JoJoJet
commented
1 year ago Not sure why this is hanging, but a workaround should be possible.
I have the following code. This is a custom system combinator akin to Bevy's PipeSystem, with the difference that the first system returns an Option
and the second system is only called if the first system returned Some.
This should be doable using CombinatorSystem, by implementing the Combine trait:
pub type ChainOptionalSystem<A, B> = CombinatorSystem<ChainOptionalMarker, A, B>;
#[doc(hidden)]
pub struct ChainOptionalMarker;
impl<A, B> Combine<A, B> for ChainOptionalMarker
where
A: System<Out = Option<B::In>>,
B: System,
{
type In = A::In;
type Out = B::Out;
fn combine(
input: A::In,
a: impl FnOnce(A::In) -> A::Out,
b: impl FnOnce(B::In) -> B::Oout
) -> B::Out {
if let Some(value) = a(input) {
b(value)
} else {
todo!()
}
}
}
inodentry
hymm
Bevy version
0.10.1
Regression from 0.9.1
System
OS: macOS 13.1 Ventura CPU: Apple M1 Pro
What you did
I have the following code. This is a custom system combinator akin to Bevy's PipeSystem, with the difference that the first system returns an
Option<T>and the second system is only called if the first system returned Some.I have carried this code forward over the past few versions of Bevy. It used to work. Now in 0.10 it no longer does. This is interesting, because I looked at Bevy's combinator system implementation (https://github.com/bevyengine/bevy/blob/v0.10.1/crates/bevy_ecs/src/system/combinator.rs#L124) for reference and made sure that my code mirrors that. I expect my thing to work, given that it is adapted from something that is already included in Bevy itself. With previous versions of Bevy, I used the implementation of PipeSystem as my reference to learn from.
Code
```rust pub struct ChainOptionalSystemI am using this thing as a building block for handling Bevy UI buttons, among other things.
Code
```rust #[derive(Component)] pub struct UiDisabled; pub fn button_handlerIt could be used like this:
Code
```rust // Example button implementation that transitions to a specific state #[derive(Component, Clone)] struct StateTransitionButton(AppState); fn setup_menu(/* ... */) { // new game button commands.spawn(( StateTransitionButton(AppState::LoadingGame), ButtonBundle { // ... }, )); // settings button commands.spawn(( StateTransitionButton(AppState::Settings), ButtonBundle { // ... }, )); // credits button commands.spawn(( StateTransitionButton(AppState::ShowCredits), ButtonBundle { // ... }, )); } fn handle_state_transition_button( In(btn_data): InWhat went wrong
If I add the button handler system to my app, Bevy hangs when it tries to run it. The window becomes frozen and unresponsive.
Additional information
Like I said, this exact thing worked in previous versions of Bevy. I am just porting it to 0.10 now. I made my custom
impl Systemby looking at the code of Bevy'sPipeSystem, and now the new generic combinator system.I tried running my app in
lldbto try to track down what is going on. I could keep stepping long after myrun_unsafeimpl, past the end of the body of the task spawned by bevy's multithreaded executor. Eventually I reached here: https://github.com/bevyengine/bevy/blob/v0.10.1/crates/bevy_tasks/src/task_pool.rs#L500 and that is when the hang happened. Continuing to step the debugger only showed assembly listings from libpthread. I suspect we are getting stuck in thisexecute_foreverthing. I do not understand this code and I have no idea what it does and why. It seems to have been introduced in #7415 .I am stumped. Please help. This whole thing is so weird.