# Objective
Fixes#14511.
`despawn` allows you to remove entities from the world. However, if the
entity does not exist, it emits a warning. This may not be intended
behavior for many users who have use cases where they need to call
`despawn` regardless of if the entity actually exists (see the issue),
or don't care in general if the entity already doesn't exist.
(Also trying to gauge interest on if this feature makes sense, I'd
personally love to have it, but I could see arguments that this might be
a footgun. Just trying to help here 😄 If there's no contention I could
also implement this for `despawn_recursive` and `despawn_descendants` in
the same PR)
## Solution
Add `try_despawn`, `try_despawn_recursive` and
`try_despawn_descendants`.
Modify `World::despawn_with_caller` to also take in a `warn` boolean
argument, which is then considered when logging the warning. Set
`log_warning` to `true` in the case of `despawn`, and `false` in the
case of `try_despawn`.
## Testing
Ran `cargo run -p ci` on macOS, it seemed fine.
As discussed in #15521
- Partial revert of #14897, reverting the change to the methods to
consume `self`
- The `insert_if` method is kept
The migration guide of #14897 should be removed
Closes#15521
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
> [!NOTE]
> This is my first PR, so if something is incorrect
> or missing, please let me know :3
# Objective
- Clarifies `spawn`, `spawn_batch` and `ParallelCommands` docs about
performance and use cases
- Fixes#15472
## Solution
Add comments to `spawn`, `spawn_batch` and `ParallelCommands` to clarify
the
intended use case and link to other/better ways of doing spawning things
for
certain use cases.
# Objective
- Fixes#6370
- Closes#6581
## Solution
- Added the following lints to the workspace:
- `std_instead_of_core`
- `std_instead_of_alloc`
- `alloc_instead_of_core`
- Used `cargo +nightly fmt` with [item level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Item%5C%3A)
to split all `use` statements into single items.
- Used `cargo clippy --workspace --all-targets --all-features --fix
--allow-dirty` to _attempt_ to resolve the new linting issues, and
intervened where the lint was unable to resolve the issue automatically
(usually due to needing an `extern crate alloc;` statement in a crate
root).
- Manually removed certain uses of `std` where negative feature gating
prevented `--all-features` from finding the offending uses.
- Used `cargo +nightly fmt` with [crate level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Crate%5C%3A)
to re-merge all `use` statements matching Bevy's previous styling.
- Manually fixed cases where the `fmt` tool could not re-merge `use`
statements due to conditional compilation attributes.
## Testing
- Ran CI locally
## Migration Guide
The MSRV is now 1.81. Please update to this version or higher.
## Notes
- This is a _massive_ change to try and push through, which is why I've
outlined the semi-automatic steps I used to create this PR, in case this
fails and someone else tries again in the future.
- Making this change has no impact on user code, but does mean Bevy
contributors will be warned to use `core` and `alloc` instead of `std`
where possible.
- This lint is a critical first step towards investigating `no_std`
options for Bevy.
---------
Co-authored-by: François Mockers <francois.mockers@vleue.com>
# Objective
- Fixes#15373
- Fixes
https://github.com/bevyengine/bevy/pull/14920#issuecomment-2370428013
## Solution
- Make `IntoSystem::pipe` and `IntoSystem::map` return two new
(possibly-ZST) types that implement `IntoSystem` and whose `into_system`
method return the systems that were previously being returned by
`IntoSystem::pipe` and `IntoSystem::map`
- Don't eagerly call `IntoSystem::into_system` on the argument given to
`RunSystemCachedWith::new` to avoid losing its ZST-ness
## Testing
- Added a regression test for each issue
## Migration Guide
- `IntoSystem::pipe` and `IntoSystem::map` now return `IntoPipeSystem`
and `IntoAdapterSystem` instead of `PipeSystem` and `AdapterSystem`.
Most notably these types don't implement `System` but rather only
`IntoSystem`.
# Objective
- Fixes#14924
- Closes#9584
## Solution
- We introduce a new trait, `SystemInput`, that serves as a type
function from the `'static` form of the input, to its lifetime'd
version, similarly to `SystemParam` or `WorldQuery`.
- System functions now take the lifetime'd wrapped version,
`SystemInput::Param<'_>`, which prevents the issue presented in #14924
(i.e. `InRef<T>`).
- Functions for running systems now take the lifetime'd unwrapped
version, `SystemInput::Inner<'_>` (i.e. `&T`).
- Due to the above change, system piping had to be re-implemented as a
standalone type, rather than `CombinatorSystem` as it was previously.
- Removes the `Trigger<'static, E, B>` transmute in observer runner
code.
## Testing
- All current tests pass.
- Added additional tests and doc-tests.
---
## Showcase
```rust
let mut world = World::new();
let mut value = 2;
// Currently possible:
fn square(In(input): In<usize>) -> usize {
input * input
}
value = world.run_system_once_with(value, square);
// Now possible:
fn square_mut(InMut(input): InMut<usize>) {
*input *= *input;
}
world.run_system_once_with(&mut value, square_mut);
// Or:
fn square_ref(InRef(input): InRef<usize>) -> usize {
*input * *input
}
value = world.run_system_once_with(&value, square_ref);
```
## Migration Guide
- All current explicit usages of the following types must be changed in
the way specified:
- `SystemId<I, O>` to `SystemId<In<I>, O>`
- `System<In = T>` to `System<In = In<T>>`
- `IntoSystem<I, O, M>` to `IntoSystem<In<I>, O, M>`
- `Condition<M, T>` to `Condition<M, In<T>>`
- `In<Trigger<E, B>>` is no longer a valid input parameter type. Use
`Trigger<E, B>` directly, instead.
---------
Co-authored-by: Giacomo Stevanato <giaco.stevanato@gmail.com>
# Objective
The goal of this PR is to introduce `SystemParam` validation in order to
reduce runtime panics.
Fixes#15265
## Solution
`SystemParam` now has a new method `validate_param(...) -> bool`, which
takes immutable variants of `get_param` arguments. The returned value
indicates whether the parameter can be acquired from the world. If
parameters cannot be acquired for a system, it won't be executed,
similarly to run conditions. This reduces panics when using params like
`Res`, `ResMut`, etc. as well as allows for new, ergonomic params like
#15264 or #15302.
Param validation happens at the level of executors. All validation
happens directly before executing a system, in case of normal systems
they are skipped, in case of conditions they return false.
Warning about system skipping is primitive and subject to change in
subsequent PRs.
## Testing
Two executor tests check that all executors:
- skip systems which have invalid parameters:
- piped systems get skipped together,
- dependent systems still run correctly,
- skip systems with invalid run conditions:
- system conditions have invalid parameters,
- system set conditions have invalid parameters.
# Objective
Working with `World` is painful due to lifetime issues and a lack of
ergonomics, so you may want to delegate to the system API. Your current
options are:
- `world.run_system_once`, which initializes the system each time it's
called (performance cost) and doesn't support `Local`. The docs
recommend users not use this method outside of diagnostic use cases like
unit tests.
- `world.run_system`, which requires you to register the system and
store the `SystemId` somewhere (made easier by implementing `FromWorld`
for a newtyped `Local`, unless you're in e.g. a custom `Command` impl).
These options work, but you're choosing between a performance cost and
an ergonomic challenge.
## Solution
Provide a cached `run_system` API that accepts an `S: IntoSystem` and
checks for a `CachedSystemId<S::System>(SystemId)` resource. If it
doesn't exist, it will register the system and save its `SystemId` in
that resource.
In other words, it hides the "save the `SystemId` in a `Local` or
`Resource`" pattern as an implementation detail.
Prior work: https://github.com/bevyengine/bevy/pull/10469.
## Testing
This approach worked in a proof-of-concept:
b34ee29531/src/util/patch/run_system_cached.rs (L35).
A new unit test was added and it passes in CI.
# Objective
It's convenient to be able to modify a component if it exist, and insert
a default value if it doesn't. You can already do most of this with
`EntityCommands::insert_if_new`, and all of this using a custom command.
However, that does not spark joy in my opinion.
Closes#10669
## Solution
Introduce a new commands type `EntityEntryCommands`, along with a method
to access it, `EntityCommands::entry`.
`EntityEntryCommands` exposes a subset of the entry API (`and_modify`,
`or_insert`, etc), however it's not an enum so it doesn't allow pattern
matching. Also, `or_insert` won't return the component because it's all
based on commands.
## Testing
Added a new test `entity_commands_entry`.
---
## Showcase
```rust
commands
.entity(player)
.entry::<Level>()
.and_modify(|mut lvl| lvl.0 += 1)
.or_default();
```
---------
Co-authored-by: Jan Hohenheim <jan@hohenheim.ch>
# Objective
- Fixes#15106
## Solution
- Trivial refactor to rename the method. The duplicate method `push` was
removed as well. This will simpify the API and make the semantics more
clear. `Add` implies that the action happens immediately, whereas in
reality, the command is queued to be run eventually.
- `ChildBuilder::add_command` has similarly been renamed to
`queue_command`.
## Testing
Unit tests should suffice for this simple refactor.
---
## Migration Guide
- `Commands::add` and `Commands::push` have been replaced with
`Commnads::queue`.
- `ChildBuilder::add_command` has been renamed to
`ChildBuilder::queue_command`.
# Objective
- Adds the missing API commands `insert_if_new_and` and
`try_insert_if_new_and` (resolves#15105)
- Adds some test coverage for existing insert commands
## Testing
- Implemented additional unit tests to add coverage
# Objective
A previous issue describes the same problem: #14248.
This particular link was seemingly missed by #14276.
## Solution
- Search repo for `bevyengine.org/learn/errors/#`
- Remove `#`
- Verify link goes to right place
# Objective
sending events tends to be low-frequency so ergonomics can be
prioritized over efficiency.
add `Commands::send_event` to send any type of event without needing a
writer in hand.
i don't know how we feel about these kind of ergonomic things, i add
this to all my projects and find it useful. adding `mut
this_particular_event_writer: EventWriter<ThisParticularEvent>` every
time i want to send something is unnecessarily cumbersome.
it also simplifies the "send and receive in the same system" pattern
significantly.
basic example before:
```rs
fn my_func(
q: Query<(Entity, &State)>,
mut damage_event_writer: EventWriter<DamageEvent>,
mut heal_event_writer: EventWriter<HealEvent>,
) {
for (entity, state) in q.iter() {
if let Some(damage) = state.get_damage() {
damage_event_writer.send(DamageEvent { entity, damage });
}
if let Some(heal) = state.get_heal() {
heal_event_writer.send(HealEvent { entity, heal });
}
}
}
```
basic example after:
```rs
import bevy::ecs::event::SendEventEx;
fn my_func(
mut commands: Commands,
q: Query<(Entity, &State)>,
) {
for (entity, state) in q.iter() {
if let Some(damage) = state.get_damage() {
commands.send_event(DamageEvent { entity, damage });
}
if let Some(heal) = state.get_heal() {
commands.send_event(HealEvent { entity, heal });
}
}
}
```
send/receive in the same system before:
```rs
fn send_and_receive_param_set(
mut param_set: ParamSet<(EventReader<DebugEvent>, EventWriter<DebugEvent>)>,
) {
// We must collect the events to resend, because we can't access the writer while we're iterating over the reader.
let mut events_to_resend = Vec::new();
// This is p0, as the first parameter in the `ParamSet` is the reader.
for event in param_set.p0().read() {
if event.resend_from_param_set {
events_to_resend.push(event.clone());
}
}
// This is p1, as the second parameter in the `ParamSet` is the writer.
for mut event in events_to_resend {
event.times_sent += 1;
param_set.p1().send(event);
}
}
```
after:
```rs
use bevy::ecs::event::SendEventEx;
fn send_via_commands_and_receive(
mut reader: EventReader<DebugEvent>,
mut commands: Commands,
) {
for event in reader.read() {
if event.resend_via_commands {
commands.send_event(DebugEvent {
times_sent: event.times_sent + 1,
..event.clone()
});
}
}
}
```
---------
Co-authored-by: Jan Hohenheim <jan@hohenheim.ch>
# Objective
Fixes#14883
## Solution
Pretty simple update to `EntityCommands` methods to consume `self` and
return it rather than taking `&mut self`. The things probably worth
noting:
* I added `#[allow(clippy::should_implement_trait)]` to the `add` method
because it causes a linting conflict with `std::ops::Add`.
* `despawn` and `log_components` now return `Self`. I'm not sure if
that's exactly the desired behavior so I'm happy to adjust if that seems
wrong.
## Testing
Tested with `cargo run -p ci`. I think that should be sufficient to call
things good.
## Migration Guide
The most likely migration needed is changing code from this:
```
let mut entity = commands.get_or_spawn(entity);
if depth_prepass {
entity.insert(DepthPrepass);
}
if normal_prepass {
entity.insert(NormalPrepass);
}
if motion_vector_prepass {
entity.insert(MotionVectorPrepass);
}
if deferred_prepass {
entity.insert(DeferredPrepass);
}
```
to this:
```
let mut entity = commands.get_or_spawn(entity);
if depth_prepass {
entity = entity.insert(DepthPrepass);
}
if normal_prepass {
entity = entity.insert(NormalPrepass);
}
if motion_vector_prepass {
entity = entity.insert(MotionVectorPrepass);
}
if deferred_prepass {
entity.insert(DeferredPrepass);
}
```
as can be seen in several of the example code updates here. There will
probably also be instances where mutable `EntityCommands` vars no longer
need to be mutable.
# Objective
Fixes#14782
## Solution
Enable the lint and fix all upcoming hints (`--fix`). Also tried to
figure out the false-positive (see review comment). Maybe split this PR
up into multiple parts where only the last one enables the lint, so some
can already be merged resulting in less many files touched / less
potential for merge conflicts?
Currently, there are some cases where it might be easier to read the
code with the qualifier, so perhaps remove the import of it and adapt
its cases? In the current stage it's just a plain adoption of the
suggestions in order to have a base to discuss.
## Testing
`cargo clippy` and `cargo run -p ci` are happy.
# Objective
Fixes Commands not being `Send` or `Sync` anymore in 0.14 by
implementing `Send` and `Sync` for `RawCommandQueue`.
## Solution
Reference discussion in
[discord](https://discord.com/channels/691052431525675048/691052431974465548/1259464518539411570).
It seems that in https://github.com/bevyengine/bevy/pull/13249, when
adding a `RawCommandQueue` variant to the `InternalQueue`, the `Send /
Sync` traits were not implemented for it, which bubbled up all the way
to `Commands` not being `Send / Sync` anymore.
I am not very familiar with the ECS internals so I can't say whether the
`RawCommandQueue` is safe to be shared between threads, but I know for
sure that before the linked PR `Commands` were indeed `Send` and `Sync`
so that PR broke "some workflows" (mandatory
[xkcd](https://xkcd.com/1172/)).
## Testing
This PR itself includes a compile test to make sure `Commands` will
implement `Send` and `Sync`. The test itself fails without the
implementation and succeeds with it.
Furthermore, if I cherry pick the test to a previous release (i.e. 0.13)
it indeed succeeds, showing that this is a regression specific to 0.14.
---------
Signed-off-by: Luca Della Vedova <lucadv@intrinsic.ai>
# Objective
Fix#14771 by adding a `try_insert_if_new` method to the
`EntityCommands`
## Solution
This simply calls the `try_insert` function with `InsertMode::Keep`
## Testing
I did not add any test because `EntityCommands::try_insert` does not
seem to be tested either. I can add some if needed.
# Objective
Often there are reasons to insert some components (e.g. Transform)
separately from the rest of a bundle (e.g. PbrBundle). However `insert`
overwrites existing components, making this difficult.
See also issue #14397Fixes#2054.
## Solution
This PR adds the method `insert_if_new` to EntityMut and Commands, which
is the same as `insert` except that the old component is kept in case of
conflicts.
It also renames some internal enums (from `ComponentStatus::Mutated` to
`Existing`), to reflect the possible change in meaning.
## Testing
*Did you test these changes? If so, how?*
Added basic unit tests; used the new behavior in my project.
*Are there any parts that need more testing?*
There should be a test that the change time isn't set if a component is
not overwritten; I wasn't sure how to write a test for that case.
*How can other people (reviewers) test your changes? Is there anything
specific they need to know?*
`cargo test` in the bevy_ecs project.
*If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?*
Only tested on Windows, but it doesn't touch anything platform-specific.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Giacomo Stevanato <giaco.stevanato@gmail.com>
# Objective
B0003 indicates that you tried to act upon a nonexistant entity, but
does not mention where the error occured:
```
2024-07-31T15:46:25.954840Z WARN bevy_ecs::world: error[B0003]: Could not despawn entity Entity { index: 4294967295, generation: 1 } because it doesn't exist in this World. See: https://bevyengine.org/learn/errors/b0003
```
## Solution
Include caller location:
```
2024-07-31T15:46:25.954840Z WARN bevy_ecs::world: error[B0003]: src/main.rs:18:11: Could not despawn entity Entity { index: 4294967295, generation: 1 } because it doesn't exist in this World. See: https://bevyengine.org/learn/errors/b0003
```
Open question: What should the exact message format be?
## Testing
None, this doesn't change any logic.
# Objective
- Make it possible to know *what* changed your component or resource.
- Common need when debugging, when you want to know the last code
location that mutated a value in the ECS.
- This feature would be very useful for the editor alongside system
stepping.
## Solution
- Adds the caller location to column data.
- Mutations now `track_caller` all the way up to the public API.
- Commands that invoke these functions immediately call
`Location::caller`, and pass this into the functions, instead of the
functions themselves attempting to get the caller. This would not work
for commands which are deferred, as the commands are executed by the
scheduler, not the user's code.
## Testing
- The `component_change_detection` example now shows where the component
was mutated:
```
2024-07-28T06:57:48.946022Z INFO component_change_detection: Entity { index: 1, generation: 1 }: New value: MyComponent(0.0)
2024-07-28T06:57:49.004371Z INFO component_change_detection: Entity { index: 1, generation: 1 }: New value: MyComponent(1.0)
2024-07-28T06:57:49.012738Z WARN component_change_detection: Change detected!
-> value: Ref(MyComponent(1.0))
-> added: false
-> changed: true
-> changed by: examples/ecs/component_change_detection.rs:36:23
```
- It's also possible to inspect change location from a debugger:
<img width="608" alt="image"
src="https://github.com/user-attachments/assets/c90ecc7a-0462-457a-80ae-42e7f5d346b4">
---
## Changelog
- Added source locations to ECS change detection behind the
`track_change_detection` flag.
## Migration Guide
- Added `changed_by` field to many internal ECS functions used with
change detection when the `track_change_detection` feature flag is
enabled. Use Location::caller() to provide the source of the function
call.
---------
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
# Objective
- Allow queuing insertion of dynamic components to an existing entity
## Solution
- Add `insert_by_id<T: Send + 'static>(commands: &mut EntityCommands,
component_id: ComponentId, value: T)` and the `try_insert_by_id`
counterpart
## Testing
TODO
- Did you test these changes? If so, how?
- Are there any parts that need more testing?
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
## Alternatives
This PR is not feature-complete for dynamic components. In particular,
it
- only supports one component
- only supports adding components with a known, sized type
These were not implemented because doing so would require enhancing
`CommandQueue` to support pushing unsized commands (or equivalently,
pushing commands with a buffer of data). Even so, the cost would not be
transparent compared to the implementation in this PR, which simply
captures the `ComponentId` and `value: T` into the command closure and
can be easily memcpy'ed to the stack during execution. For example, to
efficiently pass `&[ComponentId]` from the caller to the world, we would
need to:
1. Update `CommandQueue.bytes` from `Vec<MaybeUninit<u8>>` to
`Vec<MaybeUninit<usize>>` so that it has the same alignment as
`ComponentId` (which probably needs to be made `#[repr(transparent)]`
too)
2. After pushing the Command metadata, push padding bytes until the vec
len is a multiple of `size_of::<usize>()`
3. Store `components.len()` in the data
4. memcpy the user-provided `&[ComponentId]` to `CommandQueue.bytes`
5. During execution, round up the data pointer behind the `Command` to
skip padding, then cast the pointer and consume it as a `&[ComponentId]`
The effort here seems unnecessarily high, unless someone else has such a
requirement. At least for the use case I am working with, I only need a
single known type, and if we need multiple components, we could always
enhance this function to accept a `[ComponentId; N]`.
I recommend enhancing the `Bundle` API in the long term to achieve this
goal more elegantly.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Felix Rath <felixm.rath@gmail.com>
# Objective
`TriggerTargets` can not be borrowed for use in `World::trigger_targets`
## Solution
Drop `'static` bound on `TriggerEvent`, keep it for `Command` impl.
## Testing
n/a
# Objective
`Commands::spawn_empty` docs say that it queues a command to spawn an
entity, but it doesn't. It immediately reserves an `Entity` to be
spawned at the next flush point, which is possible because
`Entities::reserve_entity()` takes `&self` and no components are added
yet.
## Solution
Fix docs.
# Objective
- Bevy currently has lot of invalid intra-doc links, let's fix them!
- Also make CI test them, to avoid future regressions.
- Helps with #1983 (but doesn't fix it, as there could still be explicit
links to docs.rs that are broken)
## Solution
- Make `cargo r -p ci -- doc-check` check fail on warnings (could also
be changed to just some specific lints)
- Manually fix all the warnings (note that in some cases it was unclear
to me what the fix should have been, I'll try to highlight them in a
self-review)
# Objective
Fixes#14248 and other URL issues.
## Solution
- Describe the solution used to achieve the objective above.
Removed the random #s in the URL. Led users to the wrong page. For
example, https://bevyengine.org/learn/errors/#b0003 takes users to
https://bevyengine.org/learn/errors/introduction, which is not the right
page. Removing the #s fixes it.
## Testing
- Did you test these changes? If so, how?
I pasted the URL into my address bar and it took me to the right place.
- Are there any parts that need more testing?
No
# Objective
When using combinators such as `EntityCommand::with_entity` to build
commands, it can be easy to forget to apply that command, leading to
dead code. In many cases this doesn't even lead to an unused variable
warning, which can make these mistakes difficult to track down
## Solution
Annotate the method with `#[must_use]`
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
The trait method `with_entity` is used to add an `EntityCommand` to the
command queue. Currently this method returns `WithEntity<C>` which pairs
a command with an `Entity`. By replacing this explicit type with an
opaque type, implementors can override this default implementation by
returning a custom command or closure that does the same thing with a
lower memory footprint.
# Solution
Return an opaque type from the method. As a bonus this file is now
cleaner without the `WithEntity` boilerplate
# Objective
Fixes#13933.
## Solution
Changed the return type.
## Testing
Fixed and reused the pre-existing tests for `inspect_entity`.
---
## Migration Guide
- `World::inspect_entity` now returns an `Iterator` instead of a `Vec`.
If you need a `Vec`, immediately collect the iterator:
`world.inspect_entity(entity).collect<Vec<_>>()`
# Objective
- Provide an expressive way to register dynamic behavior in response to
ECS changes that is consistent with existing bevy types and traits as to
provide a smooth user experience.
- Provide a mechanism for immediate changes in response to events during
command application in order to facilitate improved query caching on the
path to relations.
## Solution
- A new fundamental ECS construct, the `Observer`; inspired by flec's
observers but adapted to better fit bevy's access patterns and rust's
type system.
---
## Examples
There are 3 main ways to register observers. The first is a "component
observer" that looks like this:
```rust
world.observe(|trigger: Trigger<OnAdd, Transform>, query: Query<&Transform>| {
let transform = query.get(trigger.entity()).unwrap();
});
```
The above code will spawn a new entity representing the observer that
will run it's callback whenever the `Transform` component is added to an
entity. This is a system-like function that supports dependency
injection for all the standard bevy types: `Query`, `Res`, `Commands`
etc. It also has a `Trigger` parameter that provides information about
the trigger such as the target entity, and the event being triggered.
Importantly these systems run during command application which is key
for their future use to keep ECS internals up to date. There are similar
events for `OnInsert` and `OnRemove`, and this will be expanded with
things such as `ArchetypeCreated`, `TableEmpty` etc. in follow up PRs.
Another way to register an observer is an "entity observer" that looks
like this:
```rust
world.entity_mut(entity).observe(|trigger: Trigger<Resize>| {
// ...
});
```
Entity observers run whenever an event of their type is triggered
targeting that specific entity. This type of observer will de-spawn
itself if the entity (or entities) it is observing is ever de-spawned so
as to not leave dangling observers.
Entity observers can also be spawned from deferred contexts such as
other observers, systems, or hooks using commands:
```rust
commands.entity(entity).observe(|trigger: Trigger<Resize>| {
// ...
});
```
Observers are not limited to in built event types, they can be used with
any type that implements `Event` (which has been extended to implement
Component). This means events can also carry data:
```rust
#[derive(Event)]
struct Resize { x: u32, y: u32 }
commands.entity(entity).observe(|trigger: Trigger<Resize>, query: Query<&mut Size>| {
let event = trigger.event();
// ...
});
// Will trigger the observer when commands are applied.
commands.trigger_targets(Resize { x: 10, y: 10 }, entity);
```
You can also trigger events that target more than one entity at a time:
```rust
commands.trigger_targets(Resize { x: 10, y: 10 }, [e1, e2]);
```
Additionally, Observers don't _need_ entity targets:
```rust
app.observe(|trigger: Trigger<Quit>| {
})
commands.trigger(Quit);
```
In these cases, `trigger.entity()` will be a placeholder.
Observers are actually just normal entities with an `ObserverState` and
`Observer` component! The `observe()` functions above are just shorthand
for:
```rust
world.spawn(Observer::new(|trigger: Trigger<Resize>| {});
```
This will spawn the `Observer` system and use an `on_add` hook to add
the `ObserverState` component.
Dynamic components and trigger types are also fully supported allowing
for runtime defined trigger types.
## Possible Follow-ups
1. Deprecate `RemovedComponents`, observers should fulfill all use cases
while being more flexible and performant.
2. Queries as entities: Swap queries to entities and begin using
observers listening to archetype creation triggers to keep their caches
in sync, this allows unification of `ObserverState` and `QueryState` as
well as unlocking several API improvements for `Query` and the
management of `QueryState`.
3. Trigger bubbling: For some UI use cases in particular users are
likely to want some form of bubbling for entity observers, this is
trivial to implement naively but ideally this includes an acceleration
structure to cache hierarchy traversals.
4. All kinds of other in-built trigger types.
5. Optimization; in order to not bloat the complexity of the PR I have
kept the implementation straightforward, there are several areas where
performance can be improved. The focus for this PR is to get the
behavior implemented and not incur a performance cost for users who
don't use observers.
I am leaving each of these to follow up PR's in order to keep each of
them reviewable as this already includes significant changes.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
The `EntityCommands::despawn` method was previously changed from
panicking behavior to a warning, but the docs continue to state that it
panics.
## Solution
- Removed panic section, copied warning blurb from `World::despawn`
- Adds a similar warning blurb to
`DespawnRecursiveExt::despawn_recursive` and
`DespawnRecursiveExt::despawn_descendants`
# Objective
Adds capability to clear all components on an entity without de-spawning
said entity.
## Testing
The function calls `remove_by_id` on every component in the entity
archetype - wasn't sure if it's worth going out of our way to create a
test for this considering `remove_by_id` is already unit tested.
---
## Changelog
Added `clear` function to `EntityWorldMut` which removes all components
on an entity.
## Migration Guide
N/A
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Prevent the case where a hook/observer is triggered but the source
entity/component no longer exists
## Solution
- Re-order command application such that all hooks/observers that are
notified will run before any have a chance to invalidate the result.
## Testing
Updated relevant tests in `bevy_ecs`, all other tests pass.
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: Mike Hsu <mike.hsu@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Better `SystemId` <-> `Entity` conversion.
## Solution
- Provide a method `SystemId::from_entity` to create a `SystemId<I, O>`
form an `Entity`. When users want to deal with the entities manually
they need a way to convert the `Entity` back to a `SystemId` to actually
run the system with `Commands` or `World`.
- Provide a method `SystemId::entity` that returns an `Entity` from
`SystemId`. The current `From` impl is not very discoverable as it does
not appear on the `SystemId` doc page.
- Remove old `From` impl.
## Migration Guide
```rust
let system_id = world.register_system(my_sys);
// old
let entity = Entity::from(system_id);
// new
let entity = system_id.entity();
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Add `remove_by_id` method to `EntityWorldMut` and `EntityCommands`
- This is a duplicate of the awesome work by @mateuseap, last updated
04/09/23 - #9663
- I'm opening a second one to ensure the feature makes it into `0.14`
- Fixes#9261
## Solution
Almost identical to #9663 with three exceptions
- Uses a closure instead of struct for commands, consistent with other
similar commands
- Does not refactor `EntityCommands::insert`, so no migration guide
- `EntityWorldMut::remove_by_id` is now safe containing unsafe blocks, I
think thats what @SkiFire13 was indicating should happen [in this
comment](https://github.com/bevyengine/bevy/pull/9663#discussion_r1314307525)
## Changelog
- Added `EntityWorldMut::remove_by_id` method and its tests.
- Added `EntityCommands::remove_by_id` method and its tests.
---------
Co-authored-by: James Liu <contact@jamessliu.com>
# Objective
- The `bundles` parameter in `insert_or_spawn_batch` method has
inconsistent naming with docs (e.g. `bundles_iter`) since #11107.
## Solution
- Replace `bundles` with `bundles_iter`, as `bundles_iter` is more
expressive to its type.
# Objective
- Allow registering of systems from Commands with
`Commands::register_one_shot_system`
- Make registering of one shot systems more easy
## Solution
- Add the Command `RegisterSystem` for Commands use.
- Creation of SystemId based on lazy insertion of the System
- Changed the privacy of the fields in SystemId so Commands can return
the SystemId
---
## Changelog
### Added
- Added command `RegisterSystem`
- Added function `Commands::register_one_shot_system`
- Added function `App::register_one_shot_system`
### Changed
- Changed the privacy and the type of struct tuple to regular struct of
SystemId
## Migration Guide
- Changed SystemId fields from tuple struct to a normal struct
If you want to access the entity field, you should use
`SystemId::entity` instead of `SystemId::0`
## Showcase
> Before, if you wanted to register a system with `Commands`, you would
need to do:
```rust
commands.add(|world: &mut World| {
let id = world.register_system(your_system);
// You would need to insert the SystemId inside an entity or similar
})
```
> Now, you can:
```rust
let id = commands.register_one_shot_system(your_system);
// Do what you want with the Id
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Pablo Reinhardt <pabloreinhardt@gmail.com>
# Objective
Fix Pr CI failing over dead code in tests and main branch CI failing
over a missing semicolon. Fixes#12620.
## Solution
Add dead_code annotations and a semicolon.
- Explain it is flushed in the same schedule run (was not obvious to me)
- Point to `apply_deferred` example
- Remove mentions of `System::apply_deferred` and
`Schedule::apply_deferred` which are probably too low level for the most
users
Co-authored-by: James Liu <contact@jamessliu.com>
# Objective
Fixes https://github.com/bevyengine/bevy/issues/11628
## Migration Guide
`Command` and `CommandQueue` have migrated from `bevy_ecs::system` to
`bevy_ecs::world`, so `use bevy_ecs::world::{Command, CommandQueue};`
when necessary.
# Objective
- A tiny nit I noticed; I think the type of these function is
`EntityCommand`, not `Command`
Co-authored-by: Charles Bournhonesque <cbournhonesque@snapchat.com>
# Objective
It would be convenient to be able to call functions with `Commands` as a
parameter without having to move your own instance of `Commands`. Since
this struct is composed entirely of references, we can easily get an
owned instance of `Commands` by shortening the lifetime.
## Solution
Add `Commands::reborrow`, `EntiyCommands::reborrow`, and
`Deferred::reborrow`, which returns an owned version of themselves with
a shorter lifetime.
Remove unnecessary lifetimes from `EntityCommands`. The `'w` and `'s`
lifetimes only have to be separate for `Commands` because it's used as a
`SystemParam` -- this is not the case for `EntityCommands`.
---
## Changelog
Added `Commands::reborrow`. This is useful if you have `&mut Commands`
but need `Commands`. Also added `EntityCommands::reborrow` and
`Deferred:reborrow` which serve the same purpose.
## Migration Guide
The lifetimes for `EntityCommands` have been simplified.
```rust
// Before (Bevy 0.12)
struct MyStruct<'w, 's, 'a> {
commands: EntityCommands<'w, 's, 'a>,
}
// After (Bevy 0.13)
struct MyStruct<'a> {
commands: EntityCommands<'a>,
}
```
The method `EntityCommands::commands` now returns `Commands` rather than
`&mut Commands`.
```rust
// Before (Bevy 0.12)
let commands = entity_commands.commands();
commands.spawn(...);
// After (Bevy 0.13)
let mut commands = entity_commands.commands();
commands.spawn(...);
```
# Objective
In #9604 we removed the ability to define an `EntityCommand` as
`fn(Entity, &mut World)`. However I have since realized that `fn(Entity,
&mut World)` is an incredibly expressive and powerful way to define a
command for an entity that may or may not exist (`fn(EntityWorldMut)`
only works on entities that are alive).
## Solution
Support `EntityCommand`s in the style of `fn(Entity, &mut World)`, as
well as `fn(EntityWorldMut)`. Use a marker generic on the
`EntityCommand` trait to allow multiple impls.
The second commit in this PR replaces all of the internal command
definitions with ones using `fn` definitions. This is mostly just to
show off how expressive this style of command is -- we can revert this
commit if we'd rather avoid breaking changes.
---
## Changelog
Re-added support for expressively defining an `EntityCommand` as a
function that takes `Entity, &mut World`.
## Migration Guide
All `Command` types in `bevy_ecs`, such as `Spawn`, `SpawnBatch`,
`Insert`, etc., have been made private. Use the equivalent methods on
`Commands` or `EntityCommands` instead.
# Objective
The `Despawn` command breaks the hierarchy whenever you use it if the
despawned entity has a parent or any children. This is a serious footgun
because the `Despawn` command has the shortest name, the behavior is
unexpected and not likely to be what you want, and the crash that it
causes can be very difficult to track down.
## Solution
Until this can be fixed by relations, add a note mentioning the footgun
in the documentation.
