Migration writing pass 2 (#2066)

Author: BD103

release-content/0.16/migration-guides/16163_Dont_reëxport_bevy_image_from_bevy_render.md

@@ -1,2 +1,23 @@
-The `ui_debug_overlay` module has been removed from `bevy_dev_tools`.
-There is a new debug overlay implemented using the `bevy_ui` renderer. To use it, enable the `bevy_ui_debug` feature and set the `enable` field of the `UiDebugOptions` resource to `true`.
+The `bevy_dev_tools::ui_debug_overlay` module has been replaced with a new debug overlay implemented using `bevy_ui`'s renderer. The new debug UI overlay still requires the `bevy_ui_debug` feature flag, but this flag is now available through `bevy` and `bevy_ui` instead of `bevy_dev_tools`. `UiDebugOptions` has been moved to `bevy_ui` as well, and now has several new options.
+
+```rust
+// 0.15
+App::new()
+    .add_plugins((DefaultPlugins, DebugUiPlugin))
+    .insert_resource(UiDebugOptions {
+        enabled: true,
+    })
+    .run();
+
+// 0.16
+App::new()
+    // You no longer need `DebugUiPlugin`; enabling the `bevy_ui_debug` feature handles this for
+    // you.
+    .add_plugins(DefaultPlugins)
+    .insert_resource(UiDebugOptions {
+        enabled: true,
+        // `UiDebugOptions` has a few new options, but for now we'll leave the defaults.
+        ..default()
+    })
+    .run();
+```

release-content/0.16/migration-guides/16693_Draw_the_UI_debug_overlay_using_the_UI_renderer.md

@@ -1,11 +1,12 @@
-The `CachedSystemId` resource has been changed:
+As part of a bug fix for system caching, the `CachedSystemId` resource has been changed to store an `Entity` instead of a `SystemId`. `CachedSystemId` construction has also been changed to use the `new()` method.
 
 ```rust
-// Before:
-let cached_id = CachedSystemId::<S::System>(id);
+// 0.15
+let cached_id = CachedSystemId::<S::System>::(id);
 assert!(id == cached_id.0);
 
-// After:
+// 0.16
 let cached_id = CachedSystemId::<S>::new(id);
+// You can convert a valid `Entity` into a `Systemid` with `SystemId::from_entity()`.
 assert!(id == SystemId::from_entity(cached_id.entity));
 ```

release-content/0.16/migration-guides/16694_Cache_systems_by_S_instead_of_SSystem.md

@@ -1 +1,17 @@
-- `BrpQueryParams` now has `strict` boolean field. It serfs as a flag to fail when encountering an invalid component rather than skipping it. Defaults to false.
+Bevy Remote Protocol's `bevy/query` request now skips missing or invalid components by default instead of returning an error. This can be configured with `BrpQueryParams`'s new `strict` boolean field.
+
+If you wish `bevy/query` to return to its previous behavior of erroring on missing / invalid components, set `"strict": true`:
+
+```json
+{
+    "method": "bevy/query",
+    "id": 0,
+    "params": {
+        "data": {
+            "components": ["foo::bar::MyComponent"]
+        },
+        // Error if `foo::bar::MyComponent` doesn't exist.
+        "strict": true
+    }
+}
+```

release-content/0.16/migration-guides/16725_BRP_strict_field_in_query.md

@@ -1 +1 @@
-Bevy now has first-class input handling, available in the `bevy::input_focus` module. As such, `bevy::a11y::Focus` has been replaced with `bevy::input_focus::Focus`. Please replace all references and imports.
+Bevy now has first-class input handling, available in the `bevy::input_focus` module. As such, `bevy::a11y::Focus` has been replaced with `bevy::input_focus::InputFocus`. Please replace all references and imports.

release-content/0.16/migration-guides/16778_Event_source_location_tracking.md

@@ -1 +1,50 @@
-- `IntoSystemConfigs` has been removed for `BoxedSystem<(), ()>`. Either use `InfallibleSystemWrapper` before boxing or make your system return `bevy::ecs::prelude::Result`.
+`bevy::ecs::IntoSystemConfigs`, now known as `IntoScheduleConfigs`, is no longer implemented for `BoxedSystem<(), ()>`. This can lead to convoluted trait errors when you try to add a `BoxedSystem<(), ()>` to a schedule or app:
+
+```
+error[E0277]: `std::boxed::Box<dyn bevy::prelude::System<In = (), Out = ()>>` does not describe a valid system configuration
+```
+
+In order to avoid this error, either wrap your system in an `InfallibleSystemWrapper` before boxing it or make the system return a `Result<(), BevyError>`.
+
+```rust
+// 0.15
+fn my_system() {
+    println!("Hello, world!");
+}
+
+// Convert the function into a boxed system, which is a `Box<dyn System<In = (), Out = ()>>`.
+let system = Box::new(IntoSystem::into_system(my_system)) as BoxedSystem;
+
+App::new()
+    .add_systems(Startup, system)
+    .run();
+
+// 0.16 (Using `InfallibleSystemWrapper`)
+fn my_system() {
+    println!("Hello, world!");
+}
+
+// Use `InfallibleSystemWrapper::new()` to make a system unconditionally return `Result::Ok`. The
+// boxed system is now a `Box<dyn System<In = (), Out = Result<(), BevyError>>>`.
+let system = Box::new(InfallibleSystemWrapper::new(IntoSystem::into_system(my_system))) as BoxedSystem<_, _>;
+
+App::new()
+    .add_systems(Startup, system)
+    .run();
+
+// 0.16 (Returning `Result<(), BevyError>`)
+fn my_system() -> Result {
+    println!("Hello, world!");
+    Ok(())
+}
+
+// The boxed system is now a `Box<dyn System<In = (), Out = Result<(), BevyError>>>`.
+let system = Box::new(IntoSystem::into_system(my_system)) as BoxedSystem<_, _>;
+
+App::new()
+    // Add the boxed system to the app.
+    .add_systems(Startup, system)
+    .run();
+```
+
+Note that in several cases you do not need to box your systems before adding them, such as with `App::add_systems()`, which lets you avoid this issue.

release-content/0.16/migration-guides/16863_Replace_bevy_a11yFocus_with_InputFocus.md

@@ -1 +1 @@
-The `track_change_detection` feature flag has been renamed to `track_location` to better reflect its extended capabilities.
+The `track_change_detection` feature flag no longer just tracks the source code location for change detection, but also where entities are spawned and despawned. As such, the feature flag has been renamed to `track_location` to better reflect its extended capabilities.

release-content/0.16/migration-guides/17051_Convert_to_fallible_system_in_IntoSystemConfigs.md

@@ -1 +1 @@
-`FrameTimeDiagnosticsPlugin` now contains two fields. Use `FrameTimeDiagnosticsPlugin::default()` to match Bevy’s previous behavior or, for example, `FrameTimeDiagnosticsPlugin::new(60)` to configure it.
+`FrameTimeDiagnosticsPlugin` now contains two fields: `max_history_length` and `smoothing_factor`. If you manually construct this plugin and wish to retain 0.15 behavior, simply call `FrameTimeDiagnosticsPlugin::default()`. If you wish to configure the maximum history length, you may use `FrameTimeDiagnosticsPlugin::new()` instead.

release-content/0.16/migration-guides/17075_Rename_track_change_detection_flag_to_track_location.md

@@ -1,2 +1 @@
-- `World::try_despawn` now returns a `Result` rather than a `bool`.
-- `World::try_insert_batch` and `World::try_insert_batch_if_new` now return a `Result` where they previously returned nothing.
+`World::try_despawn()` now returns a `Result` rather than a `bool`. Additionally, `World::try_insert_batch()` and `World::try_insert_batch_if_new()` now return a `Result` instead of silently failing.