Add remove method to Map reflection trait. (bevyengine#6564)

# Objective

- Implements removal of entries from a `dyn Map`
- Fixes bevyengine#6563

## Solution

- Adds a `remove` method to the `Map` trait which takes in a `&dyn Reflect` key and returns the value removed if it was present.

---

## Changelog

- Added `Map::remove`

## Migration Guide

- Implementors of `Map` will need to implement the `remove` method.


Co-authored-by: radiish <thesethskigamer@gmail.com>

crates/bevy_reflect/src/impls/std.rs

@@ -397,6 +397,17 @@ impl<K: FromReflect + Eq + Hash, V: FromReflect> Map for HashMap<K, V> {
  self.insert(key, value)
  .map(|old_value| Box::new(old_value) as Box<dyn Reflect>)
  }
+
+ fn remove(&mut self, key: &dyn Reflect) -> Option<Box<dyn Reflect>> {
+ let mut from_reflect = None;
+ key.downcast_ref::<K>()
+ .or_else(|| {
+ from_reflect = K::from_reflect(key);
+ from_reflect.as_ref()
+ })
+ .and_then(|key| self.remove(key))
+ .map(|value| Box::new(value) as Box<dyn Reflect>)
+ }
 }
 
 impl<K: FromReflect + Eq + Hash, V: FromReflect> Reflect for HashMap<K, V> {

crates/bevy_reflect/src/map.rs

@@ -57,6 +57,12 @@ pub trait Map: Reflect {
  key: Box<dyn Reflect>,
  value: Box<dyn Reflect>,
  ) -> Option<Box<dyn Reflect>>;
+
+ /// Removes an entry from the map.
+ ///
+ /// If the map did not have this key present, `None` is returned.
+ /// If the map did have this key present, the removed value is returned.
+ fn remove(&mut self, key: &dyn Reflect) -> Option<Box<dyn Reflect>>;
 }
 
 /// A container for compile-time map info.
@@ -246,6 +252,14 @@ impl Map for DynamicMap {
  }
  }
 
+ fn remove(&mut self, key: &dyn Reflect) -> Option<Box<dyn Reflect>> {
+ let index = self
+ .indices
+ .remove(&key.reflect_hash().expect(HASH_ERROR))?;
+ let (_key, value) = self.values.remove(index);
+ Some(value)
+ }
+
  fn drain(self: Box<Self>) -> Vec<(Box<dyn Reflect>, Box<dyn Reflect>)> {
  self.values
  }