feat(engine): add default value retrieval to type reflectionHEADmaster

3 files changed, 56 insertions, 2 deletions

diff --git a/engine-macros/src/reflection/default_value.rs b/engine-macros/src/reflection/default_value.rs
new file mode 100644
index 0000000..567c3b1
--- /dev/null
+++ b/engine-macros/src/reflection/default_value.rs
@@ -0,0 +1,42 @@
+use quote::quote;
+
+pub fn gen_get_default_value_fn(
+    type_ident: &proc_macro2::Ident,
+    type_generics: &syn::TypeGenerics,
+) -> proc_macro2::TokenStream
+{
+    quote! {
+        struct SpecializationTarget<T>(std::marker::PhantomData<T>);
+
+        trait HasDefaultValue
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>;
+        }
+
+        trait NoDefaultValue
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>;
+        }
+
+        impl<T> NoDefaultValue for &SpecializationTarget<T>
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>
+            {
+                None
+            }
+        }
+
+        impl<T> HasDefaultValue for SpecializationTarget<T>
+        where
+            T: std::default::Default + 'static
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>
+            {
+                Some(|| Box::new(T::default()))
+            }
+        }
+
+        (&SpecializationTarget::<#type_ident #type_generics>(std::marker::PhantomData))
+            .default_value_fn()
+    }
+}
diff --git a/engine-macros/src/reflection/enum_impl.rs b/engine-macros/src/reflection/enum_impl.rs
index 14142bf..611da6d 100644
--- a/engine-macros/src/reflection/enum_impl.rs
+++ b/engine-macros/src/reflection/enum_impl.rs
@@ -1,5 +1,6 @@
 use quote::{format_ident, quote, ToTokens};
 
+use crate::reflection::default_value::gen_get_default_value_fn;
 use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
 use crate::util::{find_engine_crate_path, syn_path, SynPathExt};
 
@@ -238,6 +239,8 @@ pub fn generate(input: syn::ItemEnum) -> proc_macro2::TokenStream
         }
     };
 
+    let get_default_value_fn = gen_get_default_value_fn(&input_ident, &type_generics);
+
     quote! {
         #[doc(hidden)]
         mod #mod_name {
@@ -254,7 +257,10 @@ pub fn generate(input: syn::ItemEnum) -> proc_macro2::TokenStream
                             variants: &[#(#variants),*],
                             is_unit_only: #is_unit_only,
                             discriminant_layout: #discriminant_layout,
-                            fields_layout: #fields_layout
+                            fields_layout: #fields_layout,
+                            get_default_value: || {
+                                #get_default_value_fn
+                            }
                         }
                     )
                 };
diff --git a/engine-macros/src/reflection/struct_impl.rs b/engine-macros/src/reflection/struct_impl.rs
index b1adea5..ce1086b 100644
--- a/engine-macros/src/reflection/struct_impl.rs
+++ b/engine-macros/src/reflection/struct_impl.rs
@@ -1,5 +1,6 @@
 use quote::quote;
 
+use crate::reflection::default_value::gen_get_default_value_fn;
 use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
 use crate::util::{find_engine_crate_path, syn_path, SynPathExt};
 
@@ -49,6 +50,8 @@ pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
             )
         });
 
+    let get_default_value_fn = gen_get_default_value_fn(&input_ident, &type_generics);
+
     quote! {
         unsafe impl #impl_generics #engine_crate_path::reflection::Reflection for
             #input_ident #type_generics #where_clause
@@ -59,7 +62,10 @@ pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
                         #engine_crate_path::reflection::Struct {
                             fields: &[
                                 #(#fields),*
-                            ]
+                            ],
+                            get_default_value: || {
+                                #get_default_value_fn
+                            }
                         }
                     )
                 };