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[Merged by Bors] - Allows conversion of mutable queries to immutable queries #5376

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123 changes: 123 additions & 0 deletions crates/bevy_ecs/src/system/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -927,6 +927,129 @@ mod tests {
}
}

#[test]
fn convert_mut_to_immut() {
{
let mut world = World::new();

fn mutable_query(mut query: Query<&mut A>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<&A>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<Option<&mut A>>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<Option<&A>>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &B)>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B)>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &mut B)>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B)>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &mut B), With<C>>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B), With<C>>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &mut B), Without<C>>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B), Without<C>>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &mut B), Added<C>>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B), Added<C>>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}

{
let mut world = World::new();

fn mutable_query(mut query: Query<(&mut A, &mut B), Changed<C>>) {
for _ in &mut query {}

immutable_query(query.to_readonly());
}

fn immutable_query(_: Query<(&A, &B), Changed<C>>) {}

let mut sys = IntoSystem::into_system(mutable_query);
sys.initialize(&mut world);
}
}

#[test]
fn update_archetype_component_access_works() {
use std::collections::HashSet;
Expand Down
14 changes: 14 additions & 0 deletions crates/bevy_ecs/src/system/query.rs
Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,20 @@ impl<'w, 's, Q: WorldQuery, F: WorldQuery> Query<'w, 's, Q, F> {
}
}

/// Convert the query to readonly.
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pub fn to_readonly(&self) -> Query<'w, 's, Q::ReadOnly, F::ReadOnly> {
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let new_state = self.state.as_readonly();
// SAFETY: This is memory safe because it turns the query immutable.
unsafe {
Query::new(
self.world,
new_state,
self.last_change_tick,
self.change_tick,
)
}
}

/// Returns an [`Iterator`] over the query results.
///
/// This can only return immutable data (mutable data will be cast to an immutable form).
Expand Down