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SystemParamBuilder - Support buildable Vec parameters (#14821)

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# Objective

Allow dynamic systems to take lists of system parameters whose length is
not known at compile time.

This can be used for building a system that runs a script defined at
runtime, where the script needs a variable number of query parameters.
It can also be used for building a system that collects a list of
plugins at runtime, and provides a parameter to each one.

This is most useful today with `Vec<Query<FilteredEntityMut>>`. It will
be even more useful with `Vec<DynSystemParam>` if #14817 is merged,
since the parameters in the list can then be of different types.

## Solution

Implement `SystemParam` and `SystemParamBuilder` for `Vec` and
`ParamSet<Vec>`.

## Example

```rust
let system = (vec![
    QueryParamBuilder::new_box(|builder| {
        builder.with::<B>().without::<C>();
    }),
    QueryParamBuilder::new_box(|builder| {
        builder.with::<C>().without::<B>();
    }),
],)
    .build_state(&mut world)
    .build_system(|params: Vec<Query<&mut A>>| {
        let mut count: usize = 0;
        params
            .into_iter()
            .for_each(|mut query| count += query.iter_mut().count());
        count
    });
```
This commit is contained in:
Chris Russell 2024-08-26 20:16:29 -04:00 committed by GitHub
parent 95ef8f6975
commit 6ddbf9771a
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101
crates/bevy_ecs/src/system/builder.rs
View file

@ -209,6 +209,15 @@ macro_rules! impl_system_param_builder_tuple {
all_tuples!(impl_system_param_builder_tuple, 0, 16, P, B);
// SAFETY: implementors of each `SystemParamBuilder` in the vec have validated their impls
unsafe impl<P: SystemParam, B: SystemParamBuilder<P>> SystemParamBuilder<Vec<P>> for Vec<B> {
fn build(self, world: &mut World, meta: &mut SystemMeta) -> <Vec<P> as SystemParam>::State {
self.into_iter()
.map(|builder| builder.build(world, meta))
.collect()
}
}
/// A [`SystemParamBuilder`] for a [`ParamSet`].
/// To build a [`ParamSet`] with a tuple of system parameters, pass a tuple of matching [`SystemParamBuilder`]s.
/// To build a [`ParamSet`] with a `Vec` of system parameters, pass a `Vec` of matching [`SystemParamBuilder`]s.
@ -251,6 +260,38 @@ macro_rules! impl_param_set_builder_tuple {
all_tuples!(impl_param_set_builder_tuple, 1, 8, P, B, meta);
// SAFETY: Relevant parameter ComponentId and ArchetypeComponentId access is applied to SystemMeta. If any ParamState conflicts
// with any prior access, a panic will occur.
unsafe impl<'w, 's, P: SystemParam, B: SystemParamBuilder<P>>
SystemParamBuilder<ParamSet<'w, 's, Vec<P>>> for ParamSetBuilder<Vec<B>>
{
fn build(
self,
world: &mut World,
system_meta: &mut SystemMeta,
) -> <Vec<P> as SystemParam>::State {
let mut states = Vec::with_capacity(self.0.len());
let mut metas = Vec::with_capacity(self.0.len());
for builder in self.0 {
let mut meta = system_meta.clone();
states.push(builder.build(world, &mut meta));
metas.push(meta);
}
if metas.iter().any(|m| !m.is_send()) {
system_meta.set_non_send();
}
for meta in metas {
system_meta
.component_access_set
.extend(meta.component_access_set);
system_meta
.archetype_component_access
.extend(&meta.archetype_component_access);
}
states
}
}
/// A [`SystemParamBuilder`] for a [`DynSystemParam`].
pub struct DynParamBuilder<'a>(
Box<dyn FnOnce(&mut World, &mut SystemMeta) -> DynSystemParamState + 'a>,
@ -385,6 +426,37 @@ mod tests {
assert_eq!(result, 1);
}
#[test]
fn vec_builder() {
let mut world = World::new();
world.spawn((A, B, C));
world.spawn((A, B));
world.spawn((A, C));
world.spawn((A, C));
world.spawn_empty();
let system = (vec![
QueryParamBuilder::new_box(|builder| {
builder.with::<B>().without::<C>();
}),
QueryParamBuilder::new_box(|builder| {
builder.with::<C>().without::<B>();
}),
],)
.build_state(&mut world)
.build_system(|params: Vec<Query<&mut A>>| {
let mut count: usize = 0;
params
.into_iter()
.for_each(|mut query| count += query.iter_mut().count());
count
});
let result = world.run_system_once(system);
assert_eq!(result, 3);
}
#[test]
fn param_set_builder() {
let mut world = World::new();
@ -412,6 +484,35 @@ mod tests {
assert_eq!(result, 5);
}
#[test]
fn param_set_vec_builder() {
let mut world = World::new();
world.spawn((A, B, C));
world.spawn((A, B));
world.spawn((A, C));
world.spawn((A, C));
world.spawn_empty();
let system = (ParamSetBuilder(vec![
QueryParamBuilder::new_box(|builder| {
builder.with::<B>();
}),
QueryParamBuilder::new_box(|builder| {
builder.with::<C>();
}),
]),)
.build_state(&mut world)
.build_system(|mut params: ParamSet<Vec<Query<&mut A>>>| {
let mut count = 0;
params.for_each(|mut query| count += query.iter_mut().count());
count
});
let result = world.run_system_once(system);
assert_eq!(result, 5);
}
#[test]
fn dyn_builder() {
let mut world = World::new();

133
crates/bevy_ecs/src/system/system_param.rs
View file

@ -1450,6 +1450,139 @@ unsafe impl SystemParam for SystemChangeTick {
}
}
// SAFETY: When initialized with `init_state`, `get_param` returns an empty `Vec` and does no access.
// Therefore, `init_state` trivially registers all access, and no accesses can conflict.
// Note that the safety requirements for non-empty `Vec`s are handled by the `SystemParamBuilder` impl that builds them.
unsafe impl<T: SystemParam> SystemParam for Vec<T> {
type State = Vec<T::State>;
type Item<'world, 'state> = Vec<T::Item<'world, 'state>>;
fn init_state(_world: &mut World, _system_meta: &mut SystemMeta) -> Self::State {
Vec::new()
}
unsafe fn get_param<'world, 'state>(
state: &'state mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'world>,
change_tick: Tick,
) -> Self::Item<'world, 'state> {
state
.iter_mut()
// SAFETY:
// - We initialized the state for each parameter in the builder, so the caller ensures we have access to any world data needed by each param.
// - The caller ensures this was the world used to initialize our state, and we used that world to initialize parameter states
.map(|state| unsafe { T::get_param(state, system_meta, world, change_tick) })
.collect()
}
unsafe fn new_archetype(
state: &mut Self::State,
archetype: &Archetype,
system_meta: &mut SystemMeta,
) {
for state in state {
// SAFETY: The caller ensures that `archetype` is from the World the state was initialized from in `init_state`.
unsafe { T::new_archetype(state, archetype, system_meta) };
}
}
fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World) {
for state in state {
T::apply(state, system_meta, world);
}
}
fn queue(state: &mut Self::State, system_meta: &SystemMeta, mut world: DeferredWorld) {
for state in state {
T::queue(state, system_meta, world.reborrow());
}
}
}
// SAFETY: When initialized with `init_state`, `get_param` returns an empty `Vec` and does no access.
// Therefore, `init_state` trivially registers all access, and no accesses can conflict.
// Note that the safety requirements for non-empty `Vec`s are handled by the `SystemParamBuilder` impl that builds them.
unsafe impl<T: SystemParam> SystemParam for ParamSet<'_, '_, Vec<T>> {
type State = Vec<T::State>;
type Item<'world, 'state> = ParamSet<'world, 'state, Vec<T>>;
fn init_state(_world: &mut World, _system_meta: &mut SystemMeta) -> Self::State {
Vec::new()
}
unsafe fn get_param<'world, 'state>(
state: &'state mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'world>,
change_tick: Tick,
) -> Self::Item<'world, 'state> {
ParamSet {
param_states: state,
system_meta: system_meta.clone(),
world,
change_tick,
}
}
unsafe fn new_archetype(
state: &mut Self::State,
archetype: &Archetype,
system_meta: &mut SystemMeta,
) {
for state in state {
// SAFETY: The caller ensures that `archetype` is from the World the state was initialized from in `init_state`.
unsafe { T::new_archetype(state, archetype, system_meta) }
}
}
fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World) {
for state in state {
T::apply(state, system_meta, world);
}
}
fn queue(state: &mut Self::State, system_meta: &SystemMeta, mut world: DeferredWorld) {
for state in state {
T::queue(state, system_meta, world.reborrow());
}
}
}
impl<T: SystemParam> ParamSet<'_, '_, Vec<T>> {
/// Accesses the parameter at the given index.
/// No other parameters may be accessed while this one is active.
pub fn get_mut(&mut self, index: usize) -> T::Item<'_, '_> {
// SAFETY:
// - We initialized the state for each parameter in the builder, so the caller ensures we have access to any world data needed by any param.
// We have mutable access to the ParamSet, so no other params in the set are active.
// - The caller of `get_param` ensured that this was the world used to initialize our state, and we used that world to initialize parameter states
unsafe {
T::get_param(
&mut self.param_states[index],
&self.system_meta,
self.world,
self.change_tick,
)
}
}
/// Calls a closure for each parameter in the set.
pub fn for_each(&mut self, mut f: impl FnMut(T::Item<'_, '_>)) {
self.param_states.iter_mut().for_each(|state| {
f(
// SAFETY:
// - We initialized the state for each parameter in the builder, so the caller ensures we have access to any world data needed by any param.
// We have mutable access to the ParamSet, so no other params in the set are active.
// - The caller of `get_param` ensured that this was the world used to initialize our state, and we used that world to initialize parameter states
unsafe { T::get_param(state, &self.system_meta, self.world, self.change_tick) },
);
});
}
}
macro_rules! impl_system_param_tuple {
($(#[$meta:meta])* $($param: ident),*) => {
$(#[$meta])*