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Use FromReflect when extracting entities in dynamic scenes (#15174)
# Objective
Fix#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
(#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 #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 <49806985+MrGVSV@users.noreply.github.com>
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