Resources inserted during `Startup` schedule are not available in `OnEnter` schedule.

[CooCooCaCha]

Bevy version

0.14

What you did

Insert a resource during Startup and try to use it in OnEnter.

What went wrong

Bevy crashes with Resource requested does not exist.

Additional information

Perhaps commands aren't being flushed properly before OnEnter? It seems to work during Update.

Minimal repro:

use bevy::prelude::*;

#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash, States)]
enum AppState {
    #[default]
    Menu,
    InGame,
}

#[derive(Resource)]
struct MyResource {
    value: String,
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .init_state::<AppState>()
        .add_systems(Startup, setup)
        .add_systems(OnEnter(AppState::Menu), enter_menu_state)
        .run();
}

fn setup(mut commands: Commands) {
    commands.insert_resource(MyResource {
        value: "Hello, Bevy!".to_string(),
    });
}

fn enter_menu_state(my_resource: Res<MyResource>) {
    println!("Entered menu state {}", my_resource.value);
}

[benfrankel]

My take on how this (and the related issues) should be fixed for bevy 0.15: https://github.com/bevyengine/bevy/issues/13968#issuecomment-2185259558