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Prefer App::default() over App::new() in doc, examples, test #20451

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4a2bb00
# Objective
martinfrances107 Aug 7, 2025
6b19d94
Not all App::new() call can be converted to App::default()
martinfrances107 Aug 7, 2025
8ef13ff
Merge branch 'main' into app_default
martinfrances107 Aug 9, 2025
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ To draw a window with standard functionality enabled, use:
use bevy::prelude::*;

fn main() {
App::new()
App::default()
.add_plugins(DefaultPlugins)
.run();
}
Expand Down
4 changes: 2 additions & 2 deletions benches/benches/bevy_ecs/scheduling/schedule.rs
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Expand Up @@ -81,7 +81,7 @@ pub fn build_schedule(criterion: &mut Criterion) {
// Basic benchmark without constraints.
group.bench_function(format!("{graph_size}_schedule_no_constraints"), |bencher| {
bencher.iter(|| {
let mut app = App::new();
let mut app = App::default();
for _ in 0..graph_size {
app.add_systems(Update, empty_system);
}
Expand All @@ -92,7 +92,7 @@ pub fn build_schedule(criterion: &mut Criterion) {
// Benchmark with constraints.
group.bench_function(format!("{graph_size}_schedule"), |bencher| {
bencher.iter(|| {
let mut app = App::new();
let mut app = App::default();
app.add_systems(Update, empty_system.in_set(DummySet));

// Build a fully-connected dependency graph describing the One True Ordering.
Expand Down
80 changes: 40 additions & 40 deletions crates/bevy_app/src/app.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ pub(crate) enum AppError {
/// # use bevy_ecs::prelude::*;
/// #
/// fn main() {
/// App::new()
/// App::default()
/// .add_systems(Update, hello_world_system)
/// .run();
/// }
Expand Down Expand Up @@ -142,7 +142,7 @@ impl App {
pub fn empty() -> App {
Self {
sub_apps: SubApps {
main: SubApp::new(),
main: SubApp::default(),
sub_apps: HashMap::default(),
},
runner: Box::new(run_once),
Expand Down Expand Up @@ -214,7 +214,7 @@ impl App {
/// }
/// }
///
/// App::new()
/// App::default()
/// .set_runner(my_runner);
/// ```
pub fn set_runner(&mut self, f: impl FnOnce(App) -> AppExit + 'static) -> &mut Self {
Expand Down Expand Up @@ -293,7 +293,7 @@ impl App {
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # fn system_a() {}
/// # fn system_b() {}
/// # fn system_c() {}
Expand Down Expand Up @@ -355,7 +355,7 @@ impl App {
/// #
/// # #[derive(BufferedEvent)]
/// # struct MyEvent;
/// # let mut app = App::new();
/// # let mut app = App::default();
/// #
/// app.add_event::<MyEvent>();
/// ```
Expand Down Expand Up @@ -383,7 +383,7 @@ impl App {
/// counter: usize,
/// }
///
/// App::new()
/// App::default()
/// .insert_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self {
Expand Down Expand Up @@ -417,7 +417,7 @@ impl App {
/// }
/// }
///
/// App::new()
/// App::default()
/// .init_resource::<MyCounter>();
/// ```
pub fn init_resource<R: Resource + FromWorld>(&mut self) -> &mut Self {
Expand All @@ -441,7 +441,7 @@ impl App {
/// counter: usize,
/// }
///
/// App::new()
/// App::default()
/// .insert_non_send_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_non_send_resource<R: 'static>(&mut self, resource: R) -> &mut Self {
Expand Down Expand Up @@ -524,7 +524,7 @@ impl App {
/// # impl Plugin for ImagePlugin {
/// # fn build(&self, app: &mut App) {}
/// # }
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # app.add_plugins(ImagePlugin::default());
/// let default_sampler = app.get_added_plugins::<ImagePlugin>()[0].default_sampler;
/// ```
Expand Down Expand Up @@ -562,9 +562,9 @@ impl App {
/// # impl Plugin for LogPlugin {
/// # fn build(&self, app: &mut App) {}
/// # }
/// App::new()
/// App::default()
/// .add_plugins(MinimalPlugins);
/// App::new()
/// App::default()
/// .add_plugins((MinimalPlugins, LogPlugin));
/// ```
///
Expand Down Expand Up @@ -615,7 +615,7 @@ impl App {
/// use bevy_app::App;
/// use bevy_reflect::{ReflectSerialize, ReflectDeserialize};
///
/// App::new()
/// App::default()
/// .register_type::<Option<String>>()
/// .register_type_data::<Option<String>, ReflectSerialize>()
/// .register_type_data::<Option<String>, ReflectDeserialize>();
Expand Down Expand Up @@ -662,7 +662,7 @@ impl App {
/// a + b
/// }
///
/// App::new().register_function(add);
/// App::default().register_function(add);
/// ```
///
/// Functions cannot be registered more than once.
Expand All @@ -674,7 +674,7 @@ impl App {
/// a + b
/// }
///
/// App::new()
/// App::default()
/// .register_function(add)
/// // Panic! A function has already been registered with the name "my_function"
/// .register_function(add);
Expand All @@ -686,7 +686,7 @@ impl App {
/// use bevy_app::App;
///
/// // Panic! Anonymous functions cannot be registered using `register_function`
/// App::new().register_function(|a: i32, b: i32| a + b);
/// App::default().register_function(|a: i32, b: i32| a + b);
/// ```
///
/// [`register_function_with_name`]: Self::register_function_with_name
Expand Down Expand Up @@ -738,7 +738,7 @@ impl App {
///
/// let div = |a: i32, b: i32| a / b;
///
/// App::new()
/// App::default()
/// // Registering an anonymous function with a unique name
/// .register_function_with_name("my_crate::add", |a: i32, b: i32| {
/// a + b
Expand All @@ -760,7 +760,7 @@ impl App {
/// fn one() {}
/// fn two() {}
///
/// App::new()
/// App::default()
/// .register_function_with_name("my_function", one)
/// // Panic! A function has already been registered with the name "my_function"
/// .register_function_with_name("my_function", two);
Expand Down Expand Up @@ -818,7 +818,7 @@ impl App {
/// #[derive(Component, Default, PartialEq, Eq, Debug)]
/// struct C(u32);
///
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # app.add_plugins(MinimalPlugins).add_systems(Startup, setup);
/// // Register B as required by A and C as required by B.
/// app.register_required_components::<A, B>();
Expand Down Expand Up @@ -878,7 +878,7 @@ impl App {
/// #[derive(Component, Default, PartialEq, Eq, Debug)]
/// struct C(u32);
///
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # app.add_plugins(MinimalPlugins).add_systems(Startup, setup);
/// // Register B and C as required by A and C as required by B.
/// // A requiring C directly will overwrite the indirect requirement through B.
Expand Down Expand Up @@ -943,7 +943,7 @@ impl App {
/// #[derive(Component, Default, PartialEq, Eq, Debug)]
/// struct C(u32);
///
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # app.add_plugins(MinimalPlugins).add_systems(Startup, setup);
/// // Register B as required by A and C as required by B.
/// app.register_required_components::<A, B>();
Expand Down Expand Up @@ -1005,7 +1005,7 @@ impl App {
/// #[derive(Component, Default, PartialEq, Eq, Debug)]
/// struct C(u32);
///
/// # let mut app = App::new();
/// # let mut app = App::default();
/// # app.add_plugins(MinimalPlugins).add_systems(Startup, setup);
/// // Register B and C as required by A and C as required by B.
/// // A requiring C directly will overwrite the indirect requirement through B.
Expand Down Expand Up @@ -1205,7 +1205,7 @@ impl App {
/// fn system_1(_: Query<&mut A>) {}
/// fn system_2(_: Query<&A>) {}
///
/// let mut app = App::new();
/// let mut app = App::default();
/// app.configure_schedules(ScheduleBuildSettings {
/// ambiguity_detection: LogLevel::Error,
/// ..default()
Expand Down Expand Up @@ -1243,7 +1243,7 @@ impl App {
/// fn system_1(_: ResMut<R>) {}
/// fn system_2(_: Res<R>) {}
///
/// let mut app = App::new();
/// let mut app = App::default();
/// app.configure_schedules(ScheduleBuildSettings {
/// ambiguity_detection: LogLevel::Error,
/// ..default()
Expand Down Expand Up @@ -1316,7 +1316,7 @@ impl App {
/// # use bevy_ecs::prelude::*;
/// # use bevy_utils::default;
/// #
/// # let mut app = App::new();
/// # let mut app = App::default();
/// #
/// # #[derive(Event)]
/// # struct Party {
Expand Down Expand Up @@ -1368,7 +1368,7 @@ impl App {
/// # use bevy_app::*;
/// # use bevy_ecs::error::warn;
/// # fn MyPlugins(_: &mut App) {}
/// App::new()
/// App::default()
/// .set_error_handler(warn)
/// .add_plugins(MyPlugins)
/// .run();
Expand Down Expand Up @@ -1528,23 +1528,23 @@ mod tests {

#[test]
fn can_add_two_plugins() {
App::new().add_plugins((PluginA, PluginB));
App::default().add_plugins((PluginA, PluginB));
}

#[test]
#[should_panic]
fn cant_add_twice_the_same_plugin() {
App::new().add_plugins((PluginA, PluginA));
App::default().add_plugins((PluginA, PluginA));
}

#[test]
fn can_add_twice_the_same_plugin_with_different_type_param() {
App::new().add_plugins((PluginC(0), PluginC(true)));
App::default().add_plugins((PluginC(0), PluginC(true)));
}

#[test]
fn can_add_twice_the_same_plugin_not_unique() {
App::new().add_plugins((PluginD, PluginD));
App::default().add_plugins((PluginD, PluginD));
}

#[test]
Expand All @@ -1560,7 +1560,7 @@ mod tests {
app.add_plugins(InnerPlugin).run();
}
}
App::new().add_plugins(PluginRun);
App::default().add_plugins(PluginRun);
}

#[derive(ScheduleLabel, Hash, Clone, PartialEq, Eq, Debug)]
Expand All @@ -1579,7 +1579,7 @@ mod tests {

#[test]
fn add_systems_should_create_schedule_if_it_does_not_exist() {
let mut app = App::new();
let mut app = App::default();
app.add_systems(EnterMainMenu, (foo, bar));

app.world_mut().run_schedule(EnterMainMenu);
Expand All @@ -1589,7 +1589,7 @@ mod tests {
#[test]
#[should_panic]
fn test_is_plugin_added_works_during_finish() {
let mut app = App::new();
let mut app = App::default();
app.add_plugins(PluginA);
app.add_plugins(PluginE);
app.finish();
Expand Down Expand Up @@ -1702,7 +1702,7 @@ mod tests {
#[derive(Component, Copy, Clone)]
struct Foo;

let mut app = App::new();
let mut app = App::default();
app.world_mut().spawn_batch(core::iter::repeat_n(Foo, 5));

fn despawn_one_foo(mut commands: Commands, foos: Query<Entity, With<Foo>>) {
Expand Down Expand Up @@ -1736,13 +1736,13 @@ mod tests {
#[derive(Resource)]
struct Foo(usize);

let mut app = App::new();
let mut app = App::default();
app.world_mut().insert_resource(Foo(0));
app.add_systems(Update, |mut foo: ResMut<Foo>| {
foo.0 += 1;
});

let mut sub_app = SubApp::new();
let mut sub_app = SubApp::default();
sub_app.set_extract(|main_world, _sub_world| {
assert!(main_world.get_resource_ref::<Foo>().unwrap().is_changed());
});
Expand All @@ -1762,7 +1762,7 @@ mod tests {
exits.write(AppExit::from_code(73));
}

let exit = App::new().add_systems(Update, raise_exits).run();
let exit = App::default().add_systems(Update, raise_exits).run();

assert_eq!(exit, AppExit::from_code(4));
}
Expand Down Expand Up @@ -1795,7 +1795,7 @@ mod tests {
}

// Should not panic due to missing resource
App::new()
App::default()
.set_runner(my_runner)
.add_systems(PreUpdate, my_system)
.run();
Expand Down Expand Up @@ -1830,7 +1830,7 @@ mod tests {
}
}

App::new()
App::default()
.init_non_send_resource::<NonSendTestResource>()
.init_resource::<TestResource>();
}
Expand All @@ -1848,14 +1848,14 @@ mod tests {
}
}

App::new().add_plugins(Foo);
App::default().add_plugins(Foo);
}
#[test]
fn events_should_be_updated_once_per_update() {
#[derive(BufferedEvent, Clone)]
struct TestEvent;

let mut app = App::new();
let mut app = App::default();
app.add_event::<TestEvent>();

// Starts empty
Expand Down
6 changes: 3 additions & 3 deletions crates/bevy_app/src/main_schedule.rs
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Expand Up @@ -420,7 +420,7 @@ pub enum RunFixedMainLoopSystems {
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// App::new()
/// App::default()
/// .add_systems(
/// RunFixedMainLoop,
/// update_camera_rotation.in_set(RunFixedMainLoopSystems::BeforeFixedMainLoop))
Expand All @@ -444,7 +444,7 @@ pub enum RunFixedMainLoopSystems {
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// App::new()
/// App::default()
/// .add_systems(FixedUpdate, update_physics)
/// .add_systems(
/// RunFixedMainLoop,
Expand Down Expand Up @@ -473,7 +473,7 @@ pub enum RunFixedMainLoopSystems {
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// App::new()
/// App::default()
/// .add_systems(FixedUpdate, update_physics)
/// .add_systems(
/// RunFixedMainLoop,
Expand Down
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