Add back hot reloading for `Scene`s #4552

nicopap · 2022-04-21T11:49:59Z

`SceneSpawner` refactor

This PR reworks the scene_spawner.rs module in bevy_scene. After
hunting for the bug causing #3759, I determined that it was the
culprit. Having difficulties parsing the code myself, I decided
to refactor it.

Relationship with merging of `Scene` and `DynamicScene`

There has been discussion about getting rid of either Scene or
DynamicScene, or merging the two.

This PR does not merge Scene and DynamicScene it only limits
itself to refactoring scene_spawner.rs. However, the changes
introduced will likely make it easier to transition to an
implementation where only a single Scene type exists.

Improvements

Merge code in SceneSpawner for managing DynamicScene and Scene.
- Add back hot reloading for Scenes, fixes Scenes do not hot reload #3759
Add documentation to SceneSpawner methods.
Add write_to_world method to Scene (does the same as DynamicScene::write_to_world)

Tests

The tests would require manipulating ResMut<Assets<T>>, which I don't
know how to do. So I left them out.

Further cleanup

Removing duplication in API surface

An earlier version of this PR merged the SceneSpawner::dynamic_foo and
SceneSpawner::foo methods by making them generic over the handle they accept.
However, it was judged too burdensome for the user. It required adding type specification
on existing code, since it doesn't play nice with asset_server.load() which introduces
an unbound type variable.

User migration guide

After the second commit, the migration guide consists of:

Change all calls to SceneSpawner::despawn to SceneSpawner::despawn_dynamic (note that you should be using SceneBundles and removeing the Handle<Scene> and Handle<DynamicScene> component instead in any case)

Question for reviewers

Should we revert the <T: Into<SceneHandle>> change? Now that scenes are mostly added through SceneBundle, there is not as much use of the SceneSpawner API with unbound generic types.

* Merge code in `SceneSpawner` for managing `DynamicScene` and `Scene`. * Add back hot reloading for `Scene`s, fixes bevyengine#3759 * Add ability to despawn `Scene`s * Add ability to spawn `DynamicScene` as child of existing entities * Add documentation to `SceneSpawner` methods. * Add `write_to_world` method to `Scene` (does the same as `DynamicScene::write_to_world`) This fixes bevyengine#3759 see this commit's merging PR for further details about this change. Merge PR: bevyengine#4552

nicopap · 2022-04-22T06:28:12Z

I'm going to remove the generic parameter. I don't like it and I think it's a major ergonomic loss. I'll not rebase so that it's possible to revert the removal if deemed appropriate.

nicopap · 2022-04-22T07:57:39Z

crates/bevy_scene/src/scene.rs

+    pub fn write_to_world(
+        &self,
+        world: &mut World,
+        entity_map: &mut EntityMap,
+    ) -> Result<(), SceneSpawnError> {
+        let type_registry = world.resource::<TypeRegistryArc>().clone();
+        let type_registry = type_registry.read();
+        for archetype in self.world.archetypes().iter() {
+            for scene_entity in archetype.entities() {
+                let entity = entity_map
+                    .entry(*scene_entity)
+                    .or_insert_with(|| world.spawn().id());
+                for component_id in archetype.components() {
+                    let component_info = self
+                        .world
+                        .components()
+                        .get_info(component_id)
+                        .expect("component_ids in archetypes should have ComponentInfo");
+
+                    let reflect_component = type_registry
+                        .get(component_info.type_id().unwrap())
+                        .ok_or_else(|| SceneSpawnError::UnregisteredType {
+                            type_name: component_info.name().to_string(),
+                        })
+                        .and_then(|registration| {
+                            registration.data::<ReflectComponent>().ok_or_else(|| {
+                                SceneSpawnError::UnregisteredComponent {
+                                    type_name: component_info.name().to_string(),
+                                }
+                            })
+                        })?;
+                    reflect_component.copy_component(&self.world, world, *scene_entity, *entity);
+                }
+            }
+        }
+        for registration in type_registry.iter() {
+            if let Some(map_entities_reflect) = registration.data::<ReflectMapEntities>() {
+                map_entities_reflect
+                    .map_entities(world, entity_map)
+                    .unwrap();
+            }
+        }
+        Ok(())


Note: this was extracted from the SceneSpawner::spawn_sync_internal method. I think it belongs here, the same way the code for instantiating a DynamicScene belongs in dynamic_scene.rs

nicopap · 2022-04-22T07:59:38Z

crates/bevy_scene/src/scene_spawner.rs

    }

-    pub fn spawn(&mut self, scene_handle: Handle<Scene>) -> InstanceId {
+    /// Spawn a dynamic scene. See [`SceneSpawner::spawn`].


The short doc strings with reference to the relevant Scene implementation is to avoid repeating the same doc string over and over. Since we have here 5 methods that are basically identical with a single DynamicScene, deduplicating the doc helps tremendously.

nicopap · 2022-04-22T08:01:35Z

crates/bevy_scene/src/scene_spawner.rs

+    /// This will only update the world when [`scene_spawner_system`] runs, see
+    /// [`SceneSpawner::despawn_sync`] for a method with immediate world
+    /// update.
+    pub fn despawn(&mut self, scene_handle: Handle<Scene>) {


This is one of the only API breaking change. Before, this method accepted a Handle<DynamicScene>, which is surprising, given that spawn, spawn_sync and spawn_as_child all accept a Handle<Scene> I think it's justified to change the API to be more consistent. The new equivalent method is despawn_dynamic

crates/bevy_scene/src/scene_spawner.rs

* Merge code in `SceneSpawner` for managing `DynamicScene` and `Scene`. * Add back hot reloading for `Scene`s, fixes bevyengine#3759 * Add ability to despawn `Scene`s * Add ability to spawn `DynamicScene` as child of existing entities * Add documentation to `SceneSpawner` methods. * Add `write_to_world` method to `Scene` (does the same as `DynamicScene::write_to_world`) This fixes bevyengine#3759 see this commit's merging PR for further details about this change. Merge PR: bevyengine#4552

* Merge code in `SceneSpawner` for managing `DynamicScene` and `Scene`. * Add back hot reloading for `Scene`s, fixes bevyengine#3759 * Add documentation to `SceneSpawner` methods. * Add `write_to_world` method to `Scene` (does the same as `DynamicScene::write_to_world`) This fixes bevyengine#3759 see this commit's merging PR for further details about this change. Merge PR: bevyengine#4552 A previous version of this change merged `SceneSpawner::*{,_dynamic}`, it made it too difficult to use the `SceneSpawner` so it was reverted.

mockersf · 2022-06-21T01:00:02Z

crates/bevy_scene/src/scene_spawner.rs

+}
+
+#[derive(Debug, Clone)]
+struct SpawnCommand {


I think we should avoid "Command" in the name of things that do not impl the Command trait

alice-i-cecile

The code and doc changes LGTM, and I've verified this works locally.

bors r+

bors · 2022-10-10T17:05:52Z

Merge conflict.

alice-i-cecile · 2022-10-10T17:49:58Z

@nicopap merge conflicts, sorry! Should be simple ones.

alice-i-cecile · 2022-10-17T15:34:48Z

[11:29 AM] Gibooonus: I updated the test case I designed in #3759 with more entities, and now it just crashes

Removing the Ready-For-Final-Review label until this is fixed.

nicopap · 2023-02-11T08:32:51Z

This will require an entire rewrite soon enough. I'll close it

github-actions bot added the S-Needs-Triage This issue needs to be labelled label Apr 21, 2022

nicopap force-pushed the scene_spawner-refactor branch from 937588e to a4eea6c Compare April 21, 2022 13:02

nicopap marked this pull request as ready for review April 21, 2022 13:03

nicopap commented Apr 22, 2022

View reviewed changes

crates/bevy_scene/src/scene_spawner.rs Outdated Show resolved Hide resolved

nicopap force-pushed the scene_spawner-refactor branch from 61b1634 to d1aec75 Compare April 27, 2022 07:43

alice-i-cecile added the M-Needs-Migration-Guide A breaking change to Bevy's public API that needs to be noted in a migration guide label May 2, 2022

nicopap marked this pull request as draft June 10, 2022 06:46

nicopap mentioned this pull request Jun 18, 2022

Add way to insert components to loaded scenes #4980

Closed

nicopap force-pushed the scene_spawner-refactor branch from 11fa86c to 9699f0d Compare June 18, 2022 13:30

Fix crash on reloading scenes spawned as child

ca6666f

nicopap force-pushed the scene_spawner-refactor branch from 3ca1d12 to ca6666f Compare June 18, 2022 15:00

nicopap marked this pull request as ready for review June 18, 2022 15:01

mockersf reviewed Jun 21, 2022

View reviewed changes

Rename SpawnCommand

2899ef4

alice-i-cecile approved these changes Oct 10, 2022

View reviewed changes

alice-i-cecile added the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Oct 10, 2022

alice-i-cecile removed the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Oct 17, 2022

nicopap marked this pull request as draft November 4, 2022 11:28

nicopap closed this Feb 11, 2023

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Add back hot reloading for `Scene`s #4552

Add back hot reloading for `Scene`s #4552

nicopap commented Apr 21, 2022 •

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Add back hot reloading for Scenes #4552

Add back hot reloading for Scenes #4552

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nicopap commented Apr 21, 2022 • edited Loading

SceneSpawner refactor

Relationship with merging of Scene and DynamicScene

Improvements

Tests

Further cleanup

Removing duplication in API surface

User migration guide

Question for reviewers

nicopap commented Apr 22, 2022

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Add back hot reloading for `Scene`s #4552

Add back hot reloading for `Scene`s #4552

nicopap commented Apr 21, 2022 •

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`SceneSpawner` refactor

Relationship with merging of `Scene` and `DynamicScene`