Make bevy::core::update_frame_count public

[mamekoro]

What problem does this solve or what need does it fill?

I tried to create a plugin that can capture events and their corresponding frame count to make game sessions possible to reproduce.

I'd like to get the frame count before it is incremented in the Last schedule, but it is impossible since bevy::core::update_frame_count is not pub.
Here is a simplified code.

pub struct RecorderPlugin;

impl Plugin for RecorderPlugin {
    fn build(&self, app: &mut App) {
        if !app.is_plugin_added::<FrameCountPlugin>() {
            app.add_plugins(FrameCountPlugin);
        }

        app
            // Save events before the frame count is incremented.
            .add_systems(Last, commit.before(bevy::core::update_frame_count))
            // External systems push events via the `Recorder` resource.
            .insert_resource(Recorder::new());
    }
}

pub fn commit(mut recorder: ResMut<Recorder>, frame: Res<FrameCount>) {
    let staged = std::mem::take(&mut recorder.staged);
    let current_frame = frame.0;
    save(staged, current_frame);
}

#[derive(Debug, Resource)]
pub struct Recorder<Event> {
    // Events that occurred in this frame
    staged: Vec<Event>,
}

impl<Event> Recorder<Event> {
    // ...
}

What solution would you like?

bevy::core::update_frame_count as a pub system.

What alternative(s) have you considered?

I cloned and patched the bevy_core crate, but it is painful because I have to manually track upstream updates.

[alice-i-cecile]

No objections to this: feel free to make a PR.