1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372
use bevy_utils::tracing::warn;
use core::fmt::Debug;
use crate::component::Tick;
use crate::schedule::InternedSystemSet;
use crate::world::unsafe_world_cell::UnsafeWorldCell;
use crate::world::DeferredWorld;
use crate::{archetype::ArchetypeComponentId, component::ComponentId, query::Access, world::World};
use std::any::TypeId;
use std::borrow::Cow;
use super::IntoSystem;
/// An ECS system that can be added to a [`Schedule`](crate::schedule::Schedule)
///
/// Systems are functions with all arguments implementing
/// [`SystemParam`](crate::system::SystemParam).
///
/// Systems are added to an application using `App::add_systems(Update, my_system)`
/// or similar methods, and will generally run once per pass of the main loop.
///
/// Systems are executed in parallel, in opportunistic order; data access is managed automatically.
/// It's possible to specify explicit execution order between specific systems,
/// see [`IntoSystemConfigs`](crate::schedule::IntoSystemConfigs).
#[diagnostic::on_unimplemented(message = "`{Self}` is not a system", label = "invalid system")]
pub trait System: Send + Sync + 'static {
/// The system's input. See [`In`](crate::system::In) for
/// [`FunctionSystem`](crate::system::FunctionSystem)s.
type In;
/// The system's output.
type Out;
/// Returns the system's name.
fn name(&self) -> Cow<'static, str>;
/// Returns the [`TypeId`] of the underlying system type.
#[inline]
fn type_id(&self) -> TypeId {
TypeId::of::<Self>()
}
/// Returns the system's component [`Access`].
fn component_access(&self) -> &Access<ComponentId>;
/// Returns the system's archetype component [`Access`].
fn archetype_component_access(&self) -> &Access<ArchetypeComponentId>;
/// Returns true if the system is [`Send`].
fn is_send(&self) -> bool;
/// Returns true if the system must be run exclusively.
fn is_exclusive(&self) -> bool;
/// Returns true if system as deferred buffers
fn has_deferred(&self) -> bool;
/// Runs the system with the given input in the world. Unlike [`System::run`], this function
/// can be called in parallel with other systems and may break Rust's aliasing rules
/// if used incorrectly, making it unsafe to call.
///
/// Unlike [`System::run`], this will not apply deferred parameters, which must be independently
/// applied by calling [`System::apply_deferred`] at later point in time.
///
/// # Safety
///
/// - The caller must ensure that `world` has permission to access any world data
/// registered in [`Self::archetype_component_access`]. There must be no conflicting
/// simultaneous accesses while the system is running.
/// - The method [`Self::update_archetype_component_access`] must be called at some
/// point before this one, with the same exact [`World`]. If `update_archetype_component_access`
/// panics (or otherwise does not return for any reason), this method must not be called.
unsafe fn run_unsafe(&mut self, input: Self::In, world: UnsafeWorldCell) -> Self::Out;
/// Runs the system with the given input in the world.
///
/// For [read-only](ReadOnlySystem) systems, see [`run_readonly`], which can be called using `&World`.
///
/// Unlike [`System::run_unsafe`], this will apply deferred parameters *immediately*.
///
/// [`run_readonly`]: ReadOnlySystem::run_readonly
fn run(&mut self, input: Self::In, world: &mut World) -> Self::Out {
let world_cell = world.as_unsafe_world_cell();
self.update_archetype_component_access(world_cell);
// SAFETY:
// - We have exclusive access to the entire world.
// - `update_archetype_component_access` has been called.
let ret = unsafe { self.run_unsafe(input, world_cell) };
self.apply_deferred(world);
ret
}
/// Applies any [`Deferred`](crate::system::Deferred) system parameters (or other system buffers) of this system to the world.
///
/// This is where [`Commands`](crate::system::Commands) get applied.
fn apply_deferred(&mut self, world: &mut World);
/// Enqueues any [`Deferred`](crate::system::Deferred) system parameters (or other system buffers)
/// of this system into the world's command buffer.
fn queue_deferred(&mut self, world: DeferredWorld);
/// Initialize the system.
fn initialize(&mut self, _world: &mut World);
/// Update the system's archetype component [`Access`].
///
/// ## Note for implementors
/// `world` may only be used to access metadata. This can be done in safe code
/// via functions such as [`UnsafeWorldCell::archetypes`].
fn update_archetype_component_access(&mut self, world: UnsafeWorldCell);
/// Checks any [`Tick`]s stored on this system and wraps their value if they get too old.
///
/// This method must be called periodically to ensure that change detection behaves correctly.
/// When using bevy's default configuration, this will be called for you as needed.
fn check_change_tick(&mut self, change_tick: Tick);
/// Returns the system's default [system sets](crate::schedule::SystemSet).
///
/// Each system will create a default system set that contains the system.
fn default_system_sets(&self) -> Vec<InternedSystemSet> {
Vec::new()
}
/// Gets the tick indicating the last time this system ran.
fn get_last_run(&self) -> Tick;
/// Overwrites the tick indicating the last time this system ran.
///
/// # Warning
/// This is a complex and error-prone operation, that can have unexpected consequences on any system relying on this code.
/// However, it can be an essential escape hatch when, for example,
/// you are trying to synchronize representations using change detection and need to avoid infinite recursion.
fn set_last_run(&mut self, last_run: Tick);
}
/// [`System`] types that do not modify the [`World`] when run.
/// This is implemented for any systems whose parameters all implement [`ReadOnlySystemParam`].
///
/// Note that systems which perform [deferred](System::apply_deferred) mutations (such as with [`Commands`])
/// may implement this trait.
///
/// [`ReadOnlySystemParam`]: crate::system::ReadOnlySystemParam
/// [`Commands`]: crate::system::Commands
///
/// # Safety
///
/// This must only be implemented for system types which do not mutate the `World`
/// when [`System::run_unsafe`] is called.
pub unsafe trait ReadOnlySystem: System {
/// Runs this system with the given input in the world.
///
/// Unlike [`System::run`], this can be called with a shared reference to the world,
/// since this system is known not to modify the world.
fn run_readonly(&mut self, input: Self::In, world: &World) -> Self::Out {
let world = world.as_unsafe_world_cell_readonly();
self.update_archetype_component_access(world);
// SAFETY:
// - We have read-only access to the entire world.
// - `update_archetype_component_access` has been called.
unsafe { self.run_unsafe(input, world) }
}
}
/// A convenience type alias for a boxed [`System`] trait object.
pub type BoxedSystem<In = (), Out = ()> = Box<dyn System<In = In, Out = Out>>;
pub(crate) fn check_system_change_tick(last_run: &mut Tick, this_run: Tick, system_name: &str) {
if last_run.check_tick(this_run) {
let age = this_run.relative_to(*last_run).get();
warn!(
"System '{system_name}' has not run for {age} ticks. \
Changes older than {} ticks will not be detected.",
Tick::MAX.get() - 1,
);
}
}
impl<In: 'static, Out: 'static> Debug for dyn System<In = In, Out = Out> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("System")
.field("name", &self.name())
.field("is_exclusive", &self.is_exclusive())
.field("is_send", &self.is_send())
.finish_non_exhaustive()
}
}
/// Trait used to run a system immediately on a [`World`].
///
/// # Warning
/// This function is not an efficient method of running systems and it's meant to be used as a utility
/// for testing and/or diagnostics.
///
/// Systems called through [`run_system_once`](RunSystemOnce::run_system_once) do not hold onto any state,
/// as they are created and destroyed every time [`run_system_once`](RunSystemOnce::run_system_once) is called.
/// Practically, this means that [`Local`](crate::system::Local) variables are
/// reset on every run and change detection does not work.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::system::RunSystemOnce;
/// #[derive(Resource, Default)]
/// struct Counter(u8);
///
/// fn increment(mut counter: Local<Counter>) {
/// counter.0 += 1;
/// println!("{}", counter.0);
/// }
///
/// let mut world = World::default();
/// world.run_system_once(increment); // prints 1
/// world.run_system_once(increment); // still prints 1
/// ```
///
/// If you do need systems to hold onto state between runs, use the [`World::run_system`](World::run_system)
/// and run the system by their [`SystemId`](crate::system::SystemId).
///
/// # Usage
/// Typically, to test a system, or to extract specific diagnostics information from a world,
/// you'd need a [`Schedule`](crate::schedule::Schedule) to run the system. This can create redundant boilerplate code
/// when writing tests or trying to quickly iterate on debug specific systems.
///
/// For these situations, this function can be useful because it allows you to execute a system
/// immediately with some custom input and retrieve its output without requiring the necessary boilerplate.
///
/// # Examples
///
/// ## Immediate Command Execution
///
/// This usage is helpful when trying to test systems or functions that operate on [`Commands`](crate::system::Commands):
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::system::RunSystemOnce;
/// let mut world = World::default();
/// let entity = world.run_system_once(|mut commands: Commands| {
/// commands.spawn_empty().id()
/// });
/// # assert!(world.get_entity(entity).is_some());
/// ```
///
/// ## Immediate Queries
///
/// This usage is helpful when trying to run an arbitrary query on a world for testing or debugging purposes:
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::system::RunSystemOnce;
///
/// #[derive(Component)]
/// struct T(usize);
///
/// let mut world = World::default();
/// world.spawn(T(0));
/// world.spawn(T(1));
/// world.spawn(T(1));
/// let count = world.run_system_once(|query: Query<&T>| {
/// query.iter().filter(|t| t.0 == 1).count()
/// });
///
/// # assert_eq!(count, 2);
/// ```
///
/// Note that instead of closures you can also pass in regular functions as systems:
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::system::RunSystemOnce;
///
/// #[derive(Component)]
/// struct T(usize);
///
/// fn count(query: Query<&T>) -> usize {
/// query.iter().filter(|t| t.0 == 1).count()
/// }
///
/// let mut world = World::default();
/// world.spawn(T(0));
/// world.spawn(T(1));
/// world.spawn(T(1));
/// let count = world.run_system_once(count);
///
/// # assert_eq!(count, 2);
/// ```
pub trait RunSystemOnce: Sized {
/// Runs a system and applies its deferred parameters.
fn run_system_once<T: IntoSystem<(), Out, Marker>, Out, Marker>(self, system: T) -> Out {
self.run_system_once_with((), system)
}
/// Runs a system with given input and applies its deferred parameters.
fn run_system_once_with<T: IntoSystem<In, Out, Marker>, In, Out, Marker>(
self,
input: In,
system: T,
) -> Out;
}
impl RunSystemOnce for &mut World {
fn run_system_once_with<T: IntoSystem<In, Out, Marker>, In, Out, Marker>(
self,
input: In,
system: T,
) -> Out {
let mut system: T::System = IntoSystem::into_system(system);
system.initialize(self);
system.run(input, self)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate as bevy_ecs;
use crate::prelude::*;
#[test]
fn run_system_once() {
struct T(usize);
impl Resource for T {}
fn system(In(n): In<usize>, mut commands: Commands) -> usize {
commands.insert_resource(T(n));
n + 1
}
let mut world = World::default();
let n = world.run_system_once_with(1, system);
assert_eq!(n, 2);
assert_eq!(world.resource::<T>().0, 1);
}
#[derive(Resource, Default, PartialEq, Debug)]
struct Counter(u8);
#[allow(dead_code)]
fn count_up(mut counter: ResMut<Counter>) {
counter.0 += 1;
}
#[test]
fn run_two_systems() {
let mut world = World::new();
world.init_resource::<Counter>();
assert_eq!(*world.resource::<Counter>(), Counter(0));
world.run_system_once(count_up);
assert_eq!(*world.resource::<Counter>(), Counter(1));
world.run_system_once(count_up);
assert_eq!(*world.resource::<Counter>(), Counter(2));
}
#[allow(dead_code)]
fn spawn_entity(mut commands: Commands) {
commands.spawn_empty();
}
#[test]
fn command_processing() {
let mut world = World::new();
assert_eq!(world.entities.len(), 0);
world.run_system_once(spawn_entity);
assert_eq!(world.entities.len(), 1);
}
#[test]
fn non_send_resources() {
fn non_send_count_down(mut ns: NonSendMut<Counter>) {
ns.0 -= 1;
}
let mut world = World::new();
world.insert_non_send_resource(Counter(10));
assert_eq!(*world.non_send_resource::<Counter>(), Counter(10));
world.run_system_once(non_send_count_down);
assert_eq!(*world.non_send_resource::<Counter>(), Counter(9));
}
}