thread 'main' panicked at 'Entity does not exist'

[mbaeten]

Thanks for your great work, very much appreciated. Glad to help if feasible.

I read the following: #1707, #1743, #2219

Bevy version

a1b2ec8 (bevy 0.5 from crates.io)

Operating system & version

NixOS Unstable

What you did

Created some plugins with systems running in parallel and/or serialized, only removing entites after they completed their work. Unfortunately, I'm not allowed to share the code itself. If it helps, I can try to create a MWE (if time permits).

What you expected to happen

Do not crash. Emit an error! if unavoidable.

What actually happened

thread 'main' panicked at 'Entity does not exist', ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/world/mod.rs:214:37

Additional information

thread 'main' panicked at 'Entity does not exist', ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/world/mod.rs:214:37
stack backtrace:
   0:     0x558f7b732af0 - std::backtrace_rs::backtrace::libunwind::trace::h34055254b57d8e79
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x558f7b732af0 - std::backtrace_rs::backtrace::trace_unsynchronized::h8f1e3fbd9afff6ec
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x558f7b732af0 - std::sys_common::backtrace::_print_fmt::h3a99a796b770c360
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x558f7b732af0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h32d1f94a80615d18
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x558f7b755a5c - core::fmt::write::h306731c068f7162c
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1110:17
   5:     0x558f7b72d1f5 - std::io::Write::write_fmt::hd2fa90334eee2a21
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/io/mod.rs:1588:15
   6:     0x558f7b73501b - std::sys_common::backtrace::_print::h5abaa2601a852287
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x558f7b73501b - std::sys_common::backtrace::print::h8d81445442bb638f
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x558f7b73501b - std::panicking::default_hook::{{closure}}::hcfe804496a9fa747
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:208:50
   9:     0x558f7b734af1 - std::panicking::default_hook::hbea8e3ccf2ba8901
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:225:9
  10:     0x558f7b7356e4 - std::panicking::rust_panic_with_hook::h7ee9e1a2d0f8975a
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:622:17
  11:     0x558f7b7351c7 - std::panicking::begin_panic_handler::{{closure}}::h8ab3b4491718b2c7
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:519:13
  12:     0x558f7b732fec - std::sys_common::backtrace::__rust_end_short_backtrace::hd489062ffa586a9f
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:141:18
  13:     0x558f7b735129 - rust_begin_unwind
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:515:5
  14:     0x558f7a9669c1 - core::panicking::panic_fmt::hca6330e3e14086b4
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:92:14
  15:     0x558f7a9668b3 - core::option::expect_failed::hb6407502861d5eec
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/option.rs:1243:5
  16:     0x558f7b074588 - core::option::Option<T>::expect::hb4e136231f9b0421
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/option.rs:351:21
  17:     0x558f7abec978 - bevy_ecs::world::World::entity_mut::h6ae88df730e85fe1
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/world/mod.rs:214:9
  18:     0x558f7abe650c - <bevy_ecs::system::commands::Insert<T> as bevy_ecs::system::commands::Command>::write::h9e7944a392e954b9
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/system/commands.rs:351:9
  19:     0x558f7b545ffd - bevy_ecs::system::commands::CommandQueue::apply::h35982dcacdc6f745
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/system/commands.rs:24:13
  20:     0x558f7b546174 - <bevy_ecs::system::commands::CommandQueue as bevy_ecs::system::system_param::SystemParamState>::apply::h8ebccab4f78e6fdf
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/system/system_param.rs:458:9
  21:     0x558f7aad9af4 - <(P0,P1,P2,P3) as bevy_ecs::system::system_param::SystemParamState>::apply::h2f67c391feaa9dd5
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/system/system_param.rs:1010:19
  22:     0x558f7ab0aafe - <bevy_ecs::system::into_system::FunctionSystem<In,Out,Param,Marker,F> as bevy_ecs::system::system::System>::apply_buffers::h64f439c764bf4211
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/system/into_system.rs:161:9
  23:     0x558f7b514b87 - <bevy_ecs::schedule::stage::SystemStage as bevy_ecs::schedule::stage::Stage>::run::hf5f93d4222fa3181
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/schedule/stage.rs:834:25
  24:     0x558f7b56a530 - bevy_ecs::schedule::Schedule::run_once::h2034ca144031b6fa
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/schedule/mod.rs:201:13
  25:     0x558f7b56a5a0 - <bevy_ecs::schedule::Schedule as bevy_ecs::schedule::stage::Stage>::run::h412a9d3982b9759e
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_ecs-0.5.0/src/schedule/mod.rs:219:21
  26:     0x558f7b4bdbd8 - bevy_app::app::App::update::h0328d53a82ecaab6
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_app-0.5.0/src/app.rs:58:9
  27:     0x558f7b4bc4e0 - <bevy_app::schedule_runner::ScheduleRunnerPlugin as bevy_app::plugin::Plugin>::build::{{closure}}::{{closure}}::hea28d49ac5a1a0c9
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_app-0.5.0/src/schedule_runner.rs:76:25
  28:     0x558f7b4bc8bd - <bevy_app::schedule_runner::ScheduleRunnerPlugin as bevy_app::plugin::Plugin>::build::{{closure}}::h789e0a7e190c45aa
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_app-0.5.0/src/schedule_runner.rs:101:47
  29:     0x558f7b4af048 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h4b7ce5908c896b6f
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/alloc/src/boxed.rs:1589:9
  30:     0x558f7b4bdcf1 - bevy_app::app::App::run::h116ccd77f6a71c7f
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_app-0.5.0/src/app.rs:68:9
  31:     0x558f7b4b633e - bevy_app::app_builder::AppBuilder::run::h27fd4f2a0189f1d7
                               at ~/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/bevy_app-0.5.0/src/app_builder.rs:49:9
  32:     0x558f7a96d0ca - my_project_name::main::h94e52035496abc6a
                               at ~/repos/my_project_name/src/main.rs:12:3
  33:     0x558f7a96ac3b - core::ops::function::FnOnce::call_once::h4caae3afd86d231c
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/ops/function.rs:227:5
  34:     0x558f7a96b4de - std::sys_common::backtrace::__rust_begin_short_backtrace::hb9d1c99edf362ba7
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:125:18
  35:     0x558f7a96b561 - std::rt::lang_start::{{closure}}::ha5bdfdc51a01a7b9
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/rt.rs:49:18
  36:     0x558f7b735be9 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h2aabc384aab89b7b
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/ops/function.rs:259:13
  37:     0x558f7b735be9 - std::panicking::try::do_call::hc5fcacb7a85fc7b1
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:401:40
  38:     0x558f7b735be9 - std::panicking::try::hb5d9603af3abbe3a
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:365:19
  39:     0x558f7b735be9 - std::panic::catch_unwind::h98fe6ac3925e64b4
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panic.rs:434:14
  40:     0x558f7b735be9 - std::rt::lang_start_internal::h22ac7383c516f93e
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/rt.rs:34:21
  41:     0x558f7a96b540 - std::rt::lang_start::ha3e6132f05793518
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/rt.rs:48:5
  42:     0x558f7a96d12c - main
  43:     0x7ff8afb2e780 - __libc_start_main
  44:     0x558f7a9671ba - _start
                               at /build/glibc-2.33/csu/../sysdeps/x86_64/start.S:120
  45:                0x0 - <unknown>

[alice-i-cecile]

This looks the bug documented in #2581. Basically, the order that commands are applied in mirrors system order: your system order is likely ambiguous in critical ways and entities are being despawned before they exist.

That said, a more general solution is given by #2241, which pushes towards a safer, more customizable set of behaviours for Commands error handling. If you have the bandwidth, feedback (and perhaps contributions) on that thread would be valuable: I'd like to get the ball rolling on that again.

[alice-i-cecile]

Closing as duplicate of #1743. Still important and useful to solve; it's just nice to try and keep the conversations centralized.