bevy/crates
JoJoJet 3442a13d2c
Use UnsafeWorldCell to increase code quality for SystemParam (#8174)
# Objective

The type `&World` is currently in an awkward place, since it has two
meanings:
1. Read-only access to the entire world.
2. Interior mutable access to the world; immutable and/or mutable access
to certain portions of world data.

This makes `&World` difficult to reason about, and surprising to see in
function signatures if one does not know about the interior mutable
property.

The type `UnsafeWorldCell` was added in #6404, which is meant to
alleviate this confusion by adding a dedicated type for interior mutable
world access. However, much of the engine still treats `&World` as an
interior mutable-ish type. One of those places is `SystemParam`.

## Solution

Modify `SystemParam::get_param` to accept `UnsafeWorldCell` instead of
`&World`. Simplify the safety invariants, since the `UnsafeWorldCell`
type encapsulates the concept of constrained world access.

---

## Changelog

`SystemParam::get_param` now accepts an `UnsafeWorldCell` instead of
`&World`. This type provides a high-level API for unsafe interior
mutable world access.

## Migration Guide

For manual implementers of `SystemParam`: the function `get_item` now
takes `UnsafeWorldCell` instead of `&World`. To access world data, use:

* `.get_entity()`, which returns an `UnsafeEntityCell` which can be used
to access component data.
* `get_resource()` and its variants, to access resource data.
2023-04-01 15:45:07 +00:00
..
bevy_a11y chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_animation Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_app run_if for SystemConfigs via anonymous system sets (#7676) 2023-03-30 21:39:10 +00:00
bevy_asset Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_audio Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_core Register missing types in bevy_window (#7993) 2023-03-27 21:48:29 +00:00
bevy_core_pipeline Split opaque and transparent phases (#8090) 2023-03-28 06:35:16 +00:00
bevy_derive chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_diagnostic Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_dylib chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_dynamic_plugin chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_ecs Use UnsafeWorldCell to increase code quality for SystemParam (#8174) 2023-04-01 15:45:07 +00:00
bevy_ecs_compile_fail_tests Update trybuild tests for Rust 1.68 (#8002) 2023-03-09 15:46:06 +00:00
bevy_encase_derive chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_gilrs Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_gizmos Fix segfault with 2d gizmos (#8223) 2023-03-29 18:05:03 +00:00
bevy_gltf chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_hierarchy Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_input Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_internal Document bevy_gizmos (#8186) 2023-03-28 20:58:02 +00:00
bevy_log chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_macro_utils Fix name conflicts caused by the SystemParam and WorldQuery macros (#8012) 2023-03-22 15:45:25 +00:00
bevy_math Fix CubicCurve::iter_samples iteration count (#8049) 2023-03-31 08:15:21 +00:00
bevy_mikktspace chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_pbr Use the prepass normal texture in main pass when possible (#8231) 2023-03-29 18:04:40 +00:00
bevy_ptr Simplify Clone for ThinSlicePtr (#8247) 2023-03-30 10:22:09 +00:00
bevy_reflect Fix typo in bevy_reflect README (#8281) 2023-04-01 03:01:44 +00:00
bevy_reflect_compile_fail_tests bevy_reflect: Fix trailing comma breaking derives (#8014) 2023-03-27 21:47:33 +00:00
bevy_render Use UnsafeWorldCell to increase code quality for SystemParam (#8174) 2023-04-01 15:45:07 +00:00
bevy_scene Bugfix: Scene reload fix (nonbreaking) (#7951) 2023-03-27 22:18:45 +00:00
bevy_sprite Add ReflectComponent registration for Sprite (#8207) 2023-03-27 21:18:10 +00:00
bevy_tasks chore: Release (#7920) 2023-03-06 05:13:36 +00:00
bevy_text Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_time Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
bevy_transform docs: update docs and comments that still refer to stages (#8156) 2023-03-27 21:50:21 +00:00
bevy_ui Improve UI update_clipping_system comments (#8147) 2023-03-28 20:18:02 +00:00
bevy_utils Replace some unsafe system executor code with safe code (#8274) 2023-03-31 21:56:49 +00:00
bevy_window Register missing types in bevy_window (#7993) 2023-03-27 21:48:29 +00:00
bevy_winit docs: update docs and comments that still refer to stages (#8156) 2023-03-27 21:50:21 +00:00