bevy/crates/bevy_ecs/src/world
James Liu aaf384ae58 Panic on dropping NonSend in non-origin thread. (#6534)
# Objective

Fixes #3310. Fixes #6282. Fixes #6278. Fixes #3666.

## Solution
Split out `!Send` resources into `NonSendResources`. Add a `origin_thread_id` to all `!Send` Resources, check it on dropping `NonSendResourceData`, if there's a mismatch, panic. Moved all of the checks that `MainThreadValidator` would do into `NonSendResources` instead.

All `!Send` resources now individually track which thread they were inserted from. This is validated against for every access, mutation, and drop that could be done against the value. 

A regression test using an altered version of the example from #3310 has been added.

This is a stopgap solution for the current status quo. A full solution may involve fully removing `!Send` resources/components from `World`, which will likely require a much more thorough design on how to handle the existing in-engine and ecosystem use cases.

This PR also introduces another breaking change:

```rust
    use bevy_ecs::prelude::*;

    #[derive(Resource)]
    struct Resource(u32);

    fn main() {
        let mut world = World::new();
        world.insert_resource(Resource(1));
        world.insert_non_send_resource(Resource(2));
        let res = world.get_resource_mut::<Resource>().unwrap();
        assert_eq!(res.0, 2);
    }
```

This code will run correctly on 0.9.1 but not with this PR, since NonSend resources and normal resources have become actual distinct concepts storage wise.

## Changelog
Changed: Fix soundness bug with `World: Send`. Dropping a `World` that contains a `!Send` resource on the wrong thread will now panic.

## Migration Guide
Normal resources and `NonSend` resources no longer share the same backing storage. If `R: Resource`, then `NonSend<R>` and `Res<R>` will return different instances from each other. If you are using both `Res<T>` and `NonSend<T>` (or their mutable variants), to fetch the same resources, it's strongly advised to use `Res<T>`.
2023-01-09 20:40:34 +00:00
..
entity_ref.rs Fix various typos (#7096) 2023-01-06 00:43:30 +00:00
identifier.rs Unique WorldId (#2827) 2021-09-30 20:54:47 +00:00
mod.rs Panic on dropping NonSend in non-origin thread. (#6534) 2023-01-09 20:40:34 +00:00
spawn_batch.rs add more SAFETY comments and lint for missing ones in bevy_ecs (#4835) 2022-07-04 14:44:24 +00:00
world_cell.rs Panic on dropping NonSend in non-origin thread. (#6534) 2023-01-09 20:40:34 +00:00