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FromReflect when extracting entities in dynamic scenes (bevyeng…
…ine#15174) # Objective Fix bevyengine#10284. ## Solution When `DynamicSceneBuilder` extracts entities, they are cloned via `PartialReflect::clone_value`, making them into dynamic versions of the original components. This loses any custom `ReflectSerialize` type data. Dynamic scenes are deserialized with the original types, not the dynamic versions, and so any component with a custom serialize may fail. In this case `Rect` and `Vec2`. The dynamic version includes the field names 'x' and 'y' but the `Serialize` impl doesn't, hence the "expect float" error. The solution here: Instead of using `clone_value` to clone the components, `FromReflect` clones and retains the original information needed to serialize with any custom `Serialize` impls. I think using something like `reflect_clone` from (bevyengine#13432) might make this more efficient. I also did the same when deserializing dynamic scenes to appease some of the round-trip tests which use `ReflectPartialEq`, which requires the types be the same and not a unique/proxy pair. I'm not sure it's otherwise necessary. Maybe this would also be more efficient when spawning dynamic scenes with `reflect_clone` instead of `FromReflect` again? An alternative solution would be to fall back to the dynamic version when deserializing `DynamicScene`s if the custom version fails. I think that's possible. Or maybe simply always deserializing via the dynamic route for dynamic scenes? ## Testing This example is similar to the original test case in bevyengine#10284: ``` rust #![allow(missing_docs)] use bevy::{prelude::*, scene::SceneInstanceReady}; fn main() { App::new() .add_plugins(DefaultPlugins) .add_systems(Startup, (save, load).chain()) .observe(check) .run(); } static SAVEGAME_SAVE_PATH: &str = "savegame.scn.ron"; fn save(world: &mut World) { let entity = world.spawn(OrthographicProjection::default()).id(); let scene = DynamicSceneBuilder::from_world(world) .extract_entity(entity) .build(); if let Some(registry) = world.get_resource::<AppTypeRegistry>() { let registry = registry.read(); let serialized_scene = scene.serialize(®istry).unwrap(); // println!("{}", serialized_scene); std::fs::write(format!("assets/{SAVEGAME_SAVE_PATH}"), serialized_scene).unwrap(); } world.entity_mut(entity).despawn_recursive(); } fn load(mut commands: Commands, asset_server: Res<AssetServer>) { commands.spawn(DynamicSceneBundle { scene: asset_server.load(SAVEGAME_SAVE_PATH), ..default() }); } fn check(_trigger: Trigger<SceneInstanceReady>, query: Query<&OrthographicProjection>) { dbg!(query.single()); } ``` ## Migration Guide The `DynamicScene` format is changed to use custom serialize impls so old scene files will need updating: Old: ```ron ( resources: {}, entities: { 4294967299: ( components: { "bevy_render::camera::projection::OrthographicProjection": ( near: 0.0, far: 1000.0, viewport_origin: ( x: 0.5, y: 0.5, ), scaling_mode: WindowSize(1.0), scale: 1.0, area: ( min: ( x: -1.0, y: -1.0, ), max: ( x: 1.0, y: 1.0, ), ), ), }, ), }, ) ``` New: ```ron ( resources: {}, entities: { 4294967299: ( components: { "bevy_render::camera::projection::OrthographicProjection": ( near: 0.0, far: 1000.0, viewport_origin: (0.5, 0.5), scaling_mode: WindowSize(1.0), scale: 1.0, area: ( min: (-1.0, -1.0), max: (1.0, 1.0), ), ), }, ), }, ) ``` --------- Co-authored-by: Gino Valente <[email protected]>
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