unwrap() failed in bevy_tasks/src/single_threaded_task_pool.rs:178

[kpreid]

Bevy version

bd5f924

What you did

Updated some headless rendering code from 0.16 to git, hoping to pick up the recent wgpu 25 update. It panicked instead. Somewhat minimized repro:

[package]
name = "bevy-bug"
version = "0.1.0"
edition = "2024"

[dependencies]
bevy = { git = "https://github.com/bevyengine/bevy", rev = "bd5f924290a2bb00a228405ecaefba520a50cffb", version = "0.17.0-dev", default-features = false, features = ["bevy_core_pipeline", "bevy_render", "bevy_scene", "bevy_window", "dynamic_linking"] }

use bevy::prelude as b;

fn main() {
    let mut app = b::App::new();
    app.add_plugins((
        b::MinimalPlugins,
        b::AssetPlugin::default(),
        bevy::render::RenderPlugin::default(),
        bevy::render::pipelined_rendering::PipelinedRenderingPlugin::default(),
    ));

    app.finish();
    app.cleanup();
    std::thread::sleep(std::time::Duration::from_millis(100));
}

What went wrong

thread '<unnamed>' panicked at /Users/kpreid/.cargo/git/checkouts/bevy-50d7e162b728c6c6/bd5f924/crates/bevy_tasks/src/single_threaded_task_pool.rs:178:51:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: core::option::unwrap_failed
   4: core::option::Option<T>::unwrap
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/option.rs:1003:21
   5: bevy_tasks::single_threaded_task_pool::TaskPool::scope_with_executor::{{closure}}
             at /Users/kpreid/.cargo/git/checkouts/bevy-50d7e162b728c6c6/bd5f924/crates/bevy_tasks/src/single_threaded_task_pool.rs:178:24
   6: core::iter::adapters::map::map_fold::{{closure}}
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/map.rs:88:28
   7: <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::fold
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/slice/iter/macros.rs:255:27
   8: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/adapters/map.rs:128:9
   9: core::iter::traits::iterator::Iterator::for_each
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:801:9
  10: alloc::vec::Vec<T,A>::extend_trusted
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3579:17
  11: <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<T,I>>::spec_extend
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/spec_extend.rs:29:9
  12: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/spec_from_iter_nested.rs:62:9
  13: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/spec_from_iter.rs:34:9
  14: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3438:9
  15: core::iter::traits::iterator::Iterator::collect
             at /Users/kpreid/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:2001:9
  16: bevy_tasks::single_threaded_task_pool::TaskPool::scope_with_executor
             at /Users/kpreid/.cargo/git/checkouts/bevy-50d7e162b728c6c6/bd5f924/crates/bevy_tasks/src/single_threaded_task_pool.rs:174:9
  17: bevy_tasks::single_threaded_task_pool::TaskPool::scope
             at /Users/kpreid/.cargo/git/checkouts/bevy-50d7e162b728c6c6/bd5f924/crates/bevy_tasks/src/single_threaded_task_pool.rs:123:9
  18: <bevy_render::pipelined_rendering::PipelinedRenderingPlugin as bevy_app::plugin::Plugin>::cleanup::{{closure}}
             at /Users/kpreid/.cargo/git/checkouts/bevy-50d7e162b728c6c6/bd5f924/crates/bevy_render/src/pipelined_rendering.rs:156:32

This panic should at least be changed to be informative about what I might be missing, if it’s not an actual bug.

bevy/crates/bevy_tasks/src/single_threaded_task_pool.rs

Line 178 in bd5f924

return result.borrow_mut().take().unwrap();

[tim-blackbird]

Same panic exists on 0.16
Fixed by adding the multi_threaded feature. Looks like bevy_render should depend on this feature?