bevy_reflect: implement Reflect for SmolStr

Prompted by winit's update bevyengine#8745.

crates/bevy_reflect/Cargo.toml

@@ -11,14 +11,18 @@ readme = "README.md"
 
 [features]
 default = []
-# Provides Bevy-related reflection implementations
+# When enabled, Provides Bevy-related reflection implementations
 bevy = ["glam", "smallvec", "bevy_math"]
 # When enabled, allows documentation comments to be accessed via reflection
 documentation = ["bevy_reflect_derive/documentation"]
+# When enabled, allows to reflect SmolStr, which bevy can expose through the winit dependency.
+winit = ["smol_str"]
 
 [dependencies]
 # bevy
-bevy_math = { path = "../bevy_math", version = "0.11.0-dev", features = ["serialize"], optional = true }
+bevy_math = { path = "../bevy_math", version = "0.11.0-dev", features = [
+    "serialize",
+], optional = true }
 bevy_reflect_derive = { path = "bevy_reflect_derive", version = "0.11.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.11.0-dev" }
 bevy_ptr = { path = "../bevy_ptr", version = "0.11.0-dev" }
@@ -30,8 +34,13 @@ parking_lot = "0.12.1"
 thiserror = "1.0"
 once_cell = "1.11"
 serde = "1"
-smallvec = { version = "1.6", features = ["serde", "union", "const_generics"], optional = true }
+smallvec = { version = "1.6", features = [
+    "serde",
+    "union",
+    "const_generics",
+], optional = true }
 glam = { version = "0.24", features = ["serde"], optional = true }
+smol_str = { version = "0.2.0", optional = true }
 
 [dev-dependencies]
 ron = "0.8.0"

crates/bevy_reflect/src/impls/smol_str.rs

@@ -0,0 +1,134 @@
+use std::{
+    any::Any,
+    hash::{Hash, Hasher},
+};
+
+use smol_str::SmolStr;
+
+use crate::{
+    utility::{reflect_hasher, NonGenericTypeInfoCell},
+    FromReflect, FromType, GetTypeRegistration, Reflect, ReflectDeserialize, ReflectFromPtr,
+    ReflectMut, ReflectOwned, ReflectRef, ReflectSerialize, TypeInfo, TypeRegistration, Typed,
+    ValueInfo,
+};
+
+impl Reflect for SmolStr {
+    fn type_name(&self) -> &str {
+        std::any::type_name::<Self>()
+    }
+
+    fn get_represented_type_info(&self) -> Option<&'static TypeInfo> {
+        Some(<Self as Typed>::type_info())
+    }
+
+    fn into_any(self: Box<Self>) -> Box<dyn Any> {
+        self
+    }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
+
+    fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> {
+        self
+    }
+
+    fn as_reflect(&self) -> &dyn Reflect {
+        self
+    }
+
+    fn as_reflect_mut(&mut self) -> &mut dyn Reflect {
+        self
+    }
+
+    fn apply(&mut self, value: &dyn Reflect) {
+        let value = value.as_any();
+        if let Some(value) = value.downcast_ref::<String>() {
+            *self = SmolStr::new(value);
+        } else {
+            panic!("Value is not a {}.", std::any::type_name::<Self>());
+        }
+    }
+
+    fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
+        *self = value.take()?;
+        Ok(())
+    }
+
+    fn reflect_ref(&self) -> ReflectRef {
+        ReflectRef::Value(self)
+    }
+
+    fn reflect_mut(&mut self) -> ReflectMut {
+        ReflectMut::Value(self)
+    }
+
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Value(self)
+    }
+
+    fn clone_value(&self) -> Box<dyn Reflect> {
+        Box::new(self.clone())
+    }
+
+    fn reflect_hash(&self) -> Option<u64> {
+        let mut hasher = reflect_hasher();
+        Hash::hash(&std::any::Any::type_id(self), &mut hasher);
+        Hash::hash(self, &mut hasher);
+        Some(hasher.finish())
+    }
+
+    fn reflect_partial_eq(&self, value: &dyn Reflect) -> Option<bool> {
+        let value = value.as_any();
+        if let Some(value) = value.downcast_ref::<Self>() {
+            Some(std::cmp::PartialEq::eq(self, value))
+        } else {
+            Some(false)
+        }
+    }
+}
+
+impl Typed for SmolStr {
+    fn type_info() -> &'static TypeInfo {
+        static CELL: NonGenericTypeInfoCell = NonGenericTypeInfoCell::new();
+        CELL.get_or_set(|| TypeInfo::Value(ValueInfo::new::<Self>()))
+    }
+}
+
+impl GetTypeRegistration for SmolStr {
+    fn get_type_registration() -> TypeRegistration {
+        let mut registration = TypeRegistration::of::<Self>();
+        #[cfg(feature = "serde")]
+        {
+            registration.insert::<ReflectDeserialize>(FromType::<Self>::from_type());
+            registration.insert::<ReflectSerialize>(FromType::<Self>::from_type());
+        }
+        registration.insert::<ReflectFromPtr>(FromType::<Self>::from_type());
+        registration
+    }
+}
+
+impl FromReflect for SmolStr {
+    fn from_reflect(reflect: &dyn crate::Reflect) -> Option<Self> {
+        Some(reflect.as_any().downcast_ref::<String>()?.into())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Reflect;
+    use smol_str::SmolStr;
+
+    #[test]
+    fn should_partial_eq_smolstr() {
+        let a: &dyn Reflect = &SmolStr::new("A");
+        let b: &dyn Reflect = &SmolStr::new("A");
+        let c: &dyn Reflect = &SmolStr::new("B");
+        assert!(a.reflect_partial_eq(b).unwrap_or_default());
+        assert!(!a.reflect_partial_eq(c).unwrap_or_default());
+    }
+}

crates/bevy_reflect/src/lib.rs

@@ -459,6 +459,9 @@ mod impls {
     mod rect;
     #[cfg(feature = "smallvec")]
     mod smallvec;
+    #[cfg(feature = "smol_str")]
+    mod smol_str;
+
     mod std;
 
     #[cfg(feature = "glam")]