reflect: TypePath part 2 (bevyengine#8768)

# Objective

- Followup to bevyengine#7184.
- ~Deprecate `TypeUuid` and remove its internal references.~ No longer
part of this PR.
- Use `TypePath` for the type registry, and (de)serialisation instead of
`std::any::type_name`.
- Allow accessing type path information behind proxies.

## Solution
- Introduce methods on `TypeInfo` and friends for dynamically querying
type path. These methods supersede the old `type_name` methods.
- Remove `Reflect::type_name` in favor of `DynamicTypePath::type_path`
and `TypeInfo::type_path_table`.
- Switch all uses of `std::any::type_name` in reflection, non-debugging
contexts to use `TypePath`.

---

## Changelog

- Added `TypePathTable` for dynamically accessing methods on `TypePath`
through `TypeInfo` and the type registry.
- Removed `type_name` from all `TypeInfo`-like structs.
- Added `type_path` and `type_path_table` methods to all `TypeInfo`-like
structs.
- Removed `Reflect::type_name` in favor of
`DynamicTypePath::reflect_type_path` and `TypeInfo::type_path`.
- Changed the signature of all `DynamicTypePath` methods to return
strings with a static lifetime.

## Migration Guide

- Rely on `TypePath` instead of `std::any::type_name` for all stability
guarantees and for use in all reflection contexts, this is used through
with one of the following APIs:
  - `TypePath::type_path` if you have a concrete type and not a value.
- `DynamicTypePath::reflect_type_path` if you have an `dyn Reflect`
value without a concrete type.
- `TypeInfo::type_path` for use through the registry or if you want to
work with the represented type of a `DynamicFoo`.
  
- Remove `type_name` from manual `Reflect` implementations.
- Use `type_path` and `type_path_table` in place of `type_name` on
`TypeInfo`-like structs.
- Use `get_with_type_path(_mut)` over `get_with_type_name(_mut)`.

## Note to reviewers

I think if anything we were a little overzealous in merging bevyengine#7184 and we
should take that extra care here.

In my mind, this is the "point of no return" for `TypePath` and while I
think we all agree on the design, we should carefully consider if the
finer details and current implementations are actually how we want them
moving forward.

For example [this incorrect `TypePath` implementation for
`String`](https://github.com/soqb/bevy/blob/3fea3c6c0b5719dfbd3d4230f5282ec80d82556a/crates/bevy_reflect/src/impls/std.rs#L90)
(note that `String` is in the default Rust prelude) snuck in completely
under the radar.

Author: soqb

crates/bevy_app/src/app.rs

@@ -728,7 +728,7 @@ impl App {
     /// See [`bevy_reflect::TypeRegistry::register_type_data`].
     #[cfg(feature = "bevy_reflect")]
     pub fn register_type_data<
-        T: bevy_reflect::Reflect + 'static,
+        T: bevy_reflect::Reflect + bevy_reflect::TypePath,
         D: bevy_reflect::TypeData + bevy_reflect::FromType<T>,
     >(
         &mut self,

crates/bevy_ecs/src/reflect/bundle.rs

@@ -146,7 +146,8 @@ impl<B: Bundle + Reflect + FromWorld> FromType<B> for ReflectBundle {
                         .for_each(|field| insert_field::<B>(entity, field, registry)),
                     _ => panic!(
                         "expected bundle `{}` to be named struct or tuple",
-                        std::any::type_name::<B>()
+                        // FIXME: once we have unique reflect, use `TypePath`.
+                        std::any::type_name::<B>(),
                     ),
                 }
             },
@@ -163,7 +164,8 @@ impl<B: Bundle + Reflect + FromWorld> FromType<B> for ReflectBundle {
                         .for_each(|field| apply_or_insert_field::<B>(entity, field, registry)),
                     _ => panic!(
                         "expected bundle `{}` to be named struct or tuple",
-                        std::any::type_name::<B>()
+                        // FIXME: once we have unique reflect, use `TypePath`.
+                        std::any::type_name::<B>(),
                     ),
                 }
             },
@@ -188,14 +190,14 @@ fn insert_field<B: 'static>(
             if world.components().get_id(TypeId::of::<B>()).is_some() {
                 panic!(
                     "no `ReflectComponent` registration found for `{}`",
-                    field.type_name()
+                    field.reflect_type_path(),
                 );
             };
         });
 
         panic!(
             "no `ReflectBundle` registration found for `{}`",
-            field.type_name()
+            field.reflect_type_path(),
         )
     }
 }
@@ -214,14 +216,14 @@ fn apply_or_insert_field<B: 'static>(
             if world.components().get_id(TypeId::of::<B>()).is_some() {
                 panic!(
                     "no `ReflectComponent` registration found for `{}`",
-                    field.type_name()
+                    field.reflect_type_path(),
                 );
             };
         });
 
         panic!(
             "no `ReflectBundle` registration found for `{}`",
-            field.type_name()
+            field.reflect_type_path(),
         )
     }
 }

crates/bevy_ecs/src/reflect/entity_commands.rs

@@ -161,10 +161,10 @@ impl<'w, 's, 'a> ReflectCommandExt for EntityCommands<'w, 's, 'a> {
         self
     }
 
-    fn remove_reflect(&mut self, component_type_name: impl Into<Cow<'static, str>>) -> &mut Self {
+    fn remove_reflect(&mut self, component_type_path: impl Into<Cow<'static, str>>) -> &mut Self {
         self.commands.add(RemoveReflect {
             entity: self.entity,
-            component_type_name: component_type_name.into(),
+            component_type_path: component_type_path.into(),
         });
         self
     }
@@ -189,15 +189,15 @@ fn insert_reflect(
     type_registry: &TypeRegistry,
     component: Box<dyn Reflect>,
 ) {
-    let type_info = component.type_name();
+    let type_info = component.reflect_type_path();
     let Some(mut entity) = world.get_entity_mut(entity) else {
-        panic!("error[B0003]: Could not insert a reflected component (of type {}) for entity {entity:?} because it doesn't exist in this World.", component.type_name());
+        panic!("error[B0003]: Could not insert a reflected component (of type {}) for entity {entity:?} because it doesn't exist in this World.", component.reflect_type_path());
     };
-    let Some(type_registration) = type_registry.get_with_name(type_info) else {
-        panic!("Could not get type registration (for component type {}) because it doesn't exist in the TypeRegistry.", component.type_name());
+    let Some(type_registration) = type_registry.get_with_type_path(type_info) else {
+        panic!("Could not get type registration (for component type {}) because it doesn't exist in the TypeRegistry.", component.reflect_type_path());
     };
     let Some(reflect_component) = type_registration.data::<ReflectComponent>() else {
-        panic!("Could not get ReflectComponent data (for component type {}) because it doesn't exist in this TypeRegistration.", component.type_name());
+        panic!("Could not get ReflectComponent data (for component type {}) because it doesn't exist in this TypeRegistration.", component.reflect_type_path());
     };
     reflect_component.insert(&mut entity, &*component);
 }
@@ -246,12 +246,12 @@ fn remove_reflect(
     world: &mut World,
     entity: Entity,
     type_registry: &TypeRegistry,
-    component_type_name: Cow<'static, str>,
+    component_type_path: Cow<'static, str>,
 ) {
     let Some(mut entity) = world.get_entity_mut(entity) else {
         return;
     };
-    let Some(type_registration) = type_registry.get_with_name(&component_type_name) else {
+    let Some(type_registration) = type_registry.get_with_type_path(&component_type_path) else {
         return;
     };
     let Some(reflect_component) = type_registration.data::<ReflectComponent>() else {
@@ -269,7 +269,7 @@ pub struct RemoveReflect {
     pub entity: Entity,
     /// The [`Component`](crate::component::Component) type name that will be used to remove a component
     /// of the same type from the entity.
-    pub component_type_name: Cow<'static, str>,
+    pub component_type_path: Cow<'static, str>,
 }
 
 impl Command for RemoveReflect {
@@ -279,7 +279,7 @@ impl Command for RemoveReflect {
             world,
             self.entity,
             &registry.read(),
-            self.component_type_name,
+            self.component_type_path,
         );
     }
 }
@@ -413,7 +413,7 @@ mod tests {
 
         commands
             .entity(entity)
-            .remove_reflect(boxed_reflect_component_a.type_name().to_owned());
+            .remove_reflect(boxed_reflect_component_a.reflect_type_path().to_owned());
         system_state.apply(&mut world);
 
         assert_eq!(world.entity(entity).get::<ComponentA>(), None);
@@ -443,7 +443,7 @@ mod tests {
         commands
             .entity(entity)
             .remove_reflect_with_registry::<TypeRegistryResource>(
-                boxed_reflect_component_a.type_name().to_owned(),
+                boxed_reflect_component_a.reflect_type_path().to_owned(),
             );
         system_state.apply(&mut world);
 

crates/bevy_reflect/bevy_reflect_derive/src/derive_data.rs

@@ -34,14 +34,14 @@ pub(crate) enum ReflectDerive<'a> {
 /// //                          traits
 /// //        |----------------------------------------|
 /// #[reflect(PartialEq, Serialize, Deserialize, Default)]
-/// //            type_name       generics
+/// //            type_path       generics
 /// //     |-------------------||----------|
 /// struct ThingThatImReflecting<T1, T2, T3> {/* ... */}
 /// ```
 pub(crate) struct ReflectMeta<'a> {
     /// The registered traits for this type.
     traits: ReflectTraits,
-    /// The name of this type.
+    /// The path to this type.
     type_path: ReflectTypePath<'a>,
     /// A cached instance of the path to the `bevy_reflect` crate.
     bevy_reflect_path: Path,
@@ -389,7 +389,7 @@ impl<'a> ReflectMeta<'a> {
         self.traits.from_reflect_attrs()
     }
 
-    /// The name of this struct.
+    /// The path to this type.
     pub fn type_path(&self) -> &ReflectTypePath<'a> {
         &self.type_path
     }

crates/bevy_reflect/bevy_reflect_derive/src/from_reflect.rs

@@ -73,7 +73,7 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> proc_macro2::TokenStream
                 if let #bevy_reflect_path::ReflectRef::Enum(#ref_value) = #bevy_reflect_path::Reflect::reflect_ref(#ref_value) {
                     match #bevy_reflect_path::Enum::variant_name(#ref_value) {
                         #(#variant_names => #fqoption::Some(#variant_constructors),)*
-                        name => panic!("variant with name `{}` does not exist on enum `{}`", name, ::core::any::type_name::<Self>()),
+                        name => panic!("variant with name `{}` does not exist on enum `{}`", name, <Self as #bevy_reflect_path::TypePath>::type_path()),
                     }
                 } else {
                     #FQOption::None

crates/bevy_reflect/bevy_reflect_derive/src/impls/enums.rs

@@ -58,20 +58,18 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> proc_macro2::TokenStream
             }
         });
 
-    let string_name = enum_path.get_ident().unwrap().to_string();
-
     #[cfg(feature = "documentation")]
     let info_generator = {
         let doc = reflect_enum.meta().doc();
         quote! {
-            #bevy_reflect_path::EnumInfo::new::<Self>(#string_name, &variants).with_docs(#doc)
+            #bevy_reflect_path::EnumInfo::new::<Self>(&variants).with_docs(#doc)
         }
     };
 
     #[cfg(not(feature = "documentation"))]
     let info_generator = {
         quote! {
-            #bevy_reflect_path::EnumInfo::new::<Self>(#string_name, &variants)
+            #bevy_reflect_path::EnumInfo::new::<Self>(&variants)
         }
     };
 
@@ -188,11 +186,6 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> proc_macro2::TokenStream
         }
 
         impl #impl_generics #bevy_reflect_path::Reflect for #enum_path #ty_generics #where_reflect_clause {
-            #[inline]
-            fn type_name(&self) -> &str {
-                ::core::any::type_name::<Self>()
-            }
-
             #[inline]
             fn get_represented_type_info(&self) -> #FQOption<&'static #bevy_reflect_path::TypeInfo> {
                 #FQOption::Some(<Self as #bevy_reflect_path::Typed>::type_info())
@@ -264,11 +257,11 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> proc_macro2::TokenStream
                             #(#variant_names => {
                                 *self = #variant_constructors
                             })*
-                            name => panic!("variant with name `{}` does not exist on enum `{}`", name, ::core::any::type_name::<Self>()),
+                            name => panic!("variant with name `{}` does not exist on enum `{}`", name, <Self as #bevy_reflect_path::TypePath>::type_path()),
                         }
                     }
                 } else {
-                    panic!("`{}` is not an enum", #bevy_reflect_path::Reflect::type_name(#ref_value));
+                    panic!("`{}` is not an enum", #bevy_reflect_path::DynamicTypePath::reflect_type_path(#ref_value));
                 }
             }
 

crates/bevy_reflect/bevy_reflect_derive/src/impls/structs.rs

@@ -63,20 +63,18 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> proc_macro2::TokenS
         }
     };
 
-    let string_name = struct_path.get_ident().unwrap().to_string();
-
     #[cfg(feature = "documentation")]
     let info_generator = {
         let doc = reflect_struct.meta().doc();
         quote! {
-            #bevy_reflect_path::StructInfo::new::<Self>(#string_name, &fields).with_docs(#doc)
+            #bevy_reflect_path::StructInfo::new::<Self>(&fields).with_docs(#doc)
         }
     };
 
     #[cfg(not(feature = "documentation"))]
     let info_generator = {
         quote! {
-            #bevy_reflect_path::StructInfo::new::<Self>(#string_name, &fields)
+            #bevy_reflect_path::StructInfo::new::<Self>(&fields)
         }
     };
 
@@ -163,11 +161,6 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> proc_macro2::TokenS
         }
 
         impl #impl_generics #bevy_reflect_path::Reflect for #struct_path #ty_generics #where_reflect_clause {
-            #[inline]
-            fn type_name(&self) -> &str {
-                ::core::any::type_name::<Self>()
-            }
-
             #[inline]
             fn get_represented_type_info(&self) -> #FQOption<&'static #bevy_reflect_path::TypeInfo> {
                 #FQOption::Some(<Self as #bevy_reflect_path::Typed>::type_info())

crates/bevy_reflect/bevy_reflect_derive/src/impls/tuple_structs.rs

@@ -57,20 +57,18 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> proc_macro2::
         }
     };
 
-    let string_name = struct_path.get_ident().unwrap().to_string();
-
     #[cfg(feature = "documentation")]
     let info_generator = {
         let doc = reflect_struct.meta().doc();
         quote! {
-           #bevy_reflect_path::TupleStructInfo::new::<Self>(#string_name, &fields).with_docs(#doc)
+           #bevy_reflect_path::TupleStructInfo::new::<Self>(&fields).with_docs(#doc)
         }
     };
 
     #[cfg(not(feature = "documentation"))]
     let info_generator = {
         quote! {
-            #bevy_reflect_path::TupleStructInfo::new::<Self>(#string_name, &fields)
+            #bevy_reflect_path::TupleStructInfo::new::<Self>(&fields)
         }
     };
 
@@ -133,11 +131,6 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> proc_macro2::
         }
 
         impl #impl_generics #bevy_reflect_path::Reflect for #struct_path #ty_generics #where_reflect_clause {
-            #[inline]
-            fn type_name(&self) -> &str {
-                ::core::any::type_name::<Self>()
-            }
-
             #[inline]
             fn get_represented_type_info(&self) -> #FQOption<&'static #bevy_reflect_path::TypeInfo> {
                 #FQOption::Some(<Self as #bevy_reflect_path::Typed>::type_info())

crates/bevy_reflect/bevy_reflect_derive/src/impls/values.rs

@@ -45,11 +45,6 @@ pub(crate) fn impl_value(meta: &ReflectMeta) -> proc_macro2::TokenStream {
         #typed_impl
 
         impl #impl_generics #bevy_reflect_path::Reflect for #type_path #ty_generics #where_reflect_clause  {
-            #[inline]
-            fn type_name(&self) -> &str {
-                ::core::any::type_name::<Self>()
-            }
-
             #[inline]
             fn get_represented_type_info(&self) -> #FQOption<&'static #bevy_reflect_path::TypeInfo> {
                 #FQOption::Some(<Self as #bevy_reflect_path::Typed>::type_info())
@@ -96,7 +91,7 @@ pub(crate) fn impl_value(meta: &ReflectMeta) -> proc_macro2::TokenStream {
                 if let #FQOption::Some(value) = <dyn #FQAny>::downcast_ref::<Self>(value) {
                     *self = #FQClone::clone(value);
                 } else {
-                    panic!("Value is not {}.", ::core::any::type_name::<Self>());
+                    panic!("Value is not {}.", <Self as #bevy_reflect_path::TypePath>::type_path());
                 }
             }