11f0a2dcde
# Objective - Fixes #12377 ## Solution Added simple `#[diagnostic::on_unimplemented(...)]` attributes to some critical public traits providing a more approachable initial error message. Where appropriate, a `note` is added indicating that a `derive` macro is available. ## Examples <details> <summary>Examples hidden for brevity</summary> Below is a collection of examples showing the new error messages produced by this change. In general, messages will start with a more Bevy-centric error message (e.g., _`MyComponent` is not a `Component`_), and a note directing the user to an available derive macro where appropriate. ### Missing `#[derive(Resource)]` <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; struct MyResource; fn main() { App::new() .insert_resource(MyResource) .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `MyResource` is not a `Resource` --> examples/app/empty.rs:7:26 | 7 | .insert_resource(MyResource) | --------------- ^^^^^^^^^^ invalid `Resource` | | | required by a bound introduced by this call | = help: the trait `Resource` is not implemented for `MyResource` = note: consider annotating `MyResource` with `#[derive(Resource)]` = help: the following other types implement trait `Resource`: AccessibilityRequested ManageAccessibilityUpdates bevy::bevy_a11y::Focus DiagnosticsStore FrameCount bevy::prelude::State<S> SystemInfo bevy::prelude::Axis<T> and 141 others note: required by a bound in `bevy::prelude::App::insert_resource` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:419:31 | 419 | pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self { | ^^^^^^^^ required by this bound in `App::insert_resource` ``` </details> ### Putting A `QueryData` in a `QueryFilter` Slot <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; #[derive(Component)] struct A; #[derive(Component)] struct B; fn my_system(_query: Query<&A, &B>) {} fn main() { App::new() .add_systems(Update, my_system) .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `&B` is not a valid `Query` filter --> examples/app/empty.rs:9:22 | 9 | fn my_system(_query: Query<&A, &B>) {} | ^^^^^^^^^^^^^ invalid `Query` filter | = help: the trait `QueryFilter` is not implemented for `&B` = help: the following other types implement trait `QueryFilter`: With<T> Without<T> bevy::prelude::Or<()> bevy::prelude::Or<(F0,)> bevy::prelude::Or<(F0, F1)> bevy::prelude::Or<(F0, F1, F2)> bevy::prelude::Or<(F0, F1, F2, F3)> bevy::prelude::Or<(F0, F1, F2, F3, F4)> and 28 others note: required by a bound in `bevy::prelude::Query` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\query.rs:349:51 | 349 | pub struct Query<'world, 'state, D: QueryData, F: QueryFilter = ()> { | ^^^^^^^^^^^ required by this bound in `Query` ``` </details> ### Missing `#[derive(Component)]` <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; struct A; fn my_system(mut commands: Commands) { commands.spawn(A); } fn main() { App::new() .add_systems(Startup, my_system) .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `A` is not a `Bundle` --> examples/app/empty.rs:6:20 | 6 | commands.spawn(A); | ----- ^ invalid `Bundle` | | | required by a bound introduced by this call | = help: the trait `bevy::prelude::Component` is not implemented for `A`, which is required by `A: Bundle` = note: consider annotating `A` with `#[derive(Component)]` or `#[derive(Bundle)]` = help: the following other types implement trait `Bundle`: TransformBundle SceneBundle DynamicSceneBundle AudioSourceBundle<Source> SpriteBundle SpriteSheetBundle Text2dBundle MaterialMesh2dBundle<M> and 34 others = note: required for `A` to implement `Bundle` note: required by a bound in `bevy::prelude::Commands::<'w, 's>::spawn` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\commands\mod.rs:243:21 | 243 | pub fn spawn<T: Bundle>(&mut self, bundle: T) -> EntityCommands { | ^^^^^^ required by this bound in `Commands::<'w, 's>::spawn` ``` </details> ### Missing `#[derive(Asset)]` <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; struct A; fn main() { App::new() .init_asset::<A>() .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `A` is not an `Asset` --> examples/app/empty.rs:7:23 | 7 | .init_asset::<A>() | ---------- ^ invalid `Asset` | | | required by a bound introduced by this call | = help: the trait `Asset` is not implemented for `A` = note: consider annotating `A` with `#[derive(Asset)]` = help: the following other types implement trait `Asset`: Font AnimationGraph DynamicScene Scene AudioSource Pitch bevy::bevy_gltf::Gltf GltfNode and 17 others note: required by a bound in `init_asset` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_asset\src\lib.rs:307:22 | 307 | fn init_asset<A: Asset>(&mut self) -> &mut Self; | ^^^^^ required by this bound in `AssetApp::init_asset` ``` </details> ### Mismatched Input and Output on System Piping <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; fn producer() -> u32 { 123 } fn consumer(_: In<u16>) {} fn main() { App::new() .add_systems(Update, producer.pipe(consumer)) .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `fn(bevy::prelude::In<u16>) {consumer}` is not a valid system with input `u32` and output `_` --> examples/app/empty.rs:11:44 | 11 | .add_systems(Update, producer.pipe(consumer)) | ---- ^^^^^^^^ invalid system | | | required by a bound introduced by this call | = help: the trait `bevy::prelude::IntoSystem<u32, _, _>` is not implemented for fn item `fn(bevy::prelude::In<u16>) {consumer}` = note: expecting a system which consumes `u32` and produces `_` note: required by a bound in `pipe` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\mod.rs:168:12 | 166 | fn pipe<B, Final, MarkerB>(self, system: B) -> PipeSystem<Self::System, B::System> | ---- required by a bound in this associated function 167 | where 168 | B: IntoSystem<Out, Final, MarkerB>, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `IntoSystem::pipe` ``` </details> ### Missing Reflection <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; #[derive(Component)] struct MyComponent; fn main() { App::new() .register_type::<MyComponent>() .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `MyComponent` does not provide type registration information --> examples/app/empty.rs:8:26 | 8 | .register_type::<MyComponent>() | ------------- ^^^^^^^^^^^ the trait `GetTypeRegistration` is not implemented for `MyComponent` | | | required by a bound introduced by this call | = note: consider annotating `MyComponent` with `#[derive(Reflect)]` = help: the following other types implement trait `GetTypeRegistration`: bool char isize i8 i16 i32 i64 i128 and 443 others note: required by a bound in `bevy::prelude::App::register_type` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:619:29 | 619 | pub fn register_type<T: bevy_reflect::GetTypeRegistration>(&mut self) -> &mut Self { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::register_type` ``` </details> ### Missing `#[derive(States)]` Implementation <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; #[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash)] enum AppState { #[default] Menu, InGame { paused: bool, turbo: bool, }, } fn main() { App::new() .init_state::<AppState>() .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: the trait bound `AppState: FreelyMutableState` is not satisfied --> examples/app/empty.rs:15:23 | 15 | .init_state::<AppState>() | ---------- ^^^^^^^^ the trait `FreelyMutableState` is not implemented for `AppState` | | | required by a bound introduced by this call | = note: consider annotating `AppState` with `#[derive(States)]` note: required by a bound in `bevy::prelude::App::init_state` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:282:26 | 282 | pub fn init_state<S: FreelyMutableState + FromWorld>(&mut self) -> &mut Self { | ^^^^^^^^^^^^^^^^^^ required by this bound in `App::init_state` ``` </details> ### Adding a `System` with Unhandled Output <details> <summary>Example Code</summary> ```rust use bevy::prelude::*; fn producer() -> u32 { 123 } fn main() { App::new() .add_systems(Update, consumer) .run(); } ``` </details> <details> <summary>Error Generated</summary> ```error error[E0277]: `fn() -> u32 {producer}` does not describe a valid system configuration --> examples/app/empty.rs:9:30 | 9 | .add_systems(Update, producer) | ----------- ^^^^^^^^ invalid system configuration | | | required by a bound introduced by this call | = help: the trait `IntoSystem<(), (), _>` is not implemented for fn item `fn() -> u32 {producer}`, which is required by `fn() -> u32 {producer}: IntoSystemConfigs<_>` = help: the following other types implement trait `IntoSystemConfigs<Marker>`: <Box<(dyn bevy::prelude::System<In = (), Out = ()> + 'static)> as IntoSystemConfigs<()>> <NodeConfigs<Box<(dyn bevy::prelude::System<In = (), Out = ()> + 'static)>> as IntoSystemConfigs<()>> <(S0,) as IntoSystemConfigs<(SystemConfigTupleMarker, P0)>> <(S0, S1) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1)>> <(S0, S1, S2) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2)>> <(S0, S1, S2, S3) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3)>> <(S0, S1, S2, S3, S4) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3, P4)>> <(S0, S1, S2, S3, S4, S5) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3, P4, P5)>> and 14 others = note: required for `fn() -> u32 {producer}` to implement `IntoSystemConfigs<_>` note: required by a bound in `bevy::prelude::App::add_systems` --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:342:23 | 339 | pub fn add_systems<M>( | ----------- required by a bound in this associated function ... 342 | systems: impl IntoSystemConfigs<M>, | ^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::add_systems` ``` </details> </details> ## Testing CI passed locally. ## Migration Guide Upgrade to version 1.78 (or higher) of Rust. ## Future Work - Currently, hints are not supported in this diagnostic. Ideally, suggestions like _"consider using ..."_ would be in a hint rather than a note, but that is the best option for now. - System chaining and other `all_tuples!(...)`-based traits have bad error messages due to the slightly different error message format. --------- Co-authored-by: Jamie Ridding <Themayu@users.noreply.github.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com> |
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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.