyengine/bevy/issues/18054#issuecomment-2689088899)
comment on #18054, there may be additional performance improvements
possible to the entity allocator now that `alloc_at` no longer is
supported. At a glance, I don't see anything obvious to improve, but it
may be worth further investigation in the future.
---------
Co-authored-by: JaySpruce <jsprucebruce@gmail.com>
# Objective
Prevent using exclusive systems as observers. Allowing them is unsound,
because observers are only expected to have `DeferredWorld` access, and
the observer infrastructure will keep pointers that are invalidated by
the creation of `&mut World`.
See
https://github.com/bevyengine/bevy/actions/runs/14778342801/job/41491517847?pr=19011
for a MIRI failure in a recent PR caused by an exclusive system being
used as an observer in a test.
## Solution
Have `Observer::new` panic if `System::is_exclusive()` is true. Document
that method, and methods that call it, as panicking.
(It should be possible to express this in the type system so that the
calls won't even compile, but I did not want to attempt that.)
## Testing
Added a unit test that calls `World::add_observer` with an exclusive
system.
# Objective
The goal of `bevy_platform_support` is to provide a set of platform
agnostic APIs, alongside platform-specific functionality. This is a high
traffic crate (providing things like HashMap and Instant). Especially in
light of https://github.com/bevyengine/bevy/discussions/18799, it
deserves a friendlier / shorter name.
Given that it hasn't had a full release yet, getting this change in
before Bevy 0.16 makes sense.
## Solution
- Rename `bevy_platform_support` to `bevy_platform`.
# Objective
- The `#[deprecated]` attributes supports a `since` field, which
documents in which version an item was deprecated. This field is visible
in `rustdoc`.
- We inconsistently use `since` throughout the project.
For an example of what `since` renders as, take a look at
`ChildOf::get()`:
```rust
/// The parent entity of this child entity.
#[deprecated(since = "0.16.0", note = "Use child_of.parent() instead")]
#[inline]
pub fn get(&self) -> Entity {
self.0
}
```
## Solution
- Add `since = "0.16.0"` to all `#[deprecated]` attributes that do not
already use it.
- Add an example of deprecating a struct with the `since` field in the
migration guide document.
I would appreciate if this could be included in 0.16's release, as its a
low-risk documentation improvement that is valuable for the release, but
I'd understand if this was cut.
## Testing
You can use `cargo doc` to inspect the rendered form of
`#[deprecated(since = "0.16.0", ...)]`.
# Objective
#18173 allows components to be queued without being fully registered.
But much of bevy's debug logging contained
`components.get_name(id).unwrap()`. However, this panics when the id is
queued. This PR fixes this, allowing names to be retrieved for debugging
purposes, etc, even while they're still queued.
## Solution
We change `ComponentInfo::descriptor` to be `Arc<ComponentDescriptor>`
instead of not arc'd. This lets us pass the descriptor around (as a name
or otherwise) as needed. The alternative would require some form of
`MappedRwLockReadGuard`, which is unstable, and would be terribly
blocking. Putting it in an arc also signifies that it doesn't change,
which is a nice signal to users. This does mean there's an extra pointer
dereference, but I don't think that's an issue here, as almost all paths
that use this are for debugging purposes or one-time set ups.
## Testing
Existing tests.
## Migration Guide
`Components::get_name` now returns `Option<Cow<'_, str>` instead of
`Option<&str>`. This is because it now returns results for queued
components. If that behavior is not desired, or you know the component
is not queued, you can use
`components.get_info().map(ComponentInfo::name)` instead.
Similarly, `ScheduleGraph::conflicts_to_string` now returns `impl
Iterator<Item = (String, String, Vec<Cow<str>>)>` instead of `impl
Iterator<Item = (String, String, Vec<&str>)>`. Because `Cow<str>` derefs
to `&str`, most use cases can remain unchanged.
---------
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
# Objective
Fixes#9367.
Yet another follow-up to #16547.
These traits were initially based on `Borrow<Entity>` because that trait
was what they were replacing, and it felt close enough in meaning.
However, they ultimately don't quite match: `borrow` always returns
references, whereas `EntityBorrow` always returns a plain `Entity`.
Additionally, `EntityBorrow` can imply that we are borrowing an `Entity`
from the ECS, which is not what it does.
Due to its safety contract, `TrustedEntityBorrow` is important an
important and widely used trait for `EntitySet` functionality.
In contrast, the safe `EntityBorrow` does not see much use, because even
outside of `EntitySet`-related functionality, it is a better idea to
accept `TrustedEntityBorrow` over `EntityBorrow`.
Furthermore, as #9367 points out, abstracting over returning `Entity`
from pointers/structs that contain it can skip some ergonomic friction.
On top of that, there are aspects of #18319 and #18408 that are relevant
to naming:
We've run into the issue that relying on a type default can switch
generic order. This is livable in some contexts, but unacceptable in
others.
To remedy that, we'd need to switch to a type alias approach:
The "defaulted" `Entity` case becomes a
`UniqueEntity*`/`Entity*Map`/`Entity*Set` alias, and the base type
receives a more general name. `TrustedEntityBorrow` does not mesh
clearly with sensible base type names.
## Solution
Replace any `EntityBorrow` bounds with `TrustedEntityBorrow`.
+
Rename them as such:
`EntityBorrow` -> `ContainsEntity`
`TrustedEntityBorrow` -> `EntityEquivalent`
For `EntityBorrow` we produce a change in meaning; We designate it for
types that aren't necessarily strict wrappers around `Entity` or some
pointer to `Entity`, but rather any of the myriad of types that contain
a single associated `Entity`.
This pattern can already be seen in the common `entity`/`id` methods
across the engine.
We do not mean for `ContainsEntity` to be a trait that abstracts input
API (like how `AsRef<T>` is often used, f.e.), because eliding
`entity()` would be too implicit in the general case.
We prefix "Contains" to match the intuition of a struct with an `Entity`
field, like some contain a `length` or `capacity`.
It gives the impression of structure, which avoids the implication of a
relationship to the `ECS`.
`HasEntity` f.e. could be interpreted as "a currently live entity",
As an input trait for APIs like #9367 envisioned, `TrustedEntityBorrow`
is a better fit, because it *does* restrict itself to strict wrappers
and pointers. Which is why we replace any
`EntityBorrow`/`ContainsEntity` bounds with
`TrustedEntityBorrow`/`EntityEquivalent`.
Here, the name `EntityEquivalent` is a lot closer to its actual meaning,
which is "A type that is both equivalent to an `Entity`, and forms the
same total order when compared".
Prior art for this is the
[`Equivalent`](https://docs.rs/hashbrown/latest/hashbrown/trait.Equivalent.html)
trait in `hashbrown`, which utilizes both `Borrow` and `Eq` for its one
blanket impl!
Given that we lose the `Borrow` moniker, and `Equivalent` can carry
various meanings, we expand on the safety comment of `EntityEquivalent`
somewhat. That should help prevent the confusion we saw in
[#18408](https://github.com/bevyengine/bevy/pull/18408#issuecomment-2742094176).
The new name meshes a lot better with the type aliasing approach in
#18408, by aligning with the base name `EntityEquivalentHashMap`.
For a consistent scheme among all set types, we can use this scheme for
the `UniqueEntity*` wrapper types as well!
This allows us to undo the switched generic order that was introduced to
`UniqueEntityArray` by its `Entity` default.
Even without the type aliases, I think these renames are worth doing!
## Migration Guide
Any use of `EntityBorrow` becomes `ContainsEntity`.
Any use of `TrustedEntityBorrow` becomes `EntityEquivalent`.
# Objective
Unlike for their helper typers, the import paths for
`unique_array::UniqueEntityArray`, `unique_slice::UniqueEntitySlice`,
`unique_vec::UniqueEntityVec`, `hash_set::EntityHashSet`,
`hash_map::EntityHashMap`, `index_set::EntityIndexSet`,
`index_map::EntityIndexMap` are quite redundant.
When looking at the structure of `hashbrown`, we can also see that while
both `HashSet` and `HashMap` have their own modules, the main types
themselves are re-exported to the crate level.
## Solution
Re-export the types in their shared `entity` parent module, and simplify
the imports where they're used.
# Objective
Requires are currently more verbose than they need to be. People would
like to define inline component values. Additionally, the current
`#[require(Foo(custom_constructor))]` and `#[require(Foo(|| Foo(10))]`
syntax doesn't really make sense within the context of the Rust type
system. #18309 was an attempt to improve ergonomics for some cases, but
it came at the cost of even more weirdness / unintuitive behavior. Our
approach as a whole needs a rethink.
## Solution
Rework the `#[require()]` syntax to make more sense. This is a breaking
change, but I think it will make the system easier to learn, while also
improving ergonomics substantially:
```rust
#[derive(Component)]
#[require(
A, // this will use A::default()
B(1), // inline tuple-struct value
C { value: 1 }, // inline named-struct value
D::Variant, // inline enum variant
E::SOME_CONST, // inline associated const
F::new(1), // inline constructor
G = returns_g(), // an expression that returns G
H = SomethingElse::new(), // expression returns SomethingElse, where SomethingElse: Into<H>
)]
struct Foo;
```
## Migration Guide
Custom-constructor requires should use the new expression-style syntax:
```rust
// before
#[derive(Component)]
#[require(A(returns_a))]
struct Foo;
// after
#[derive(Component)]
#[require(A = returns_a())]
struct Foo;
```
Inline-closure-constructor requires should use the inline value syntax
where possible:
```rust
// before
#[derive(Component)]
#[require(A(|| A(10))]
struct Foo;
// after
#[derive(Component)]
#[require(A(10)]
struct Foo;
```
In cases where that is not possible, use the expression-style syntax:
```rust
// before
#[derive(Component)]
#[require(A(|| A(10))]
struct Foo;
// after
#[derive(Component)]
#[require(A = A(10)]
struct Foo;
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François Mockers <mockersf@gmail.com>
# Objective
- Fixes#16861
## Solution
- Added:
- `UnsafeEntityCell::get_mut_assume_mutable_by_id`
- `EntityMut::get_mut_assume_mutable_by_id`
- `EntityMut::get_mut_assume_mutable_by_id_unchecked`
- `EntityWorldMut::into_mut_assume_mutable_by_id`
- `EntityWorldMut::into_mut_assume_mutable`
- `EntityWorldMut::get_mut_assume_mutable_by_id`
- `EntityWorldMut::into_mut_assume_mutable_by_id`
- `EntityWorldMut::modify_component_by_id`
- `World::modify_component_by_id`
- `DeferredWorld::modify_component_by_id`
- Added `fetch_mut_assume_mutable` to `DynamicComponentFetch` trait
(this is a breaking change)
## Testing
- CI
---
## Migration Guide
If you had previously implemented `DynamicComponentFetch` you must now
include a definition for `fetch_mut_assume_mutable`. In general this
will be identical to `fetch_mut` using the relevant alternatives for
actually getting a component.
---
## Notes
All of the added methods are minor variations on existing functions and
should therefore be of low risk for inclusion during the RC process.
# Objective
fixes#18452.
## Solution
Spawning used to flush commands only, but those commands can reserve
entities. Now, spawning flushes everything, including reserved entities.
I checked, and this was the only place where `flush_commands` is used
instead of `flush` by mistake.
## Testing
I simplified the MRE from #18452 into its own test, which fails on main,
but passes on this branch.
# Objective
I was looking over a PR yesterday, and got confused by the docs on
deferred world. I thought I would add a little more detail to the struct
in order to clarify it a little.
## Solution
Document some more about deferred worlds.
# Objective
Fixes#18357
## Solution
Generalize `RelationshipInsertHookMode` to `RelationshipHookMode`, wire
it up to on_replace execution, and use it in the
`Relationship::on_replace` hook.
# Objective
FilteredResource::get should return a Result instead of Option
Fixes#17480
---
## Migration Guide
Users will need to handle the different return type on
FilteredResource::get, FilteredResource::get_id,
FilteredResource::get_mut as it is now a Result not an Option.
# Objective
Currently experimenting with manually implementing
`Relationship`/`RelationshipTarget` to support associated edge data,
which means I need to replace the default hook implementations provided
by those traits. However, copying them over for editing revealed that
`UnsafeWorldCell::get_raw_command_queue` is `pub(crate)`, and I would
like to not have to clone the source collection, like the default impl.
So instead, I've taken to providing a safe abstraction for being able to
access entities and queue commands simultaneously.
## Solution
Added `World::entities_and_commands` and
`DeferredWorld::entities_and_commands`, which can be used like so:
```rust
let eid: Entity = /* ... */;
let (mut fetcher, mut commands) = world.entities_and_commands();
let emut = fetcher.get_mut(eid).unwrap();
commands.entity(eid).despawn();
```
## Testing
- Added a new test for each of the added functions.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Registering dynamic bundles was not possible for the user yet.
It is alone not very useful though as there are no methods to clone,
move or remove components via a `BundleId`. This could be a follow-up
work if this PR is approved and such a third (besides `T: Bundle` and
`ComponentId`(s)) API for structural operation is desired. I certainly
would use a hypothetical `EntityClonerBuilder::allow_by_bundle_id`.
I personally still would like this register method because I have a
`Bundles`-like custom data structure and I would like to not reinvent
the wheel. Then instead of having boxed `ComponentId` slices in my
collection I could look up explicit and required components there.
For reference scroll up to the typed version right above the new one.
# Objective
- Prevent usage of `println!`, `eprintln!` and the like because they
require `std`
- Fixes#17446
## Solution
- Enable the `print_stdout` and `print_stderr` clippy lints
- Replace all `println!` and `eprintln!` occurrences with `log::*` where
applicable or alternatively ignore the warnings
## Testing
- Run `cargo clippy --workspace` to ensure that there are no warnings
relating to printing to `stdout` or `stderr`
# 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>
# Objective
Based on #18054, this PR builds on #18035 to deprecate:
- `Commands::insert_or_spawn_batch`
- `Entities::alloc_at_without_replacement`
- `Entities::alloc_at`
- `World::insert_or_spawn_batch`
- `World::insert_or_spawn_batch_with_caller`
## Testing
Just deprecation, so no new tests. Note that as of writing #18035 is
still under testing and review.
## Open Questions
- [x] Should `entity::AllocAtWithoutReplacement` be deprecated? It is
internal and only used in `Entities::alloc_at_without_replacement`.
**EDIT:** Now deprecated.
## Migration Guide
The following functions have been deprecated:
- `Commands::insert_or_spawn_batch`
- `World::insert_or_spawn_batch`
- `World::insert_or_spawn_batch_with_caller`
These functions, when used incorrectly, can cause major performance
problems and are generally viewed as anti-patterns and foot guns. These
are planned to be removed altogether in 0.17.
Instead of these functions consider doing one of the following:
Option A) Instead of despawing entities and re-spawning them at a
particular id, insert the new `Disabled` component without despawning
the entity, and use `try_insert_batch` or `insert_batch` and remove
`Disabled` instead of re-spawning it.
Option B) Instead of giving special meaning to an entity id, simply use
`spawn_batch` and ensure entity references are valid when despawning.
---------
Co-authored-by: JaySpruce <jsprucebruce@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
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>
# Objective
Many systems like `Schedule` rely on the fact that every structural ECS
changes are deferred until an exclusive system flushes the `World`
itself. This gives us the benefits of being able to run systems in
parallel without worrying about dangling references caused by memory
(re)allocations, which will in turn lead to **Undefined Behavior**.
However, this isn't explicitly documented in `SystemParam`; currently it
only vaguely hints that in `init_state`, based on the fact that
structural ECS changes require mutable access to the _whole_ `World`.
## Solution
Document this behavior explicitly in `SystemParam`'s type-level
documentations.
# Objective
As discussed in #14275, Bevy is currently too prone to panic, and makes
the easy / beginner-friendly way to do a large number of operations just
to panic on failure.
This is seriously frustrating in library code, but also slows down
development, as many of the `Query::single` panics can actually safely
be an early return (these panics are often due to a small ordering issue
or a change in game state.
More critically, in most "finished" products, panics are unacceptable:
any unexpected failures should be handled elsewhere. That's where the
new
With the advent of good system error handling, we can now remove this.
Note: I was instrumental in a) introducing this idea in the first place
and b) pushing to make the panicking variant the default. The
introduction of both `let else` statements in Rust and the fancy system
error handling work in 0.16 have changed my mind on the right balance
here.
## Solution
1. Make `Query::single` and `Query::single_mut` (and other random
related methods) return a `Result`.
2. Handle all of Bevy's internal usage of these APIs.
3. Deprecate `Query::get_single` and friends, since we've moved their
functionality to the nice names.
4. Add detailed advice on how to best handle these errors.
Generally I like the diff here, although `get_single().unwrap()` in
tests is a bit of a downgrade.
## Testing
I've done a global search for `.single` to track down any missed
deprecated usages.
As to whether or not all the migrations were successful, that's what CI
is for :)
## Future work
~~Rename `Query::get_single` and friends to `Query::single`!~~
~~I've opted not to do this in this PR, and smear it across two releases
in order to ease the migration. Successive deprecations are much easier
to manage than the semantics and types shifting under your feet.~~
Cart has convinced me to change my mind on this; see
https://github.com/bevyengine/bevy/pull/18082#discussion_r1974536085.
## Migration guide
`Query::single`, `Query::single_mut` and their `QueryState` equivalents
now return a `Result`. Generally, you'll want to:
1. Use Bevy 0.16's system error handling to return a `Result` using the
`?` operator.
2. Use a `let else Ok(data)` block to early return if it's an expected
failure.
3. Use `unwrap()` or `Ok` destructuring inside of tests.
The old `Query::get_single` (etc) methods which did this have been
deprecated.
## Objective
`insert_by_id` is unsafe, but I forgot to add that to the
manually-queueable version in `entity_command`.
It also can only insert using `InsertMode::Replace`, when it could
easily be configurable by threading an `InsertMode` parameter to the
final `BundleInserter::insert` call.
## Solution
- Add `unsafe` and safety comment.
- Add `InsertMode` parameter to `entity_command::insert_by_id`,
`EntityWorldMut::insert_by_id_with_caller`, and
`EntityWorldMut::insert_dynamic_bundle`.
- Add `InsertMode` parameter to `entity_command::insert` and remove
`entity_command::insert_if_new`, for consistency with the other
manually-queued insertion commands.
# Objective
This prevents overflowing the `last_trigger_id` property that leads to a
panic in debug mode.
```bash
panicked at C:\XXX\.cargo\registry\src\index.crates.io-6f17d22bba15001f\bevy_ecs-0.15.2\src\world\unsafe_world_cell.rs:630:18:
attempt to add with overflow
Encountered a panic when applying buffers for system `bevy_sprite::calculate_bounds_2d`!
Encountered a panic in system `bevy_ecs::schedule::executor::apply_deferred`!
```
## Solution
As this value is only used for detecting a change, we can wrap when it
reaches max value.
## Testing
This can be verified by running `cargo run --example observers`
# 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>
# Objective
- Fixes#17897.
## Solution
- When removing components, we filter the list of components in the
removed bundle based on whether they are actually in the archetype.
## Testing
- Added a test.
# 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>
## Objective
There's no general error for when an entity doesn't exist, and some
methods are going to need one when they get Resultified. The closest
thing is `EntityFetchError`, but that error has a slightly more specific
purpose.
## Solution
- Added `EntityDoesNotExistError`.
- Contains `Entity` and `EntityDoesNotExistDetails`.
- Changed `EntityFetchError` and `QueryEntityError`:
- Changed `NoSuchEntity` variant to wrap `EntityDoesNotExistError` and
renamed the variant to `EntityDoesNotExist`.
- Renamed `EntityFetchError` to `EntityMutableFetchError` to make its
purpose clearer.
- Renamed `TryDespawnError` to `EntityDespawnError` to make it more
general.
- Changed `World::inspect_entity` to return `Result<[ok],
EntityDoesNotExistError>` instead of panicking.
- Changed `World::get_entity` and `WorldEntityFetch::fetch_ref` to
return `Result<[ok], EntityDoesNotExistError>` instead of `Result<[ok],
Entity>`.
- Changed `UnsafeWorldCell::get_entity` to return
`Result<UnsafeEntityCell, EntityDoesNotExistError>` instead of
`Option<UnsafeEntityCell>`.
## Migration Guide
- `World::inspect_entity` now returns `Result<impl Iterator<Item =
&ComponentInfo>, EntityDoesNotExistError>` instead of `impl
Iterator<Item = &ComponentInfo>`.
- `World::get_entity` now returns `EntityDoesNotExistError` as an error
instead of `Entity`. You can still access the entity's ID through the
error's `entity` field.
- `UnsafeWorldCell::get_entity` now returns `Result<UnsafeEntityCell,
EntityDoesNotExistError>` instead of `Option<UnsafeEntityCell>`.
# Objective
Related to #17784. The ticket is actually about just getting rid of
`Entity{Ref,Mut}Except` in favor of `FilteredEntity{Ref,Mut}`, but I got
told the unification of Entity types is a bigger endeavor that has been
going on for a while now (as the "Pointing Fingers" working group) and I
should just add the functions I actually need in the meantime.
## Solution
This PR adds all of the functions necessary to access components by
TypeId or ComponentId instead of static types.
## Testing
> Did you test these changes? If so, how?
Haven't tested it yet, but the changes are mostly copy/paste from other
implementations in the same file, since there is a lot of duplicated
functionality there.
## Not a Migration Guide
There shouldn't be any breaking changes, it's just a few new functions
on existing types.
I had to shuffle around the lifetimes in `From<&EntityMutExcept<'a, B>>
for EntityRefExcept<'a, B>` (originally it was `From<&'a
EntityMutExcept<'_, B>> for EntityRefExcept<'_, B>`) to make the borrow
checker happy, but I don't think that this should have an impact on user
code (correct me if I'm wrong).
You can now configure error handlers for fallible systems. These can be
configured on several levels:
- Globally via `App::set_systems_error_handler`
- Per-schedule via `Schedule::set_error_handler`
- Per-system via a piped system (this is existing functionality)
The default handler of panicking on error keeps the same behavior as
before this commit.
The "fallible_systems" example demonstrates the new functionality.
This builds on top of #17731, #16589, #17051.
---------
Signed-off-by: Jean Mertz <git@jeanmertz.com>
# Objective
Currently, default query filters, as added in #13120 / #17514 are
hardcoded to only use a single query filter.
This is limiting, as multiple distinct disabling components can serve
important distinct roles. I ran into this limitation when experimenting
with a workflow for prefabs, which don't represent the same state as "an
entity which is temporarily nonfunctional".
## Solution
1. Change `DefaultQueryFilters` to store a SmallVec of ComponentId,
rather than an Option.
2. Expose methods on `DefaultQueryFilters`, `World` and `App` to
actually configure this.
3. While we're here, improve the docs, write some tests, make use of
FromWorld and make some method names more descriptive.
## Follow-up
I'm not convinced that supporting sparse set disabling components is
useful, given the hit to iteration performance and runtime checks
incurred. That's disjoint from this PR though, so I'm not doing it here.
The existing warnings are fine for now.
## Testing
I've added both a doc test and an mid-level unit test to verify that
this works!
# 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.
## Objective
A major critique of Bevy at the moment is how boilerplatey it is to
compose (and read) entity hierarchies:
```rust
commands
.spawn(Foo)
.with_children(|p| {
p.spawn(Bar).with_children(|p| {
p.spawn(Baz);
});
p.spawn(Bar).with_children(|p| {
p.spawn(Baz);
});
});
```
There is also currently no good way to statically define and return an
entity hierarchy from a function. Instead, people often do this
"internally" with a Commands function that returns nothing, making it
impossible to spawn the hierarchy in other cases (direct World spawns,
ChildSpawner, etc).
Additionally, because this style of API results in creating the
hierarchy bits _after_ the initial spawn of a bundle, it causes ECS
archetype changes (and often expensive table moves).
Because children are initialized after the fact, we also can't count
them to pre-allocate space. This means each time a child inserts itself,
it has a high chance of overflowing the currently allocated capacity in
the `RelationshipTarget` collection, causing literal worst-case
reallocations.
We can do better!
## Solution
The Bundle trait has been extended to support an optional
`BundleEffect`. This is applied directly to World immediately _after_
the Bundle has fully inserted. Note that this is
[intentionally](https://github.com/bevyengine/bevy/discussions/16920)
_not done via a deferred Command_, which would require repeatedly
copying each remaining subtree of the hierarchy to a new command as we
walk down the tree (_not_ good performance).
This allows us to implement the new `SpawnRelated` trait for all
`RelationshipTarget` impls, which looks like this in practice:
```rust
world.spawn((
Foo,
Children::spawn((
Spawn((
Bar,
Children::spawn(Spawn(Baz)),
)),
Spawn((
Bar,
Children::spawn(Spawn(Baz)),
)),
))
))
```
`Children::spawn` returns `SpawnRelatedBundle<Children, L:
SpawnableList>`, which is a `Bundle` that inserts `Children`
(preallocated to the size of the `SpawnableList::size_hint()`).
`Spawn<B: Bundle>(pub B)` implements `SpawnableList` with a size of 1.
`SpawnableList` is also implemented for tuples of `SpawnableList` (same
general pattern as the Bundle impl).
There are currently three built-in `SpawnableList` implementations:
```rust
world.spawn((
Foo,
Children::spawn((
Spawn(Name::new("Child1")),
SpawnIter(["Child2", "Child3"].into_iter().map(Name::new),
SpawnWith(|parent: &mut ChildSpawner| {
parent.spawn(Name::new("Child4"));
parent.spawn(Name::new("Child5"));
})
)),
))
```
We get the benefits of "structured init", but we have nice flexibility
where it is required!
Some readers' first instinct might be to try to remove the need for the
`Spawn` wrapper. This is impossible in the Rust type system, as a tuple
of "child Bundles to be spawned" and a "tuple of Components to be added
via a single Bundle" is ambiguous in the Rust type system. There are two
ways to resolve that ambiguity:
1. By adding support for variadics to the Rust type system (removing the
need for nested bundles). This is out of scope for this PR :)
2. Using wrapper types to resolve the ambiguity (this is what I did in
this PR).
For the single-entity spawn cases, `Children::spawn_one` does also
exist, which removes the need for the wrapper:
```rust
world.spawn((
Foo,
Children::spawn_one(Bar),
))
```
## This works for all Relationships
This API isn't just for `Children` / `ChildOf` relationships. It works
for any relationship type, and they can be mixed and matched!
```rust
world.spawn((
Foo,
Observers::spawn((
Spawn(Observer::new(|trigger: Trigger<FuseLit>| {})),
Spawn(Observer::new(|trigger: Trigger<Exploded>| {})),
)),
OwnerOf::spawn(Spawn(Bar))
Children::spawn(Spawn(Baz))
))
```
## Macros
While `Spawn` is necessary to satisfy the type system, we _can_ remove
the need to express it via macros. The example above can be expressed
more succinctly using the new `children![X]` macro, which internally
produces `Children::spawn(Spawn(X))`:
```rust
world.spawn((
Foo,
children![
(
Bar,
children![Baz],
),
(
Bar,
children![Baz],
),
]
))
```
There is also a `related!` macro, which is a generic version of the
`children!` macro that supports any relationship type:
```rust
world.spawn((
Foo,
related!(Children[
(
Bar,
related!(Children[Baz]),
),
(
Bar,
related!(Children[Baz]),
),
])
))
```
## Returning Hierarchies from Functions
Thanks to these changes, the following pattern is now possible:
```rust
fn button(text: &str, color: Color) -> impl Bundle {
(
Node {
width: Val::Px(300.),
height: Val::Px(100.),
..default()
},
BackgroundColor(color),
children![
Text::new(text),
]
)
}
fn ui() -> impl Bundle {
(
Node {
width: Val::Percent(100.0),
height: Val::Percent(100.0),
..default(),
},
children![
button("hello", BLUE),
button("world", RED),
]
)
}
// spawn from a system
fn system(mut commands: Commands) {
commands.spawn(ui());
}
// spawn directly on World
world.spawn(ui());
```
## Additional Changes and Notes
* `Bundle::from_components` has been split out into
`BundleFromComponents::from_components`, enabling us to implement
`Bundle` for types that cannot be "taken" from the ECS (such as the new
`SpawnRelatedBundle`).
* The `NoBundleEffect` trait (which implements `BundleEffect`) is
implemented for empty tuples (and tuples of empty tuples), which allows
us to constrain APIs to only accept bundles that do not have effects.
This is critical because the current batch spawn APIs cannot efficiently
apply BundleEffects in their current form (as doing so in-place could
invalidate the cached raw pointers). We could consider allocating a
buffer of the effects to be applied later, but that does have
performance implications that could offset the balance and value of the
batched APIs (and would likely require some refactors to the underlying
code). I've decided to be conservative here. We can consider relaxing
that requirement on those APIs later, but that should be done in a
followup imo.
* I've ported a few examples to illustrate real-world usage. I think in
a followup we should port all examples to the `children!` form whenever
possible (and for cases that require things like SpawnIter, use the raw
APIs).
* Some may ask "why not use the `Relationship` to spawn (ex:
`ChildOf::spawn(Foo)`) instead of the `RelationshipTarget` (ex:
`Children::spawn(Spawn(Foo))`)?". That _would_ allow us to remove the
`Spawn` wrapper. I've explicitly chosen to disallow this pattern.
`Bundle::Effect` has the ability to create _significant_ weirdness.
Things in `Bundle` position look like components. For example
`world.spawn((Foo, ChildOf::spawn(Bar)))` _looks and reads_ like Foo is
a child of Bar. `ChildOf` is in Foo's "component position" but it is not
a component on Foo. This is a huge problem. Now that `Bundle::Effect`
exists, we should be _very_ principled about keeping the "weird and
unintuitive behavior" to a minimum. Things that read like components
_should be the components they appear to be".
## Remaining Work
* The macros are currently trivially implemented using macro_rules and
are currently limited to the max tuple length. They will require a
proc_macro implementation to work around the tuple length limit.
## Next Steps
* Port the remaining examples to use `children!` where possible and raw
`Spawn` / `SpawnIter` / `SpawnWith` where the flexibility of the raw API
is required.
## Migration Guide
Existing spawn patterns will continue to work as expected.
Manual Bundle implementations now require a `BundleEffect` associated
type. Exisiting bundles would have no bundle effect, so use `()`.
Additionally `Bundle::from_components` has been moved to the new
`BundleFromComponents` trait.
```rust
// Before
unsafe impl Bundle for X {
unsafe fn from_components<T, F>(ctx: &mut T, func: &mut F) -> Self {
}
/* remaining bundle impl here */
}
// After
unsafe impl Bundle for X {
type Effect = ();
/* remaining bundle impl here */
}
unsafe impl BundleFromComponents for X {
unsafe fn from_components<T, F>(ctx: &mut T, func: &mut F) -> Self {
}
}
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
Co-authored-by: Emerson Coskey <emerson@coskey.dev>
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>
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>
# 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>
# Objective
Simplify and expand the API for `QueryState`.
`QueryState` has a lot of methods that mirror those on `Query`. These
are then multiplied by variants that take `&World`, `&mut World`, and
`UnsafeWorldCell`. In addition, many of them have `_manual` variants
that take `&QueryState` and avoid calling `update_archetypes()`. Not all
of the combinations exist, however, so some operations are not possible.
## Solution
Introduce methods to get a `Query` from a `QueryState`. That will reduce
duplication between the types, and ensure that the full `Query` API is
always available for `QueryState`.
Introduce methods on `Query` that consume the query to return types with
the full `'w` lifetime. This avoids issues with borrowing where things
like `query_state.query(&world).get(entity)` don't work because they
borrow from the temporary `Query`.
Finally, implement `Copy` for read-only `Query`s. `get_inner` and
`iter_inner` currently take `&self`, so changing them to consume `self`
would be a breaking change. By making `Query: Copy`, they can consume a
copy of `self` and continue to work.
The consuming methods also let us simplify the implementation of methods
on `Query`, by doing `fn foo(&self) { self.as_readonly().foo_inner() }`
and `fn foo_mut(&mut self) { self.reborrow().foo_inner() }`. That
structure makes it more difficult to accidentally extend lifetimes,
since the safe `as_readonly()` and `reborrow()` methods shrink them
appropriately. The optimizer is able to see that they are both identity
functions and inline them, so there should be no performance cost.
Note that this change would conflict with #15848. If `QueryState` is
stored as a `Cow`, then the consuming methods cannot be implemented, and
`Copy` cannot be implemented.
## Future Work
The next step is to mark the methods on `QueryState` as `#[deprecated]`,
and move the implementations into `Query`.
## Migration Guide
`Query::to_readonly` has been renamed to `Query::as_readonly`.
