From ee1807395e70bfcfe164ff84f2693ea71b083028 Mon Sep 17 00:00:00 2001
From: Alix Bott <bott.alix@gmail.com>
Date: Wed, 2 Jul 2025 16:50:55 +0200
Subject: [PATCH] Implement `MapEntities` for arrays, `HashMap`, `BTreeMap`,
 `IndexMap` (#19908)

# Objective

- `MapEntities` is not implemented for arrays, `HashMap`, `BTreeMap`,
and `IndexMap`.

## Solution

- Implement `MapEntities` for arrays, `HashMap`, `BTreeMap`, `IndexMap`

## Testing

- I didn't add a test for this as the implementations seems pretty
trivial
---
 crates/bevy_ecs/src/entity/map_entities.rs | 66 +++++++++++++++++++---
 1 file changed, 58 insertions(+), 8 deletions(-)

diff --git a/crates/bevy_ecs/src/entity/map_entities.rs b/crates/bevy_ecs/src/entity/map_entities.rs
index 647bde983a..2c59655275 100644
--- a/crates/bevy_ecs/src/entity/map_entities.rs
+++ b/crates/bevy_ecs/src/entity/map_entities.rs
@@ -1,5 +1,5 @@
 pub use bevy_ecs_macros::MapEntities;
-use indexmap::IndexSet;
+use indexmap::{IndexMap, IndexSet};
 
 use crate::{
     entity::{hash_map::EntityHashMap, Entity},
@@ -7,11 +7,14 @@ use crate::{
 };
 
 use alloc::{
-    collections::{BTreeSet, VecDeque},
+    collections::{BTreeMap, BTreeSet, VecDeque},
     vec::Vec,
 };
-use bevy_platform::collections::HashSet;
-use core::{hash::BuildHasher, mem};
+use bevy_platform::collections::{HashMap, HashSet};
+use core::{
+    hash::{BuildHasher, Hash},
+    mem,
+};
 use smallvec::SmallVec;
 
 use super::EntityIndexSet;
@@ -72,9 +75,22 @@ impl<T: MapEntities> MapEntities for Option<T> {
     }
 }
 
-impl<T: MapEntities + Eq + core::hash::Hash, S: BuildHasher + Default> MapEntities
-    for HashSet<T, S>
+impl<K: MapEntities + Eq + Hash, V: MapEntities, S: BuildHasher + Default> MapEntities
+    for HashMap<K, V, S>
 {
+    fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
+        *self = self
+            .drain()
+            .map(|(mut key_entities, mut value_entities)| {
+                key_entities.map_entities(entity_mapper);
+                value_entities.map_entities(entity_mapper);
+                (key_entities, value_entities)
+            })
+            .collect();
+    }
+}
+
+impl<T: MapEntities + Eq + Hash, S: BuildHasher + Default> MapEntities for HashSet<T, S> {
     fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
         *self = self
             .drain()
@@ -86,9 +102,22 @@ impl<T: MapEntities + Eq + core::hash::Hash, S: BuildHasher + Default> MapEntiti
     }
 }
 
-impl<T: MapEntities + Eq + core::hash::Hash, S: BuildHasher + Default> MapEntities
-    for IndexSet<T, S>
+impl<K: MapEntities + Eq + Hash, V: MapEntities, S: BuildHasher + Default> MapEntities
+    for IndexMap<K, V, S>
 {
+    fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
+        *self = self
+            .drain(..)
+            .map(|(mut key_entities, mut value_entities)| {
+                key_entities.map_entities(entity_mapper);
+                value_entities.map_entities(entity_mapper);
+                (key_entities, value_entities)
+            })
+            .collect();
+    }
+}
+
+impl<T: MapEntities + Eq + Hash, S: BuildHasher + Default> MapEntities for IndexSet<T, S> {
     fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
         *self = self
             .drain(..)
@@ -109,6 +138,19 @@ impl MapEntities for EntityIndexSet {
     }
 }
 
+impl<K: MapEntities + Ord, V: MapEntities> MapEntities for BTreeMap<K, V> {
+    fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
+        *self = mem::take(self)
+            .into_iter()
+            .map(|(mut key_entities, mut value_entities)| {
+                key_entities.map_entities(entity_mapper);
+                value_entities.map_entities(entity_mapper);
+                (key_entities, value_entities)
+            })
+            .collect();
+    }
+}
+
 impl<T: MapEntities + Ord> MapEntities for BTreeSet<T> {
     fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
         *self = mem::take(self)
@@ -121,6 +163,14 @@ impl<T: MapEntities + Ord> MapEntities for BTreeSet<T> {
     }
 }
 
+impl<T: MapEntities, const N: usize> MapEntities for [T; N] {
+    fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
+        for entities in self.iter_mut() {
+            entities.map_entities(entity_mapper);
+        }
+    }
+}
+
 impl<T: MapEntities> MapEntities for Vec<T> {
     fn map_entities<E: EntityMapper>(&mut self, entity_mapper: &mut E) {
         for entities in self.iter_mut() {