Serialization of Name component may not be working correctly

[rparrett]

Bevy version

0.13

What you did

Modified the scene example to include Name::new("TEST").

Weirdly, I also had to .register_type::<Name>() in the example's App, despite it being registered in bevy_core.

Diff

diff --git a/examples/scene/scene.rs b/examples/scene/scene.rs
index dac36e96d..3acb19f11 100644
--- a/examples/scene/scene.rs
+++ b/examples/scene/scene.rs
@@ -8,6 +8,7 @@ fn main() {
         .register_type::<ComponentA>()
         .register_type::<ComponentB>()
         .register_type::<ResourceA>()
+        .register_type::<Name>()
         .add_systems(
             Startup,
             (save_scene_system, load_scene_system, infotext_system),
@@ -114,6 +115,7 @@ fn save_scene_system(world: &mut World) {
         component_b,
         ComponentA { x: 1.0, y: 2.0 },
         Transform::IDENTITY,
+        Name::new("TEST"),
     ));
     scene_world.spawn(ComponentA { x: 3.0, y: 4.0 });
     scene_world.insert_resource(ResourceA { score: 1 });

cargo run --example scene

And observe the serialized scene in the logged output.

What went wrong

Name is serialized as:

"bevy_core::name::Name": (
  hash: 778249913144375361,
  name: "TEST",
),

Which is contrary to this comment on name:

bevy/crates/bevy_core/src/name.rs

Lines 23 to 29 in abb8c35

	#[derive(Reflect, Component, Clone)]
	#[reflect(Component, Default, Debug)]
	#[cfg_attr(feature = "serialize", reflect(Serialize, Deserialize))]
	pub struct Name {
	hash: u64, // Won't be serialized (see: `bevy_core::serde` module)
	name: Cow<'static, str>,
	}

And the stated goal of #11447.

And the migration guide text which suggests that Name will be serialized as a plain string.

Additional information

Scenes will properly deserialize without hash, but only as a struct with a name field. Not as a plain string.

See also: #1037 where we removed the migration guide entry related to #11447.

[alice-i-cecile]

@coreh, any clues on what happened here?

[MrGVSV]

Do you have the serialize feature enabled? I wonder if it's causing issues if it's not enabled

[rparrett]

Name seems to serialize the same way (struct with hash and name) with both
cargo run --example scene --features=serialize and
cargo run --example scene.

(but the manual type registration is no longer needed when serialize is enabled.)

[rparrett]

However, deserialization requires the "bevy_core::name::Name": "TEST" format if the serialize feature is enabled.

So with serialize, the serialized output is not deserializable.

[soqb]

i've tracked this down to a combination of things:

1. allowing different formats of serialization based on a feature flag is inconsistent and flaky behavior. (we should probably make the features required or at the very least, default).
2. DynamicScene converts all its reflected components into proxy types via clone_value(is it impossible to take by reference? — it would fix everything below).
3. in bevy_reflect, we have a get_serializable function, which uses the proxy type's TypeId instead of the one we actually need (via get_represented_type_info).

bevy/crates/bevy_reflect/src/serde/ser.rs

Lines 31 to 44 in 8531033

	fn get_serializable<'a, E: Error>(
	reflect_value: &'a dyn Reflect,
	type_registry: &TypeRegistry,
	) -> Result<Serializable<'a>, E> {
	let reflect_serialize = type_registry
	.get_type_data::<ReflectSerialize>(reflect_value.type_id())
	.ok_or_else(|| {
	Error::custom(format_args!(
	"Type '{}' did not register ReflectSerialize",
	reflect_value.reflect_type_path()
	))
	})?;
	Ok(reflect_serialize.get_serializable(reflect_value))
	}

4. ReflectSerializable doesn't support proxy types, so even if we did have the right TypeId, the operation would panic.

therefore, we need to fix 3 and come up with a solution to 4. i have some ideas i'll try to throw together this week.

[coreh]

Sorry for missing this, and thanks @soqb for the investigation/solution!