Debugging Schedules / SystemSets ?

[ERobsham]

I'm just getting started with Bevy and I'm looking for some advice on how to debug when systems embedded in different Schedules / SystemSets are ...scheduled (for lack of a better term)...?

As of right now, I was assuming I could order things within the main Update schedule using a custom SystemSet, and then add Systems using the .in_set(..) to ensure things are processed with some level of ordering.. but I'm seeing weird behavior I can't explain...

My custom SystemSet:

#[derive(SystemSet, Debug, Clone, Hash, PartialEq, Eq)]
pub enum GameLoopSchedules {
    ProcessInput,
    Spawn,
    // flush commands here to ensure all things
    // are created before continuing
    PostSpawn,
    EntityUpdates,
    CollisionDetection,
    Despawn,
}

Then I added it using a Plugin that all my other systems can refer to:

pub struct SchedulesPlugin;
impl Plugin for SchedulesPlugin {
    fn build(&self, app: &mut App) {
        app.configure_sets(Update, (
            GameLoopSchedules::ProcessInput,
            GameLoopSchedules::Spawn,
            GameLoopSchedules::PostSpawn,
            GameLoopSchedules::EntityUpdates,
            GameLoopSchedules::CollisionDetection,
            GameLoopSchedules::Despawn,
        ).chain())
        .add_systems(Update, 
            apply_deferred
            .after(GameLoopSchedules::Spawn)
            .before(GameLoopSchedules::PostSpawn));
    }
}

So I was expecting any systems added to the Update schedule with .in_set(GameLoopSchedules::EntityUpdates) set to definitely fire after a system added to Update with .in_set(GameLoopSchedules::PostSpawn) set... but it seems some systems actually can fire before somehow...??

The root problem I was trying to fix is a need to associate an the Entitys for AnimationPlayers to a root Entity (the parent's parent's parent's...etc etc), so I setup the following that gets triggered anytime a new AnimationPlayer is added:

.add_systems(Update, 
    associate_animation_players_to_root_entities
        .in_set(GameLoopSchedules::PostSpawn),
)
// in that system I printed a debug log to make sure it was all working as expected:
info!("entity {:?} with animation player added --> mapped to root entity {:?}", entity, root_entity);

In my player component, I start by spawning the player bundle in PostStartup to ensure its added once, and added early:

.add_systems(PostStartup, spawn_player)

Then I schedule a system to start its 'idle' animation:

.add_systems(Update, 
    start_idle_animation
        .in_set(GameLoopSchedules::EntityUpdates),
);


// system signature:
fn start_idle_animation(
    assets: Res<MeshAssets>,
    animator_map: Res<AnimationPlayerMapping>,
    q_players: Query<Entity, Added<PlayerComponent>>,
    mut q_animators: Query<&mut AnimationPlayer>,
) {
    for player_entity in q_players.iter() {
        info!("player {:?} added", player_entity);
        ...
        // in a failure case:
        warn!("no animator mapped for this player entity yet!");
        //
    }
}

And in the console I'm seeing the following output:

## logs from `start_idle_animation(...)` scheduled in `Update` / `GameLoopSchedules::EntityUpdates`
2024-03-04T01:19:15.520900Z  INFO {modulepath}::player: player 6v1 added
2024-03-04T01:19:15.520925Z  WARN {modulepath}::player: no animator mapped for this player entity yet!

## log from `associate_animation_players_to_root_entities(...)` scheduled in `Update` / `GameLoopSchedules::PostSpawn`
2024-03-04T01:19:15.697815Z  INFO {modulepath}::asset_loader: entity 86v1 with animation player added --> mapped to root entity 6v1

???

I even tried added another Command flush between GameLoopSchedules::PostSpawn and GameLoopSchedules::EntityUpdates to try and ensure PostSpawn would really be entirely blocked / synced off by the flushes:

// in `SchedulesPlugin::build(..)`
.add_systems(Update, 
    apply_deferred
    .after(GameLoopSchedules::PostSpawn)
    .before(GameLoopSchedules::EntityUpdates)
)

But I'm still seeing the same results... I'm hoping there's a simple explanation that I'm just totally missing, but I feel like I can't see the forest through the trees at this point... Help!

[ERobsham]

For anyone also having similar issues and not sure where to start. bevy_mod_debugdump has a great function print_schedule_graph(..) to help visualize how everything will get scheduled.

Turns out everything was correctly scheduled in my case. Its just the animations weren't loaded by the time the 'player' was added, so the systems would run on different frames, which was throwing me for a big ol loop. Big thanks to the Discord community for pointing me in the right direction!