Implement IntoIterator for &Extract<P> (#6025)

# Objective

Implement `IntoIterator` for `&Extract<P>` if the system parameter it wraps implements `IntoIterator`.

Enables the use of `IntoIterator` with an extracted query.

Co-authored-by: devil-ira <justthecooldude@gmail.com>

crates/bevy_core_pipeline/src/core_2d/mod.rs

@@ -128,7 +128,7 @@ pub fn extract_core_2d_camera_phases(
     mut commands: Commands,
     cameras_2d: Extract<Query<(Entity, &Camera), With<Camera2d>>>,
 ) {
-    for (entity, camera) in cameras_2d.iter() {
+    for (entity, camera) in &cameras_2d {
         if camera.is_active {
             commands
                 .get_or_spawn(entity)

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -211,7 +211,7 @@ pub fn extract_core_3d_camera_phases(
     mut commands: Commands,
     cameras_3d: Extract<Query<(Entity, &Camera), With<Camera3d>>>,
 ) {
-    for (entity, camera) in cameras_3d.iter() {
+    for (entity, camera) in &cameras_3d {
         if camera.is_active {
             commands.get_or_spawn(entity).insert_bundle((
                 RenderPhase::<Opaque3d>::default(),

crates/bevy_pbr/src/render/light.rs

@@ -393,7 +393,7 @@ pub fn extract_clusters(
     mut commands: Commands,
     views: Extract<Query<(Entity, &Clusters), With<Camera>>>,
 ) {
-    for (entity, clusters) in views.iter() {
+    for (entity, clusters) in &views {
         commands.get_or_spawn(entity).insert_bundle((
             ExtractedClustersPointLights {
                 data: clusters.lights.clone(),

crates/bevy_pbr/src/render/mesh.rs

@@ -229,7 +229,7 @@ pub fn extract_skinned_meshes(
     let mut joints = Vec::with_capacity(*previous_joint_len);
     let mut last_start = 0;
 
-    for (entity, computed_visibility, skin) in query.iter() {
+    for (entity, computed_visibility, skin) in &query {
         if !computed_visibility.is_visible() {
             continue;
         }

crates/bevy_pbr/src/wireframe.rs

@@ -52,7 +52,7 @@ impl Plugin for WireframePlugin {
 }
 
 fn extract_wireframes(mut commands: Commands, query: Extract<Query<Entity, With<Wireframe>>>) {
-    for entity in query.iter() {
+    for entity in &query {
         commands.get_or_spawn(entity).insert(Wireframe);
     }
 }

crates/bevy_render/src/extract_component.rs

@@ -183,10 +183,10 @@ impl<T: Asset> ExtractComponent for Handle<T> {
 fn extract_components<C: ExtractComponent>(
     mut commands: Commands,
     mut previous_len: Local<usize>,
-    mut query: Extract<Query<(Entity, C::Query), C::Filter>>,
+    query: Extract<Query<(Entity, C::Query), C::Filter>>,
 ) {
     let mut values = Vec::with_capacity(*previous_len);
-    for (entity, query_item) in query.iter_mut() {
+    for (entity, query_item) in &query {
         values.push((entity, (C::extract_component(query_item),)));
     }
     *previous_len = values.len();
@@ -197,10 +197,10 @@ fn extract_components<C: ExtractComponent>(
 fn extract_visible_components<C: ExtractComponent>(
     mut commands: Commands,
     mut previous_len: Local<usize>,
-    mut query: Extract<Query<(Entity, &ComputedVisibility, C::Query), C::Filter>>,
+    query: Extract<Query<(Entity, &ComputedVisibility, C::Query), C::Filter>>,
 ) {
     let mut values = Vec::with_capacity(*previous_len);
-    for (entity, computed_visibility, query_item) in query.iter_mut() {
+    for (entity, computed_visibility, query_item) in &query {
         if computed_visibility.is_visible() {
             values.push((entity, (C::extract_component(query_item),)));
         }

crates/bevy_render/src/extract_param.rs

@@ -3,7 +3,7 @@ use bevy_ecs::{
     prelude::*,
     system::{
         ReadOnlySystemParamFetch, ResState, SystemMeta, SystemParam, SystemParamFetch,
-        SystemParamState, SystemState,
+        SystemParamItem, SystemParamState, SystemState,
     },
 };
 use std::ops::{Deref, DerefMut};
@@ -34,7 +34,7 @@ use std::ops::{Deref, DerefMut};
 /// # #[derive(Component)]
 /// # struct Cloud;
 /// fn extract_clouds(mut commands: Commands, clouds: Extract<Query<Entity, With<Cloud>>>) {
-///     for cloud in clouds.iter() {
+///     for cloud in &clouds {
 ///         commands.get_or_spawn(cloud).insert(Cloud);
 ///     }
 /// }
@@ -118,3 +118,16 @@ where
         &mut self.item
     }
 }
+
+impl<'a, 'w, 's, P: SystemParam> IntoIterator for &'a Extract<'w, 's, P>
+where
+    P::Fetch: ReadOnlySystemParamFetch,
+    &'a SystemParamItem<'w, 's, P>: IntoIterator,
+{
+    type Item = <&'a SystemParamItem<'w, 's, P> as IntoIterator>::Item;
+    type IntoIter = <&'a SystemParamItem<'w, 's, P> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        (&self.item).into_iter()
+    }
+}

crates/bevy_sprite/src/mesh2d/mesh.rs

@@ -127,7 +127,7 @@ pub fn extract_mesh2d(
     query: Extract<Query<(Entity, &ComputedVisibility, &GlobalTransform, &Mesh2dHandle)>>,
 ) {
     let mut values = Vec::with_capacity(*previous_len);
-    for (entity, computed_visibility, transform, handle) in query.iter() {
+    for (entity, computed_visibility, transform, handle) in &query {
         if !computed_visibility.is_visible() {
             continue;
         }

crates/bevy_ui/src/render/mod.rs

@@ -233,7 +233,7 @@ pub fn extract_default_ui_camera_view<T: Component>(
     mut commands: Commands,
     query: Extract<Query<(Entity, &Camera, Option<&UiCameraConfig>), With<T>>>,
 ) {
-    for (entity, camera, camera_ui) in query.iter() {
+    for (entity, camera, camera_ui) in &query {
         // ignore cameras with disabled ui
         if matches!(camera_ui, Some(&UiCameraConfig { show_ui: false, .. })) {
             continue;

examples/2d/mesh2d_manual.rs

@@ -294,7 +294,7 @@ pub fn extract_colored_mesh2d(
     query: Extract<Query<(Entity, &ComputedVisibility), With<ColoredMesh2d>>>,
 ) {
     let mut values = Vec::with_capacity(*previous_len);
-    for (entity, computed_visibility) in query.iter() {
+    for (entity, computed_visibility) in &query {
         if !computed_visibility.is_visible() {
             continue;
         }