bevy/crates/bevy_scene/src/scene_loader.rs
ira 992681b59b Make Resource trait opt-in, requiring #[derive(Resource)] V2 (#5577)
*This PR description is an edited copy of #5007, written by @alice-i-cecile.*
# Objective
Follow-up to https://github.com/bevyengine/bevy/pull/2254. The `Resource` trait currently has a blanket implementation for all types that meet its bounds.

While ergonomic, this results in several drawbacks:

* it is possible to make confusing, silent mistakes such as inserting a function pointer (Foo) rather than a value (Foo::Bar) as a resource
* it is challenging to discover if a type is intended to be used as a resource
* we cannot later add customization options (see the [RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/27-derive-component.md) for the equivalent choice for Component).
* dependencies can use the same Rust type as a resource in invisibly conflicting ways
* raw Rust types used as resources cannot preserve privacy appropriately, as anyone able to access that type can read and write to internal values
* we cannot capture a definitive list of possible resources to display to users in an editor
## Notes to reviewers
 * Review this commit-by-commit; there's effectively no back-tracking and there's a lot of churn in some of these commits.
   *ira: My commits are not as well organized :')*
 * I've relaxed the bound on Local to Send + Sync + 'static: I don't think these concerns apply there, so this can keep things simple. Storing e.g. a u32 in a Local is fine, because there's a variable name attached explaining what it does.
 * I think this is a bad place for the Resource trait to live, but I've left it in place to make reviewing easier. IMO that's best tackled with https://github.com/bevyengine/bevy/issues/4981.

## Changelog
`Resource` is no longer automatically implemented for all matching types. Instead, use the new `#[derive(Resource)]` macro.

## Migration Guide
Add `#[derive(Resource)]` to all types you are using as a resource.

If you are using a third party type as a resource, wrap it in a tuple struct to bypass orphan rules. Consider deriving `Deref` and `DerefMut` to improve ergonomics.

`ClearColor` no longer implements `Component`. Using `ClearColor` as a component in 0.8 did nothing.
Use the `ClearColorConfig` in the `Camera3d` and `Camera2d` components instead.


Co-authored-by: Alice <alice.i.cecile@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: devil-ira <justthecooldude@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-08-08 21:36:35 +00:00

45 lines
1.2 KiB
Rust

use crate::serde::SceneDeserializer;
use anyhow::Result;
use bevy_app::AppTypeRegistry;
use bevy_asset::{AssetLoader, LoadContext, LoadedAsset};
use bevy_ecs::world::{FromWorld, World};
use bevy_reflect::TypeRegistryArc;
use bevy_utils::BoxedFuture;
use serde::de::DeserializeSeed;
#[derive(Debug)]
pub struct SceneLoader {
type_registry: TypeRegistryArc,
}
impl FromWorld for SceneLoader {
fn from_world(world: &mut World) -> Self {
let type_registry = world.resource::<AppTypeRegistry>();
SceneLoader {
type_registry: type_registry.0.clone(),
}
}
}
impl AssetLoader for SceneLoader {
fn load<'a>(
&'a self,
bytes: &'a [u8],
load_context: &'a mut LoadContext,
) -> BoxedFuture<'a, Result<()>> {
Box::pin(async move {
let mut deserializer = ron::de::Deserializer::from_bytes(bytes)?;
let scene_deserializer = SceneDeserializer {
type_registry: &*self.type_registry.read(),
};
let scene = scene_deserializer.deserialize(&mut deserializer)?;
load_context.set_default_asset(LoadedAsset::new(scene));
Ok(())
})
}
fn extensions(&self) -> &[&str] {
&["scn", "scn.ron"]
}
}