# Objective
- Addresses **Support processing and loading files without extensions**
from #9714
- Addresses **More runtime loading configuration** from #9714
- Fixes#367
- Fixes#10703
## Solution
`AssetServer::load::<A>` and `AssetServer::load_with_settings::<A>` can
now use the `Asset` type parameter `A` to select a registered
`AssetLoader` without inspecting the provided `AssetPath`. This change
cascades onto `LoadContext::load` and `LoadContext::load_with_settings`.
This allows the loading of assets which have incorrect or ambiguous file
extensions.
```rust
// Allow the type to be inferred by context
let handle = asset_server.load("data/asset_no_extension");
// Hint the type through the handle
let handle: Handle<CustomAsset> = asset_server.load("data/asset_no_extension");
// Explicit through turbofish
let handle = asset_server.load::<CustomAsset>("data/asset_no_extension");
```
Since a single `AssetPath` no longer maps 1:1 with an `Asset`, I've also
modified how assets are loaded to permit multiple asset types to be
loaded from a single path. This allows for two different `AssetLoaders`
(which return different types of assets) to both load a single path (if
requested).
```rust
// Uses GltfLoader
let model = asset_server.load::<Gltf>("cube.gltf");
// Hypothetical Blob loader for data transmission (for example)
let blob = asset_server.load::<Blob>("cube.gltf");
```
As these changes are reflected in the `LoadContext` as well as the
`AssetServer`, custom `AssetLoaders` can also take advantage of this
behaviour to create more complex assets.
---
## Change Log
- Updated `custom_asset` example to demonstrate extension-less assets.
- Added `AssetServer::get_handles_untyped` and Added
`AssetServer::get_path_ids`
## Notes
As a part of that refactor, I chose to store `AssetLoader`s (within
`AssetLoaders`) using a `HashMap<TypeId, ...>` instead of a `Vec<...>`.
My reasoning for this was I needed to add a relationship between `Asset`
`TypeId`s and the `AssetLoader`, so instead of having a `Vec` and a
`HashMap`, I combined the two, removing the `usize` index from the
adjacent maps.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fixes#10518
## Solution
I've added a method to `LoadContext`, `load_direct_with_reader`, which
mirrors the behaviour of `load_direct` with a single key difference: it
is provided with the `Reader` by the caller, rather than getting it from
the contained `AssetServer`. This allows for an `AssetLoader` to process
its `Reader` stream, and then directly hand the results off to the
`LoadContext` to handle further loading. The outer `AssetLoader` can
control how the `Reader` is interpreted by providing a relevant
`AssetPath`.
For example, a Gzip decompression loader could process the asset
`images/my_image.png.gz` by decompressing the bytes, then handing the
decompressed result to the `LoadContext` with the new path
`images/my_image.png.gz/my_image.png`. This intuitively reflects the
nature of contained assets, whilst avoiding unintended behaviour, since
the generated path cannot be a real file path (a file and folder of the
same name cannot coexist in most file-systems).
```rust
#[derive(Asset, TypePath)]
pub struct GzAsset {
pub uncompressed: ErasedLoadedAsset,
}
#[derive(Default)]
pub struct GzAssetLoader;
impl AssetLoader for GzAssetLoader {
type Asset = GzAsset;
type Settings = ();
type Error = GzAssetLoaderError;
fn load<'a>(
&'a self,
reader: &'a mut Reader,
_settings: &'a (),
load_context: &'a mut LoadContext,
) -> BoxedFuture<'a, Result<Self::Asset, Self::Error>> {
Box::pin(async move {
let compressed_path = load_context.path();
let file_name = compressed_path
.file_name()
.ok_or(GzAssetLoaderError::IndeterminateFilePath)?
.to_string_lossy();
let uncompressed_file_name = file_name
.strip_suffix(".gz")
.ok_or(GzAssetLoaderError::IndeterminateFilePath)?;
let contained_path = compressed_path.join(uncompressed_file_name);
let mut bytes_compressed = Vec::new();
reader.read_to_end(&mut bytes_compressed).await?;
let mut decoder = GzDecoder::new(bytes_compressed.as_slice());
let mut bytes_uncompressed = Vec::new();
decoder.read_to_end(&mut bytes_uncompressed)?;
// Now that we have decompressed the asset, let's pass it back to the
// context to continue loading
let mut reader = VecReader::new(bytes_uncompressed);
let uncompressed = load_context
.load_direct_with_reader(&mut reader, contained_path)
.await?;
Ok(GzAsset { uncompressed })
})
}
fn extensions(&self) -> &[&str] {
&["gz"]
}
}
```
Because this example is so prudent, I've included an
`asset_decompression` example which implements this exact behaviour:
```rust
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.init_asset::<GzAsset>()
.init_asset_loader::<GzAssetLoader>()
.add_systems(Startup, setup)
.add_systems(Update, decompress::<Image>)
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(Camera2dBundle::default());
commands.spawn((
Compressed::<Image> {
compressed: asset_server.load("data/compressed_image.png.gz"),
..default()
},
Sprite::default(),
TransformBundle::default(),
VisibilityBundle::default(),
));
}
fn decompress<A: Asset>(
mut commands: Commands,
asset_server: Res<AssetServer>,
mut compressed_assets: ResMut<Assets<GzAsset>>,
query: Query<(Entity, &Compressed<A>)>,
) {
for (entity, Compressed { compressed, .. }) in query.iter() {
let Some(GzAsset { uncompressed }) = compressed_assets.remove(compressed) else {
continue;
};
let uncompressed = uncompressed.take::<A>().unwrap();
commands
.entity(entity)
.remove::<Compressed<A>>()
.insert(asset_server.add(uncompressed));
}
}
```
A key limitation to this design is how to type the internally loaded
asset, since the example `GzAssetLoader` is unaware of the internal
asset type `A`. As such, in this example I store the contained asset as
an `ErasedLoadedAsset`, and leave it up to the consumer of the `GzAsset`
to handle typing the final result, which is the purpose of the
`decompress` system. This limitation can be worked around by providing
type information to the `GzAssetLoader`, such as `GzAssetLoader<Image,
ImageAssetLoader>`, but this would require registering the asset loader
for every possible decompression target.
Aside from this limitation, nested asset containerisation works as an
end user would expect; if the user registers a `TarAssetLoader`, and a
`GzAssetLoader`, then they can load assets with compound
containerisation, such as `images.tar.gz`.
---
## Changelog
- Added `LoadContext::load_direct_with_reader`
- Added `asset_decompression` example
## Notes
- While I believe my implementation of a Gzip asset loader is
reasonable, I haven't included it as a public feature of `bevy_asset` to
keep the scope of this PR as focussed as possible.
- I have included `flate2` as a `dev-dependency` for the example; it is
not included in the main dependency graph.
