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https://github.com/bevyengine/bevy
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dd46fd3aee
# Objective - Fixes #8140 ## Solution - Added Explicit Error Typing for `AssetLoader` and `AssetSaver`, which were the last instances of `anyhow` in use across Bevy. --- ## Changelog - Added an associated type `Error` to `AssetLoader` and `AssetSaver` for use with the `load` and `save` methods respectively. - Changed `ErasedAssetLoader` and `ErasedAssetSaver` `load` and `save` methods to use `Box<dyn Error + Send + Sync + 'static>` to allow for arbitrary `Error` types from the non-erased trait variants. Note the strict requirements match the pre-existing requirements around `anyhow::Error`. ## Migration Guide - `anyhow` is no longer exported by `bevy_asset`; Add it to your own project (if required). - `AssetLoader` and `AssetSaver` have an associated type `Error`; Define an appropriate error type (e.g., using `thiserror`), or use a pre-made error type (e.g., `anyhow::Error`). Note that using `anyhow::Error` is a drop-in replacement. - `AssetLoaderError` has been removed; Define a new error type, or use an alternative (e.g., `anyhow::Error`) - All the first-party `AssetLoader`'s and `AssetSaver`'s now return relevant (and narrow) error types instead of a single ambiguous type; Match over the specific error type, or encapsulate (`Box<dyn>`, `thiserror`, `anyhow`, etc.) ## Notes A simpler PR to resolve this issue would simply define a Bevy `Error` type defined as `Box<dyn std::error::Error + Send + Sync + 'static>`, but I think this type of error handling should be discouraged when possible. Since only 2 traits required the use of `anyhow`, it isn't a substantive body of work to solidify these error types, and remove `anyhow` entirely. End users are still encouraged to use `anyhow` if that is their preferred error handling style. Arguably, adding the `Error` associated type gives more freedom to end-users to decide whether they want more or less explicit error handling (`anyhow` vs `thiserror`). As an aside, I didn't perform any testing on Android or WASM. CI passed locally, but there may be mistakes for those platforms I missed.
86 lines
2.2 KiB
Rust
86 lines
2.2 KiB
Rust
//! Implements loader for a custom asset type.
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use bevy::utils::thiserror;
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use bevy::{
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asset::{io::Reader, AssetLoader, LoadContext},
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prelude::*,
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reflect::TypePath,
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utils::BoxedFuture,
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};
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use futures_lite::AsyncReadExt;
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use serde::Deserialize;
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use thiserror::Error;
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#[derive(Asset, TypePath, Debug, Deserialize)]
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pub struct CustomAsset {
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pub value: i32,
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}
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#[derive(Default)]
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pub struct CustomAssetLoader;
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/// Possible errors that can be produced by [`CustomAssetLoader`]
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#[non_exhaustive]
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#[derive(Debug, Error)]
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pub enum CustomAssetLoaderError {
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/// An [IO](std::io) Error
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#[error("Could load shader: {0}")]
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Io(#[from] std::io::Error),
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/// A [RON](ron) Error
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#[error("Could not parse RON: {0}")]
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RonSpannedError(#[from] ron::error::SpannedError),
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}
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impl AssetLoader for CustomAssetLoader {
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type Asset = CustomAsset;
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type Settings = ();
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type Error = CustomAssetLoaderError;
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fn load<'a>(
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&'a self,
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reader: &'a mut Reader,
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_settings: &'a (),
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_load_context: &'a mut LoadContext,
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) -> BoxedFuture<'a, Result<Self::Asset, Self::Error>> {
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Box::pin(async move {
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let mut bytes = Vec::new();
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reader.read_to_end(&mut bytes).await?;
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let custom_asset = ron::de::from_bytes::<CustomAsset>(&bytes)?;
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Ok(custom_asset)
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})
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}
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fn extensions(&self) -> &[&str] {
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&["custom"]
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}
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.init_resource::<State>()
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.init_asset::<CustomAsset>()
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.init_asset_loader::<CustomAssetLoader>()
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.add_systems(Startup, setup)
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.add_systems(Update, print_on_load)
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.run();
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}
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#[derive(Resource, Default)]
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struct State {
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handle: Handle<CustomAsset>,
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printed: bool,
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}
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fn setup(mut state: ResMut<State>, asset_server: Res<AssetServer>) {
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state.handle = asset_server.load("data/asset.custom");
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}
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fn print_on_load(mut state: ResMut<State>, custom_assets: ResMut<Assets<CustomAsset>>) {
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let custom_asset = custom_assets.get(&state.handle);
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if state.printed || custom_asset.is_none() {
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return;
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}
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info!("Custom asset loaded: {:?}", custom_asset.unwrap());
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state.printed = true;
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}
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