Add FromReflect trait to convert dynamic types to concrete types

crates/bevy_asset/src/handle.rs

@@ -10,14 +10,25 @@ use crate::{
     Asset, Assets,
 };
 use bevy_ecs::{component::Component, reflect::ReflectComponent};
-use bevy_reflect::{Reflect, ReflectDeserialize};
+use bevy_reflect::{FromReflect, Reflect, ReflectDeserialize};
 use bevy_utils::Uuid;
 use crossbeam_channel::{Receiver, Sender};
 use serde::{Deserialize, Serialize};
 
 /// A unique, stable asset id
 #[derive(
-    Debug, Clone, Copy, Eq, PartialEq, Hash, Ord, PartialOrd, Serialize, Deserialize, Reflect,
+    Debug,
+    Clone,
+    Copy,
+    Eq,
+    PartialEq,
+    Hash,
+    Ord,
+    PartialOrd,
+    Serialize,
+    Deserialize,
+    Reflect,
+    FromReflect,
 )]
 #[reflect_value(Serialize, Deserialize, PartialEq, Hash)]
 pub enum HandleId {
@@ -58,7 +69,7 @@ impl HandleId {
 ///
 /// Handles contain a unique id that corresponds to a specific asset in the [Assets](crate::Assets)
 /// collection.
-#[derive(Component, Reflect)]
+#[derive(Component, Reflect, FromReflect)]
 #[reflect(Component)]
 pub struct Handle<T>
 where
@@ -77,6 +88,13 @@ enum HandleType {
     Strong(Sender<RefChange>),
 }
 
+// FIXME: This only is needed because `Handle`'s field `handle_type` is currently ignored for reflection
+impl Default for HandleType {
+    fn default() -> Self {
+        Self::Weak
+    }
+}
+
 impl Debug for HandleType {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {

crates/bevy_ecs/src/reflect.rs

@@ -6,7 +6,9 @@ use crate::{
     entity::{Entity, EntityMap, MapEntities, MapEntitiesError},
     world::{FromWorld, World},
 };
-use bevy_reflect::{impl_reflect_value, FromType, Reflect, ReflectDeserialize};
+use bevy_reflect::{
+    impl_from_reflect_value, impl_reflect_value, FromType, Reflect, ReflectDeserialize,
+};
 
 #[derive(Clone)]
 pub struct ReflectComponent {
@@ -121,6 +123,7 @@ impl<C: Component + Reflect + FromWorld> FromType<C> for ReflectComponent {
 }
 
 impl_reflect_value!(Entity(Hash, PartialEq, Serialize, Deserialize));
+impl_from_reflect_value!(Entity);
 
 #[derive(Clone)]
 pub struct ReflectMapEntities {

crates/bevy_reflect/bevy_reflect_derive/src/from_reflect.rs

@@ -0,0 +1,151 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{Field, Generics, Ident, Index, Member, Path};
+
+pub fn impl_struct(
+    struct_name: &Ident,
+    generics: &Generics,
+    bevy_reflect_path: &Path,
+    active_fields: &[(&Field, usize)],
+    ignored_fields: &[(&Field, usize)],
+) -> TokenStream {
+    let field_names = active_fields
+        .iter()
+        .map(|(field, index)| {
+            field
+                .ident
+                .as_ref()
+                .map(|i| i.to_string())
+                .unwrap_or_else(|| index.to_string())
+        })
+        .collect::<Vec<String>>();
+    let field_idents = active_fields
+        .iter()
+        .map(|(field, index)| {
+            field
+                .ident
+                .as_ref()
+                .map(|ident| Member::Named(ident.clone()))
+                .unwrap_or_else(|| Member::Unnamed(Index::from(*index)))
+        })
+        .collect::<Vec<_>>();
+
+    let field_types = active_fields
+        .iter()
+        .map(|(field, _index)| field.ty.clone())
+        .collect::<Vec<_>>();
+    let field_count = active_fields.len();
+    let ignored_field_idents = ignored_fields
+        .iter()
+        .map(|(field, index)| {
+            field
+                .ident
+                .as_ref()
+                .map(|ident| Member::Named(ident.clone()))
+                .unwrap_or_else(|| Member::Unnamed(Index::from(*index)))
+        })
+        .collect::<Vec<_>>();
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    // Add FromReflect bound for each active field
+    let mut where_from_reflect_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if field_count > 0 {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_from_reflect_clause.extend(quote! {
+        #(#field_types: #bevy_reflect_path::FromReflect,)*
+    });
+
+    TokenStream::from(quote! {
+        impl #impl_generics #bevy_reflect_path::FromReflect for #struct_name #ty_generics #where_from_reflect_clause
+        {
+            fn from_reflect(reflect: &dyn #bevy_reflect_path::Reflect) -> Option<Self> {
+                use #bevy_reflect_path::Struct;
+                if let #bevy_reflect_path::ReflectRef::Struct(ref_struct) = reflect.reflect_ref() {
+                    Some(
+                        Self{
+                            #(#field_idents: {
+                                <#field_types as #bevy_reflect_path::FromReflect>::from_reflect(ref_struct.field(#field_names)?)?
+                            },)*
+                            #(#ignored_field_idents: Default::default(),)*
+                        }
+                    )
+                } else {
+                    None
+                }
+            }
+        }
+    })
+}
+
+pub fn impl_tuple_struct(
+    struct_name: &Ident,
+    generics: &Generics,
+    bevy_reflect_path: &Path,
+    active_fields: &[(&Field, usize)],
+    ignored_fields: &[(&Field, usize)],
+) -> TokenStream {
+    let field_idents = active_fields
+        .iter()
+        .map(|(_field, index)| Member::Unnamed(Index::from(*index)))
+        .collect::<Vec<_>>();
+    let field_types = active_fields
+        .iter()
+        .map(|(field, _index)| field.ty.clone())
+        .collect::<Vec<_>>();
+    let field_count = active_fields.len();
+    let field_indices = (0..field_count).collect::<Vec<usize>>();
+    let ignored_field_idents = ignored_fields
+        .iter()
+        .map(|(_field, index)| Member::Unnamed(Index::from(*index)))
+        .collect::<Vec<_>>();
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+    // Add FromReflect bound for each active field
+    let mut where_from_reflect_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if field_count > 0 {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_from_reflect_clause.extend(quote! {
+        #(#field_types: #bevy_reflect_path::FromReflect,)*
+    });
+
+    TokenStream::from(quote! {
+        impl #impl_generics #bevy_reflect_path::FromReflect for #struct_name #ty_generics #where_from_reflect_clause
+        {
+            fn from_reflect(reflect: &dyn #bevy_reflect_path::Reflect) -> Option<Self> {
+                use #bevy_reflect_path::TupleStruct;
+                if let #bevy_reflect_path::ReflectRef::TupleStruct(ref_tuple_struct) = reflect.reflect_ref() {
+                    Some(
+                        Self{
+                            #(#field_idents:
+                                <#field_types as #bevy_reflect_path::FromReflect>::from_reflect(ref_tuple_struct.field(#field_indices)?)?
+                            ,)*
+                            #(#ignored_field_idents: Default::default(),)*
+                        }
+                    )
+                } else {
+                    None
+                }
+            }
+        }
+    })
+}
+
+pub fn impl_value(type_name: &Ident, generics: &Generics, bevy_reflect_path: &Path) -> TokenStream {
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+    TokenStream::from(quote! {
+        impl #impl_generics #bevy_reflect_path::FromReflect for #type_name #ty_generics #where_clause  {
+            fn from_reflect(reflect: &dyn #bevy_reflect_path::Reflect) -> Option<Self> {
+                Some(reflect.any().downcast_ref::<#type_name #ty_generics>()?.clone())
+            }
+        }
+    })
+}

crates/bevy_reflect/bevy_reflect_derive/src/lib.rs

@@ -1,5 +1,6 @@
 extern crate proc_macro;
 
+mod from_reflect;
 mod reflect_trait;
 mod type_uuid;
 
@@ -740,3 +741,118 @@ pub fn external_type_uuid(tokens: proc_macro::TokenStream) -> proc_macro::TokenS
 pub fn reflect_trait(args: TokenStream, input: TokenStream) -> TokenStream {
     reflect_trait::reflect_trait(args, input)
 }
+
+#[proc_macro_derive(FromReflect)]
+pub fn derive_from_reflect(input: TokenStream) -> TokenStream {
+    let ast = parse_macro_input!(input as DeriveInput);
+    let unit_struct_punctuated = Punctuated::new();
+    let (fields, mut derive_type) = match &ast.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Named(fields),
+            ..
+        }) => (&fields.named, DeriveType::Struct),
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(fields),
+            ..
+        }) => (&fields.unnamed, DeriveType::TupleStruct),
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => (&unit_struct_punctuated, DeriveType::UnitStruct),
+        _ => (&unit_struct_punctuated, DeriveType::Value),
+    };
+
+    let fields_and_args = fields
+        .iter()
+        .enumerate()
+        .map(|(i, f)| {
+            (
+                f,
+                f.attrs
+                    .iter()
+                    .find(|a| *a.path.get_ident().as_ref().unwrap() == REFLECT_ATTRIBUTE_NAME)
+                    .map(|a| {
+                        syn::custom_keyword!(ignore);
+                        let mut attribute_args = PropAttributeArgs { ignore: None };
+                        a.parse_args_with(|input: ParseStream| {
+                            if input.parse::<Option<ignore>>()?.is_some() {
+                                attribute_args.ignore = Some(true);
+                                return Ok(());
+                            }
+                            Ok(())
+                        })
+                        .expect("Invalid 'property' attribute format.");
+
+                        attribute_args
+                    }),
+                i,
+            )
+        })
+        .collect::<Vec<(&Field, Option<PropAttributeArgs>, usize)>>();
+    let active_fields = fields_and_args
+        .iter()
+        .filter(|(_field, attrs, _i)| {
+            attrs.is_none()
+                || match attrs.as_ref().unwrap().ignore {
+                    Some(ignore) => !ignore,
+                    None => true,
+                }
+        })
+        .map(|(f, _attr, i)| (*f, *i))
+        .collect::<Vec<(&Field, usize)>>();
+    let ignored_fields = fields_and_args
+        .iter()
+        .filter(|(_field, attrs, _i)| {
+            attrs
+                .as_ref()
+                .map(|attrs| attrs.ignore.unwrap_or(false))
+                .unwrap_or(false)
+        })
+        .map(|(f, _attr, i)| (*f, *i))
+        .collect::<Vec<(&Field, usize)>>();
+
+    let bevy_reflect_path = BevyManifest::default().get_path("bevy_reflect");
+    let type_name = &ast.ident;
+
+    for attribute in ast.attrs.iter().filter_map(|attr| attr.parse_meta().ok()) {
+        let meta_list = if let Meta::List(meta_list) = attribute {
+            meta_list
+        } else {
+            continue;
+        };
+
+        if let Some(ident) = meta_list.path.get_ident() {
+            if ident == REFLECT_ATTRIBUTE_NAME {
+            } else if ident == REFLECT_VALUE_ATTRIBUTE_NAME {
+                derive_type = DeriveType::Value;
+            }
+        }
+    }
+
+    match derive_type {
+        DeriveType::Struct | DeriveType::UnitStruct => from_reflect::impl_struct(
+            type_name,
+            &ast.generics,
+            &bevy_reflect_path,
+            &active_fields,
+            &ignored_fields,
+        ),
+        DeriveType::TupleStruct => from_reflect::impl_tuple_struct(
+            type_name,
+            &ast.generics,
+            &bevy_reflect_path,
+            &active_fields,
+            &ignored_fields,
+        ),
+        DeriveType::Value => from_reflect::impl_value(type_name, &ast.generics, &bevy_reflect_path),
+    }
+}
+
+#[proc_macro]
+pub fn impl_from_reflect_value(input: TokenStream) -> TokenStream {
+    let reflect_value_def = parse_macro_input!(input as ReflectDef);
+
+    let bevy_reflect_path = BevyManifest::default().get_path("bevy_reflect");
+    let ty = &reflect_value_def.type_name;
+    from_reflect::impl_value(ty, &reflect_value_def.generics, &bevy_reflect_path)
+}

crates/bevy_reflect/src/impls/glam.rs

@@ -1,6 +1,6 @@
 use crate as bevy_reflect;
 use crate::ReflectDeserialize;
-use bevy_reflect_derive::impl_reflect_value;
+use bevy_reflect_derive::{impl_from_reflect_value, impl_reflect_value};
 use glam::{IVec2, IVec3, IVec4, Mat3, Mat4, Quat, UVec2, UVec3, UVec4, Vec2, Vec3, Vec4};
 
 impl_reflect_value!(IVec2(PartialEq, Serialize, Deserialize));
@@ -15,3 +15,16 @@ impl_reflect_value!(Vec4(PartialEq, Serialize, Deserialize));
 impl_reflect_value!(Mat3(PartialEq, Serialize, Deserialize));
 impl_reflect_value!(Mat4(PartialEq, Serialize, Deserialize));
 impl_reflect_value!(Quat(PartialEq, Serialize, Deserialize));
+
+impl_from_reflect_value!(IVec2);
+impl_from_reflect_value!(IVec3);
+impl_from_reflect_value!(IVec4);
+impl_from_reflect_value!(UVec2);
+impl_from_reflect_value!(UVec3);
+impl_from_reflect_value!(UVec4);
+impl_from_reflect_value!(Vec2);
+impl_from_reflect_value!(Vec3);
+impl_from_reflect_value!(Vec4);
+impl_from_reflect_value!(Mat3);
+impl_from_reflect_value!(Mat4);
+impl_from_reflect_value!(Quat);