Added docs for bevy_transform (#3516)

# Objective

bevy_transform needed documentation and warn(missing_docs) as requested by #3492 

## Solution

warn(missing_docs) was activated and documentation was added to cover the crate


Co-authored-by: Troels Jessen <kairyuka@gmail.com>

crates/bevy_transform/src/components/children.rs

@@ -7,6 +7,7 @@ use bevy_reflect::Reflect;
 use smallvec::SmallVec;
 use std::ops::Deref;
 
+/// Contains references to the child entities of this entity
 #[derive(Component, Default, Clone, Debug, Reflect)]
 #[reflect(Component, MapEntities)]
 pub struct Children(pub(crate) SmallVec<[Entity; 8]>);
@@ -22,6 +23,7 @@ impl MapEntities for Children {
 }
 
 impl Children {
+    /// Builds and returns a [`Children`] component with the given entities
     pub fn with(entity: &[Entity]) -> Self {
         Self(SmallVec::from_slice(entity))
     }

crates/bevy_transform/src/components/global_transform.rs

@@ -36,8 +36,11 @@ use std::ops::Mul;
 #[derive(Component, Debug, PartialEq, Clone, Copy, Reflect)]
 #[reflect(Component, PartialEq)]
 pub struct GlobalTransform {
+    /// The position of the global transform
     pub translation: Vec3,
+    /// The rotation of the global transform
     pub rotation: Quat,
+    /// The scale of the global transform
     pub scale: Vec3,
 }
 

crates/bevy_transform/src/components/parent.rs

@@ -7,6 +7,8 @@ use bevy_ecs::{
 use bevy_reflect::Reflect;
 use std::ops::{Deref, DerefMut};
 
+/// Holds a reference to the parent entity of this entity.
+/// This component should only be present on entities that actually have a parent entity.
 #[derive(Component, Debug, Copy, Clone, Eq, PartialEq, Reflect)]
 #[reflect(Component, MapEntities, PartialEq)]
 pub struct Parent(pub Entity);
@@ -42,6 +44,7 @@ impl DerefMut for Parent {
     }
 }
 
+/// Component that holds the [`Parent`] this entity had previously
 #[derive(Component, Debug, Copy, Clone, Eq, PartialEq, Reflect)]
 #[reflect(Component, MapEntities, PartialEq)]
 pub struct PreviousParent(pub(crate) Entity);

crates/bevy_transform/src/hierarchy/child_builder.rs

@@ -7,9 +7,12 @@ use bevy_ecs::{
 };
 use smallvec::SmallVec;
 
+/// Command that adds a child to an entity
 #[derive(Debug)]
 pub struct AddChild {
+    /// Parent entity to add the child to
     pub parent: Entity,
+    /// Child entity to add
     pub child: Entity,
 }
 
@@ -29,6 +32,7 @@ impl Command for AddChild {
     }
 }
 
+/// Command that inserts a child at a given index of a parent's children, shifting following children back
 #[derive(Debug)]
 pub struct InsertChildren {
     parent: Entity,
@@ -56,6 +60,7 @@ impl Command for InsertChildren {
     }
 }
 
+/// Command that pushes children to the end of the entity's children
 #[derive(Debug)]
 pub struct PushChildren {
     parent: Entity,
@@ -88,6 +93,7 @@ impl Command for PushChildren {
     }
 }
 
+/// Command that removes children from an entity, and removes that child's parent and inserts it into the previous parent component
 pub struct RemoveChildren {
     parent: Entity,
     children: SmallVec<[Entity; 8]>,
@@ -123,39 +129,50 @@ impl Command for RemoveChildren {
     }
 }
 
+/// Struct for building children onto an entity
 pub struct ChildBuilder<'w, 's, 'a> {
     commands: &'a mut Commands<'w, 's>,
     push_children: PushChildren,
 }
 
 impl<'w, 's, 'a> ChildBuilder<'w, 's, 'a> {
+    /// Spawns an entity with the given bundle and inserts it into the children defined by the [`ChildBuilder`]
     pub fn spawn_bundle(&mut self, bundle: impl Bundle) -> EntityCommands<'w, 's, '_> {
         let e = self.commands.spawn_bundle(bundle);
         self.push_children.children.push(e.id());
         e
     }
 
+    /// Spawns an [`Entity`] with no components and inserts it into the children defined by the [`ChildBuilder`] which adds the [`Parent`] component to it.
     pub fn spawn(&mut self) -> EntityCommands<'w, 's, '_> {
         let e = self.commands.spawn();
         self.push_children.children.push(e.id());
         e
     }
 
+    /// Returns the parent entity of this [`ChildBuilder`]
     pub fn parent_entity(&self) -> Entity {
         self.push_children.parent
     }
 
+    /// Adds a command to this [`ChildBuilder`]
     pub fn add_command<C: Command + 'static>(&mut self, command: C) -> &mut Self {
         self.commands.add(command);
         self
     }
 }
 
+/// Trait defining how to build children
 pub trait BuildChildren {
+    /// Creates a [`ChildBuilder`] with the given children built in the given closure
     fn with_children(&mut self, f: impl FnOnce(&mut ChildBuilder)) -> &mut Self;
+    /// Pushes children to the back of the builder's children
     fn push_children(&mut self, children: &[Entity]) -> &mut Self;
+    /// Inserts children at the given index
     fn insert_children(&mut self, index: usize, children: &[Entity]) -> &mut Self;
+    /// Removes the given children
     fn remove_children(&mut self, children: &[Entity]) -> &mut Self;
+    /// Adds a single child
     fn add_child(&mut self, child: Entity) -> &mut Self;
 }
 
@@ -213,6 +230,7 @@ impl<'w, 's, 'a> BuildChildren for EntityCommands<'w, 's, 'a> {
     }
 }
 
+/// Struct for adding children to an entity directly through the [`World`] for use in exclusive systems
 #[derive(Debug)]
 pub struct WorldChildBuilder<'w> {
     world: &'w mut World,
@@ -221,6 +239,7 @@ pub struct WorldChildBuilder<'w> {
 }
 
 impl<'w> WorldChildBuilder<'w> {
+    /// Spawns an entity with the given bundle and inserts it into the children defined by the [`WorldChildBuilder`]
     pub fn spawn_bundle(&mut self, bundle: impl Bundle + Send + Sync + 'static) -> EntityMut<'_> {
         let parent_entity = self.parent_entity();
         let entity = self
@@ -240,6 +259,7 @@ impl<'w> WorldChildBuilder<'w> {
         self.world.entity_mut(entity)
     }
 
+    /// Spawns an [`Entity`] with no components and inserts it into the children defined by the [`WorldChildBuilder`] which adds the [`Parent`] component to it.
     pub fn spawn(&mut self) -> EntityMut<'_> {
         let parent_entity = self.parent_entity();
         let entity = self
@@ -258,6 +278,7 @@ impl<'w> WorldChildBuilder<'w> {
         self.world.entity_mut(entity)
     }
 
+    /// Returns the parent entity of this [`WorldChildBuilder`]
     pub fn parent_entity(&self) -> Entity {
         self.parent_entities
             .last()
@@ -266,10 +287,15 @@ impl<'w> WorldChildBuilder<'w> {
     }
 }
 
+/// Trait that defines adding children to an entity directly through the [`World`]
 pub trait BuildWorldChildren {
+    /// Creates a [`WorldChildBuilder`] with the given children built in the given closure
     fn with_children(&mut self, spawn_children: impl FnOnce(&mut WorldChildBuilder)) -> &mut Self;
+    /// Pushes children to the back of the builder's children
     fn push_children(&mut self, children: &[Entity]) -> &mut Self;
+    /// Inserts children at the given index
     fn insert_children(&mut self, index: usize, children: &[Entity]) -> &mut Self;
+    /// Removes the given children
     fn remove_children(&mut self, children: &[Entity]) -> &mut Self;
 }
 

crates/bevy_transform/src/hierarchy/hierarchy.rs

@@ -6,16 +6,19 @@ use bevy_ecs::{
 };
 use bevy_utils::tracing::debug;
 
+/// Despawns the given entity and all its children recursively
 #[derive(Debug)]
 pub struct DespawnRecursive {
     entity: Entity,
 }
 
+/// Despawns the given entity's children recursively
 #[derive(Debug)]
 pub struct DespawnChildrenRecursive {
     entity: Entity,
 }
 
+/// Function for despawning an entity and all its children
 pub fn despawn_with_children_recursive(world: &mut World, entity: Entity) {
     // first, make the entity's own parent forget about it
     if let Some(parent) = world.get::<Parent>(entity).map(|parent| parent.0) {
@@ -61,6 +64,7 @@ impl Command for DespawnChildrenRecursive {
     }
 }
 
+/// Trait that holds functions for despawning recursively down the transform hierarchy
 pub trait DespawnRecursiveExt {
     /// Despawns the provided entity alongside all descendants.
     fn despawn_recursive(self);

crates/bevy_transform/src/hierarchy/hierarchy_maintenance_system.rs

@@ -8,6 +8,7 @@ use bevy_ecs::{
 use bevy_utils::HashMap;
 use smallvec::SmallVec;
 
+/// Updates parents when the hierarchy is changed
 pub fn parent_update_system(
     mut commands: Commands,
     removed_parent_query: Query<(Entity, &PreviousParent), Without<Parent>>,

crates/bevy_transform/src/lib.rs

@@ -1,9 +1,14 @@
+#![warn(missing_docs)]
 #![doc = include_str!("../README.md")]
 
+/// The basic components of the transform crate
 pub mod components;
+/// Establishing and updating the transform hierarchy
 pub mod hierarchy;
+/// Propagating transform changes down the transform hierarchy
 pub mod transform_propagate_system;
 
+#[doc(hidden)]
 pub mod prelude {
     #[doc(hidden)]
     pub use crate::{components::*, hierarchy::*, TransformPlugin};
@@ -13,12 +18,16 @@ use bevy_app::prelude::*;
 use bevy_ecs::schedule::{ParallelSystemDescriptorCoercion, SystemLabel};
 use prelude::{parent_update_system, Children, GlobalTransform, Parent, PreviousParent, Transform};
 
+/// The base plugin for handling [`Transform`] components
 #[derive(Default)]
 pub struct TransformPlugin;
 
+/// Label enum for the types of systems relating to transform
 #[derive(Debug, Hash, PartialEq, Eq, Clone, SystemLabel)]
 pub enum TransformSystem {
+    /// Propagates changes in transform to childrens' [`GlobalTransform`]
     TransformPropagate,
+    /// Updates [`Parent`] when changes in the hierarchy occur
     ParentUpdate,
 }