mirror of
https://github.com/bevyengine/bevy
synced 2024-12-18 17:13:10 +00:00
d4ffd4ff28
# Objective - Example in error B0003 is not failing anymore after #9822 ## Solution - Update the example code so that is always fail - Also update logs and instructions on how to debug as it's easier now --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
# B0003
|
|
|
|
As commands are executed asynchronously, it is possible to issue a command on an entity that will no longer exist at the time of the command execution.
|
|
|
|
Erroneous code example:
|
|
|
|
```rust,should_panic
|
|
use bevy::prelude::*;
|
|
|
|
fn main() {
|
|
App::new()
|
|
.add_plugins(DefaultPlugins)
|
|
.add_systems(Startup, setup)
|
|
.add_systems(Update, (use_0_and_despawn_1, use_1_and_despawn_0))
|
|
.run();
|
|
}
|
|
|
|
#[derive(Resource)]
|
|
struct MyEntities(Entity, Entity);
|
|
|
|
#[derive(Component)]
|
|
struct Hello;
|
|
|
|
fn setup(mut commands: Commands) {
|
|
let entity1 = commands.spawn_empty().id();
|
|
let entity2 = commands.spawn_empty().id();
|
|
commands.insert_resource(MyEntities(entity1, entity2));
|
|
}
|
|
|
|
fn use_0_and_despawn_1(mut commands: Commands, my_entities: Res<MyEntities>) {
|
|
commands.entity(my_entities.0).insert(Hello);
|
|
commands.entity(my_entities.1).despawn();
|
|
}
|
|
|
|
fn use_1_and_despawn_0(mut commands: Commands, my_entities: Res<MyEntities>) {
|
|
commands.entity(my_entities.1).insert(Hello);
|
|
commands.entity(my_entities.0).despawn();
|
|
}
|
|
```
|
|
|
|
This will panic, as the system that is executed first will despawn the entity used by the second.
|
|
|
|
The default panic message is telling you which entity doesn't exist (`2v0` in the example log just below), the command that failed (adding a component `Hello`) and the system from which it originated (`use_1_and_despawn_0`):
|
|
|
|
```text
|
|
thread 'main' panicked at /bevy/crates/bevy_ecs/src/system/commands/mod.rs:1097:13:
|
|
error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 2v0 because it doesn't exist in this World.
|
|
Encountered a panic when applying buffers for system `use_entity_after_despawn::use_1_and_despawn_0`!
|
|
Encountered a panic in system `bevy_app::main_schedule::Main::run_main`!
|
|
```
|
|
|
|
To get the system that created the despawn command, you can enable DEBUG logs for crate `bevy_ecs`, for example by setting the environment variable `RUST_LOG=bevy_ecs=debug` or by configuring the `LogPlugin`. This will log:
|
|
|
|
```text
|
|
DEBUG system_commands{name="use_entity_after_despawn::use_0_and_despawn_1"}: bevy_ecs::world::entity_ref: Despawning entity 2v0
|
|
thread 'main' panicked at /bevy/crates/bevy_ecs/src/system/commands/mod.rs:1097:13:
|
|
error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 2v0 because it doesn't exist in this World.
|
|
Encountered a panic when applying buffers for system `use_entity_after_despawn::use_1_and_despawn_0`!
|
|
Encountered a panic in system `bevy_app::main_schedule::Main::run_main`!
|
|
```
|
|
|
|
From the first line, you know the entity `2v0` was despawned when executing a command from system `use_0_and_despawn_1`. In a real case, you could have many log lines, you will need to search for the exact entity from the panic message.
|