57931ce42f
**NOTE: Also see https://github.com/bevyengine/bevy/pull/15548 for the serializer equivalent** # Objective The current `ReflectDeserializer` and `TypedReflectDeserializer` use the `TypeRegistration` and/or `ReflectDeserialize` of a given type in order to determine how to deserialize a value of that type. However, there is currently no way to statefully override deserialization of a given type when using these two deserializers - that is, to have some local data in the same scope as the `ReflectDeserializer`, and make use of that data when deserializing. The motivating use case for this came up when working on [`bevy_animation_graph`](https://github.com/aecsocket/bevy_animation_graph/tree/feat/dynamic-nodes), when loading an animation graph asset. The `AnimationGraph` stores `Vec<Box<dyn NodeLike>>`s which we have to load in. Those `Box<dyn NodeLike>`s may store `Handle`s to e.g. `Handle<AnimationClip>`. I want to trigger a `load_context.load()` for that handle when it's loaded. ```rs #[derive(Reflect)] struct Animation { clips: Vec<Handle<AnimationClip>>, } ``` ```rs ( clips: [ "animation_clips/walk.animclip.ron", "animation_clips/run.animclip.ron", "animation_clips/jump.animclip.ron", ], ) ```` Currently, if this were deserialized from an asset loader, this would be deserialized as a vec of `Handle::default()`s, which isn't useful since we also need to `load_context.load()` those handles for them to be used. With this processor field, a processor can detect when `Handle<T>`s are being loaded, then actually load them in. ## Solution ```rs trait ReflectDeserializerProcessor { fn try_deserialize<'de, D>( &mut self, registration: &TypeRegistration, deserializer: D, ) -> Result<Result<Box<dyn PartialReflect>, D>, D::Error> where D: serde::Deserializer<'de>; } ``` ```diff - pub struct ReflectDeserializer<'a> { + pub struct ReflectDeserializer<'a, P = ()> { // also for ReflectTypedDeserializer registry: &'a TypeRegistry, + processor: Option<&'a mut P>, } ``` ```rs impl<'a, P: ReflectDeserializerProcessor> ReflectDeserializer<'a, P> { // also for ReflectTypedDeserializer pub fn with_processor(registry: &'a TypeRegistry, processor: &'a mut P) -> Self { Self { registry, processor: Some(processor), } } } ``` This does not touch the existing `fn new`s. This `processor` field is also added to all internal visitor structs. When `TypedReflectDeserializer` runs, it will first try to deserialize a value of this type by passing the `TypeRegistration` and deserializer to the processor, and fallback to the default logic. This processor runs the earliest, and takes priority over all other deserialization logic. ## Testing Added unit tests to `bevy_reflect::serde::de`. Also using almost exactly the same implementation in [my fork of `bevy_animation_graph`](https://github.com/aecsocket/bevy_animation_graph/tree/feat/dynamic-nodes). ## Migration Guide (Since I added `P = ()`, I don't think this is actually a breaking change anymore, but I'll leave this in) `bevy_reflect`'s `ReflectDeserializer` and `TypedReflectDeserializer` now take a `ReflectDeserializerProcessor` as the type parameter `P`, which allows you to customize deserialization for specific types when they are found. However, the rest of the API surface (`new`) remains the same. <details> <summary>Original implementation</summary> Add `ReflectDeserializerProcessor`: ```rs struct ReflectDeserializerProcessor { pub can_deserialize: Box<dyn FnMut(&TypeRegistration) -> bool + 'p>, pub deserialize: Box< dyn FnMut( &TypeRegistration, &mut dyn erased_serde::Deserializer, ) -> Result<Box<dyn PartialReflect>, erased_serde::Error> + 'p, } ``` Along with `ReflectDeserializer::new_with_processor` and `TypedReflectDeserializer::new_with_processor`. This does not touch the public API of the existing `new` fns. This is stored as an `Option<&mut ReflectDeserializerProcessor>` on the deserializer and any of the private `-Visitor` structs, and when we attempt to deserialize a value, we first pass it through this processor. Also added a very comprehensive doc test to `ReflectDeserializerProcessor`, which is actually a scaled down version of the code for the `bevy_animation_graph` loader. This should give users a good motivating example for when and why to use this feature. ### Why `Box<dyn ..>`? When I originally implemented this, I added a type parameter to `ReflectDeserializer` to determine the processor used, with `()` being "no processor". However when using this, I kept running into rustc errors where it failed to validate certain type bounds and led to overflows. I then switched to a dynamic dispatch approach. The dynamic dispatch should not be that expensive, nor should it be a performance regression, since it's only used if there is `Some` processor. (Note: I have not benchmarked this, I am just speculating.) Also, it means that we don't infect the rest of the code with an extra type parameter, which is nicer to maintain. ### Why the `'p` on `ReflectDeserializerProcessor<'p>`? Without a lifetime here, the `Box`es would automatically become `Box<dyn FnMut(..) + 'static>`. This makes them practically useless, since any local data you would want to pass in must then be `'static`. In the motivating example, you couldn't pass in that `&mut LoadContext` to the function. This means that the `'p` infects the rest of the Visitor types, but this is acceptable IMO. This PR also elides the lifetimes in the `impl<'de> Visitor<'de> for -Visitor` blocks where possible. ### Future possibilities I think it's technically possible to turn the processor into a trait, and make the deserializers generic over that trait. This would also open the door to an API like: ```rs type Seed; fn seed_deserialize(&mut self, r: &TypeRegistration) -> Option<Self::Seed>; fn deserialize(&mut self, r: &TypeRegistration, d: &mut dyn erased_serde::Deserializer, s: Self::Seed) -> ...; ``` A similar processor system should also be added to the serialization side, but that's for another PR. Ideally, both PRs will be in the same release, since one isn't very useful without the other. ## Testing Added unit tests to `bevy_reflect::serde::de`. Also using almost exactly the same implementation in [my fork of `bevy_animation_graph`](https://github.com/aecsocket/bevy_animation_graph/tree/feat/dynamic-nodes). ## Migration Guide `bevy_reflect`'s `ReflectDeserializer` and `TypedReflectDeserializer` now take a second lifetime parameter `'p` for storing the `ReflectDeserializerProcessor` field lifetimes. However, the rest of the API surface (`new`) remains the same, so if you are not storing these deserializers or referring to them with lifetimes, you should not have to make any changes. </details> |
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What is Bevy?
Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!
WARNING
Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
Design Goals
- Capable: Offer a complete 2D and 3D feature set
- Simple: Easy for newbies to pick up, but infinitely flexible for power users
- Data Focused: Data-oriented architecture using the Entity Component System paradigm
- Modular: Use only what you need. Replace what you don't like
- Fast: App logic should run quickly, and when possible, in parallel
- Productive: Changes should compile quickly ... waiting isn't fun
About
- Features: A quick overview of Bevy's features.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- Quick Start Guide: Bevy's official Quick Start Guide. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
Contributing
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out the Quick Start Guide for a brief introduction.
Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:
# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main(){
App::new()
.add_plugins(DefaultPlugins)
.run();
}
Fast Compiles
Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.
Bevy Cargo Features
This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
Thanks
Bevy is the result of the hard work of many people. A huge thanks to all Bevy contributors, the many open source projects that have come before us, the Rust gamedev ecosystem, and the many libraries we build on.
A huge thanks to Bevy's generous sponsors. Bevy will always be free and open source, but it isn't free to make. Please consider sponsoring our work if you like what we're building.
This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.
Some of the engine's code carries additional copyright notices and license terms due to their external origins.
These are generally BSD-like, but exact details vary by crate:
If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed.
The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms.
The license field of each crate will also reflect this.
For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).
The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.
Your contributions
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.