Added resource_id and changed init_resource and `init_non_send_re…

…source` to return `ComponentId` (bevyengine#7284)

# Objective

- `Components::resource_id` doesn't exist. Like `Components::component_id` but for resources.

## Solution

- Created `Components::resource_id` and added some docs.

---

## Changelog

- Added `Components::resource_id`.
- Changed `World::init_resource` to return the generated `ComponentId`.
- Changed `World::init_non_send_resource` to return the generated `ComponentId`.

crates/bevy_ecs/src/component.rs

@@ -498,13 +498,40 @@ impl Components {
  self.get_id(TypeId::of::<T>())
  }
 
+ /// Type-erased equivalent of [`Components::resource_id`].
  #[inline]
  pub fn get_resource_id(&self, type_id: TypeId) -> Option<ComponentId> {
  self.resource_indices
  .get(&type_id)
  .map(|index| ComponentId(*index))
  }
 
+ /// Returns the [`ComponentId`] of the given [`Resource`] type `T`.
+ ///
+ /// The returned `ComponentId` is specific to the `Components` instance
+ /// it was retrieved from and should not be used with another `Components`
+ /// instance.
+ ///
+ /// Returns [`None`] if the `Resource` type has not
+ /// yet been initialized using [`Components::init_resource`].
+ ///
+ /// ```rust
+ /// use bevy_ecs::prelude::*;
+ ///
+ /// let mut world = World::new();
+ ///
+ /// #[derive(Resource, Default)]
+ /// struct ResourceA;
+ ///
+ /// let resource_a_id = world.init_resource::<ResourceA>();
+ ///
+ /// assert_eq!(resource_a_id, world.components().resource_id::<ResourceA>().unwrap())
+ /// ```
+ #[inline]
+ pub fn resource_id<T: Resource>(&self) -> Option<ComponentId> {
+ self.get_resource_id(TypeId::of::<T>())
+ }
+
  #[inline]
  pub fn init_resource<T: Resource>(&mut self) -> ComponentId {
  // SAFETY: The [`ComponentDescriptor`] matches the [`TypeId`]

crates/bevy_ecs/src/world/mod.rs

@@ -769,15 +769,15 @@ impl World {
  }
  }
 
- /// Inserts a new resource with standard starting values.
+ /// Initializes a new resource and returns the [`ComponentId`] created for it.
  ///
  /// If the resource already exists, nothing happens.
  ///
  /// The value given by the [`FromWorld::from_world`] method will be used.
- /// Note that any resource with the `Default` trait automatically implements `FromWorld`,
+ /// Note that any resource with the [`Default`] trait automatically implements [`FromWorld`],
  /// and those default values will be here instead.
  #[inline]
- pub fn init_resource<R: Resource + FromWorld>(&mut self) {
+ pub fn init_resource<R: Resource + FromWorld>(&mut self) -> ComponentId {
  let component_id = self.components.init_resource::<R>();
  if self
  .storages
@@ -793,6 +793,7 @@ impl World {
  }
  });
  }
+ component_id
  }
 
  /// Inserts a new resource with the given `value`.
@@ -811,7 +812,7 @@ impl World {
  });
  }
 
- /// Inserts a new non-send resource with standard starting values.
+ /// Initializes a new non-send resource and returns the [`ComponentId`] created for it.
  ///
  /// If the resource already exists, nothing happens.
  ///
@@ -823,7 +824,7 @@ impl World {
  ///
  /// Panics if called from a thread other than the main thread.
  #[inline]
- pub fn init_non_send_resource<R: 'static + FromWorld>(&mut self) {
+ pub fn init_non_send_resource<R: 'static + FromWorld>(&mut self) -> ComponentId {
  let component_id = self.components.init_non_send::<R>();
  if self
  .storages
@@ -839,6 +840,7 @@ impl World {
  }
  });
  }
+ component_id
  }
 
  /// Inserts a new non-send resource with the given `value`.