# 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
Newest installment of the #16547 series.
In #18319 we introduced `Entity` defaults to accomodate the most common
use case for these types, however that resulted in the switch of the `T`
and `N` generics of `UniqueEntityArray`.
Swapping generics might be somewhat acceptable for `UniqueEntityArray`,
it is not at all acceptable for map and set types, which we would make
generic over `T: EntityEquivalent` in #18408.
Leaving these defaults in place would result in a glaring inconsistency
between these set collections and the others.
Additionally, the current standard in the engine is for "entity" to mean
`Entity`. APIs could be changed to accept `EntityEquivalent`, however
that is a separate and contentious discussion.
## Solution
Name these set collections `UniqueEntityEquivalent*`, and retain the
`UniqueEntity*` name for an alias of the `Entity` case.
While more verbose, this allows for all generics to be in proper order,
full consistency between all set types*, and the "entity" name to be
restricted to `Entity`.
On top of that, `UniqueEntity*` now always have 1 generic less, when
previously this was not enforced for the default case.
*`UniqueEntityIter<I: Iterator<T: EntityEquivalent>>` is the sole
exception to this. Aliases are unable to enforce bounds
(`lazy_type_alias` is needed for this), so for this type, doing this
split would be a mere suggestion, and in no way enforced.
Iterator types are rarely ever named, and this specific one is intended
to be aliased when it sees more use, like we do for the corresponding
set collection iterators.
Furthermore, the `EntityEquivalent` precursor `Borrow<Entity>` was used
exactly because of such iterator bounds!
Because of that, we leave it as is.
While no migration guide for 0.15 users, for those that upgrade from
main:
`UniqueEntityVec<T>` -> `UniqueEntityEquivalentVec<T>`
`UniqueEntitySlice<T>` -> `UniqueEntityEquivalentSlice<T>`
`UniqueEntityArray<N, T>` -> `UniqueEntityEquivalentArray<T, N>`
# Objective
In #17905 we swapped to a named field on `ChildOf` to help resolve
variable naming ambiguity of child vs parent (ex: `child_of.parent`
clearly reads as "I am accessing the parent of the child_of
relationship", whereas `child_of.0` is less clear).
Unfortunately this has the side effect of making initialization less
ideal. `ChildOf { parent }` reads just as well as `ChildOf(parent)`, but
`ChildOf { parent: root }` doesn't read nearly as well as
`ChildOf(root)`.
## Solution
Move back to `ChildOf(pub Entity)` but add a `child_of.parent()`
function and use it for all accesses. The downside here is that users
are no longer "forced" to access the parent field with `parent`
nomenclature, but I think this strikes the right balance.
Take a look at the diff. I think the results provide strong evidence for
this change. Initialization has the benefit of reading much better _and_
of taking up significantly less space, as many lines go from 3 to 1, and
we're cutting out a bunch of syntax in some cases.
Sadly I do think this should land in 0.16 as the cost of doing this
_after_ the relationships migration is high.
# 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
- `bevy_ecs` has lint errors without some features
## Solution
- Fix `clippy::allow-attributes-without-reason` when `bevy_reflect` is
disabled by adding a reason
- Fix `clippy::needless_return` when `std` is disabled by adding a gated
`expect` attribute and a comment to remove it when the `no_std` stuff is
addressed
## Testing
- `cargo clippy -p bevy_ecs --no-default-features --no-deps -- --D
warnings`
- CI
# 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,
}
```
# 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
Continuation of #17449.
#17449 implemented the wrapper types around `IndexMap`/`Set` and co.,
however punted on the slice types.
They are needed to support creating `EntitySetIterator`s from their
slices, not just the base maps and sets.
## Solution
Add the wrappers, in the same vein as #17449 and #17589 before.
The `Index`/`IndexMut` implementations take up a lot of space, however
they cannot be merged because we'd then get overlaps.
They are simply named `Slice` to match the `indexmap` naming scheme, but
this means they cannot be differentiated properly until their modules
are made public, which is already a follow-up mentioned in #17954.
# Objective
Now that #13432 has been merged, it's important we update our reflected
types to properly opt into this feature. If we do not, then this could
cause issues for users downstream who want to make use of
reflection-based cloning.
## Solution
This PR is broken into 4 commits:
1. Add `#[reflect(Clone)]` on all types marked `#[reflect(opaque)]` that
are also `Clone`. This is mandatory as these types would otherwise cause
the cloning operation to fail for any type that contains it at any
depth.
2. Update the reflection example to suggest adding `#[reflect(Clone)]`
on opaque types.
3. Add `#[reflect(clone)]` attributes on all fields marked
`#[reflect(ignore)]` that are also `Clone`. This prevents the ignored
field from causing the cloning operation to fail.
Note that some of the types that contain these fields are also `Clone`,
and thus can be marked `#[reflect(Clone)]`. This makes the
`#[reflect(clone)]` attribute redundant. However, I think it's safer to
keep it marked in the case that the `Clone` impl/derive is ever removed.
I'm open to removing them, though, if people disagree.
4. Finally, I added `#[reflect(Clone)]` on all types that are also
`Clone`. While not strictly necessary, it enables us to reduce the
generated output since we can just call `Clone::clone` directly instead
of calling `PartialReflect::reflect_clone` on each variant/field. It
also means we benefit from any optimizations or customizations made in
the `Clone` impl, including directly dereferencing `Copy` values and
increasing reference counters.
Along with that change I also took the liberty of adding any missing
registrations that I saw could be applied to the type as well, such as
`Default`, `PartialEq`, and `Hash`. There were hundreds of these to
edit, though, so it's possible I missed quite a few.
That last commit is **_massive_**. There were nearly 700 types to
update. So it's recommended to review the first three before moving onto
that last one.
Additionally, I can break the last commit off into its own PR or into
smaller PRs, but I figured this would be the easiest way of doing it
(and in a timely manner since I unfortunately don't have as much time as
I used to for code contributions).
## Testing
You can test locally with a `cargo check`:
```
cargo check --workspace --all-features
```
# Objective
Installment of the #16547 series.
The vast majority of uses for these types will be the `Entity` case, so
it makes sense for it to be the default.
## Solution
`UniqueEntityVec`, `UniqueEntitySlice`, `UniqueEntityArray` and their
helper iterator aliases now have `Entity` as a default.
Unfortunately, this means the the `T` parameter for `UniqueEntityArray`
now has to be ordered after the `N` constant, which breaks the
consistency to `[T; N]`.
Same with about a dozen iterator aliases that take some `P`/`F`
predicate/function parameter.
This should however be an ergonomic improvement in most cases, so we'll
just have to live with this inconsistency.
## Migration Guide
Switch type parameter order for the relevant wrapper types/aliases.
# Objective
#13432 added proper reflection-based cloning. This is a better method
than cloning via `clone_value` for reasons detailed in the description
of that PR. However, it may not be immediately apparent to users why one
should be used over the other, and what the gotchas of `clone_value`
are.
## Solution
This PR marks `PartialReflect::clone_value` as deprecated, with the
deprecation notice pointing users to `PartialReflect::reflect_clone`.
However, it also suggests using a new method introduced in this PR:
`PartialReflect::to_dynamic`.
`PartialReflect::to_dynamic` is essentially a renaming of
`PartialReflect::clone_value`. By naming it `to_dynamic`, we make it
very obvious that what's returned is a dynamic type. The one caveat to
this is that opaque types still use `reflect_clone` as they have no
corresponding dynamic type.
Along with changing the name, the method is now optional, and comes with
a default implementation that calls out to the respective reflection
subtrait method. This was done because there was really no reason to
require manual implementors provide a method that almost always calls
out to a known set of methods.
Lastly, to make this default implementation work, this PR also did a
similar thing with the `clone_dynamic ` methods on the reflection
subtraits. For example, `Struct::clone_dynamic` has been marked
deprecated and is superseded by `Struct::to_dynamic_struct`. This was
necessary to avoid the "multiple names in scope" issue.
### Open Questions
This PR maintains the original signature of `clone_value` on
`to_dynamic`. That is, it takes `&self` and returns `Box<dyn
PartialReflect>`.
However, in order for this to work, it introduces a panic if the value
is opaque and doesn't override the default `reflect_clone`
implementation.
One thing we could do to avoid the panic would be to make the conversion
fallible, either returning `Option<Box<dyn PartialReflect>>` or
`Result<Box<dyn PartialReflect>, ReflectCloneError>`.
This makes using the method a little more involved (i.e. users have to
either unwrap or handle the rare possibility of an error), but it would
set us up for a world where opaque types don't strictly need to be
`Clone`. Right now this bound is sort of implied by the fact that
`clone_value` is a required trait method, and the default behavior of
the macro is to use `Clone` for opaque types.
Alternatively, we could keep the signature but make the method required.
This maintains that implied bound where manual implementors must provide
some way of cloning the value (or YOLO it and just panic), but also
makes the API simpler to use.
Finally, we could just leave it with the panic. It's unlikely this would
occur in practice since our macro still requires `Clone` for opaque
types, and thus this would only ever be an issue if someone were to
manually implement `PartialReflect` without a valid `to_dynamic` or
`reflect_clone` method.
## Testing
You can test locally using the following command:
```
cargo test --package bevy_reflect --all-features
```
---
## Migration Guide
`PartialReflect::clone_value` is being deprecated. Instead, use
`PartialReflect::to_dynamic` if wanting to create a new dynamic instance
of the reflected value. Alternatively, use
`PartialReflect::reflect_clone` to attempt to create a true clone of the
underlying value.
Similarly, the following methods have been deprecated and should be
replaced with these alternatives:
- `Array::clone_dynamic` → `Array::to_dynamic_array`
- `Enum::clone_dynamic` → `Enum::to_dynamic_enum`
- `List::clone_dynamic` → `List::to_dynamic_list`
- `Map::clone_dynamic` → `Map::to_dynamic_map`
- `Set::clone_dynamic` → `Set::to_dynamic_set`
- `Struct::clone_dynamic` → `Struct::to_dynamic_struct`
- `Tuple::clone_dynamic` → `Tuple::to_dynamic_tuple`
- `TupleStruct::clone_dynamic` → `TupleStruct::to_dynamic_tuple_struct`
# Objective
Part of the #16547 series.
The entity wrapper types often have some associated types an aliases
with them that cannot be re-exported into an outer module together.
Some helper types are best used with part of their path:
`bevy::ecs::entity::index_set::Slice` as `index_set::Slice`.
This has already been done for `entity::hash_set` and
`entity::hash_map`.
## Solution
Publicize the `index_set`, `index_map`, `unique_vec`, `unique_slice`,
and `unique_array` modules.
## Migration Guide
Any mention or import of types in the affected modules have to add the
respective module name to the import path.
F.e.:
`bevy::ecs::entity::EntityIndexSet` ->
`bevy::ecs::entity::index_set::EntityIndexSet`
# Objective
I was recently exploreing `Entities` and stumbled on something strange.
`Entities::len` (the field) has the comment `Stores the number of free
entities for [`len`](Entities::len)`, refering to the method. But that
method says `The count of currently allocated entities.` Looking at the
code, the field's comment is wrong, and the public `len()` is correct.
Phew!
## Solution
So, I was just going to fix the comment, so it didn't confuse anyone
else, but as it turns out, we can just remove the field entirely. As a
bonus, this saves some book keeping work too. We can just calculate it
on the fly.
Also, add additional length methods and documentation for completeness.
These new length methods might be useful debug tools in the future.
---------
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
# Objective
- Fixes#15460 (will open new issues for further `no_std` efforts)
- Supersedes #17715
## Solution
- Threaded in new features as required
- Made certain crates optional but default enabled
- Removed `compile-check-no-std` from internal `ci` tool since GitHub CI
can now simply check `bevy` itself now
- Added CI task to check `bevy` on `thumbv6m-none-eabi` to ensure
`portable-atomic` support is still valid [^1]
[^1]: This may be controversial, since it could be interpreted as
implying Bevy will maintain support for `thumbv6m-none-eabi` going
forward. In reality, just like `x86_64-unknown-none`, this is a
[canary](https://en.wiktionary.org/wiki/canary_in_a_coal_mine) target to
make it clear when `portable-atomic` no longer works as intended (fixing
atomic support on atomically challenged platforms). If a PR comes
through and makes supporting this class of platforms impossible, then
this CI task can be removed. I however wager this won't be a problem.
## Testing
- CI
---
## Release Notes
Bevy now has support for `no_std` directly from the `bevy` crate.
Users can disable default features and enable a new `default_no_std`
feature instead, allowing `bevy` to be used in `no_std` applications and
libraries.
```toml
# Bevy for `no_std` platforms
bevy = { version = "0.16", default-features = false, features = ["default_no_std"] }
```
`default_no_std` enables certain required features, such as `libm` and
`critical-section`, and as many optional crates as possible (currently
just `bevy_state`). For atomically-challenged platforms such as the
Raspberry Pi Pico, `portable-atomic` will be used automatically.
For library authors, we recommend depending on `bevy` with
`default-features = false` to allow `std` and `no_std` users to both
depend on your crate. Here are some recommended features a library crate
may want to expose:
```toml
[features]
# Most users will be on a platform which has `std` and can use the more-powerful `async_executor`.
default = ["std", "async_executor"]
# Features for typical platforms.
std = ["bevy/std"]
async_executor = ["bevy/async_executor"]
# Features for `no_std` platforms.
libm = ["bevy/libm"]
critical-section = ["bevy/critical-section"]
[dependencies]
# We disable default features to ensure we don't accidentally enable `std` on `no_std` targets, for example.
bevy = { version = "0.16", default-features = false }
```
While this is verbose, it gives the maximum control to end-users to
decide how they wish to use Bevy on their platform.
We encourage library authors to experiment with `no_std` support. For
libraries relying exclusively on `bevy` and no other dependencies, it
may be as simple as adding `#![no_std]` to your `lib.rs` and exposing
features as above! Bevy can also provide many `std` types, such as
`HashMap`, `Mutex`, and `Instant` on all platforms. See
`bevy::platform_support` for details on what's available out of the box!
## Migration Guide
- If you were previously relying on `bevy` with default features
disabled, you may need to enable the `std` and `async_executor`
features.
- `bevy_reflect` has had its `bevy` feature removed. If you were relying
on this feature, simply enable `smallvec` and `smol_str` instead.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# 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>
# Objective
Component `require()` IDE integration is fully broken, as of #16575.
## Solution
This reverts us back to the previous "put the docs on Component trait"
impl. This _does_ reduce the accessibility of the required components in
rust docs, but the complete erasure of "required component IDE
experience" is not worth the price of slightly increased prominence of
requires in docs.
Additionally, Rust Analyzer has recently started including derive
attributes in suggestions, so we aren't losing that benefit of the
proc_macro attribute impl.
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
fixes#17896
## Solution
Change ChildOf ( Entity ) to ChildOf { parent: Entity }
by doing this we also allow users to use named structs for relationship
derives, When you have more than 1 field in a struct with named fields
the macro will look for a field with the attribute #[relationship] and
all of the other fields should implement the Default trait. Unnamed
fields are still supported.
When u have a unnamed struct with more than one field the macro will
fail.
Do we want to support something like this ?
```rust
#[derive(Component)]
#[relationship_target(relationship = ChildOf)]
pub struct Children (#[relationship] Entity, u8);
```
I could add this, it but doesn't seem nice.
## Testing
crates/bevy_ecs - cargo test
## Showcase
```rust
use bevy_ecs::component::Component;
use bevy_ecs::entity::Entity;
#[derive(Component)]
#[relationship(relationship_target = Children)]
pub struct ChildOf {
#[relationship]
pub parent: Entity,
internal: u8,
};
#[derive(Component)]
#[relationship_target(relationship = ChildOf)]
pub struct Children {
children: Vec<Entity>
};
```
---------
Co-authored-by: Tim Overbeek <oorbecktim@Tims-MacBook-Pro.local>
Co-authored-by: Tim Overbeek <oorbecktim@c-001-001-042.client.nl.eduvpn.org>
Co-authored-by: Tim Overbeek <oorbecktim@c-001-001-059.client.nl.eduvpn.org>
Co-authored-by: Tim Overbeek <oorbecktim@c-001-001-054.client.nl.eduvpn.org>
Co-authored-by: Tim Overbeek <oorbecktim@c-001-001-027.client.nl.eduvpn.org>
## Objective
The closure argument for
`EntityClonerBuilder::without_required_components` has `Send + Sync +
'static` bounds, but the closure immediately gets called and never needs
to be sent anywhere. (This was my fault :P )
## Solution
Remove the bounds so that users aren't unnecessarily restricted.
I also took the opportunity to expand the tests a little.
# Objective
Continuation of #17589 and #16547.
`get_many` is last of the `many` methods with a missing `unique`
counterpart.
It both takes and returns arrays, thus necessitates a matching
`UniqueEntityArray` type!
Plus, some slice methods involve returning arrays, which are currently
missing from `UniqueEntitySlice`.
## Solution
Add the type, the related methods and trait impls.
Note that for this PR, we abstain from some methods/trait impls that
create `&mut UniqueEntityArray`, because it can be successfully
mem-swapped. This can potentially invalidate a larger slice, which is
the same reason we punted on some mutable slice methods in #17589. We
can follow-up on all of these together in a following PR.
The new `unique_array` module is not glob-exported, because the trait
alias `unique_array::IntoIter` would conflict with
`unique_vec::IntoIter`.
The solution for this is to make the various `unique_*` modules public,
which I intend to do in yet another PR.
# 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
Update typos, fix new typos.
1.29.6 was just released to fix an
[issue](https://github.com/crate-ci/typos/issues/1228) where January's
corrections were not included in the binaries for the last release.
Reminder: typos can be tossed in the monthly [non-critical corrections
issue](https://github.com/crate-ci/typos/issues/1221).
## Solution
I chose to allow `implementors`, because a good argument seems to be
being made [here](https://github.com/crate-ci/typos/issues/1226) and
there is now a PR to address that.
## Discussion
Should I exclude `bevy_mikktspace`?
At one point I think we had an informal policy of "don't mess with
mikktspace until https://github.com/bevyengine/bevy/pull/9050 is merged"
but it doesn't seem like that is likely to be merged any time soon.
I think these particular corrections in mikktspace are fine because
- The same typo mistake seems to have been fixed in that PR
- The entire file containing these corrections was deleted in that PR
## Typo of the Month
correspindong -> corresponding
# Objective
Continuation of #17589 and #16547.
Slices have several methods that return iterators which themselves yield
slices, which we have not yet implemented.
An example use is `par_iter_many` style logic.
## Solution
Their implementation is rather straightforward, we simply delegate all
impls to `[T]`.
The resulting iterator types need their own wrappers in the form of
`UniqueEntitySliceIter` and `UniqueEntitySliceIterMut`.
We also add three free functions that cast slices of entity slices to
slices of `UniqueEntitySlice`.
These three should be sufficient, though infinite nesting is achievable
with a trait (like `TrustedEntityBorrow` works over infinite reference
nesting), should the need ever arise.
This method returns `None` if `meta.location.archetype_id` is
`ArchetypeId::INVALID`.
`EntityLocation::INVALID.archetype_id` is `ArchetypeId::INVALID`.
Therefore this method cannot return `Some(EntityLocation::INVALID)`.
Linking to it in the docs is futile anyway as that constant is not
public.
# 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.
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
Follow-up to #17549 and #16547.
A large part of `Vec`s usefulness is behind its ability to be sliced,
like sorting f.e., so we want the same to be possible for
`UniqueEntityVec`.
## Solution
Add a `UniqueEntitySlice` type. It is a wrapper around `[T]`, and itself
a DST.
Because `mem::swap` has a `Sized` bound, DSTs cannot be swapped, and we
can freely hand out mutable subslices without worrying about the
uniqueness invariant of the backing collection!
`UniqueEntityVec` and the relevant `UniqueEntityIter`s now have methods
and trait impls that return `UniqueEntitySlice`s.
`UniqueEntitySlice` itself can deref into normal slices, which means we
can avoid implementing the vast majority of immutable slice methods.
Most of the remaining methods:
- split a slice/collection in further unique subsections/slices
- reorder the slice: `sort`, `rotate_*`, `swap`
- construct/deconstruct/convert pointer-like types: `Box`, `Arc`, `Rc`,
`Cow`
- are comparison trait impls
As this PR is already larger than I'd like, we leave several things to
follow-ups:
- `UniqueEntityArray` and the related slice methods that would return it
- denoted by "chunk", "array_*" for iterators
- Methods that return iterators with `UniqueEntitySlice` as their item
- `windows`, `chunks` and `split` families
- All methods that are capable of actively mutating individual elements.
While they could be offered unsafely, subslicing makes their safety
contract weird enough to warrant its own discussion.
- `fill_with`, `swap_with_slice`, `iter_mut`, `split_first/last_mut`,
`select_nth_unstable_*`
Note that `Arc`, `Rc` and `Cow` are not fundamental types, so even if
they contain `UniqueEntitySlice`, we cannot write direct trait impls for
them.
On top of that, `Cow` is not a receiver (like `self: Arc<Self>` is) so
we cannot write inherent methods for it either.
# Objective
Follow-up to #17615.
Bevy's entity collection types like `EntityHashSet` no longer implement
serde's `Serialize` and `Deserialize` after becoming newtypes instead of
type aliases in #16912. This broke some types that support serde for me
in Avian.
I also missed creating const constructors for `EntityIndexMap` and
`EntityIndexSet` in #17615. Oops!
## Solution
Implement `Serialize` and `Deserialize` for Bevy's entity collection
types, and add const constructors for `EntityIndexMap` and
`EntityIndexSet`.
I didn't implement `ReflectSerialize` or `ReflectDeserialize` here,
because I had some trouble fixing the resulting errors, and they were
not implemented previously either.
# Objective
#16912 turned `EntityHashMap` and `EntityHashSet` into proper newtypes
instead of type aliases. However, this removed the ability to create
these collections in const contexts; previously, you could use
`EntityHashSet::with_hasher(EntityHash)`, but it doesn't exist anymore.
## Solution
Make `EntityHashMap::new` and `EntityHashSet::new` const methods.
# Objective
In #16547, we added `EntitySet`s/`EntitySetIterator`s. We can know
whenever an iterator only contains unique entities, however we do not
yet have the ability to collect and reuse these without either the
unsafe `UniqueEntityIter::from_iterator_unchecked`, or the expensive
`HashSet::from_iter`.
An important piece for being able to do this is a `Vec` that maintains
the uniqueness property, can be collected into, and is itself
`EntitySet`.
A lot of entity collections are already intended to be "unique", but
have no way of expressing that when stored, other than using an
aforementioned `HashSet`. Such a type helps by limiting or even removing
the need for unsafe on the user side when not using a validated `Set`
type, and makes it easier to interface with other infrastructure like
f.e. `RelationshipSourceCollection`s.
## Solution
We implement `UniqueEntityVec`.
This is a wrapper around `Vec`, that only ever contains unique elements.
It mirrors the API of `Vec`, however restricts any mutation as to not
violate the uniqueness guarantee. Meaning:
- Any inherent method which can introduce new elements or mutate
existing ones is now unsafe, f.e.: `insert`, `retain_mut`
- Methods that are impossible to use safely are omitted, f.e.: `fill`,
`extend_from_within`
A handful of the unsafe methods can do element-wise mutation
(`retain_mut`, `dedup_by`), which can be an unwind safety hazard were
the element-wise operation to panic. For those methods, we require that
each individual execution of the operation upholds uniqueness, not just
the entire method as a whole.
To be safe for mutable usage, slicing and the associated slice methods
require a matching `UniqueEntitySlice` type , which we leave for a
follow-up PR.
Because this type will deref into the `UniqueEntitySlice` type, we also
offer the immutable `Vec` methods on this type (which only amount to a
handful). "as inner" functionality is covered by additional
`as_vec`/`as_mut_vec` methods + `AsRef`/`Borrow` trait impls.
Like `UniqueEntityIter::from_iterator_unchecked`, this type has a
`from_vec_unchecked` method as well.
The canonical way to safely obtain this type however is via
`EntitySetIterator::collect_set` or
`UniqueEntityVec::from_entity_set_iter`. Like mentioned in #17513, these
are named suboptimally until supertrait item shadowing arrives, since a
normal `collect` will still run equality checks.
# Objective
We do not have `EntityIndexMap`/`EntityIndexSet`.
Usual `HashMap`s/`HashSet`s do not guarantee any order, which can be
awkward for some use cases.
The `indexmap` versions remember insertion order, which then also
becomes their iteration order.
They can be thought of as a `HashTable` + `Vec`, which means fast
iteration and removal, indexing by index (not just key), and slicing!
Performance should otherwise be comparable.
## Solution
Because `indexmap` is structured to mirror `hashbrown`, it suffers the
same issue of not having the `Hasher` generic on their iterators. #16912
solved this issue for `EntityHashMap`/`EntityHashSet` with a wrapper
around the hashbrown version, so this PR does the same.
Hopefully these wrappers can be removed again in the future by having
`hashbrown`/`indexmap` adopt that generic in their iterators themselves!
# Objective
Some collections are more efficient to construct when we know that every
element is unique in advance.
We have `EntitySetIterator`s from #16547, but currently no API to safely
make use of them this way.
## Solution
Add `FromEntitySetIterator` as a subtrait to `FromIterator`, and
implement it for the `EntityHashSet`/`hashbrown::HashSet` types.
To match the normal `FromIterator`, we also add a
`EntitySetIterator::collect_set` method.
It'd be better if these methods could shadow `from_iter` and `collect`
completely, but https://github.com/rust-lang/rust/issues/89151 is needed
for that.
While currently only `HashSet`s implement this trait, future
`UniqueEntityVec`/`UniqueEntitySlice` functionality comes with more
implementors.
Because `HashMap`s are collected from tuples instead of singular types,
implementing this same optimization for them is more complex, and has to
be done separately.
## Showcase
This is basically a free speedup for collecting `EntityHashSet`s!
```rust
pub fn collect_milk_dippers(dippers: Query<Entity, (With<Milk>, With<Cookies>)>) {
dippers.iter().collect_set::<EntityHashSet>();
// or
EntityHashSet::from_entity_set_iter(dippers);
}
---------
Co-authored-by: SpecificProtagonist <vincentjunge@posteo.net>
# 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.
# 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>
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`.
# Objective
Noticed while doing #17449, I had left these `DerefMut` impls in.
Obtaining mutable references to those inner iterator types allows for
`mem::swap`, which can be used to swap an incorrectly behaving instance
into the wrappers.
## Solution
Remove them!
# 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.
# Objective
- Contributes to #16877
## Solution
- Initial creation of `bevy_platform_support` crate.
- Moved `bevy_utils::Instant` into new `bevy_platform_support` crate.
- Moved `portable-atomic`, `portable-atomic-util`, and
`critical-section` into new `bevy_platform_support` crate.
## Testing
- CI
---
## Showcase
Instead of needing code like this to import an `Arc`:
```rust
#[cfg(feature = "portable-atomic")]
use portable_atomic_util::Arc;
#[cfg(not(feature = "portable-atomic"))]
use alloc::sync::Arc;
```
We can now use:
```rust
use bevy_platform_support::sync::Arc;
```
This applies to many other types, but the goal is overall the same:
allowing crates to use `std`-like types without the boilerplate of
conditional compilation and platform-dependencies.
## Migration Guide
- Replace imports of `bevy_utils::Instant` with
`bevy_platform_support::time::Instant`
- Replace imports of `bevy::utils::Instant` with
`bevy::platform_support::time::Instant`
## Notes
- `bevy_platform_support` hasn't been reserved on `crates.io`
- ~~`bevy_platform_support` is not re-exported from `bevy` at this time.
It may be worthwhile exporting this crate, but I am unsure of a
reasonable name to export it under (`platform_support` may be a bit
wordy for user-facing).~~
- I've included an implementation of `Instant` which is suitable for
`no_std` platforms that are not Wasm for the sake of eliminating feature
gates around its use. It may be a controversial inclusion, so I'm happy
to remove it if required.
- There are many other items (`spin`, `bevy_utils::Sync(Unsafe)Cell`,
etc.) which should be added to this crate. I have kept the initial scope
small to demonstrate utility without making this too unwieldy.
---------
Co-authored-by: TimJentzsch <TimJentzsch@users.noreply.github.com>
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>
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#17301Fixes#12235Fixes#15299Fixes#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>
# Objective
- https://github.com/bevyengine/bevy/issues/17111
## Solution
Set the `clippy::allow_attributes` and
`clippy::allow_attributes_without_reason` lints to `warn`, and bring
`bevy_ecs` in line with the new restrictions.
## Testing
This PR is a WIP; testing will happen after it's finished.
# Objective
With the `track_location` feature, the error message of trying to
acquire an entity that was despawned pointed to the wrong line if the
entity index has been reused.
## Showcase
```rust
use bevy_ecs::prelude::*;
fn main() {
let mut world = World::new();
let e = world.spawn_empty().id();
world.despawn(e);
world.flush();
let _ = world.spawn_empty();
world.entity(e);
}
```
Old message:
```
Entity 0v1 was despawned by src/main.rs:8:19
```
New message:
```
Entity 0v1 does not exist (its index has been reused)
```
## Objective
The error `EntityFetchError::NoSuchEntity` has an `UnsafeWorldCell`
inside it, which it uses to call
`Entities::entity_does_not_exist_error_details_message` when being
printed. That method returns a `String` that, if the `track_location`
feature is enabled, contains the location of whoever despawned the
relevant entity.
I initially had to modify this error while working on #17043. The
`UnsafeWorldCell` was causing borrow problems when being returned from a
command, so I tried replacing it with the `String` that the method
returns, since that was the world cell's only purpose.
Unfortunately, `String`s are slow, and it significantly impacted
performance (on top of that PR's performance hit):
<details>
<summary>17043 benchmarks</summary>
### With `String`
### No `String`
</details>
For that PR, I just removed the error details entirely, but I figured
I'd try to find a way to keep them around.
## Solution
- Replace the `String` with a helper struct that holds the location, and
only turn it into a string when someone actually wants to print it.
- Replace the `UnsafeWorldCell` with the aforementioned struct.
- Do the same for `QueryEntityError::NoSuchEntity`.
## Benchmarking
This had some interesting performance impact:
<details>
<summary>This PR vs main</summary>
</details>
## Other work
`QueryEntityError::QueryDoesNotMatch` also has an `UnsafeWorldCell`
inside it. This one would be more complicated to rework while keeping
the same functionality.
## Migration Guide
The errors `EntityFetchError::NoSuchEntity` and
`QueryEntityError::NoSuchEntity` now contain an
`EntityDoesNotExistDetails` struct instead of an `UnsafeWorldCell`. If
you were just printing these, they should work identically.
---------
Co-authored-by: Benjamin Brienen <benjamin.brienen@outlook.com>
# 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.
# Objective
- As stated in the related issue, this PR is to better align the feature
flag name with what it actually does and the plans for the future.
- Fixes#16852
## Solution
- Simple find / replace
## Testing
- Local run of `cargo run -p ci`
## Migration Guide
The `track_change_detection` feature flag has been renamed to
`track_location` to better reflect its extended capabilities.
