Remove unused parts of AssetLoaders::find

[greeble-dev]

Objective

AssetLoaders::find maps from various properties to an asset loader:

fn find(
    &self,
    type_name: Option<&str>,
    asset_type_id: Option<TypeId>,
    extension: Option<&str>,
    asset_path: Option<&AssetPath<'_>>,
) -> Option<MaybeAssetLoader> {

But in practice the type_name and extension parameters are always None, and the asset_path parameter is always Some.

Solution

This PR removes the unused parts:

 fn find(
     &self,
-    type_name: Option<&str>,
     asset_type_id: Option<TypeId>,
-    extension: Option<&str>,
-    asset_path: Option<&AssetPath<'_>>,
+    asset_path: &AssetPath<'_>,
 ) -> Option<MaybeAssetLoader> {

AssetLoaders::find is pub(crate), so this should not affect users.

I looked back at the original PR and couldn't spot any cases where these parameters were ever used. I'm not sure if that's an oversight or if they were intended for future use.

I also made matching changes to AssetLoaderError::MissingAssetLoaders. This is pub so technically should have a migration guide. I'm not entirely convinced that's necessary for such a trivial change, but happy to add one if requested.

 MissingAssetLoader {
-    loader_name: Option<String>,
     asset_type_id: Option<TypeId>,
-    extension: Option<String>,
-    asset_path: Option<String>,
+    asset_path: String,
 },

Testing

cargo test -p bevy_asset
cargo run --example asset_loading
cargo run --example asset_processing --features="file_watcher asset_processor"

[andriyDev]

Nice! Funnily enough I think I made a similar change in one of my branches. Not sure where that ended up haha. Good to see this make it in though, thanks!