Illiux eebc92a7d4 Make scene handling of entity references robust (#7335) ... # Objective - Handle dangling entity references inside scenes - Handle references to entities with generation > 0 inside scenes - Fix a latent bug in `Parent`'s `MapEntities` implementation, which would, if the parent was outside the scene, cause the scene to be loaded into the new world with a parent reference potentially pointing to some random entity in that new world. - Fixes #4793 and addresses #7235 ## Solution - DynamicScenes now identify entities with a `Entity` instead of a u32, therefore including generation - `World` exposes a new `reserve_generations` function that despawns an entity and advances its generation by some extra amount. - `MapEntities` implementations have a new `get_or_reserve` function available that will always return an `Entity`, establishing a new mapping to a dead entity when the entity they are called with is not in the `EntityMap`. Subsequent calls with that same `Entity` will return the same newly created dead entity reference, preserving equality semantics. - As a result, after loading a scene containing references to dead entities (or entities otherwise outside the scene), those references will all point to different generations on a single entity id in the new world. --- ## Changelog ### Changed - In serialized scenes, entities are now identified by a u64 instead of a u32. - In serialized scenes, components with entity references now have those references serialize as u64s instead of structs. ### Fixed - Scenes containing components with entity references will now deserialize and add to a world reliably. ## Migration Guide - `MapEntities` implementations must change from a `&EntityMap` parameter to a `&mut EntityMapper` parameter and can no longer return a `Result`. Finally, they should switch from calling `EntityMap::get` to calling `EntityMapper::get_or_reserve`. --------- Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>		2023-05-01 15:49:27 +00:00
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src	Make scene handling of entity references robust (#7335)	2023-05-01 15:49:27 +00:00
Cargo.toml	Make bevy_render an optional dependency of bevy_scene (#8136)	2023-04-03 21:23:26 +00:00