Configurable Asset Storage

crates/bevy_asset/macros/src/lib.rs

@@ -12,9 +12,10 @@ pub(crate) fn bevy_asset_path() -> Path {
 }
 
 const DEPENDENCY_ATTRIBUTE: &str = "dependency";
+const ASSET_STORAGE_ATTRIBUTE: &str = "asset_storage";
 
 /// Implement the `Asset` trait.
-#[proc_macro_derive(Asset, attributes(dependency))]
+#[proc_macro_derive(Asset, attributes(dependency, asset_storage))]
 pub fn derive_asset(input: TokenStream) -> TokenStream {
     let ast = parse_macro_input!(input as DeriveInput);
     let bevy_asset_path: Path = bevy_asset_path();
@@ -26,8 +27,22 @@ pub fn derive_asset(input: TokenStream) -> TokenStream {
         Err(err) => return err.into_compile_error().into(),
     };
 
+    // Check for custom asset_storage attribute
+    let storage_type = ast
+        .attrs
+        .iter()
+        .find(|attr| attr.path().is_ident(ASSET_STORAGE_ATTRIBUTE))
+        .and_then(|attr| attr.parse_args::<syn::Type>().ok())
+        .unwrap_or_else(|| {
+            // Default to StackAssetStorage if no custom storage is specified
+            let raw_storage = format_ident!("StackAssetStorage");
+            syn::parse_quote!(#bevy_asset_path::#raw_storage)
+        });
+
     TokenStream::from(quote! {
-        impl #impl_generics #bevy_asset_path::Asset for #struct_name #type_generics #where_clause { }
+        impl #impl_generics #bevy_asset_path::Asset for #struct_name #type_generics #where_clause {
+            type AssetStorage = #storage_type;
+        }
         #dependency_visitor
     })
 }

crates/bevy_asset/src/handle.rs

@@ -646,15 +646,17 @@ mod tests {
     /// `PartialReflect::reflect_clone`/`PartialReflect::to_dynamic` should increase the strong count of a strong handle
     #[test]
     fn strong_handle_reflect_clone() {
-        use crate::{AssetApp, AssetPlugin, Assets, VisitAssetDependencies};
+        use crate::{AssetApp, AssetPlugin, Assets, StackAssetStorage, VisitAssetDependencies};
         use bevy_app::App;
         use bevy_reflect::FromReflect;
 
         #[derive(Reflect)]
         struct MyAsset {
             value: u32,
         }
-        impl Asset for MyAsset {}
+        impl Asset for MyAsset {
+            type AssetStorage = StackAssetStorage;
+        }
         impl VisitAssetDependencies for MyAsset {
             fn visit_dependencies(&self, _visit: &mut impl FnMut(UntypedAssetId)) {}
         }

crates/bevy_asset/src/lib.rs

@@ -167,8 +167,8 @@ pub mod prelude {
 
     #[doc(hidden)]
     pub use crate::{
-        Asset, AssetApp, AssetEvent, AssetId, AssetMode, AssetPlugin, AssetServer, Assets,
-        DirectAssetAccessExt, Handle, UntypedHandle,
+        Asset, AssetApp, AssetEvent, AssetId, AssetMode, AssetMut, AssetPlugin, AssetRef,
+        AssetServer, AssetSnapshot, Assets, DirectAssetAccessExt, Handle, UntypedHandle,
     };
 }
 
@@ -185,6 +185,7 @@ mod path;
 mod reflect;
 mod render_asset;
 mod server;
+mod storage;
 
 pub use assets::*;
 pub use bevy_asset_macros::Asset;
@@ -203,6 +204,7 @@ pub use path::*;
 pub use reflect::*;
 pub use render_asset::*;
 pub use server::*;
+pub use storage::*;
 
 pub use uuid;
 
@@ -453,7 +455,9 @@ impl Plugin for AssetPlugin {
     label = "invalid `Asset`",
     note = "consider annotating `{Self}` with `#[derive(Asset)]`"
 )]
-pub trait Asset: VisitAssetDependencies + TypePath + Send + Sync + 'static {}
+pub trait Asset: VisitAssetDependencies + TypePath + Send + Sync + Sized + 'static {
+    type AssetStorage: AssetStorageStrategy<Self>;
+}
 
 /// A trait for components that can be used as asset identifiers, e.g. handle wrappers.
 pub trait AsAssetId: Component {
@@ -581,7 +585,8 @@ pub trait AssetApp {
     /// This enables reflection code to access assets. For detailed information, see the docs on [`ReflectAsset`] and [`ReflectHandle`].
     fn register_asset_reflect<A>(&mut self) -> &mut Self
     where
-        A: Asset + Reflect + FromReflect + GetTypeRegistration;
+        A: Asset + Reflect + FromReflect + GetTypeRegistration,
+        A::AssetStorage: AssetWriteStrategy<A>;
     /// Preregisters a loader for the given extensions, that will block asset loads until a real loader
     /// is registered.
     fn preregister_asset_loader<L: AssetLoader>(&mut self, extensions: &[&str]) -> &mut Self;
@@ -671,6 +676,7 @@ impl AssetApp for App {
     fn register_asset_reflect<A>(&mut self) -> &mut Self
     where
         A: Asset + Reflect + FromReflect + GetTypeRegistration,
+        A::AssetStorage: AssetWriteStrategy<A>,
     {
         let type_registry = self.world().resource::<AppTypeRegistry>();
         {
@@ -716,8 +722,8 @@ mod tests {
         },
         loader::{AssetLoader, LoadContext},
         Asset, AssetApp, AssetEvent, AssetId, AssetLoadError, AssetLoadFailedEvent, AssetPath,
-        AssetPlugin, AssetServer, Assets, InvalidGenerationError, LoadState, UnapprovedPathMode,
-        UntypedHandle,
+        AssetPlugin, AssetRef, AssetServer, Assets, InvalidGenerationError, LoadState,
+        UnapprovedPathMode, UntypedHandle,
     };
     use alloc::{
         boxed::Box,
@@ -927,7 +933,7 @@ mod tests {
 
     const LARGE_ITERATION_COUNT: usize = 10000;
 
-    fn get<A: Asset>(world: &World, id: AssetId<A>) -> Option<&A> {
+    fn get<'w, A: Asset>(world: &'w World, id: AssetId<A>) -> Option<AssetRef<'w, A>> {
         world.resource::<Assets<A>>().get(id)
     }
 

crates/bevy_asset/src/meta.rs

@@ -6,7 +6,7 @@ use alloc::{
 
 use crate::{
     loader::AssetLoader, processor::Process, Asset, AssetPath, DeserializeMetaError,
-    VisitAssetDependencies,
+    StackAssetStorage, VisitAssetDependencies,
 };
 use downcast_rs::{impl_downcast, Downcast};
 use ron::ser::PrettyConfig;
@@ -189,7 +189,9 @@ impl Process for () {
     }
 }
 
-impl Asset for () {}
+impl Asset for () {
+    type AssetStorage = StackAssetStorage;
+}
 
 impl VisitAssetDependencies for () {
     fn visit_dependencies(&self, _visit: &mut impl FnMut(bevy_asset::UntypedAssetId)) {