From d1158288d5977ccea8c87adf80359ff9e21a852e Mon Sep 17 00:00:00 2001
From: lelo <15314665+hate@users.noreply.github.com>
Date: Fri, 2 Jun 2023 13:48:47 -0400
Subject: [PATCH] Update B0003 error docs to stageless (#8736)

# Objective

- Fixes https://github.com/bevyengine/bevy/issues/8641

## Solution

- Update the B0003 docs to reflect the changes brought to Bevy with the
release of ECS Schedule v3
---
 errors/B0003.md | 56 +++++++++++++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 20 deletions(-)

diff --git a/errors/B0003.md b/errors/B0003.md
index cbd44d3f0e..314ad7bc94 100644
--- a/errors/B0003.md
+++ b/errors/B0003.md
@@ -43,10 +43,10 @@ fn use_entity(mut commands: Commands, entity: Option<Res<MyEntity>>) {
 
 This will panic, as system `use_entity` is executed after system `despawning`. Without the system ordering specified here, the ordering would be random and this code would panic half the time.
 
-The default panic message is telling you the entity id (`0v0`) and the command that failed (adding a component `Hello`):
+The default panic message is telling you the entity id (`1v0`) and the command that failed (adding a component `Hello`):
 
 ```text
-thread 'main' panicked at 'error[B0003]: Could not add a component (of type `use_entity_after_despawn::Hello`) to entity 0v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:752:13
+thread 'main' panicked at 'error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 1v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:934:13
 ```
 
 But you don't know which system tried to add a component, and which system despawned the entity.
@@ -54,17 +54,27 @@ But you don't know which system tried to add a component, and which system despa
 To get the system that created the command that panics, you can enable the `trace` feature of Bevy. This will add a panic handler that will print more information:
 
 ```text
-   0: bevy_ecs::schedule::stage::system_commands
+   0: bevy_ecs::system::commands::system_commands
            with name="use_entity_after_despawn::use_entity"
-             at crates/bevy_ecs/src/schedule/stage.rs:880
-   1: bevy_ecs::schedule::stage
+             at crates/bevy_ecs/src/system/commands/mod.rs:117
+   1: bevy_ecs::world::schedule
            with name=Update
-             at crates/bevy_ecs/src/schedule/mod.rs:337
-   2: bevy_app::app::frame
-             at crates/bevy_app/src/app.rs:113
-   3: bevy_app::app::bevy_app
-             at crates/bevy_app/src/app.rs:126
-thread 'main' panicked at 'error[B0003]: Could not add a component (of type `use_entity_after_despawn::Hello`) to entity 0v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:752:13
+             at crates/bevy_ecs/src/world/mod.rs:1755
+   2: bevy_ecs::schedule::executor::single_threaded::system
+           with name="bevy_app::main_schedule::Main::run_main"
+             at crates/bevy_ecs/src/schedule/executor/single_threaded.rs:98
+   3: bevy_ecs::world::schedule
+           with name=Main
+             at crates/bevy_ecs/src/world/mod.rs:1755
+   4: bevy_app::app::main app
+             at crates/bevy_app/src/app.rs:249
+   5: bevy_app::app::update
+             at crates/bevy_app/src/app.rs:246
+   6: bevy_winit::winit event_handler
+             at crates/bevy_winit/src/lib.rs:338
+   7: bevy_app::app::bevy_app
+             at crates/bevy_app/src/app.rs:290
+thread 'main' panicked at 'error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 1v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:934:13
 ```
 
 From the first two lines, you now know that it panics while executing a command from the system `use_entity`.
@@ -72,21 +82,27 @@ From the first two lines, you now know that it panics while executing a command
 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`. This will log:
 
 ```text
-DEBUG stage{name=Update}:system_commands{name="use_entity_after_despawn::despawning"}: bevy_ecs::world: Despawning entity 0v0
-thread 'main' panicked at 'error[B0003]: Could not add a component (of type `use_entity_after_despawn::Hello`) to entity 0v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:752:13
+DEBUG schedule{name=Main}:system{name="bevy_app::main_schedule::Main::run_main"}:schedule{name=Update}:system_commands{name="use_entity_after_despawn::despawning"}: bevy_ecs::world::entity_ref: Despawning entity 1v0
+thread 'main' panicked at 'error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 1v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:934:13
 ```
 
-From the first line, you know the entity `0v0` was despawned when executing a command from system `despawning`. In a real case, you could have many log lines, you will need to search for the exact entity from the panic message.
+From the first line, you know the entity `1v0` was despawned when executing a command from system `despawning`. In a real case, you could have many log lines, you will need to search for the exact entity from the panic message.
 
 Combining those two, you should get enough information to understand why this panic is happening and how to fix it:
 
 ```text
-DEBUG stage{name=Update}:system_commands{name="use_entity_after_despawn::despawning"}: bevy_ecs::world: Despawning entity 0v0
-   0: bevy_ecs::schedule::stage::system_commands
+DEBUG schedule{name=Main}:system{name="bevy_app::main_schedule::Main::run_main"}:schedule{name=Update}:system_commands{name="use_entity_after_despawn::despawning"}: bevy_ecs::world::entity_ref: Despawning entity 1v0
+   0: bevy_ecs::system::commands::system_commands
            with name="use_entity_after_despawn::use_entity"
-             at crates/bevy_ecs/src/schedule/stage.rs:880
-   1: bevy_ecs::schedule::stage
+             at crates/bevy_ecs/src/system/commands/mod.rs:117
+   1: bevy_ecs::world::schedule
            with name=Update
-             at crates/bevy_ecs/src/schedule/mod.rs:337
-thread 'main' panicked at 'error[B0003]: Could not add a component (of type `use_entity_after_despawn::Hello`) to entity 0v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:752:13
+             at crates/bevy_ecs/src/world/mod.rs:1755
+   2: bevy_ecs::schedule::executor::single_threaded::system
+           with name="bevy_app::main_schedule::Main::run_main"
+             at crates/bevy_ecs/src/schedule/executor/single_threaded.rs:98
+   3: bevy_ecs::world::schedule
+           with name=Main
+             at crates/bevy_ecs/src/world/mod.rs:1755
+thread 'main' panicked at 'error[B0003]: Could not insert a bundle (of type `use_entity_after_despawn::Hello`) for entity 1v0 because it doesn't exist in this World.', /bevy/crates/bevy_ecs/src/system/commands/mod.rs:934:13
 ```