This MR is a rebased and alternative proposal to
https://github.com/bevyengine/bevy/pull/5602
# Objective
- https://github.com/bevyengine/bevy/pull/4447 implemented untyped
(using component ids instead of generics and TypeId) APIs for
inserting/accessing resources and accessing components, but left
inserting components for another PR (this one)
## Solution
- add `EntityMut::insert_by_id`
- split `Bundle` into `DynamicBundle` with `get_components` and `Bundle:
DynamicBundle`. This allows the `BundleInserter` machinery to be reused
for bundles that can only be written, not read, and have no statically
available `ComponentIds`
- Compared to the original MR this approach exposes unsafe endpoints and
requires the user to manage instantiated `BundleIds`. This is quite easy
for the end user to do and does not incur the performance penalty of
checking whether component input is correctly provided for the
`BundleId`.
- This MR does ensure that constructing `BundleId` itself is safe
---
## Changelog
- add methods for inserting bundles and components to:
`world.entity_mut(entity).insert_by_id`
# Objective
#7863 introduced a potential footgun. When trying to incorrectly add a user-defined type using `in_base_set`, the compiler will suggest that the user implement `BaseSystemSet` for their type. This is a reasonable-sounding suggestion, however this is not the correct way to make a base set, and will lead to a confusing panic message when a marker trait is implemented for the wrong type.
## Solution
Rewrite the documentation for these traits, making it more clear that `BaseSystemSet` is a marker for types that are already base sets, and not a way to define a base set.
# Objective
The trait `IntoSystemConfig<>` requires each implementer to repeat every single member method, even though they can all be implemented by just deferring to `SystemConfig`.
## Solution
Add default implementations to most member methods.
# Objective
Base sets, added in #7466 are a special type of system set. Systems can only be added to base sets via `in_base_set`, while non-base sets can only be added via `in_set`. Unfortunately this is currently guarded by a runtime panic, which presents an unfortunate toe-stub when the wrong method is used. The delayed response between writing code and encountering the error (possibly hours) makes the distinction between base sets and other sets much more difficult to learn.
## Solution
Add the marker traits `BaseSystemSet` and `FreeSystemSet`. `in_base_set` and `in_set` now respectively accept these traits, which moves the runtime panic to a compile time error.
---
## Changelog
+ Added the marker trait `BaseSystemSet`, which is distinguished from a `FreeSystemSet`. These are both subtraits of `SystemSet`.
## Migration Guide
None if merged with 0.10
…or's ticker for one thread.
# Objective
- Fix debug_asset_server hang.
## Solution
- Reuse the thread_local executor for MainThreadExecutor resource, so there will be only one ThreadExecutor for main thread.
- If ThreadTickers from same executor, they are conflict with each other. Then only tick one.
# Objective
The `ScheduleBuildError` type has a `Display` implementation which beautifully formats the error. However, schedule build errors are currently reported using `unwrap()`, which uses the `Debug` implementation and makes the error message look unfished.
## Solution
Use `unwrap_or_else` so we can customize the formatting of the error message.
# Objective
Several `Query` methods unnecessarily place the call to `Query::update_archetypes` inside of unsafe blocks.
## Solution
Move the method calls out of the unsafe blocks.
# Objective
There is a panic that occurs when creating a run condition that accesses `NonSend` resources, but it refers to them as 'thread-local' resources instead.
## Solution
Correct the terminology.
# Objective
This is a follow-up to #7745. An unbounded `async_channel` occasionally allocates whenever it exceeds the capacity of the current buffer in it's internal linked list. This is avoidable.
This also used to be a bounded channel before stageless, which was introduced in #4919.
## Solution
Use a bounded channel to avoid allocations on system completion.
This shouldn't conflict with #7745, as it's impossible for the scheduler to exceed the channel capacity, even if somehow every system completed at the same time.
`EntityMut::move_entity_from_remove` had two soundness bugs:
- When removing the entity from the archetype, the swapped entity had its table row updated to the same as the removed entity's
- When removing the entity from the table, the swapped entity did not have its table row updated
`BundleInsert::insert` had two/three soundness bugs
- When moving an entity to a new archetype from an `insert`, the swapped entity had its table row set to a different entities
- When moving an entity to a new table from an `insert`, the swapped entity did not have its table row updated
See added tests for examples that trigger those bugs
`EntityMut::despawn` had two soundness bugs
- When despawning an entity, the swapped entity had its table row set to a different entities even if the table didnt change
- When despawning an entity, the swapped entity did not have its table row updated
# Objective
- A more intuitive distinction between the two. `remove_intersection` is verbose and unclear.
- `EntityMut::remove` and `Commands::remove` should match.
## Solution
- What the title says.
---
## Migration Guide
Before
```rust
fn clear_children(parent: Entity, world: &mut World) {
if let Some(children) = world.entity_mut(parent).remove::<Children>() {
for &child in &children.0 {
world.entity_mut(child).remove_intersection::<Parent>();
}
}
}
```
After
```rust
fn clear_children(parent: Entity, world: &mut World) {
if let Some(children) = world.entity_mut(parent).take::<Children>() {
for &child in &children.0 {
world.entity_mut(child).remove::<Parent>();
}
}
}
```
# Objective
Support the following syntax for adding systems:
```rust
App::new()
.add_system(setup.on_startup())
.add_systems((
show_menu.in_schedule(OnEnter(GameState::Paused)),
menu_ssytem.in_set(OnUpdate(GameState::Paused)),
hide_menu.in_schedule(OnExit(GameState::Paused)),
))
```
## Solution
Add the traits `IntoSystemAppConfig{s}`, which provide the extension methods necessary for configuring which schedule a system belongs to. These extension methods return `IntoSystemAppConfig{s}`, which `App::add_system{s}` uses to choose which schedule to add systems to.
---
## Changelog
+ Added the extension methods `in_schedule(label)` and `on_startup()` for configuring the schedule a system belongs to.
## Future Work
* Replace all uses of `add_startup_system` in the engine.
* Deprecate this method
# Objective
While we use `#[doc(hidden)]` to try and hide marker generics from the user, these types reveal themselves in compiler errors, adding visual noise and confusion.
## Solution
Replace the `AlreadyWasSystem` marker generic with `()`, to reduce visual noise in error messages. This also makes it possible to return `impl Condition<()>` from combinators.
For function systems, use their function signature as the marker type. This should drastically improve the legibility of some error messages.
The `InputMarker` type has been removed, since it is unnecessary.
# Objective
Several places in the ECS use marker generics to avoid overlapping trait implementations, but different places alternately refer to it as `Params` and `Marker`. This is potentially confusing, since it might not be clear that the same pattern is being used. Additionally, users might be misled into thinking that the `Params` type corresponds to the `SystemParam`s of a system.
## Solution
Rename `Params` to `Marker`.
# Objective
Fixes#3980
## Solution
Added examples to show how to run a `Schedule`, one with a unique system, and another with several systems
---
## Changelog
- Added: examples in docs to show how to run a `Schedule`
Co-authored-by: remiCzn <77072160+remiCzn@users.noreply.github.com>
# Objective
The `BoxedCondition` type alias does not require the underlying system to be read-only.
## Solution
Define the type alias using `ReadOnlySystem` instead of `System`.
Graph theory make head hurty. Closes#7367.
Basically, when we topologically sort the dependency graph, we already find its strongly-connected components (a really [neat algorithm][1]). This PR adds an algorithm that can dissect those into simple cycles, giving us more useful error reports.
test: `system_build_errors::dependency_cycle`
```
schedule has 1 before/after cycle(s):
cycle 1: system set 'A' must run before itself
system set 'A'
... which must run before system set 'B'
... which must run before system set 'A'
```
```
schedule has 1 before/after cycle(s):
cycle 1: system 'foo' must run before itself
system 'foo'
... which must run before system 'bar'
... which must run before system 'foo'
```
test: `system_build_errors::hierarchy_cycle`
```
schedule has 1 in_set cycle(s):
cycle 1: system set 'A' contains itself
system set 'A'
... which contains system set 'B'
... which contains system set 'A'
```
[1]: https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm
Add some more useful common run conditions.
Some of these existed in `iyes_loopless`. I know people used them, and it would be a regression for those users, when they try to migrate to new Bevy stageless, if they are missing.
I also took the opportunity to add a few more new ones.
---
## Changelog
### Added
- More "common run conditions": on_event, resource change detection, state_changed, any_with_component
# Objective
Fix#5026.
## Solution
Only make a `trace!` log if the event count changed.
---
## Changelog
Changed: `EventWriter::send_batch` will only log a TRACE level log if the batch is non-empty.
