cBournhonesque/lightyear

`handle_client_disconnect` panics if an entity was manually despawned when a client disconnected

vladbat00 opened this issue · 4 comments

vladbat00 commented

I accidentally triggered this by despawning an entity when handling a EventReader<DisconnectEvent> event on the server side (at the time, I didn't know lightyear already handled despawning).

cBournhonesque commented

You mean this system?

lightyear/lightyear/src/server/clients.rs

Line 73 in deec7e6

pub(super) fn handle_client_disconnect(

I'm surprised that it panics, there doesn't seem to be any part of the code that can panic.

Do you have a stacktrace?

Nul-led commented

Its prob just that controlled entities contains an invalid entity ref since he despawned it beforehand. The system doesnt account for this and simply derefs it with .entity (not get_entity)

mvlabat commented

Yeah, apologies, I didn't have the stacktrace as I forgot to save it and then changed my code.

handle_client_disconnect calls commands.entity(*entity), which panics if an entity doesn't exist:

    pub fn entity(&mut self, entity: Entity) -> EntityCommands {
        #[inline(never)]
        #[cold]
        #[track_caller]
        fn panic_no_entity(entity: Entity) -> ! {
            panic!(
                "Attempting to create an EntityCommands for entity {entity:?}, which doesn't exist.",
            );
        }

        match self.get_entity(entity) {
            Some(entity) => entity,
            None => panic_no_entity(entity),
        }
    }

I hope this provides enough details, but if you still need a stacktrace, please let me know.

cBournhonesque commented

Thanks, I didn't realize that commands.entity() could panic.
I fixed this, but only in the cb/0.16 branch (which tracks bevy 0.14)

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