Remove bevy_core (#16897)

# Objective

- Fixes #16892

## Solution

- Removed `TypeRegistryPlugin` (`Name` is now automatically registered
with a default `App`)
- Moved `TaskPoolPlugin` to `bevy_app`
- Moved `FrameCountPlugin` to `bevy_diagnostic`
- Deleted now-empty `bevy_core`

## Testing

- CI

## Migration Guide

- `TypeRegistryPlugin` no longer exists. If you can't use a default
`App` but still need `Name` registered, do so manually with
`app.register_type::<Name>()`.
- References to `TaskPoolPlugin` and associated types will need to
import it from `bevy_app` instead of `bevy_core`
- References to `FrameCountPlugin` and associated types will need to
import it from `bevy_diagnostic` instead of `bevy_core`

## Notes

This strategy was agreed upon by Cart and several other members in
[Discord](https://discord.com/channels/691052431525675048/692572690833473578/1319137218312278077).

Author: bushrat011899

assets/scenes/load_scene_example.scn.ron

@@ -7,7 +7,7 @@
   entities: {
     4294967296: (
       components: {
-        "bevy_core::name::Name": (
+        "bevy_ecs::name::Name": (
           hash: 17588334858059901562,
           name: "joe",
         ),

crates/bevy_animation/Cargo.toml

@@ -13,7 +13,6 @@ keywords = ["bevy"]
 bevy_app = { path = "../bevy_app", version = "0.15.0-dev" }
 bevy_asset = { path = "../bevy_asset", version = "0.15.0-dev" }
 bevy_color = { path = "../bevy_color", version = "0.15.0-dev" }
-bevy_core = { path = "../bevy_core", version = "0.15.0-dev" }
 bevy_derive = { path = "../bevy_derive", version = "0.15.0-dev" }
 bevy_log = { path = "../bevy_log", version = "0.15.0-dev" }
 bevy_math = { path = "../bevy_math", version = "0.15.0-dev" }

crates/bevy_app/Cargo.toml

@@ -55,11 +55,20 @@ std = [
 
 ## `critical-section` provides the building blocks for synchronization primitives
 ## on all platforms, including `no_std`.
-critical-section = ["bevy_tasks?/critical-section", "bevy_ecs/critical-section"]
+critical-section = [
+  "portable-atomic?/critical-section",
+  "bevy_tasks?/critical-section",
+  "bevy_ecs/critical-section",
+]
 
 ## `portable-atomic` provides additional platform support for atomic types and
 ## operations, even on targets without native support. 
-portable-atomic = ["bevy_tasks?/portable-atomic", "bevy_ecs/portable-atomic"]
+portable-atomic = [
+  "dep:portable-atomic",
+  "dep:portable-atomic-util",
+  "bevy_tasks?/portable-atomic",
+  "bevy_ecs/portable-atomic",
+]
 
 [dependencies]
 # bevy
@@ -77,6 +86,12 @@ thiserror = { version = "2", default-features = false }
 variadics_please = "1.1"
 tracing = { version = "0.1", default-features = false, optional = true }
 log = { version = "0.4", default-features = false }
+portable-atomic = { version = "1", default-features = false, features = [
+  "fallback",
+], optional = true }
+portable-atomic-util = { version = "0.2.4", features = [
+  "alloc",
+], optional = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 ctrlc = { version = "3.4.4", optional = true }
@@ -86,6 +101,9 @@ wasm-bindgen = { version = "0.2" }
 web-sys = { version = "0.3", features = ["Window"] }
 console_error_panic_hook = "0.1.6"
 
+[dev-dependencies]
+crossbeam-channel = "0.5.0"
+
 [lints]
 workspace = true
 

crates/bevy_app/src/app.rs

@@ -103,7 +103,10 @@ impl Default for App {
         app.sub_apps.main.update_schedule = Some(Main.intern());
 
         #[cfg(feature = "bevy_reflect")]
-        app.init_resource::<AppTypeRegistry>();
+        {
+            app.init_resource::<AppTypeRegistry>();
+            app.register_type::<Name>();
+        }
 
         #[cfg(feature = "reflect_functions")]
         app.init_resource::<AppFunctionRegistry>();

crates/bevy_app/src/lib.rs

@@ -24,6 +24,8 @@ mod plugin;
 mod plugin_group;
 mod schedule_runner;
 mod sub_app;
+#[cfg(feature = "bevy_tasks")]
+mod task_pool_plugin;
 #[cfg(all(not(target_arch = "wasm32"), feature = "std"))]
 mod terminal_ctrl_c_handler;
 
@@ -34,6 +36,8 @@ pub use plugin::*;
 pub use plugin_group::*;
 pub use schedule_runner::*;
 pub use sub_app::*;
+#[cfg(feature = "bevy_tasks")]
+pub use task_pool_plugin::*;
 #[cfg(all(not(target_arch = "wasm32"), feature = "std"))]
 pub use terminal_ctrl_c_handler::*;
 
@@ -52,4 +56,8 @@ pub mod prelude {
         sub_app::SubApp,
         Plugin, PluginGroup,
     };
+
+    #[cfg(feature = "bevy_tasks")]
+    #[doc(hidden)]
+    pub use crate::{NonSendMarker, TaskPoolOptions, TaskPoolPlugin};
 }

crates/bevy_core/src/task_pool_options.rs renamed to crates/bevy_app/src/task_pool_plugin.rs

@@ -1,8 +1,55 @@
+#![cfg_attr(
+    feature = "portable-atomic",
+    expect(
+        clippy::redundant_closure,
+        reason = "portable_atomic_util::Arc has subtly different implicit behavior"
+    )
+)]
+
+use crate::{App, Last, Plugin};
+
+use alloc::string::ToString;
+use bevy_ecs::prelude::*;
 use bevy_tasks::{AsyncComputeTaskPool, ComputeTaskPool, IoTaskPool, TaskPoolBuilder};
-use bevy_utils::tracing::trace;
+use core::{fmt::Debug, marker::PhantomData};
+use log::trace;
+
+#[cfg(feature = "portable-atomic")]
+use portable_atomic_util::Arc;
 
+#[cfg(not(feature = "portable-atomic"))]
 use alloc::sync::Arc;
-use core::fmt::Debug;
+
+#[cfg(not(target_arch = "wasm32"))]
+use bevy_tasks::tick_global_task_pools_on_main_thread;
+
+/// Setup of default task pools: [`AsyncComputeTaskPool`], [`ComputeTaskPool`], [`IoTaskPool`].
+#[derive(Default)]
+pub struct TaskPoolPlugin {
+    /// Options for the [`TaskPool`](bevy_tasks::TaskPool) created at application start.
+    pub task_pool_options: TaskPoolOptions,
+}
+
+impl Plugin for TaskPoolPlugin {
+    fn build(&self, _app: &mut App) {
+        // Setup the default bevy task pools
+        self.task_pool_options.create_default_pools();
+
+        #[cfg(not(target_arch = "wasm32"))]
+        _app.add_systems(Last, tick_global_task_pools);
+    }
+}
+/// A dummy type that is [`!Send`](Send), to force systems to run on the main thread.
+pub struct NonSendMarker(PhantomData<*mut ()>);
+
+/// A system used to check and advanced our task pools.
+///
+/// Calls [`tick_global_task_pools_on_main_thread`],
+/// and uses [`NonSendMarker`] to ensure that this system runs on the main thread
+#[cfg(not(target_arch = "wasm32"))]
+fn tick_global_task_pools(_main_thread_marker: Option<NonSend<NonSendMarker>>) {
+    tick_global_task_pools_on_main_thread();
+}
 
 /// Defines a simple way to determine how many threads to use given the number of remaining cores
 /// and number of total cores
@@ -37,7 +84,14 @@ impl TaskPoolThreadAssignmentPolicy {
     /// Determine the number of threads to use for this task pool
     fn get_number_of_threads(&self, remaining_threads: usize, total_threads: usize) -> usize {
         assert!(self.percent >= 0.0);
-        let mut desired = (total_threads as f32 * self.percent).round() as usize;
+        let proportion = total_threads as f32 * self.percent;
+        let mut desired = proportion as usize;
+
+        // Equivalent to round() for positive floats without libm requirement for
+        // no_std compatibility
+        if proportion - desired as f32 >= 0.5 {
+            desired += 1;
+        }
 
         // Limit ourselves to the number of cores available
         desired = desired.min(remaining_threads);
@@ -50,7 +104,7 @@ impl TaskPoolThreadAssignmentPolicy {
 }
 
 /// Helper for configuring and creating the default task pools. For end-users who want full control,
-/// set up [`TaskPoolPlugin`](super::TaskPoolPlugin)
+/// set up [`TaskPoolPlugin`]
 #[derive(Clone, Debug)]
 pub struct TaskPoolOptions {
     /// If the number of physical cores is less than `min_total_threads`, force using
@@ -208,3 +262,42 @@ impl TaskPoolOptions {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use bevy_tasks::prelude::{AsyncComputeTaskPool, ComputeTaskPool, IoTaskPool};
+
+    #[test]
+    fn runs_spawn_local_tasks() {
+        let mut app = App::new();
+        app.add_plugins(TaskPoolPlugin::default());
+
+        let (async_tx, async_rx) = crossbeam_channel::unbounded();
+        AsyncComputeTaskPool::get()
+            .spawn_local(async move {
+                async_tx.send(()).unwrap();
+            })
+            .detach();
+
+        let (compute_tx, compute_rx) = crossbeam_channel::unbounded();
+        ComputeTaskPool::get()
+            .spawn_local(async move {
+                compute_tx.send(()).unwrap();
+            })
+            .detach();
+
+        let (io_tx, io_rx) = crossbeam_channel::unbounded();
+        IoTaskPool::get()
+            .spawn_local(async move {
+                io_tx.send(()).unwrap();
+            })
+            .detach();
+
+        app.run();
+
+        async_rx.try_recv().unwrap();
+        compute_rx.try_recv().unwrap();
+        io_rx.try_recv().unwrap();
+    }
+}

crates/bevy_asset/Cargo.toml

@@ -65,7 +65,6 @@ js-sys = "0.3"
 notify-debouncer-full = { version = "0.4.0", optional = true }
 
 [dev-dependencies]
-bevy_core = { path = "../bevy_core", version = "0.15.0-dev" }
 bevy_log = { path = "../bevy_log", version = "0.15.0-dev" }
 
 [lints]

crates/bevy_asset/src/asset_changed.rs

@@ -296,8 +296,7 @@ mod tests {
     use core::num::NonZero;
 
     use crate::{AssetApp, Assets};
-    use bevy_app::{App, AppExit, Last, Startup, Update};
-    use bevy_core::TaskPoolPlugin;
+    use bevy_app::{App, AppExit, Last, Startup, TaskPoolPlugin, Update};
     use bevy_ecs::schedule::IntoSystemConfigs;
     use bevy_ecs::{
         component::Component,

crates/bevy_asset/src/lib.rs

@@ -633,8 +633,7 @@ mod tests {
         AssetPlugin, AssetServer, Assets,
     };
     use alloc::sync::Arc;
-    use bevy_app::{App, Update};
-    use bevy_core::TaskPoolPlugin;
+    use bevy_app::{App, TaskPoolPlugin, Update};
     use bevy_ecs::{
         event::EventCursor,
         prelude::*,