Remove last uses of string-labels (#5420)

# Objective

* Related: #4341
* Remove all remaining uses of stringly-typed labels in the repo. Right now, it's just a bunch of tests and examples.

Author: joseph-gio

benches/benches/bevy_ecs/scheduling/run_criteria.rs

@@ -1,7 +1,7 @@
 use bevy_ecs::{
     component::Component,
     prelude::{ParallelSystemDescriptorCoercion, Res, Resource, RunCriteriaDescriptorCoercion},
-    schedule::{ShouldRun, Stage, SystemStage},
+    schedule::{RunCriteriaLabel, ShouldRun, Stage, SystemStage},
     system::Query,
     world::World,
 };
@@ -11,6 +11,13 @@ fn run_stage(stage: &mut SystemStage, world: &mut World) {
     stage.run(world);
 }
 
+/// Labels for run criteria which either always return yes, or always return no.
+#[derive(RunCriteriaLabel)]
+enum Always {
+    Yes,
+    No,
+}
+
 pub fn run_criteria_yes(criterion: &mut Criterion) {
     let mut world = World::new();
     let mut group = criterion.benchmark_group("run_criteria/yes");
@@ -85,14 +92,15 @@ pub fn run_criteria_yes_with_labels(criterion: &mut Criterion) {
     }
     for amount in 0..21 {
         let mut stage = SystemStage::parallel();
-        stage.add_system(empty.with_run_criteria(always_yes.label("always yes")));
+
+        stage.add_system(empty.with_run_criteria(always_yes.label(Always::Yes)));
         for _ in 0..amount {
             stage
-                .add_system(empty.with_run_criteria("always yes"))
-                .add_system(empty.with_run_criteria("always yes"))
-                .add_system(empty.with_run_criteria("always yes"))
-                .add_system(empty.with_run_criteria("always yes"))
-                .add_system(empty.with_run_criteria("always yes"));
+                .add_system(empty.with_run_criteria(Always::Yes))
+                .add_system(empty.with_run_criteria(Always::Yes))
+                .add_system(empty.with_run_criteria(Always::Yes))
+                .add_system(empty.with_run_criteria(Always::Yes))
+                .add_system(empty.with_run_criteria(Always::Yes));
         }
         // run once to initialize systems
         run_stage(&mut stage, &mut world);
@@ -116,14 +124,15 @@ pub fn run_criteria_no_with_labels(criterion: &mut Criterion) {
     }
     for amount in 0..21 {
         let mut stage = SystemStage::parallel();
-        stage.add_system(empty.with_run_criteria(always_no.label("always no")));
+
+        stage.add_system(empty.with_run_criteria(always_no.label(Always::No)));
         for _ in 0..amount {
             stage
-                .add_system(empty.with_run_criteria("always no"))
-                .add_system(empty.with_run_criteria("always no"))
-                .add_system(empty.with_run_criteria("always no"))
-                .add_system(empty.with_run_criteria("always no"))
-                .add_system(empty.with_run_criteria("always no"));
+                .add_system(empty.with_run_criteria(Always::No))
+                .add_system(empty.with_run_criteria(Always::No))
+                .add_system(empty.with_run_criteria(Always::No))
+                .add_system(empty.with_run_criteria(Always::No))
+                .add_system(empty.with_run_criteria(Always::No));
         }
         // run once to initialize systems
         run_stage(&mut stage, &mut world);

crates/bevy_app/src/app.rs

@@ -151,7 +151,9 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
-    /// app.add_stage("my_stage", SystemStage::parallel());
+    /// #[derive(StageLabel)]
+    /// struct MyStage;
+    /// app.add_stage(MyStage, SystemStage::parallel());
     /// ```
     pub fn add_stage<S: Stage>(&mut self, label: impl StageLabel, stage: S) -> &mut Self {
         self.schedule.add_stage(label, stage);
@@ -168,7 +170,9 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
-    /// app.add_stage_after(CoreStage::Update, "my_stage", SystemStage::parallel());
+    /// #[derive(StageLabel)]
+    /// struct MyStage;
+    /// app.add_stage_after(CoreStage::Update, MyStage, SystemStage::parallel());
     /// ```
     pub fn add_stage_after<S: Stage>(
         &mut self,
@@ -190,7 +194,9 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
-    /// app.add_stage_before(CoreStage::Update, "my_stage", SystemStage::parallel());
+    /// #[derive(StageLabel)]
+    /// struct MyStage;
+    /// app.add_stage_before(CoreStage::Update, MyStage, SystemStage::parallel());
     /// ```
     pub fn add_stage_before<S: Stage>(
         &mut self,
@@ -212,7 +218,9 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
-    /// app.add_startup_stage("my_startup_stage", SystemStage::parallel());
+    /// #[derive(StageLabel)]
+    /// struct MyStartupStage;
+    /// app.add_startup_stage(MyStartupStage, SystemStage::parallel());
     /// ```
     pub fn add_startup_stage<S: Stage>(&mut self, label: impl StageLabel, stage: S) -> &mut Self {
         self.schedule
@@ -234,9 +242,11 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
+    /// #[derive(StageLabel)]
+    /// struct MyStartupStage;
     /// app.add_startup_stage_after(
     ///     StartupStage::Startup,
-    ///     "my_startup_stage",
+    ///     MyStartupStage,
     ///     SystemStage::parallel()
     /// );
     /// ```
@@ -265,9 +275,11 @@ impl App {
     /// # use bevy_ecs::prelude::*;
     /// # let mut app = App::new();
     /// #
+    /// #[derive(StageLabel)]
+    /// struct MyStartupStage;
     /// app.add_startup_stage_before(
     ///     StartupStage::Startup,
-    ///     "my_startup_stage",
+    ///     MyStartupStage,
     ///     SystemStage::parallel()
     /// );
     /// ```

crates/bevy_ecs/README.md

@@ -148,9 +148,13 @@ fn main() {
     // Create a new Schedule, which defines an execution strategy for Systems
     let mut schedule = Schedule::default();
 
+    // Define a unique public name for a new Stage.
+    #[derive(StageLabel)]
+    pub struct UpdateLabel;
+
     // Add a Stage to our schedule. Each Stage in a schedule runs all of its systems
     // before moving on to the next Stage
-    schedule.add_stage("update", SystemStage::parallel()
+    schedule.add_stage(UpdateLabel, SystemStage::parallel()
         .with_system(movement)
     );
 

crates/bevy_ecs/examples/change_detection.rs

@@ -30,7 +30,9 @@ fn main() {
     update.add_system(remove_old_entities.after(SimulationSystem::Age));
     update.add_system(print_changed_entities.after(SimulationSystem::Age));
     // Add the Stage with our systems to the Schedule
-    schedule.add_stage("update", update);
+    #[derive(StageLabel)]
+    struct Update;
+    schedule.add_stage(Update, update);
 
     // Simulate 10 frames in our world
     for iteration in 1..=10 {

crates/bevy_ecs/examples/events.rs

@@ -10,22 +10,28 @@ fn main() {
     // Create a schedule and a stage
     let mut schedule = Schedule::default();
 
+    #[derive(StageLabel)]
+    enum Stages {
+        First,
+        Second,
+    }
+
     // Events need to be updated in every frame. This update should happen before we use
     // the events. To guarantee this, we can let the update run in an earlier stage than our logic.
     // Here we will use a stage called "first" that will always run it's systems before the Stage
     // called "second". In "first" we update the events and in "second" we run our systems
     // sending and receiving events.
     let mut first = SystemStage::parallel();
     first.add_system(Events::<MyEvent>::update_system);
-    schedule.add_stage("first", first);
+    schedule.add_stage(Stages::First, first);
 
     // Add systems sending and receiving events to a "second" Stage
     let mut second = SystemStage::parallel();
     second.add_system(sending_system);
     second.add_system(receiving_system.after(sending_system));
 
     // Run the "second" Stage after the "first" Stage, so our Events always get updated before we use them
-    schedule.add_stage_after("first", "second", second);
+    schedule.add_stage_after(Stages::First, Stages::Second, second);
 
     // Simulate 10 frames of our world
     for iteration in 1..=10 {

crates/bevy_ecs/examples/resources.rs

@@ -18,7 +18,13 @@ fn main() {
     // Add systems to increase the counter and to print out the current value
     update.add_system(increase_counter);
     update.add_system(print_counter.after(increase_counter));
-    schedule.add_stage("update", update);
+
+    // Declare a unique label for the stage.
+    #[derive(StageLabel)]
+    struct Update;
+
+    // Add the stage to the schedule.
+    schedule.add_stage(Update, update);
 
     for iteration in 1..=10 {
         println!("Simulating frame {}/10", iteration);

crates/bevy_ecs/src/schedule/mod.rs

@@ -106,7 +106,11 @@ impl Schedule {
     /// # use bevy_ecs::prelude::*;
     /// #
     /// # let mut schedule = Schedule::default();
-    /// schedule.add_stage("my_stage", SystemStage::parallel());
+    /// // Define a new label for the stage.
+    /// #[derive(StageLabel)]
+    /// struct MyStage;
+    /// // Add a stage with that label to the schedule.
+    /// schedule.add_stage(MyStage, SystemStage::parallel());
     /// ```
     pub fn add_stage<S: Stage>(&mut self, label: impl StageLabel, stage: S) -> &mut Self {
         let label = label.as_label();
@@ -124,8 +128,14 @@ impl Schedule {
     /// # use bevy_ecs::prelude::*;
     /// #
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("target_stage", SystemStage::parallel());
-    /// schedule.add_stage_after("target_stage", "my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct TargetStage;
+    /// # schedule.add_stage(TargetStage, SystemStage::parallel());
+    /// // Define a new label for the stage.
+    /// #[derive(StageLabel)]
+    /// struct NewStage;
+    /// // Add a stage with that label to the schedule.
+    /// schedule.add_stage_after(TargetStage, NewStage, SystemStage::parallel());
     /// ```
     pub fn add_stage_after<S: Stage>(
         &mut self,
@@ -157,9 +167,15 @@ impl Schedule {
     /// # use bevy_ecs::prelude::*;
     /// #
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("target_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct TargetStage;
+    /// # schedule.add_stage(TargetStage, SystemStage::parallel());
     /// #
-    /// schedule.add_stage_before("target_stage", "my_stage", SystemStage::parallel());
+    /// // Define a new, private label for the stage.
+    /// #[derive(StageLabel)]
+    /// struct NewStage;
+    /// // Add a stage with that label to the schedule.
+    /// schedule.add_stage_before(TargetStage, NewStage, SystemStage::parallel());
     /// ```
     pub fn add_stage_before<S: Stage>(
         &mut self,
@@ -192,9 +208,11 @@ impl Schedule {
     /// #
     /// # fn my_system() {}
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct MyStage;
+    /// # schedule.add_stage(MyStage, SystemStage::parallel());
     /// #
-    /// schedule.add_system_to_stage("my_stage", my_system);
+    /// schedule.add_system_to_stage(MyStage, my_system);
     /// ```
     pub fn add_system_to_stage<Params>(
         &mut self,
@@ -228,10 +246,12 @@ impl Schedule {
     /// #
     /// # fn my_system() {}
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct MyStage;
+    /// # schedule.add_stage(MyStage, SystemStage::parallel());
     /// #
     /// schedule.add_system_set_to_stage(
-    ///     "my_stage",
+    ///     MyStage,
     ///     SystemSet::new()
     ///         .with_system(system_a)
     ///         .with_system(system_b)
@@ -265,9 +285,11 @@ impl Schedule {
     /// # use bevy_ecs::prelude::*;
     /// #
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct MyStage;
+    /// # schedule.add_stage(MyStage, SystemStage::parallel());
     /// #
-    /// schedule.stage("my_stage", |stage: &mut SystemStage| {
+    /// schedule.stage(MyStage, |stage: &mut SystemStage| {
     ///     stage.add_system(my_system)
     /// });
     /// #
@@ -301,9 +323,11 @@ impl Schedule {
     /// #
     /// # fn my_system() {}
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct MyStage;
+    /// # schedule.add_stage(MyStage, SystemStage::parallel());
     /// #
-    /// let stage = schedule.get_stage::<SystemStage>("my_stage").unwrap();
+    /// let stage = schedule.get_stage::<SystemStage>(MyStage).unwrap();
     /// ```
     pub fn get_stage<T: Stage>(&self, stage_label: impl StageLabel) -> Option<&T> {
         let label = stage_label.as_label();
@@ -323,9 +347,11 @@ impl Schedule {
     /// #
     /// # fn my_system() {}
     /// # let mut schedule = Schedule::default();
-    /// # schedule.add_stage("my_stage", SystemStage::parallel());
+    /// # #[derive(StageLabel)]
+    /// # struct MyStage;
+    /// # schedule.add_stage(MyStage, SystemStage::parallel());
     /// #
-    /// let stage = schedule.get_stage_mut::<SystemStage>("my_stage").unwrap();
+    /// let stage = schedule.get_stage_mut::<SystemStage>(MyStage).unwrap();
     /// ```
     pub fn get_stage_mut<T: Stage>(&mut self, stage_label: impl StageLabel) -> Option<&mut T> {
         let label = stage_label.as_label();