bevy/crates/bevy_app
Zachary Harrold 6250698b56
Added on_unimplemented Diagnostic for IntoObserverSystem (#14840)
# Objective

- Fixes #14658.

## Solution

- Added `on_unimplemented` Diagnostic for `IntoObserverSystem` calling
out argument ordering in a `note`
- Added an example to the documentation on `App::observe` to provide
some explanation to users.

## Testing

- Ran CI locally
- Deliberately introduced a parameter order error in the
`ecs/observers.rs` example as a test.

---

## Showcase

<details>
  <summary>Error Before</summary>

```
error[E0277]: the trait bound `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>` is not satisfied
   --> examples/ecs/observers.rs:19:13
    |
18  |           .observe(
    |            ------- required by a bound introduced by this call
19  | /             |mines: Query<&Mine>,
20  | |             trigger: Trigger<ExplodeMines>,
21  | |             index: Res<SpatialIndex>,
22  | |              mut commands: Commands| {
...   |
34  | |                 }
35  | |             },
    | |_____________^ the trait `bevy::prelude::IntoSystem<bevy::prelude::Trigger<'static, _, _>, (), _>` is not implemented for closure `{closure@examples/ecs/observers.rs:19:13: 22:37}`, which is required by `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>`
    |
    = note: required for `{closure@examples/ecs/observers.rs:19:13: 22:37}` to implement `IntoObserverSystem<_, _, _>`
note: required by a bound in `bevy::prelude::App::observe`
   --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:995:24
    |
993 |     pub fn observe<E: Event, B: Bundle, M>(
    |            ------- required by a bound in this associated function
994 |         &mut self,
995 |         observer: impl IntoObserverSystem<E, B, M>,
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::observe`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `bevy` (example "observers") due to 1 previous error
```

</details>

<details>
  <summary>Error After</summary>

```
error[E0277]: `{closure@examples/ecs/observers.rs:19:13: 22:37}` cannot become an `ObserverSystem`
    --> examples/ecs/observers.rs:19:13
     |
18   |           .observe(
     |            ------- required by a bound introduced by this call
19   | /             |mines: Query<&Mine>,
20   | |             trigger: Trigger<ExplodeMines>,
21   | |             index: Res<SpatialIndex>,
22   | |              mut commands: Commands| {
...    |
34   | |                 }
35   | |             },
     | |_____________^ the trait `IntoObserverSystem` is not implemented
     |
     = help: the trait `bevy::prelude::IntoSystem<bevy::prelude::Trigger<'static, _, _>, (), _>` is not implemented for closure `{closure@examples/ecs/observers.rs:19:13: 22:37}`, which is required by `{closure@examples/ecs/observers.rs:19:13: 22:37}: IntoObserverSystem<_, _, _>`
     = note: for function `ObserverSystem`s, ensure the first argument is a `Trigger<T>` and any subsequent ones are `SystemParam`
     = note: required for `{closure@examples/ecs/observers.rs:19:13: 22:37}` to implement `IntoObserverSystem<_, _, _>`
note: required by a bound in `bevy::prelude::App::observe`
    --> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:1025:24
     |
1023 |     pub fn observe<E: Event, B: Bundle, M>(
     |            ------- required by a bound in this associated function
1024 |         &mut self,
1025 |         observer: impl IntoObserverSystem<E, B, M>,
     |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::observe`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `bevy` (example "observers") due to 1 previous error
```

</details>
2024-08-25 14:15:49 +00:00
..
src Added on_unimplemented Diagnostic for IntoObserverSystem (#14840) 2024-08-25 14:15:49 +00:00
Cargo.toml bevy_reflect: Function registry (#14098) 2024-08-06 01:09:48 +00:00
README.md add and fix shields in Readmes (#9993) 2023-10-15 00:52:31 +00:00

Bevy App

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This crate is about everything concerning the highest-level, application layer of a Bevy app.