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Remove WorldCell (#12551)

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# Objective
Fixes #12549. WorldCell's support of everything a World can do is
incomplete, and represents an alternative, potentially confusing, and
less performant way of pulling multiple fetches from a `World`. The
typical approach is to use `SystemState` for a runtime cached and safe
way, or `UnsafeWorldCell` if the use of `unsafe` is tolerable.

## Solution
Remove it!

---

## Changelog
Removed: `WorldCell`
Removed: `World::cell`

## Migration Guide
`WorldCell` has been removed. If you were using it to fetch multiple
distinct values from a `&mut World`, use `SystemState` by calling
`SystemState::get` instead. Alternatively, if `SystemState` cannot be
used, `UnsafeWorldCell` can instead be used in unsafe contexts.
This commit is contained in:
James Liu 2024-03-17 23:28:31 -07:00 committed by GitHub
parent fc4716f56c
commit 6760b6e8a5
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 1 additions and 522 deletions
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12
crates/bevy_ecs/src/world/mod.rs
View File

@ -6,7 +6,6 @@ mod entity_ref;
pub mod error;
mod spawn_batch;
pub mod unsafe_world_cell;
mod world_cell;
pub use crate::change_detection::{Mut, Ref, CHECK_TICK_THRESHOLD};
pub use crate::world::command_queue::CommandQueue;
@ -16,7 +15,6 @@ pub use entity_ref::{
OccupiedEntry, VacantEntry,
};
pub use spawn_batch::*;
pub use world_cell::*;
use crate::{
archetype::{ArchetypeComponentId, ArchetypeId, ArchetypeRow, Archetypes},
@ -111,8 +109,6 @@ pub struct World {
pub(crate) storages: Storages,
pub(crate) bundles: Bundles,
pub(crate) removed_components: RemovedComponentEvents,
/// Access cache used by [`WorldCell`]. Is only accessed in the `Drop` impl of `WorldCell`.
pub(crate) archetype_component_access: ArchetypeComponentAccess,
pub(crate) change_tick: AtomicU32,
pub(crate) last_change_tick: Tick,
pub(crate) last_check_tick: Tick,
@ -129,7 +125,6 @@ impl Default for World {
storages: Default::default(),
bundles: Default::default(),
removed_components: Default::default(),
archetype_component_access: Default::default(),
// Default value is `1`, and `last_change_tick`s default to `0`, such that changes
// are detected on first system runs and for direct world queries.
change_tick: AtomicU32::new(1),
@ -217,13 +212,6 @@ impl World {
&self.removed_components
}
/// Retrieves a [`WorldCell`], which safely enables multiple mutable World accesses at the same
/// time, provided those accesses do not conflict with each other.
#[inline]
pub fn cell(&mut self) -> WorldCell<'_> {
WorldCell::new(self)
}
/// Creates a new [`Commands`] instance that writes to the world's command queue
/// Use [`World::flush_commands`] to apply all queued commands
#[inline]

32
crates/bevy_ecs/src/world/unsafe_world_cell.rs
View File

@ -4,7 +4,7 @@
use super::{command_queue::CommandQueue, Mut, Ref, World, WorldId};
use crate::{
archetype::{Archetype, ArchetypeComponentId, Archetypes},
archetype::{Archetype, Archetypes},
bundle::Bundles,
change_detection::{MutUntyped, Ticks, TicksMut},
component::{ComponentId, ComponentTicks, Components, StorageType, Tick, TickCells},
@ -284,36 +284,6 @@ impl<'w> UnsafeWorldCell<'w> {
&unsafe { self.unsafe_world() }.storages
}
/// Shorthand helper function for getting the [`ArchetypeComponentId`] for a resource.
#[inline]
pub(crate) fn get_resource_archetype_component_id(
self,
component_id: ComponentId,
) -> Option<ArchetypeComponentId> {
// SAFETY:
// - we only access world metadata
let resource = unsafe { self.world_metadata() }
.storages
.resources
.get(component_id)?;
Some(resource.id())
}
/// Shorthand helper function for getting the [`ArchetypeComponentId`] for a resource.
#[inline]
pub(crate) fn get_non_send_archetype_component_id(
self,
component_id: ComponentId,
) -> Option<ArchetypeComponentId> {
// SAFETY:
// - we only access world metadata
let resource = unsafe { self.world_metadata() }
.storages
.non_send_resources
.get(component_id)?;
Some(resource.id())
}
/// Retrieves an [`UnsafeEntityCell`] that exposes read and write operations for the given `entity`.
/// Similar to the [`UnsafeWorldCell`], you are in charge of making sure that no aliasing rules are violated.
#[inline]

479
crates/bevy_ecs/src/world/world_cell.rs
View File

@ -1,479 +0,0 @@
use bevy_utils::tracing::error;
use crate::{
archetype::ArchetypeComponentId,
event::{Event, Events},
storage::SparseSet,
system::Resource,
world::{Mut, World},
};
use std::{
any::TypeId,
cell::RefCell,
ops::{Deref, DerefMut},
rc::Rc,
};
use super::unsafe_world_cell::UnsafeWorldCell;
/// Exposes safe mutable access to multiple resources at a time in a World. Attempting to access
/// World in a way that violates Rust's mutability rules will panic thanks to runtime checks.
pub struct WorldCell<'w> {
pub(crate) world: UnsafeWorldCell<'w>,
pub(crate) access: Rc<RefCell<ArchetypeComponentAccess>>,
}
pub(crate) struct ArchetypeComponentAccess {
access: SparseSet<ArchetypeComponentId, usize>,
}
impl Default for ArchetypeComponentAccess {
fn default() -> Self {
Self {
access: SparseSet::new(),
}
}
}
const UNIQUE_ACCESS: usize = 0;
const BASE_ACCESS: usize = 1;
impl ArchetypeComponentAccess {
const fn new() -> Self {
Self {
access: SparseSet::new(),
}
}
fn read(&mut self, id: ArchetypeComponentId) -> bool {
let id_access = self.access.get_or_insert_with(id, || BASE_ACCESS);
if *id_access == UNIQUE_ACCESS {
false
} else {
*id_access += 1;
true
}
}
fn drop_read(&mut self, id: ArchetypeComponentId) {
let id_access = self.access.get_or_insert_with(id, || BASE_ACCESS);
*id_access -= 1;
}
fn write(&mut self, id: ArchetypeComponentId) -> bool {
let id_access = self.access.get_or_insert_with(id, || BASE_ACCESS);
if *id_access == BASE_ACCESS {
*id_access = UNIQUE_ACCESS;
true
} else {
false
}
}
fn drop_write(&mut self, id: ArchetypeComponentId) {
let id_access = self.access.get_or_insert_with(id, || BASE_ACCESS);
*id_access = BASE_ACCESS;
}
}
impl<'w> Drop for WorldCell<'w> {
fn drop(&mut self) {
let mut access = self.access.borrow_mut();
{
// SAFETY: `WorldCell` does not hand out `UnsafeWorldCell` to anywhere else so this is the only
// `UnsafeWorldCell` and we have exclusive access to it.
let world = unsafe { self.world.world_mut() };
let world_cached_access = &mut world.archetype_component_access;
// give world ArchetypeComponentAccess back to reuse allocations
std::mem::swap(world_cached_access, &mut *access);
}
}
}
/// A read-only borrow of some data stored in a [`World`]. This type is returned by [`WorldCell`],
/// which uses run-time checks to ensure that the borrow does not violate Rust's aliasing rules.
pub struct WorldBorrow<'w, T> {
value: &'w T,
archetype_component_id: ArchetypeComponentId,
access: Rc<RefCell<ArchetypeComponentAccess>>,
}
impl<'w, T> WorldBorrow<'w, T> {
fn try_new(
value: impl FnOnce() -> Option<&'w T>,
archetype_component_id: ArchetypeComponentId,
access: Rc<RefCell<ArchetypeComponentAccess>>,
) -> Option<Self> {
assert!(
access.borrow_mut().read(archetype_component_id),
"Attempted to immutably access {}, but it is already mutably borrowed",
std::any::type_name::<T>(),
);
let value = value()?;
Some(Self {
value,
archetype_component_id,
access,
})
}
}
impl<'w, T> Deref for WorldBorrow<'w, T> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
self.value
}
}
impl<'w, T> Drop for WorldBorrow<'w, T> {
fn drop(&mut self) {
let mut access = self.access.borrow_mut();
access.drop_read(self.archetype_component_id);
}
}
/// A mutable borrow of some data stored in a [`World`]. This type is returned by [`WorldCell`],
/// which uses run-time checks to ensure that the borrow does not violate Rust's aliasing rules.
pub struct WorldBorrowMut<'w, T> {
value: Mut<'w, T>,
archetype_component_id: ArchetypeComponentId,
access: Rc<RefCell<ArchetypeComponentAccess>>,
}
impl<'w, T> WorldBorrowMut<'w, T> {
fn try_new(
value: impl FnOnce() -> Option<Mut<'w, T>>,
archetype_component_id: ArchetypeComponentId,
access: Rc<RefCell<ArchetypeComponentAccess>>,
) -> Option<Self> {
assert!(
access.borrow_mut().write(archetype_component_id),
"Attempted to mutably access {}, but it is already mutably borrowed",
std::any::type_name::<T>(),
);
let value = value()?;
Some(Self {
value,
archetype_component_id,
access,
})
}
}
impl<'w, T> Deref for WorldBorrowMut<'w, T> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
self.value.deref()
}
}
impl<'w, T> DerefMut for WorldBorrowMut<'w, T> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.value
}
}
impl<'w, T> Drop for WorldBorrowMut<'w, T> {
fn drop(&mut self) {
let mut access = self.access.borrow_mut();
access.drop_write(self.archetype_component_id);
}
}
impl<'w> WorldCell<'w> {
pub(crate) fn new(world: &'w mut World) -> Self {
// this is cheap because ArchetypeComponentAccess::new() is const / allocation free
let access = std::mem::replace(
&mut world.archetype_component_access,
ArchetypeComponentAccess::new(),
);
// world's ArchetypeComponentAccess is recycled to cut down on allocations
Self {
world: world.as_unsafe_world_cell(),
access: Rc::new(RefCell::new(access)),
}
}
/// Gets a reference to the resource of the given type
pub fn get_resource<T: Resource>(&self) -> Option<WorldBorrow<'_, T>> {
let component_id = self.world.components().get_resource_id(TypeId::of::<T>())?;
let archetype_component_id = self
.world
.get_resource_archetype_component_id(component_id)?;
WorldBorrow::try_new(
// SAFETY: access is checked by WorldBorrow
|| unsafe { self.world.get_resource::<T>() },
archetype_component_id,
self.access.clone(),
)
}
/// Gets a reference to the resource of the given type
///
/// # Panics
///
/// Panics if the resource does not exist. Use [`get_resource`](WorldCell::get_resource) instead
/// if you want to handle this case.
pub fn resource<T: Resource>(&self) -> WorldBorrow<'_, T> {
match self.get_resource() {
Some(x) => x,
None => panic!(
"Requested resource {} does not exist in the `World`.
Did you forget to add it using `app.insert_resource` / `app.init_resource`?
Resources are also implicitly added via `app.add_event`,
and can be added by plugins.",
std::any::type_name::<T>()
),
}
}
/// Gets a mutable reference to the resource of the given type
pub fn get_resource_mut<T: Resource>(&self) -> Option<WorldBorrowMut<'_, T>> {
let component_id = self.world.components().get_resource_id(TypeId::of::<T>())?;
let archetype_component_id = self
.world
.get_resource_archetype_component_id(component_id)?;
WorldBorrowMut::try_new(
// SAFETY: access is checked by WorldBorrowMut
|| unsafe { self.world.get_resource_mut::<T>() },
archetype_component_id,
self.access.clone(),
)
}
/// Gets a mutable reference to the resource of the given type
///
/// # Panics
///
/// Panics if the resource does not exist. Use [`get_resource_mut`](WorldCell::get_resource_mut)
/// instead if you want to handle this case.
pub fn resource_mut<T: Resource>(&self) -> WorldBorrowMut<'_, T> {
match self.get_resource_mut() {
Some(x) => x,
None => panic!(
"Requested resource {} does not exist in the `World`.
Did you forget to add it using `app.insert_resource` / `app.init_resource`?
Resources are also implicitly added via `app.add_event`,
and can be added by plugins.",
std::any::type_name::<T>()
),
}
}
/// Gets an immutable reference to the non-send resource of the given type, if it exists.
pub fn get_non_send_resource<T: 'static>(&self) -> Option<WorldBorrow<'_, T>> {
let component_id = self.world.components().get_resource_id(TypeId::of::<T>())?;
let archetype_component_id = self
.world
.get_non_send_archetype_component_id(component_id)?;
WorldBorrow::try_new(
// SAFETY: access is checked by WorldBorrowMut
|| unsafe { self.world.get_non_send_resource::<T>() },
archetype_component_id,
self.access.clone(),
)
}
/// Gets an immutable reference to the non-send resource of the given type, if it exists.
///
/// # Panics
///
/// Panics if the resource does not exist. Use
/// [`get_non_send_resource`](WorldCell::get_non_send_resource) instead if you want to handle
/// this case.
pub fn non_send_resource<T: 'static>(&self) -> WorldBorrow<'_, T> {
match self.get_non_send_resource() {
Some(x) => x,
None => panic!(
"Requested non-send resource {} does not exist in the `World`.
Did you forget to add it using `app.insert_non_send_resource` / `app.init_non_send_resource`?
Non-send resources can also be added by plugins.",
std::any::type_name::<T>()
),
}
}
/// Gets a mutable reference to the non-send resource of the given type, if it exists.
pub fn get_non_send_resource_mut<T: 'static>(&self) -> Option<WorldBorrowMut<'_, T>> {
let component_id = self.world.components().get_resource_id(TypeId::of::<T>())?;
let archetype_component_id = self
.world
.get_non_send_archetype_component_id(component_id)?;
WorldBorrowMut::try_new(
// SAFETY: access is checked by WorldBorrowMut
|| unsafe { self.world.get_non_send_resource_mut::<T>() },
archetype_component_id,
self.access.clone(),
)
}
/// Gets a mutable reference to the non-send resource of the given type, if it exists.
///
/// # Panics
///
/// Panics if the resource does not exist. Use
/// [`get_non_send_resource_mut`](WorldCell::get_non_send_resource_mut) instead if you want to
/// handle this case.
pub fn non_send_resource_mut<T: 'static>(&self) -> WorldBorrowMut<'_, T> {
match self.get_non_send_resource_mut() {
Some(x) => x,
None => panic!(
"Requested non-send resource {} does not exist in the `World`.
Did you forget to add it using `app.insert_non_send_resource` / `app.init_non_send_resource`?
Non-send resources can also be added by plugins.",
std::any::type_name::<T>()
),
}
}
/// Sends an [`Event`].
#[inline]
pub fn send_event<E: Event>(&self, event: E) {
self.send_event_batch(std::iter::once(event));
}
/// Sends the default value of the [`Event`] of type `E`.
#[inline]
pub fn send_event_default<E: Event + Default>(&self) {
self.send_event_batch(std::iter::once(E::default()));
}
/// Sends a batch of [`Event`]s from an iterator.
#[inline]
pub fn send_event_batch<E: Event>(&self, events: impl Iterator<Item = E>) {
match self.get_resource_mut::<Events<E>>() {
Some(mut events_resource) => events_resource.extend(events),
None => error!(
"Unable to send event `{}`\n\tEvent must be added to the app with `add_event()`\n\thttps://docs.rs/bevy/*/bevy/app/struct.App.html#method.add_event ",
std::any::type_name::<E>()
),
}
}
}
#[cfg(test)]
mod tests {
use super::BASE_ACCESS;
use crate as bevy_ecs;
use crate::{system::Resource, world::World};
use std::any::TypeId;
#[derive(Resource)]
struct A(u32);
#[derive(Resource)]
struct B(u64);
#[test]
fn world_cell() {
let mut world = World::default();
world.insert_resource(A(1));
world.insert_resource(B(1));
let cell = world.cell();
{
let mut a = cell.resource_mut::<A>();
assert_eq!(1, a.0);
a.0 = 2;
}
{
let a = cell.resource::<A>();
assert_eq!(2, a.0, "ensure access is dropped");
let a2 = cell.resource::<A>();
assert_eq!(
2, a2.0,
"ensure multiple immutable accesses can occur at the same time"
);
}
{
let a = cell.resource_mut::<A>();
assert_eq!(
2, a.0,
"ensure both immutable accesses are dropped, enabling a new mutable access"
);
let b = cell.resource::<B>();
assert_eq!(
1, b.0,
"ensure multiple non-conflicting mutable accesses can occur at the same time"
);
}
}
#[test]
fn world_access_reused() {
let mut world = World::default();
world.insert_resource(A(1));
{
let cell = world.cell();
{
let mut a = cell.resource_mut::<A>();
assert_eq!(1, a.0);
a.0 = 2;
}
}
let u32_component_id = world.components.get_resource_id(TypeId::of::<A>()).unwrap();
let u32_archetype_component_id = world
.get_resource_archetype_component_id(u32_component_id)
.unwrap();
assert_eq!(world.archetype_component_access.access.len(), 1);
assert_eq!(
world
.archetype_component_access
.access
.get(u32_archetype_component_id),
Some(&BASE_ACCESS),
"reused access count is 'base'"
);
}
#[test]
#[should_panic]
fn world_cell_double_mut() {
let mut world = World::default();
world.insert_resource(A(1));
let cell = world.cell();
let _value_a = cell.resource_mut::<A>();
let _value_b = cell.resource_mut::<A>();
}
#[test]
#[should_panic]
fn world_cell_ref_and_mut() {
let mut world = World::default();
world.insert_resource(A(1));
let cell = world.cell();
let _value_a = cell.resource::<A>();
let _value_b = cell.resource_mut::<A>();
}
#[test]
#[should_panic]
fn world_cell_mut_and_ref() {
let mut world = World::default();
world.insert_resource(A(1));
let cell = world.cell();
let _value_a = cell.resource_mut::<A>();
let _value_b = cell.resource::<A>();
}
#[test]
fn world_cell_ref_and_ref() {
let mut world = World::default();
world.insert_resource(A(1));
let cell = world.cell();
let _value_a = cell.resource::<A>();
let _value_b = cell.resource::<A>();
}
}