# Objective
* Enable `Res` and `Query` parameter mutual exclusion
* Required for https://github.com/bevyengine/bevy/pull/5080
The `FilteredAccessSet::get_conflicts` methods didn't work properly with
`Res` and `ResMut` parameters. Because those added their access by using
the `combined_access_mut` method and directly modifying the global
access state of the FilteredAccessSet. This caused an inconsistency,
because get_conflicts assumes that ALL added access have a corresponding
`FilteredAccess` added to the `filtered_accesses` field.
In practice, that means that SystemParam that adds their access through
the `Access` returned by `combined_access_mut` and the ones that add
their access using the `add` method lived in two different universes. As
a result, they could never be mutually exclusive.
## Solution
This commit fixes it by removing the `combined_access_mut` method. This
ensures that the `combined_access` field of FilteredAccessSet is always
updated consistently with the addition of a filter. When checking for
filtered access, it is now possible to account for `Res` and `ResMut`
invalid access. This is currently not needed, but might be in the
future.
We add the `add_unfiltered_{read,write}` methods to replace previous
usages of `combined_access_mut`.
We also add improved Debug implementations on FixedBitSet so that their
meaning is much clearer in debug output.
---
## Changelog
* Fix `Res` and `Query` parameter never being mutually exclusive.
## Migration Guide
Note: this mostly changes ECS internals, but since the API is public, it is technically breaking:
* Removed `FilteredAccessSet::combined_access_mut`
* Replace _immutable_ usage of those by `combined_access`
* For _mutable_ usages, use the new `add_unfiltered_{read,write}` methods instead of `combined_access_mut` followed by `add_{read,write}`
# Objective
Make core types in ECS smaller. The column sparse set in Tables is never updated after creation.
## Solution
Create `ImmutableSparseSet` which removes the capacity fields in the backing vec's and the APIs for inserting or removing elements. Drops the size of the sparse set by 3 usizes (24 bytes on 64-bit systems)
## Followup
~~After #4809, Archetype's component SparseSet should be replaced with it.~~ This has been done.
---
## Changelog
Removed: `Table::component_capacity`
## Migration Guide
`Table::component_capacity()` has been removed as Tables do not support adding/removing columns after construction.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
Archetype is a deceptively large type in memory. It stores metadata about which components are in which storage in multiple locations, which is only used when creating new Archetypes while moving entities.
## Solution
Remove the redundant `Box<[ComponentId]>`s and iterate over the sparse set of component metadata instead. Reduces Archetype's size by 4 usizes (32 bytes on 64-bit systems), as well as the additional allocations for holding these slices.
It'd seem like there's a downside that the origin archetype has it's component metadata iterated over twice when creating a new archetype, but this change also removes the extra `Vec<ArchetypeComponentId>` allocations when creating a new archetype which may amortize out to a net gain here. This change likely negatively impacts creating new archetypes with a large number of components, but that's a cost mitigated by the fact that these archetypal relationships are cached in Edges and is incurred only once for each edge created.
## Additional Context
There are several other in-flight PRs that shrink Archetype:
- #4800 merges the entities and rows Vecs together (shaves off 24 bytes per archetype)
- #4809 removes unique_components and moves it to it's own dedicated storage (shaves off 72 bytes per archetype)
---
## Changelog
Changed: `Archetype::table_components` and `Archetype::sparse_set_components` return iterators instead of slices. `Archetype::new` requires iterators instead of parallel slices/vecs.
## Migration Guide
Do I still need to do this? I really hope people were not relying on the public facing APIs changed here.
# Objective
In bevy 0.8 you could list all resources using `world.archetypes().resource().components()`. As far as I can tell the resource archetype has been replaced with the `Resources` storage, and it would be nice if it could be used to iterate over all resource component IDs as well.
## Solution
- add `fn Resources::iter(&self) -> impl Iterator<Item = (ComponentId, &ResourceData)>`
# Objective
Fixes#6615.
`BlobVec` does not respect alignment for zero-sized types, which results in UB whenever a ZST with alignment other than 1 is used in the world.
## Solution
Add the fn `bevy_ptr::dangling_with_align`.
---
## Changelog
+ Added the function `dangling_with_align` to `bevy_ptr`, which creates a well-aligned dangling pointer to a type whose alignment is not known at compile time.
# Objective
Fix#6548. Most of these methods were already made `const` in #5688. `Entity::to_bits` is the only one that remained.
## Solution
Make it const.
# Objective
Copy `send_event` and friends from `World` to `WorldCell`.
Clean up `bevy_winit` using `WorldCell::send_event`.
## Changelog
Added `send_event`, `send_event_default`, and `send_event_batch` to `WorldCell`.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
* Move the despawn debug log from `World::despawn` to `EntityMut::despawn`.
* Move the despawn non-existent warning log from `Commands::despawn` to `World::despawn`.
This should make logging consistent regardless of which of the three `despawn` methods is used.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
When an error causes `debug_checked_unreachable` to be called, the panic message unhelpfully points to the function definition instead of the place that caused the error.
## Solution
Add the `#[track_caller]` attribute in debug mode.
`EntityMut::remove_children` does not call `self.update_location()` which is unsound.
Verified by adding the following assertion, which fails when running the tests.
```rust
let before = self.location();
self.update_location();
assert_eq!(before, self.location());
```
I also removed incorrect messages like "parent entity is not modified" and the unhelpful "Inserting a bundle in the children entities may change the parent entity's location if they were of the same archetype" which might lead people to think that's the *only* thing that can change the entity's location.
# Changelog
Added `EntityMut::world_scope`.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
Alternative to #6424Fixes#6226
Fixes spawning empty bundles
## Solution
Add `BundleComponentStatus` trait and implement it for `AddBundle` and a new `SpawnBundleStatus` type (which always returns an Added status). `write_components` is now generic on `BundleComponentStatus` instead of taking `AddBundle` directly. This means BundleSpawner can now avoid needing AddBundle from the Empty archetype, which means BundleSpawner no longer needs a reference to the original archetype.
In theory this cuts down on the work done in `write_components` when spawning, but I'm seeing no change in the spawn benchmarks.
# Objective
Replace `WorldQueryGats` trait with actual gats
## Solution
Replace `WorldQueryGats` trait with actual gats
---
## Changelog
- Replaced `WorldQueryGats` trait with actual gats
## Migration Guide
- Replace usage of `WorldQueryGats` assoc types with the actual gats on `WorldQuery` trait
# Objective
Right now, the `TaskPool` implementation allows panics to permanently kill worker threads upon panicking. This is currently non-recoverable without using a `std::panic::catch_unwind` in every scheduled task. This is poor ergonomics and even poorer developer experience. This is exacerbated by #2250 as these threads are global and cannot be replaced after initialization.
Removes the need for temporary fixes like #4998. Fixes#4996. Fixes#6081. Fixes#5285. Fixes#5054. Supersedes #2307.
## Solution
The current solution is to wrap `Executor::run` in `TaskPool` with a `catch_unwind`, and discarding the potential panic. This was taken straight from [smol](404c7bcc0a/src/spawn.rs (L44))'s current implementation. ~~However, this is not entirely ideal as:~~
- ~~the signaled to the awaiting task. We would need to change `Task<T>` to use `async_task::FallibleTask` internally, and even then it doesn't signal *why* it panicked, just that it did.~~ (See below).
- ~~no error is logged of any kind~~ (See below)
- ~~it's unclear if it drops other tasks in the executor~~ (it does not)
- ~~This allows the ECS parallel executor to keep chugging even though a system's task has been dropped. This inevitably leads to deadlock in the executor.~~ Assuming we don't catch the unwind in ParallelExecutor, this will naturally kill the main thread.
### Alternatives
A final solution likely will incorporate elements of any or all of the following.
#### ~~Log and Ignore~~
~~Log the panic, drop the task, keep chugging. This only addresses the discoverability of the panic. The process will continue to run, probably deadlocking the executor. tokio's detatched tasks operate in this fashion.~~
Panics already do this by default, even when caught by `catch_unwind`.
#### ~~`catch_unwind` in `ParallelExecutor`~~
~~Add another layer catching system-level panics into the `ParallelExecutor`. How the executor continues when a core dependency of many systems fails to run is up for debate.~~
`async_task::Task` bubbles up panics already, this will transitively push panics all the way to the main thread.
#### ~~Emulate/Copy `tokio::JoinHandle` with `Task<T>`~~
~~`tokio::JoinHandle<T>` bubbles up the panic from the underlying task when awaited. This can be transitively applied across other APIs that also use `Task<T>` like `Query::par_for_each` and `TaskPool::scope`, bubbling up the panic until it's either caught or it reaches the main thread.~~
`async_task::Task` bubbles up panics already, this will transitively push panics all the way to the main thread.
#### Abort on Panic
The nuclear option. Log the error, abort the entire process on any thread in the task pool panicking. Definitely avoids any additional infrastructure for passing the panic around, and might actually lead to more efficient code as any unwinding is optimized out. However gives the developer zero options for dealing with the issue, a seemingly poor choice for debuggability, and prevents graceful shutdown of the process. Potentially an option for handling very low-level task management (a la #4740). Roughly takes the shape of:
```rust
struct AbortOnPanic;
impl Drop for AbortOnPanic {
fn drop(&mut self) {
abort!();
}
}
let guard = AbortOnPanic;
// Run task
std::mem::forget(AbortOnPanic);
```
---
## Changelog
Changed: `bevy_tasks::TaskPool`'s threads will no longer terminate permanently when a task scheduled onto them panics.
Changed: `bevy_tasks::Task` and`bevy_tasks::Scope` will propagate panics in the spawned tasks/scopes to the parent thread.
This reverts commit 53d387f340.
# Objective
Reverts #6448. This didn't have the intended effect: we're now getting bevy::prelude shown in the docs again.
Co-authored-by: Alejandro Pascual <alejandro.pascual.pozo@gmail.com>
# Objective
- Right now re-exports are completely hidden in prelude docs.
- Fixes#6433
## Solution
- We could show the re-exports without inlining their documentation.
# Objective
Fixes#6059, changing all incorrect occurrences of ``id`` in the ``entity`` module to ``index``:
* struct level documentation,
* ``id`` struct field,
* ``id`` method and its documentation.
## Solution
Renaming and verifying using CI.
Co-authored-by: Edvin Kjell <43633999+Edwox@users.noreply.github.com>
For `derive(WorldQuery)`, there are three structs generated, `Item`, `Fetch` and `State`.
These inherit the visibility of the derived structure, thus `#![warn(missing_docs)]` would
warn about missing documentation for these structures.
- [ ] I'd like some advice on what to write here, as I personally don't really understand `Fetch` nor `State`.
# Objective
* Add benchmarks for `Query::get_many`.
* Speed up `Query::get_many`.
## Solution
Previously, `get_many` and `get_many_mut` used the method `array::map`, which tends to optimize very poorly. This PR replaces uses of that method with loops.
## Benchmarks
| Benchmark name | Execution time | Change from this PR |
|--------------------------------------|----------------|---------------------|
| query_get_many_2/50000_calls_table | 1.3732 ms | -24.967% |
| query_get_many_2/50000_calls_sparse | 1.3826 ms | -24.572% |
| query_get_many_5/50000_calls_table | 2.6833 ms | -30.681% |
| query_get_many_5/50000_calls_sparse | 2.9936 ms | -30.672% |
| query_get_many_10/50000_calls_table | 5.7771 ms | -36.950% |
| query_get_many_10/50000_calls_sparse | 7.4345 ms | -36.987% |
# Objective
Add documentation `#[world_query(ignore)]`. Fixes#6283.
---
I've only described it's behavior so far (which appears to be the same as with `system_param`). Is there another use-case for this besides with `PhantomData`? I could only find a single usage of this construct on GitHub, which is [here](ffcb816927/bevy/examples/ecs/custom_query_param.rs (L102)).
I was also wondering if it would make sense to add a usage example to the `custom_query_example`? 🤔 That's why it's currently still in there.
Co-authored-by: Lucas Jenß <243719+x3ro@users.noreply.github.com>
# Objective
Bevy still has many instances of using single-tuples `(T,)` to create a bundle. Due to #2975, this is no longer necessary.
## Solution
Search for regex `\(.+\s*,\)`. This should have found every instance.
# Objective
Fix the soundness issue outlined in #5866. In short the problem is that `query.to_readonly().get_component_mut::<T>()` can provide unsound mutable access to the component. This PR is an alternative to just removing the offending api. Given that `to_readonly` is a useful tool, I think this approach is a preferable short term solution. Long term I think theres a better solution out there, but we can find that on its own time.
## Solution
Add what amounts to a "dirty flag" that marks Queries that have been converted to their read-only variant via `to_readonly` as dirty. When this flag is set to true, `get_component_mut` will fail with an error, preventing the unsound access.
# Objective
Currently for entities we serialize only `id`. But this is not very expected behavior. For example, in networking, when the server sends its state, it contains entities and components. On the client, I create new objects and map them (using `EntityMap`) to those received from the server (to know which one matches which). And if `generation` field is missing, this mapping can be broken. Example:
1. Server sends an entity `Entity{ id: 2, generation: 1}` with components.
2. Client puts the received entity in a map and create a new entity that maps to this received entity. The new entity have different `id` and `generation`. Let's call it `Entity{ id: 12, generation: 4}`.
3. Client sends a command for `Entity{ id: 12, generation: 4}`. To do so, it maps local entity to the one from server. But `generation` field is 0 because it was omitted for serialization on the server. So it maps to `Entity{ id: 2, generation: 0}`.
4. Server receives `Entity{ id: 2, generation: 0}` which is invalid.
In my game I worked around it by [writing custom serialization](https://github.com/dollisgame/dollis/blob/master/src/core/network/entity_serde.rs) and using `serde(with = "...")`. But it feels like a bad default to me.
Using `Entity` over a custom `NetworkId` also have the following advantages:
1. Re-use `MapEntities` trait to map `Entity`s in replicated components.
2. Instead of server `Entity <-> NetworkId ` and `Entity <-> NetworkId`, we map entities only on client.
3. No need to handling uniqueness. It's a rare case, but makes things simpler. For example, I don't need to query for a resource to create an unique ID.
Closes#6143.
## Solution
Use default serde impls. If anyone want to avoid wasting memory on `generation`, they can create a new type that holds `u32`. This is what Bevy do for [DynamicEntity](https://docs.rs/bevy/latest/bevy/scene/struct.DynamicEntity.html) to serialize scenes. And I don't see any use case to serialize an entity id expect this one.
---
## Changelog
### Changed
- Entity now serializes / deserializes `generation` field.
## Migration Guide
- Entity now fully serialized. If you want to serialze only `id`, as it was before, you can create a new type that wraps `u32`.
# Objective
- fix new clippy lints before they get stable and break CI
## Solution
- run `clippy --fix` to auto-fix machine-applicable lints
- silence `clippy::should_implement_trait` for `fn HandleId::default<T: Asset>`
## Changes
- always prefer `format!("{inline}")` over `format!("{}", not_inline)`
- prefer `Box::default` (or `Box::<T>::default` if necessary) over `Box::new(T::default())`
# Objective
Clean up code surrounding fetch by pulling out the common parts into the iteration code.
## Solution
Merge `Fetch::table_fetch` and `Fetch::archetype_fetch` into a single API: `Fetch::fetch(&mut self, entity: &Entity, table_row: &usize)`. This provides everything any fetch requires to internally decide which storage to read from and get the underlying data. All of these functions are marked as `#[inline(always)]` and the arguments are passed as references to attempt to optimize out the argument that isn't being used.
External to `Fetch`, Query iteration has been changed to keep track of the table row and entity outside of fetch, which moves a lot of the expensive bookkeeping `Fetch` structs had previously done internally into the outer loop.
~~TODO: Benchmark, docs~~ Done.
---
## Changelog
Changed: `Fetch::table_fetch` and `Fetch::archetype_fetch` have been merged into a single `Fetch::fetch` function.
## Migration Guide
TODO
Co-authored-by: Brian Merchant <bhmerchang@gmail.com>
Co-authored-by: Saverio Miroddi <saverio.pub2@gmail.com>
# Objective
- Proactive changing of code to comply with warnings generated by beta of rustlang version of cargo clippy.
## Solution
- Code changed as recommended by `rustup update`, `rustup default beta`, `cargo run -p ci -- clippy`.
- Tested using `beta` and `stable`. No clippy warnings in either after changes made.
---
## Changelog
- Warnings fixed were: `clippy::explicit-auto-deref` (present in 11 files), `clippy::needless-borrow` (present in 2 files), and `clippy::only-used-in-recursion` (only 1 file).
# Objective
- Do not implement `Copy` or `Clone` for `Fetch` types as this is kind of sus soundness wise (it feels like cloning an `IterMut` in safe code to me). Cloning a fetch seems important to think about soundness wise when doing it so I prefer this over adding a `Clone` bound to the assoc type definition (i.e. `type Fetch: Clone`) even though that would also solve the other listed things here.
- Remove a bunch of `QueryFetch<'w, Q>: Clone` bounds from our API as now all fetches can be "cloned" for use in `iter_combinations`. This should also help avoid the type inference regression ptrification introduced where `for<'a> QueryFetch<'a, Q>: Trait` bounds misbehave since we no longer need any of those kind of higher ranked bounds (although in practice we had none anyway).
- Stop being able to "forget" to implement clone for fetches, we've had a lot of issues where either `derive(Clone)` was used instead of a manual impl (so we ended up with too tight bounds on the impl) or flat out forgot to implement Clone at all. With this change all fetches are able to be cloned for `iter_combinations` so this will no longer be possible to mess up.
On an unrelated note, while making this PR I realised we probably want safety invariants on `archetype/table_fetch` that nothing aliases the table_row/archetype_index according to the access we set.
---
## Changelog
`Clone` and `Copy` were removed from all `Fetch` types.
## Migration Guide
- Call `WorldQuery::clone_fetch` instead of `fetch.clone()`. Make sure to add safety comments :)
# Objective
I was trying to implement a collision system for my game, and believed that the iter_combinations method might be what I need. But I couldn't find a simple explanation of what a combination was in Bevy and thought it could use some more explanation.
## Solution
I added some description to the documentation that can hopefully further elaborate on what a combination is.
I also changed up the docs for the method because a combination is a different thing than a permutation but the Bevy docs seemed to use them interchangeably.
# Objective
- `QueryCombinationIter` can have sizes greater than `usize::MAX`.
- Fixes#5846
## Solution
- Only the implementation of `ExactSizeIterator` has been removed. Instead of using `query_combination.len()`, you can use `query_combination.size_hint().0` to get the same value as before.
---
## Migration Guide
- Switch to using other methods of getting the length.
# Objective
Improve ergonomics by passing on the `IntoIterator` impl of the underlying type to wrapper types.
## Solution
Implement `IntoIterator` for ECS wrapper types (Mut, Local, Res, etc.).
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
- Improve #3953
## Solution
- The very specific circumstances under which the render world is reset meant that the flush_as_invalid function could be replaced with one that had a noop as its init method.
- This removes a double-writing issue leading to greatly increased performance.
Running the reproduction code in the linked issue, this change nearly doubles the framerate.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
Fixes#5559
Replaces #5628
## Solution
Because the generated method from_components() creates an instance of Self my implementation requires any field type that is marked to be ignored to implement Default.
---
## Changelog
Added the possibility to ignore fields in a bundle with `#[bundle(ignore)]`. Typically used when `PhantomData` needs to be added to a `Bundle`.
# Objective
- Fix disabling features in bevy_ecs (broken by #5630)
- Add tests in CI for bevy_ecs, bevy_reflect and bevy as those crates could be use standalone
Add the following message:
```
Items are returned in the order of the list of entities.
Entities that don't match the query are skipped.
```
Additionally, the docs in `iter.rs` and `state.rs` were updated to match those in `query.rs`.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
At least partially addresses #6282.
Resources are currently stored as a dedicated Resource archetype (ID 1). This allows for easy code reusability, but unnecessarily adds 72 bytes (on 64-bit systems) to the struct that is only used for that one archetype. It also requires several fields to be `pub(crate)` which isn't ideal.
This should also remove one sparse-set lookup from fetching, inserting, and removing resources from a `World`.
## Solution
- Add `Resources` parallel to `Tables` and `SparseSets` and extract the functionality used by `Archetype` in it.
- Remove `unique_components` from `Archetype`
- Remove the `pub(crate)` on `Archetype::components`.
- Remove `ArchetypeId::RESOURCE`
- Remove `Archetypes::resource` and `Archetypes::resource_mut`
---
## Changelog
Added: `Resources` type to store resources.
Added: `Storages::resource`
Removed: `ArchetypeId::RESOURCE`
Removed: `Archetypes::resource` and `Archetypes::resources`
Removed: `Archetype::unique_components` and `Archetypes::unique_components_mut`
## Migration Guide
Resources have been moved to `Resources` under `Storages` in `World`. All code dependent on `Archetype::unique_components(_mut)` should access it via `world.storages().resources()` instead.
All APIs accessing the raw data of individual resources (mutable *and* read-only) have been removed as these APIs allowed for unsound unsafe code. All usages of these APIs should be changed to use `World::{get, insert, remove}_resource`.
# Objective
Speed up queries that are fragmented over many empty archetypes and tables.
## Solution
Add a early-out to check if the table or archetype is empty before iterating over it. This adds an extra branch for every archetype matched, but skips setting the archetype/table to the underlying state and any iteration over it.
This may not be worth it for the default `Query::iter` and maybe even the `Query::for_each` implementations, but this definitely avoids scheduling unnecessary tasks in the `Query::par_for_each` case.
Ideally, `matched_archetypes` should only contain archetypes where there's actually work to do, but this would add a `O(n)` flat cost to every call to `update_archetypes` that scales with the number of matched archetypes.
TODO: Benchmark
# Objective
- Fixes#6206
## Solution
- Create a constructor for creating `ReflectComponent` and `ReflectResource`
---
## Changelog
> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.
### Added
- Created constructors for `ReflectComponent` and `ReflectResource`, allowing for advanced scripting use-cases.
# Objective
There is currently no good way of getting the width (# of components) of a table outside of `bevy_ecs`.
# Solution
Added the methods `Table::{component_count, component_capacity}`
For consistency and clarity, renamed `Table::{len, capacity}` to `entity_count` and `entity_capacity`.
## Changelog
- Added the methods `Table::component_count` and `Table::component_capacity`
- Renamed `Table::len` and `Table::capacity` to `entity_count` and `entity_capacity`
## Migration Guide
Any use of `Table::len` should now be `Table::entity_count`. Any use of `Table::capacity` should now be `Table::entity_capacity`.
# Objective
- Add a way to iterate over all entities from &World
## Solution
- Added a function `iter_entities` on World which returns an iterator of `Entity` derived from the entities in the `World`'s `archetypes`
---
## Changelog
- Added a function `iter_entities` on World, allowing iterating over all entities in contexts where you only have read-only access to the World.
# Objective
> System chaining is a confusing name: it implies the ability to construct non-linear graphs, and suggests a sense of system ordering that is only incidentally true. Instead, it actually works by passing data from one system to the next, much like the pipe operator.
> In the accepted [stageless RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/45-stageless.md), this concept is renamed to piping, and "system chaining" is used to construct groups of systems with ordering dependencies between them.
Fixes#6225.
## Changelog
System chaining has been renamed to system piping to improve clarity (and free up the name for new ordering APIs).
## Migration Guide
The `.chain(handler_system)` method on systems is now `.pipe(handler_system)`.
The `IntoChainSystem` trait is now `IntoPipeSystem`, and the `ChainSystem` struct is now `PipeSystem`.
# Objective
- Adding Debug implementations for App, Stage, Schedule, Query, QueryState.
- Fixes#1130.
## Solution
- Implemented std::fmt::Debug for a number of structures.
---
## Changelog
Also added Debug implementations for ParallelSystemExecutor, SingleThreadedExecutor, various RunCriteria structures, SystemContainer, and SystemDescriptor.
Opinions are sure to differ as to what information to provide in a Debug implementation. Best guess was taken for this initial version for these structures.
Co-authored-by: targrub <62773321+targrub@users.noreply.github.com>
# Objective
When designing an API, you may wish to provide access only to a specific field of a component or resource. The current options for doing this in safe code are
* `*Mut::into_inner`, which flags a change no matter what.
* `*Mut::bypass_change_detection`, which misses all changes.
## Solution
Add the method `map_unchanged`.
### Example
```rust
// When run, zeroes the translation of every entity.
fn reset_all(mut transforms: Query<&mut Transform>) {
for transform in &mut transforms {
// We pinky promise not to modify `t` within the closure.
let translation = transform.map_unchanged(|t| &mut t.translation);
// Only reset the translation if it isn't already zero.
translation.set_if_not_equal(Vec2::ZERO);
}
}
```
---
## Changelog
+ Added the method `map_unchanged` to types `Mut<T>`, `ResMut<T>`, and `NonSendMut<T>`.
# Background
Incremental implementation of #4299. The code is heavily borrowed from that PR.
# Objective
The execution order ambiguity checker often emits false positives, since bevy is not aware of invariants upheld by the user.
## Solution
Title
---
## Changelog
+ Added methods `SystemDescriptor::ignore_all_ambiguities` and `::ambiguous_with`. These allow you to silence warnings for specific system-order ambiguities.
## Migration Guide
***Note for maintainers**: This should replace the migration guide for #5916*
Ambiguity sets have been replaced with a simpler API.
```rust
// These systems technically conflict, but we don't care which order they run in.
fn jump_on_click(mouse: Res<Input<MouseButton>>, mut transforms: Query<&mut Transform>) { ... }
fn jump_on_spacebar(keys: Res<Input<KeyCode>>, mut transforms: Query<&mut Transform>) { ... }
//
// Before
#[derive(AmbiguitySetLabel)]
struct JumpSystems;
app
.add_system(jump_on_click.in_ambiguity_set(JumpSystems))
.add_system(jump_on_spacebar.in_ambiguity_set(JumpSystems));
//
// After
app
.add_system(jump_on_click.ambiguous_with(jump_on_spacebar))
.add_system(jump_on_spacebar);
```
