Refactor Schedule (#289)

## Description

- Tweak the system schedule to be more parallel-friendly and explicit.
Dependencies between systems is clearer.
- System and resource configuration is better encapsulated in each
module by using plugins.

The schedule graph for `Main` now looks like this (using
`bevy_mod_debugdump`):


![graph](https://user-images.githubusercontent.com/31678482/225321113-0ec4f4dd-86f6-45fe-8158-12a451536770.svg)

### Unresolved

- What to do about ambiguous systems? Many systems here are ambiguous
because they take `&mut Client`, but the order they write packets isn't
really important. Marking them as ambiguous explicitly with
`.ambiguous_with*` across module boundaries seems difficult and
cumbersome.

## Test Plan

Steps:
1. Run examples. Check that I didn't screw up the system order.

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = ["crates/*"]
 exclude = ["rust-mc-bot"]
+resolver = "2"
 
 [profile.dev.package."*"]
 opt-level = 3

crates/valence/src/client.rs

@@ -3,9 +3,9 @@ use std::net::IpAddr;
 use std::num::Wrapping;
 use std::time::Instant;
 
+use bevy_app::{CoreSet, Plugin};
 use bevy_ecs::prelude::*;
 use bevy_ecs::query::WorldQuery;
-use bevy_ecs::schedule::SystemConfigs;
 use bevy_ecs::system::Command;
 use bytes::BytesMut;
 use glam::{DVec3, Vec3};
@@ -38,10 +38,10 @@ use crate::component::{
 };
 use crate::dimension::DimensionId;
 use crate::entity::{velocity_to_packet_units, EntityStatus, McEntity, TrackedData};
-use crate::instance::Instance;
+use crate::instance::{Instance, UpdateInstancesPreClientSet};
 use crate::inventory::{Inventory, InventoryKind};
 use crate::packet::WritePacket;
-use crate::prelude::ScratchBuffer;
+use crate::prelude::ScratchBuf;
 use crate::server::{NewClientInfo, Server};
 use crate::view::{ChunkPos, ChunkView};
 
@@ -52,8 +52,8 @@ pub mod event;
 #[derive(Bundle)]
 pub(crate) struct ClientBundle {
     client: Client,
-    scratch: ScratchBuffer,
+    scratch: ScratchBuf,
-    entity_remove_buffer: EntityRemoveBuffer,
+    entity_remove_buffer: EntityRemoveBuf,
     username: Username,
     uuid: UniqueId,
     ip: Ip,
@@ -95,8 +95,8 @@ impl ClientBundle {
     ) -> Self {
         Self {
             client: Client { conn, enc, dec },
-            scratch: ScratchBuffer::default(),
+            scratch: ScratchBuf::default(),
-            entity_remove_buffer: EntityRemoveBuffer(vec![]),
+            entity_remove_buffer: EntityRemoveBuf(vec![]),
             username: Username(info.username),
             uuid: UniqueId(info.uuid),
             ip: Ip(info.ip),
@@ -396,9 +396,9 @@ impl Command for DisconnectClient {
 ///
 /// You should not need to use this directly under normal circumstances.
 #[derive(Component, Debug)]
-pub struct EntityRemoveBuffer(Vec<VarInt>);
+pub struct EntityRemoveBuf(Vec<VarInt>);
 
-impl EntityRemoveBuffer {
+impl EntityRemoveBuf {
     pub fn push(&mut self, entity_id: i32) {
         debug_assert!(
             entity_id != 0,
@@ -599,25 +599,45 @@ pub fn despawn_disconnected_clients(
     }
 }
 
-pub(crate) fn update_clients() -> SystemConfigs {
+pub(crate) struct ClientPlugin;
+
+/// When clients have their packet buffer flushed. Any system that writes
+/// packets to clients should happen before this. Otherwise, the data
+/// will arrive one tick late.
+#[derive(SystemSet, Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct FlushPacketsSet;
+
+impl Plugin for ClientPlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        app.add_systems(
             (
                 initial_join,
                 update_chunk_load_dist,
-        respawn,
+                read_data_in_view
-        send_keepalive,
+                    .after(UpdateInstancesPreClientSet)
-        read_data_in_view,
+                    .after(update_chunk_load_dist),
-        update_view,
+                update_view.after(initial_join).after(read_data_in_view),
-        remove_entities,
+                respawn.after(update_view),
+                remove_entities.after(update_view),
+                update_spawn_position.after(update_view),
+                update_old_view_dist.after(update_view),
+                teleport.after(update_view),
                 update_game_mode,
-        teleport,
+                send_keepalive,
-        update_view_dist,
-        update_compass_pos,
                 update_tracked_data,
                 update_op_level,
                 acknowledge_player_actions,
-        flush_packets,
             )
-        .chain()
+                .in_base_set(CoreSet::PostUpdate)
+                .before(FlushPacketsSet),
+        )
+        .configure_set(
+            FlushPacketsSet
+                .in_base_set(CoreSet::PostUpdate)
+                .after(UpdateInstancesPreClientSet),
+        )
+        .add_system(flush_packets.in_set(FlushPacketsSet));
+    }
 }
 
 #[derive(WorldQuery)]
@@ -766,8 +786,8 @@ fn update_chunk_load_dist(
 fn read_data_in_view(
     mut clients: Query<(
         &mut Client,
-        &mut ScratchBuffer,
+        &mut ScratchBuf,
-        &mut EntityRemoveBuffer,
+        &mut EntityRemoveBuf,
         &OldLocation,
         &OldPosition,
         &OldViewDistance,
@@ -845,12 +865,15 @@ fn read_data_in_view(
 
 /// Updates the clients' view, i.e. the set of chunks that are visible from the
 /// client's chunk position.
+///
+/// This handles the situation when a client changes instances or chunk
+/// position. It must run after [`read_data_in_view`].
 fn update_view(
     mut clients: Query<
         (
             &mut Client,
-            &mut ScratchBuffer,
+            &mut ScratchBuf,
-            &mut EntityRemoveBuffer,
+            &mut EntityRemoveBuf,
             &Location,
             &OldLocation,
             &Position,
@@ -1004,8 +1027,9 @@ fn update_view(
     );
 }
 
+/// Removes all the entities that are queued to be removed for each client.
 fn remove_entities(
-    mut clients: Query<(&mut Client, &mut EntityRemoveBuffer), Changed<EntityRemoveBuffer>>,
+    mut clients: Query<(&mut Client, &mut EntityRemoveBuf), Changed<EntityRemoveBuf>>,
 ) {
     for (mut client, mut buf) in &mut clients {
         if !buf.0.is_empty() {
@@ -1032,6 +1056,10 @@ fn update_game_mode(mut clients: Query<(&mut Client, &GameMode), Changed<GameMod
     }
 }
 
+/// Syncs the client's position and look with the server.
+///
+/// This should happen after chunks are loaded so the client doesn't fall though
+/// the floor.
 fn teleport(
     mut clients: Query<
         (&mut Client, &mut TeleportState, &Position, &Look),
@@ -1069,7 +1097,7 @@ fn teleport(
     }
 }
 
-fn update_view_dist(
+fn update_old_view_dist(
     mut clients: Query<(&mut OldViewDistance, &ViewDistance), Changed<ViewDistance>>,
 ) {
     for (mut old_dist, dist) in &mut clients {
@@ -1077,9 +1105,11 @@ fn update_view_dist(
     }
 }
 
-fn update_compass_pos(mut clients: Query<(&mut Client, &CompassPos), Changed<CompassPos>>) {
+/// Sets the client's compass position.
-    // This also closes the "downloading terrain" screen when first joining, so
+///
-    // we should do this after the initial chunks are written.
+/// This also closes the "downloading terrain" screen when first joining, so
+/// it should happen after the initial chunks are written.
+fn update_spawn_position(mut clients: Query<(&mut Client, &CompassPos), Changed<CompassPos>>) {
     for (mut client, compass_pos) in &mut clients {
         client.write_packet(&PlayerSpawnPositionS2c {
             position: compass_pos.0,

crates/valence/src/client/event.rs

@@ -1,8 +1,10 @@
 use std::cmp;
 
 use anyhow::bail;
+use bevy_app::{CoreSet, Plugin};
 use bevy_ecs::prelude::*;
 use bevy_ecs::query::WorldQuery;
+use bevy_ecs::schedule::ScheduleLabel;
 use bevy_ecs::system::{SystemParam, SystemState};
 use glam::{DVec3, Vec3};
 use paste::paste;
@@ -39,7 +41,6 @@ use crate::client::Client;
 use crate::component::{Look, OnGround, Ping, Position};
 use crate::entity::{EntityAnimation, EntityKind, McEntity, TrackedData};
 use crate::inventory::Inventory;
-use crate::server::EventLoopSchedule;
 
 #[derive(Clone, Debug)]
 pub struct QueryBlockNbt {
@@ -527,7 +528,7 @@ macro_rules! events {
         )*
     ) => {
         /// Inserts [`Events`] resources into the world for each client event.
-        pub(crate) fn register_client_events(world: &mut World) {
+        fn register_client_events(world: &mut World) {
             $(
                 $(
                     world.insert_resource(Events::<$name>::default());
@@ -641,6 +642,31 @@ events! {
     }
 }
 
+pub(crate) struct ClientEventPlugin;
+
+/// The [`ScheduleLabel`] for the event loop [`Schedule`].
+#[derive(ScheduleLabel, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug)]
+pub struct EventLoopSchedule;
+
+/// The default base set for [`EventLoopSchedule`].
+#[derive(SystemSet, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug)]
+pub struct EventLoopSet;
+
+impl Plugin for ClientEventPlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        register_client_events(&mut app.world);
+
+        app.configure_set(EventLoopSet.in_base_set(CoreSet::PreUpdate))
+            .add_system(run_event_loop.in_set(EventLoopSet));
+
+        // Add the event loop schedule.
+        let mut event_loop = Schedule::new();
+        event_loop.set_default_base_set(EventLoopSet);
+
+        app.add_schedule(EventLoopSchedule, event_loop);
+    }
+}
+
 #[derive(WorldQuery)]
 #[world_query(mutable)]
 pub(crate) struct EventLoopQuery {
@@ -659,7 +685,7 @@ pub(crate) struct EventLoopQuery {
 }
 
 /// An exclusive system for running the event loop schedule.
-pub(crate) fn run_event_loop(
+fn run_event_loop(
     world: &mut World,
     state: &mut SystemState<(Query<EventLoopQuery>, ClientEvents, Commands)>,
     mut clients_to_check: Local<Vec<Entity>>,
@@ -1384,7 +1410,7 @@ fn handle_one_packet(
 /// is subject to change.
 ///
 /// This system must be scheduled to run in the
-/// [`EventLoopSchedule`](crate::server::EventLoopSchedule). Otherwise, it may
+/// [`EventLoopSchedule`]. Otherwise, it may
 /// not function correctly.
 #[allow(clippy::too_many_arguments)]
 pub fn default_event_handler(

crates/valence/src/component.rs

@@ -1,11 +1,13 @@
 use std::fmt;
 
+use bevy_app::{CoreSet, Plugin};
 /// Contains shared components and world queries.
 use bevy_ecs::prelude::*;
 use glam::{DVec3, Vec3};
 use uuid::Uuid;
 use valence_protocol::types::{GameMode as ProtocolGameMode, Property};
 
+use crate::prelude::FlushPacketsSet;
 use crate::util::{from_yaw_and_pitch, to_yaw_and_pitch};
 use crate::view::ChunkPos;
 use crate::NULL_ENTITY;
@@ -111,12 +113,6 @@ impl Default for Location {
 pub struct OldLocation(Entity);
 
 impl OldLocation {
-    pub(crate) fn update(mut query: Query<(&Location, &mut OldLocation), Changed<Location>>) {
-        for (loc, mut old_loc) in &mut query {
-            old_loc.0 = loc.0;
-        }
-    }
-
     pub fn new(instance: Entity) -> Self {
         Self(instance)
     }
@@ -153,12 +149,6 @@ impl Position {
 pub struct OldPosition(DVec3);
 
 impl OldPosition {
-    pub(crate) fn update(mut query: Query<(&Position, &mut OldPosition), Changed<Position>>) {
-        for (pos, mut old_pos) in &mut query {
-            old_pos.0 = pos.0;
-        }
-    }
-
     pub fn new(pos: DVec3) -> Self {
         Self(pos)
     }
@@ -201,4 +191,39 @@ impl Look {
 pub struct OnGround(pub bool);
 
 #[derive(Component, Default, Debug)]
-pub struct ScratchBuffer(pub Vec<u8>);
+pub struct ScratchBuf(pub Vec<u8>);
+
+pub(crate) struct ComponentPlugin;
+
+impl Plugin for ComponentPlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        app.add_systems(
+            (update_old_position, update_old_location)
+                .in_base_set(CoreSet::PostUpdate)
+                .after(FlushPacketsSet),
+        )
+        // This is fine because we're applying system buffers later.
+        .add_system(despawn_marked_entities.in_base_set(CoreSet::PostUpdate
+        ));
+    }
+}
+
+fn update_old_position(mut query: Query<(&Position, &mut OldPosition), Changed<Position>>) {
+    for (pos, mut old_pos) in &mut query {
+        old_pos.0 = pos.0;
+    }
+}
+
+fn update_old_location(mut query: Query<(&Location, &mut OldLocation), Changed<Location>>) {
+    for (loc, mut old_loc) in &mut query {
+        old_loc.0 = loc.0;
+    }
+}
+
+/// Despawns all the entities marked as despawned with the [`Despawned`]
+/// component.
+fn despawn_marked_entities(mut commands: Commands, entities: Query<Entity, With<Despawned>>) {
+    for entity in &entities {
+        commands.entity(entity).despawn();
+    }
+}

crates/valence/src/entity.rs

@@ -3,6 +3,7 @@ use std::fmt;
 use std::fmt::Formatter;
 use std::ops::Range;
 
+use bevy_app::{App, CoreSet, Plugin};
 use bevy_ecs::prelude::*;
 pub use data::{EntityKind, TrackedData};
 use glam::{DVec3, UVec3, Vec3};
@@ -21,6 +22,7 @@ use valence_protocol::var_int::VarInt;
 use crate::component::Despawned;
 use crate::config::DEFAULT_TPS;
 use crate::packet::WritePacket;
+use crate::prelude::FlushPacketsSet;
 use crate::util::Aabb;
 use crate::NULL_ENTITY;
 
@@ -28,30 +30,32 @@ pub mod data;
 
 include!(concat!(env!("OUT_DIR"), "/entity_event.rs"));
 
-/// A [`Resource`] which maintains information about all the [`McEntity`]
+pub(crate) struct EntityPlugin;
-/// components on the server.
-#[derive(Resource, Debug)]
-pub struct McEntityManager {
-    protocol_id_to_mcentity: FxHashMap<i32, Entity>,
-    next_protocol_id: i32,
-}
 
-impl McEntityManager {
+/// When new Minecraft entities are initialized and added to
-    pub(crate) fn new() -> Self {
+/// [`McEntityManager`]. Systems that need all Minecraft entities to be in a
-        Self {
+/// valid state should run after this.
-            protocol_id_to_mcentity: HashMap::default(),
+#[derive(SystemSet, Copy, Clone, PartialEq, Eq, Hash, Debug)]
-            next_protocol_id: 1,
+pub(crate) struct InitEntitiesSet;
+
+impl Plugin for EntityPlugin {
+    fn build(&self, app: &mut App) {
+        app.insert_resource(McEntityManager::new())
+            .configure_set(InitEntitiesSet.in_base_set(CoreSet::PostUpdate))
+            .add_system(init_mcentities.in_set(InitEntitiesSet))
+            .add_systems(
+                (
+                    remove_despawned_from_manager.after(init_mcentities),
+                    update_mcentities.after(FlushPacketsSet),
+                )
+                    .in_base_set(CoreSet::PostUpdate),
+            );
     }
 }
 
-    /// Gets the [`Entity`] of the [`McEntity`] with the given protocol ID.
+/// Sets the protocol ID of new mcentities and adds them to the
-    pub fn get_with_protocol_id(&self, id: i32) -> Option<Entity> {
+/// [`McEntityManager`].
-        self.protocol_id_to_mcentity.get(&id).cloned()
+fn init_mcentities(
-    }
-}
-
-/// Sets the protocol ID of new mcentities.
-pub(crate) fn init_mcentities(
     mut entities: Query<(Entity, &mut McEntity), Added<McEntity>>,
     mut manager: ResMut<McEntityManager>,
 ) {
@@ -72,7 +76,7 @@ pub(crate) fn init_mcentities(
 }
 
 /// Removes despawned mcentities from the mcentity manager.
-pub(crate) fn deinit_despawned_mcentities(
+fn remove_despawned_from_manager(
     entities: Query<&mut McEntity, With<Despawned>>,
     mut manager: ResMut<McEntityManager>,
 ) {
@@ -81,7 +85,7 @@ pub(crate) fn deinit_despawned_mcentities(
     }
 }
 
-pub(crate) fn update_mcentities(mut mcentities: Query<&mut McEntity, Changed<McEntity>>) {
+fn update_mcentities(mut mcentities: Query<&mut McEntity, Changed<McEntity>>) {
     for mut ent in &mut mcentities {
         ent.data.clear_modifications();
         ent.old_position = ent.position;
@@ -94,6 +98,28 @@ pub(crate) fn update_mcentities(mut mcentities: Query<&mut McEntity, Changed<McE
     }
 }
 
+/// A [`Resource`] which maintains information about all the [`McEntity`]
+/// components on the server.
+#[derive(Resource, Debug)]
+pub struct McEntityManager {
+    protocol_id_to_mcentity: FxHashMap<i32, Entity>,
+    next_protocol_id: i32,
+}
+
+impl McEntityManager {
+    fn new() -> Self {
+        Self {
+            protocol_id_to_mcentity: HashMap::default(),
+            next_protocol_id: 1,
+        }
+    }
+
+    /// Gets the [`Entity`] of the [`McEntity`] with the given protocol ID.
+    pub fn get_with_protocol_id(&self, id: i32) -> Option<Entity> {
+        self.protocol_id_to_mcentity.get(&id).cloned()
+    }
+}
+
 /// A component for Minecraft entities. For Valence to recognize a
 /// Minecraft entity, it must have this component attached.
 ///

crates/valence/src/instance.rs

@@ -3,6 +3,7 @@ use std::collections::hash_map::Entry;
 use std::collections::BTreeSet;
 use std::iter::FusedIterator;
 
+use bevy_app::{CoreSet, Plugin};
 use bevy_ecs::prelude::*;
 pub use chunk::{Block, BlockEntity, BlockMut, BlockRef, Chunk};
 pub use chunk_entry::*;
@@ -20,8 +21,9 @@ use valence_protocol::Packet;
 
 use crate::component::Despawned;
 use crate::dimension::DimensionId;
-use crate::entity::McEntity;
+use crate::entity::{InitEntitiesSet, McEntity};
 use crate::packet::{PacketWriter, WritePacket};
+use crate::prelude::FlushPacketsSet;
 use crate::server::{Server, SharedServer};
 use crate::view::ChunkPos;
 
@@ -433,7 +435,31 @@ impl Instance {
     }
 }
 
-pub(crate) fn update_instances_pre_client(
+pub(crate) struct InstancePlugin;
+
+#[derive(SystemSet, Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct UpdateInstancesPreClientSet;
+
+impl Plugin for InstancePlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        app.configure_set(
+            UpdateInstancesPreClientSet
+                .after(InitEntitiesSet)
+                .in_base_set(CoreSet::PostUpdate),
+        )
+        .add_system(update_instances_pre_client.in_set(UpdateInstancesPreClientSet))
+        .add_system(
+            update_instances_post_client
+                .after(FlushPacketsSet)
+                .in_base_set(CoreSet::PostUpdate),
+        );
+
+        #[cfg(debug_assertions)]
+        app.add_system(check_instance_invariants.in_base_set(CoreSet::PostUpdate));
+    }
+}
+
+fn update_instances_pre_client(
     mut instances: Query<&mut Instance>,
     mut entities: Query<(Entity, &mut McEntity, Option<&Despawned>)>,
     server: Res<Server>,
@@ -575,7 +601,7 @@ pub(crate) fn update_instances_pre_client(
     }
 }
 
-pub(crate) fn update_instances_post_client(mut instances: Query<&mut Instance>) {
+fn update_instances_post_client(mut instances: Query<&mut Instance>) {
     for mut instance in &mut instances {
         instance.partition.retain(|_, cell| {
             cell.packet_buf.clear();
@@ -594,8 +620,8 @@ pub(crate) fn update_instances_post_client(mut instances: Query<&mut Instance>)
     }
 }
 
-pub(crate) fn check_instance_invariants(instances: Query<&Instance>, entities: Query<&McEntity>) {
 #[cfg(debug_assertions)]
+fn check_instance_invariants(instances: Query<&Instance>, entities: Query<&McEntity>) {
     for instance in &instances {
         for (pos, cell) in &instance.partition {
             for &id in &cell.entities {
@@ -606,7 +632,4 @@ pub(crate) fn check_instance_invariants(instances: Query<&Instance>, entities: Q
             }
         }
     }
-
-    let _ = instances;
-    let _ = entities;
 }

crates/valence/src/inventory.rs

@@ -30,8 +30,8 @@ use std::borrow::Cow;
 use std::iter::FusedIterator;
 use std::ops::Range;
 
+use bevy_app::{CoreSet, Plugin};
 use bevy_ecs::prelude::*;
-use bevy_ecs::schedule::SystemConfigs;
 use tracing::{debug, warn};
 use valence_protocol::item::ItemStack;
 use valence_protocol::packet::s2c::play::{
@@ -47,6 +47,7 @@ use crate::client::event::{
 use crate::client::{Client, CursorItem, PlayerInventoryState};
 use crate::component::GameMode;
 use crate::packet::WritePacket;
+use crate::prelude::FlushPacketsSet;
 
 #[derive(Debug, Clone, Component)]
 pub struct Inventory {
@@ -302,8 +303,11 @@ impl OpenInventory {
     }
 }
 
-/// The systems needed for updating the inventories.
+pub(crate) struct InventoryPlugin;
-pub(crate) fn update_inventories() -> SystemConfigs {
+
+impl Plugin for InventoryPlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        app.add_systems(
             (
                 handle_set_held_item,
                 handle_click_container
@@ -317,7 +321,10 @@ pub(crate) fn update_inventories() -> SystemConfigs {
                 update_client_on_close_inventory.after(update_open_inventories),
                 update_player_inventories,
             )
-        .into_configs()
+                .in_base_set(CoreSet::PostUpdate)
+                .before(FlushPacketsSet),
+        );
+    }
 }
 
 /// Send updates for each client's player inventory.

crates/valence/src/lib.rs

@@ -49,6 +49,7 @@ pub mod prelude {
     pub use bevy_app::prelude::*;
     pub use bevy_ecs::prelude::*;
     pub use biome::{Biome, BiomeId};
+    pub use client::event::{EventLoopSchedule, EventLoopSet};
     pub use client::*;
     pub use component::*;
     pub use config::{
@@ -66,7 +67,7 @@ pub mod prelude {
     pub use protocol::ident::Ident;
     pub use protocol::item::{ItemKind, ItemStack};
     pub use protocol::text::{Color, Text, TextFormat};
-    pub use server::{EventLoopSchedule, EventLoopSet, NewClientInfo, Server, SharedServer};
+    pub use server::{NewClientInfo, Server, SharedServer};
     pub use uuid::Uuid;
     pub use valence_nbt::Compound;
     pub use valence_protocol::block::BlockKind;

crates/valence/src/player_list.rs

@@ -4,6 +4,7 @@ use std::collections::HashMap;
 use std::iter::FusedIterator;
 use std::mem;
 
+use bevy_app::{CoreSet, Plugin};
 use bevy_ecs::prelude::*;
 use bevy_ecs::schedule::SystemConfigs;
 use tracing::warn;
@@ -18,6 +19,7 @@ use valence_protocol::types::Property;
 use crate::client::Client;
 use crate::component::{GameMode, Ping, Properties, UniqueId, Username};
 use crate::packet::{PacketWriter, WritePacket};
+use crate::prelude::FlushPacketsSet;
 use crate::server::Server;
 
 /// The global list of players on a server visible by pressing the tab key by
@@ -92,7 +94,7 @@ impl PlayerList {
 
 impl PlayerList {
     /// Create a new empty player list.
-    pub(crate) fn new() -> Self {
+    fn new() -> Self {
         Self {
             cached_update_packets: vec![],
             entries: HashMap::new(),
@@ -551,8 +553,20 @@ impl<'a> VacantEntry<'a> {
     }
 }
 
+pub(crate) struct PlayerListPlugin;
+
+impl Plugin for PlayerListPlugin {
+    fn build(&self, app: &mut bevy_app::App) {
+        app.insert_resource(PlayerList::new()).add_system(
+            update_player_list
+                .before(FlushPacketsSet)
+                .in_base_set(CoreSet::PostUpdate),
+        );
+    }
+}
+
 /// Manage all player lists on the server and send updates to clients.
-pub(crate) fn update_player_list(
+fn update_player_list(
     player_list: ResMut<PlayerList>,
     server: Res<Server>,
     mut clients: Query<&mut Client>,

crates/valence/src/server.rs

@@ -8,7 +8,6 @@ use anyhow::ensure;
 use bevy_app::prelude::*;
 use bevy_app::{ScheduleRunnerPlugin, ScheduleRunnerSettings};
 use bevy_ecs::prelude::*;
-use bevy_ecs::schedule::ScheduleLabel;
 use flume::{Receiver, Sender};
 use rand::rngs::OsRng;
 use rsa::{PublicKeyParts, RsaPrivateKey};
@@ -20,19 +19,16 @@ use valence_protocol::ident;
 use valence_protocol::types::Property;
 
 use crate::biome::{validate_biomes, Biome, BiomeId};
-use crate::client::event::{register_client_events, run_event_loop};
+use crate::client::event::EventLoopSet;
-use crate::client::{update_clients, ClientBundle};
+use crate::client::{ClientBundle, ClientPlugin};
-use crate::component::{Despawned, OldLocation, OldPosition};
 use crate::config::{AsyncCallbacks, ConnectionMode, ServerPlugin};
 use crate::dimension::{validate_dimensions, Dimension, DimensionId};
-use crate::entity::{
+use crate::entity::EntityPlugin;
-    deinit_despawned_mcentities, init_mcentities, update_mcentities, McEntityManager,
+use crate::instance::{Instance, InstancePlugin};
-};
+use crate::inventory::InventoryPlugin;
-use crate::instance::{
+use crate::player_list::PlayerListPlugin;
-    check_instance_invariants, update_instances_post_client, update_instances_pre_client, Instance,
+use crate::prelude::event::ClientEventPlugin;
-};
+use crate::prelude::ComponentPlugin;
-use crate::inventory::update_inventories;
-use crate::player_list::{update_player_list, PlayerList};
 use crate::server::connect::do_accept_loop;
 
 mod byte_channel;
@@ -305,17 +301,7 @@ pub fn build_plugin(
     let shared = server.shared.clone();
 
     // Insert resources.
-    app.insert_resource(server)
+    app.insert_resource(server);
-        .insert_resource(McEntityManager::new())
-        .insert_resource(PlayerList::new());
-    register_client_events(&mut app.world);
-
-    // Add the event loop schedule.
-    let mut event_loop = Schedule::new();
-    event_loop.configure_set(EventLoopSet);
-    event_loop.set_default_base_set(EventLoopSet);
-
-    app.add_schedule(EventLoopSchedule, event_loop);
 
     // Make the app loop forever at the configured TPS.
     {
@@ -333,59 +319,41 @@ pub fn build_plugin(
             .in_base_set(StartupSet::PostStartup),
     );
 
-    // Add `CoreSet:::PreUpdate` systems.
+    // Spawn new clients before the event loop starts.
-    app.add_systems(
+    app.add_system(
-        (spawn_new_clients.before(run_event_loop), run_event_loop).in_base_set(CoreSet::PreUpdate),
+        spawn_new_clients
+            .in_base_set(CoreSet::PreUpdate)
+            .before(EventLoopSet),
     );
 
-    // Add internal valence systems that run after `CoreSet::Update`.
+    app.add_system(increment_tick_counter.in_base_set(CoreSet::Last));
-    app.add_systems(
+
-        (
+    // Add internal plugins.
-            init_mcentities,
+    app.add_plugin(ComponentPlugin)
-            check_instance_invariants,
+        .add_plugin(ClientPlugin)
-            update_player_list.before(update_instances_pre_client),
+        .add_plugin(ClientEventPlugin)
-            update_instances_pre_client.after(init_mcentities),
+        .add_plugin(EntityPlugin)
-            update_instances_post_client.after(update_instances_pre_client),
+        .add_plugin(InstancePlugin)
-            deinit_despawned_mcentities.after(update_instances_post_client),
+        .add_plugin(InventoryPlugin)
-            despawn_marked_entities.after(deinit_despawned_mcentities),
+        .add_plugin(PlayerListPlugin);
-            update_mcentities.after(despawn_marked_entities),
+
-            OldPosition::update.after(despawn_marked_entities),
+    /*
-            OldLocation::update.after(despawn_marked_entities),
+    println!(
+        "{}",
+        bevy_mod_debugdump::schedule_graph_dot(
+            app,
+            CoreSchedule::Main,
+            &bevy_mod_debugdump::schedule_graph::Settings {
+                ambiguity_enable: false,
+                ..Default::default()
+            },
         )
-            .in_base_set(CoreSet::PostUpdate),
+    );
-    )
+    */
-    .add_systems(
-        update_inventories()
-            .in_base_set(CoreSet::PostUpdate)
-            .before(init_mcentities),
-    )
-    .add_systems(
-        update_clients()
-            .in_base_set(CoreSet::PostUpdate)
-            .after(update_instances_pre_client)
-            .before(update_instances_post_client),
-    )
-    .add_system(increment_tick_counter.in_base_set(CoreSet::Last));
 
     Ok(())
 }
 
-/// The [`ScheduleLabel`] for the event loop [`Schedule`].
-#[derive(ScheduleLabel, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug)]
-pub struct EventLoopSchedule;
-
-/// The default base set for [`EventLoopSchedule`].
-#[derive(SystemSet, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug)]
-pub struct EventLoopSet;
-
-/// Despawns all the entities marked as despawned with the [`Despawned`]
-/// component.
-fn despawn_marked_entities(mut commands: Commands, entities: Query<Entity, With<Despawned>>) {
-    for entity in &entities {
-        commands.entity(entity).despawn();
-    }
-}
-
 fn increment_tick_counter(mut server: ResMut<Server>) {
     server.current_tick += 1;
 }

crates/valence_protocol/src/packet/s2c/play/scoreboard_display.rs

@@ -1,6 +1,5 @@
-use crate::{Decode, Encode};
-
 use super::team::TeamColor;
+use crate::{Decode, Encode};
 
 #[derive(Copy, Clone, Debug, Encode, Decode)]
 pub struct ScoreboardDisplayS2c<'a> {