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Add 'World::run_system_with_input' function + allow World::run_system to get system output (#10380)

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# Objective

Allows chained systems taking an `In<_>` input parameter to be run as
one-shot systems. This API was mentioned in #8963.

In addition, `run_system(_with_input)` returns the system output, for
any `'static` output type.

## Solution

A new function, `World::run_system_with_input` allows a `SystemId<I, O>`
to be run by providing an `I` value as input and producing `O` as an
output.

`SystemId<I, O>` is now generic over the input type `I` and output type
`O`, along with the related functions and types `RegisteredSystem`,
`RemovedSystem`, `register_system`, `remove_system`, and
`RegisteredSystemError`. These default to `()`, preserving the existing
API, for all of the public types.

---

## Changelog

- Added `World::run_system_with_input` function to allow one-shot
systems that take `In<_>` input parameters
- Changed `World::run_system` and `World::register_system` to support
systems with return types beyond `()`
- Added `Commands::run_system_with_input` command that schedules a
one-shot system with an `In<_>` input parameter
This commit is contained in:
Nathan Fenner 2023-11-15 05:44:44 -08:00 committed by GitHub
parent bad55c1ad8
commit 1f05e1e2ab
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 309 additions and 39 deletions
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22
crates/bevy_ecs/src/system/commands/mod.rs
View file

@ -5,7 +5,7 @@ use crate::{
self as bevy_ecs,
bundle::Bundle,
entity::{Entities, Entity},
system::{RunSystem, SystemId},
system::{RunSystemWithInput, SystemId},
world::{EntityWorldMut, FromWorld, World},
};
use bevy_ecs_macros::SystemParam;
@ -523,8 +523,26 @@ impl<'w, 's> Commands<'w, 's> {
/// Running slow systems can become a bottleneck.
///
/// Calls [`World::run_system`](crate::system::World::run_system).
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
pub fn run_system(&mut self, id: SystemId) {
self.queue.push(RunSystem::new(id));
self.run_system_with_input(id, ());
}
/// Runs the system corresponding to the given [`SystemId`].
/// Systems are ran in an exclusive and single threaded way.
/// Running slow systems can become a bottleneck.
///
/// Calls [`World::run_system_with_input`](crate::system::World::run_system_with_input).
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
pub fn run_system_with_input<I: 'static + Send>(&mut self, id: SystemId<I>, input: I) {
self.queue
.push(RunSystemWithInput::new_with_input(id, input));
}
/// Pushes a generic [`Command`] to the command queue.

326
crates/bevy_ecs/src/system/system_registry.rs
View file

@ -7,18 +7,18 @@ use thiserror::Error;
/// A small wrapper for [`BoxedSystem`] that also keeps track whether or not the system has been initialized.
#[derive(Component)]
struct RegisteredSystem {
struct RegisteredSystem<I, O> {
initialized: bool,
system: BoxedSystem,
system: BoxedSystem<I, O>,
}
/// A system that has been removed from the registry.
/// It contains the system and whether or not it has been initialized.
///
/// This struct is returned by [`World::remove_system`].
pub struct RemovedSystem {
pub struct RemovedSystem<I = (), O = ()> {
initialized: bool,
system: BoxedSystem,
system: BoxedSystem<I, O>,
}
impl RemovedSystem {
@ -38,8 +38,41 @@ impl RemovedSystem {
///
/// These are opaque identifiers, keyed to a specific [`World`],
/// and are created via [`World::register_system`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct SystemId(Entity);
#[derive(Eq)]
pub struct SystemId<I = (), O = ()>(Entity, std::marker::PhantomData<fn(I) -> O>);
// A manual impl is used because the trait bounds should ignore the `I` and `O` phantom parameters.
impl<I, O> Copy for SystemId<I, O> {}
// A manual impl is used because the trait bounds should ignore the `I` and `O` phantom parameters.
impl<I, O> Clone for SystemId<I, O> {
fn clone(&self) -> Self {
*self
}
}
// A manual impl is used because the trait bounds should ignore the `I` and `O` phantom parameters.
impl<I, O> PartialEq for SystemId<I, O> {
fn eq(&self, other: &Self) -> bool {
self.0 == other.0 && self.1 == other.1
}
}
// A manual impl is used because the trait bounds should ignore the `I` and `O` phantom parameters.
impl<I, O> std::hash::Hash for SystemId<I, O> {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
self.0.hash(state);
}
}
impl<I, O> std::fmt::Debug for SystemId<I, O> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_tuple("SystemId")
.field(&self.0)
.field(&self.1)
.finish()
}
}
impl World {
/// Registers a system and returns a [`SystemId`] so it can later be called by [`World::run_system`].
@ -51,10 +84,10 @@ impl World {
/// This allows for running systems in a pushed-based fashion.
/// Using a [`Schedule`](crate::schedule::Schedule) is still preferred for most cases
/// due to its better performance and abillity to run non-conflicting systems simultaneously.
pub fn register_system<M, S: IntoSystem<(), (), M> + 'static>(
pub fn register_system<I: 'static, O: 'static, M, S: IntoSystem<I, O, M> + 'static>(
&mut self,
system: S,
) -> SystemId {
) -> SystemId<I, O> {
self.register_boxed_system(Box::new(IntoSystem::into_system(system)))
}
@ -62,13 +95,17 @@ impl World {
///
/// This is useful if the [`IntoSystem`] implementor has already been turned into a
/// [`System`](crate::system::System) trait object and put in a [`Box`].
pub fn register_boxed_system(&mut self, system: BoxedSystem) -> SystemId {
pub fn register_boxed_system<I: 'static, O: 'static>(
&mut self,
system: BoxedSystem<I, O>,
) -> SystemId<I, O> {
SystemId(
self.spawn(RegisteredSystem {
initialized: false,
system,
})
.id(),
std::marker::PhantomData,
)
}
@ -78,11 +115,14 @@ impl World {
///
/// If no system corresponds to the given [`SystemId`], this method returns an error.
/// Systems are also not allowed to remove themselves, this returns an error too.
pub fn remove_system(&mut self, id: SystemId) -> Result<RemovedSystem, RegisteredSystemError> {
pub fn remove_system<I: 'static, O: 'static>(
&mut self,
id: SystemId<I, O>,
) -> Result<RemovedSystem<I, O>, RegisteredSystemError<I, O>> {
match self.get_entity_mut(id.0) {
Some(mut entity) => {
let registered_system = entity
.take::<RegisteredSystem>()
.take::<RegisteredSystem<I, O>>()
.ok_or(RegisteredSystemError::SelfRemove(id))?;
entity.despawn();
Ok(RemovedSystem {
@ -100,14 +140,17 @@ impl World {
/// This is different from [`RunSystemOnce::run_system_once`](crate::system::RunSystemOnce::run_system_once),
/// because it keeps local state between calls and change detection works correctly.
///
/// In order to run a chained system with an input, use [`World::run_system_with_input`] instead.
///
/// # Limitations
///
/// - Stored systems cannot be chained: they can neither have an [`In`](crate::system::In) nor return any values.
/// - Stored systems cannot be recursive, they cannot call themselves through [`Commands::run_system`](crate::system::Commands).
/// - Exclusive systems cannot be used.
///
/// # Examples
///
/// ## Running a system
///
/// ```rust
/// # use bevy_ecs::prelude::*;
/// #[derive(Resource, Default)]
@ -126,7 +169,7 @@ impl World {
/// world.run_system(counter_two); // -> 1
/// ```
///
/// Change detection:
/// ## Change detection
///
/// ```rust
/// # use bevy_ecs::prelude::*;
@ -149,7 +192,81 @@ impl World {
/// world.resource_mut::<ChangeDetector>().set_changed();
/// let _ = world.run_system(detector); // -> Something happened!
/// ```
pub fn run_system(&mut self, id: SystemId) -> Result<(), RegisteredSystemError> {
///
/// ## Getting system output
///
/// ```rust
/// # use bevy_ecs::prelude::*;
///
/// #[derive(Resource)]
/// struct PlayerScore(i32);
///
/// #[derive(Resource)]
/// struct OpponentScore(i32);
///
/// fn get_player_score(player_score: Res<PlayerScore>) -> i32 {
/// player_score.0
/// }
///
/// fn get_opponent_score(opponent_score: Res<OpponentScore>) -> i32 {
/// opponent_score.0
/// }
///
/// let mut world = World::default();
/// world.insert_resource(PlayerScore(3));
/// world.insert_resource(OpponentScore(2));
///
/// let scoring_systems = [
/// ("player", world.register_system(get_player_score)),
/// ("opponent", world.register_system(get_opponent_score)),
/// ];
///
/// for (label, scoring_system) in scoring_systems {
/// println!("{label} has score {}", world.run_system(scoring_system).expect("system succeeded"));
/// }
/// ```
pub fn run_system<O: 'static>(
&mut self,
id: SystemId<(), O>,
) -> Result<O, RegisteredSystemError<(), O>> {
self.run_system_with_input(id, ())
}
/// Run a stored chained system by its [`SystemId`], providing an input value.
/// Before running a system, it must first be registered.
/// The method [`World::register_system`] stores a given system and returns a [`SystemId`].
///
/// # Limitations
///
/// - Stored systems cannot be recursive, they cannot call themselves through [`Commands::run_system`](crate::system::Commands).
/// - Exclusive systems cannot be used.
///
/// # Examples
///
/// ```rust
/// # use bevy_ecs::prelude::*;
/// #[derive(Resource, Default)]
/// struct Counter(u8);
///
/// fn increment(In(increment_by): In<u8>, mut counter: Local<Counter>) {
/// counter.0 += increment_by;
/// println!("{}", counter.0);
/// }
///
/// let mut world = World::default();
/// let counter_one = world.register_system(increment);
/// let counter_two = world.register_system(increment);
/// world.run_system_with_input(counter_one, 1); // -> 1
/// world.run_system_with_input(counter_one, 20); // -> 21
/// world.run_system_with_input(counter_two, 30); // -> 51
/// ```
///
/// See [`World::run_system`] for more examples.
pub fn run_system_with_input<I: 'static, O: 'static>(
&mut self,
id: SystemId<I, O>,
input: I,
) -> Result<O, RegisteredSystemError<I, O>> {
// lookup
let mut entity = self
.get_entity_mut(id.0)
@ -160,7 +277,7 @@ impl World {
mut initialized,
mut system,
} = entity
.take::<RegisteredSystem>()
.take::<RegisteredSystem<I, O>>()
.ok_or(RegisteredSystemError::Recursive(id))?;
// run the system
@ -168,57 +285,98 @@ impl World {
system.initialize(self);
initialized = true;
}
system.run((), self);
let result = system.run(input, self);
system.apply_deferred(self);
// return ownership of system trait object (if entity still exists)
if let Some(mut entity) = self.get_entity_mut(id.0) {
entity.insert::<RegisteredSystem>(RegisteredSystem {
entity.insert::<RegisteredSystem<I, O>>(RegisteredSystem {
initialized,
system,
});
}
Ok(())
Ok(result)
}
}
/// The [`Command`] type for [`World::run_system`] or [`World::run_system_with_input`].
///
/// This command runs systems in an exclusive and single threaded way.
/// Running slow systems can become a bottleneck.
///
/// If the system needs an [`In<_>`](crate::system::In) input value to run, it must
/// be provided as part of the command.
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
#[derive(Debug, Clone)]
pub struct RunSystemWithInput<I: 'static> {
system_id: SystemId<I>,
input: I,
}
/// The [`Command`] type for [`World::run_system`].
///
/// This command runs systems in an exclusive and single threaded way.
/// Running slow systems can become a bottleneck.
#[derive(Debug, Clone)]
pub struct RunSystem {
system_id: SystemId,
}
///
/// If the system needs an [`In<_>`](crate::system::In) input value to run, use the
/// [`crate::system::RunSystemWithInput`] type instead.
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
pub type RunSystem = RunSystemWithInput<()>;
impl RunSystem {
/// Creates a new [`Command`] struct, which can be added to [`Commands`](crate::system::Commands)
pub fn new(system_id: SystemId) -> Self {
Self { system_id }
Self::new_with_input(system_id, ())
}
}
impl Command for RunSystem {
impl<I: 'static> RunSystemWithInput<I> {
/// Creates a new [`Command`] struct, which can be added to [`Commands`](crate::system::Commands)
/// in order to run the specified system with the provided [`In<_>`](crate::system::In) input value.
pub fn new_with_input(system_id: SystemId<I>, input: I) -> Self {
Self { system_id, input }
}
}
impl<I: 'static + Send> Command for RunSystemWithInput<I> {
#[inline]
fn apply(self, world: &mut World) {
let _ = world.run_system(self.system_id);
let _ = world.run_system_with_input(self.system_id, self.input);
}
}
/// An operation with stored systems failed.
#[derive(Debug, Error)]
pub enum RegisteredSystemError {
#[derive(Error)]
pub enum RegisteredSystemError<I = (), O = ()> {
/// A system was run by id, but no system with that id was found.
///
/// Did you forget to register it?
#[error("System {0:?} was not registered")]
SystemIdNotRegistered(SystemId),
SystemIdNotRegistered(SystemId<I, O>),
/// A system tried to run itself recursively.
#[error("System {0:?} tried to run itself recursively")]
Recursive(SystemId),
Recursive(SystemId<I, O>),
/// A system tried to remove itself.
#[error("System {0:?} tried to remove itself")]
SelfRemove(SystemId),
SelfRemove(SystemId<I, O>),
}
impl<I, O> std::fmt::Debug for RegisteredSystemError<I, O> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::SystemIdNotRegistered(arg0) => {
f.debug_tuple("SystemIdNotRegistered").field(arg0).finish()
}
Self::Recursive(arg0) => f.debug_tuple("Recursive").field(arg0).finish(),
Self::SelfRemove(arg0) => f.debug_tuple("SelfRemove").field(arg0).finish(),
}
}
}
mod tests {
@ -248,14 +406,14 @@ mod tests {
assert_eq!(*world.resource::<Counter>(), Counter(0));
// Resources are changed when they are first added.
let id = world.register_system(count_up_iff_changed);
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(1));
// Nothing changed
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(1));
// Making a change
world.resource_mut::<ChangeDetector>().set_changed();
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(2));
}
@ -271,16 +429,82 @@ mod tests {
world.insert_resource(Counter(1));
assert_eq!(*world.resource::<Counter>(), Counter(1));
let id = world.register_system(doubling);
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(1));
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(2));
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(4));
let _ = world.run_system(id);
world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(8));
}
#[test]
fn input_values() {
// Verify that a non-Copy, non-Clone type can be passed in.
struct NonCopy(u8);
fn increment_sys(In(NonCopy(increment_by)): In<NonCopy>, mut counter: ResMut<Counter>) {
counter.0 += increment_by;
}
let mut world = World::new();
let id = world.register_system(increment_sys);
// Insert the resource after registering the system.
world.insert_resource(Counter(1));
assert_eq!(*world.resource::<Counter>(), Counter(1));
world
.run_system_with_input(id, NonCopy(1))
.expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(2));
world
.run_system_with_input(id, NonCopy(1))
.expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(3));
world
.run_system_with_input(id, NonCopy(20))
.expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(23));
world
.run_system_with_input(id, NonCopy(1))
.expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(24));
}
#[test]
fn output_values() {
// Verify that a non-Copy, non-Clone type can be returned.
#[derive(Eq, PartialEq, Debug)]
struct NonCopy(u8);
fn increment_sys(mut counter: ResMut<Counter>) -> NonCopy {
counter.0 += 1;
NonCopy(counter.0)
}
let mut world = World::new();
let id = world.register_system(increment_sys);
// Insert the resource after registering the system.
world.insert_resource(Counter(1));
assert_eq!(*world.resource::<Counter>(), Counter(1));
let output = world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(2));
assert_eq!(output, NonCopy(2));
let output = world.run_system(id).expect("system runs successfully");
assert_eq!(*world.resource::<Counter>(), Counter(3));
assert_eq!(output, NonCopy(3));
}
#[test]
fn nested_systems() {
use crate::system::SystemId;
@ -310,4 +534,32 @@ mod tests {
let _ = world.run_system(nested_id);
assert_eq!(*world.resource::<Counter>(), Counter(5));
}
#[test]
fn nested_systems_with_inputs() {
use crate::system::SystemId;
#[derive(Component)]
struct Callback(SystemId<u8>, u8);
fn nested(query: Query<&Callback>, mut commands: Commands) {
for callback in query.iter() {
commands.run_system_with_input(callback.0, callback.1);
}
}
let mut world = World::new();
world.insert_resource(Counter(0));
let increment_by =
world.register_system(|In(amt): In<u8>, mut counter: ResMut<Counter>| {
counter.0 += amt;
});
let nested_id = world.register_system(nested);
world.spawn(Callback(increment_by, 2));
world.spawn(Callback(increment_by, 3));
let _ = world.run_system(nested_id);
assert_eq!(*world.resource::<Counter>(), Counter(5));
}
}