Pumpkin-MC/Pumpkin · error

unexpected event

Error message

unexpected event

What it means

This panic fires in `FromIntoEvent::data_from_event` when an `Event` passed to `EntitySpawnEvent`'s converter carries any variant other than `Event::EntitySpawnEvent`. The trait bridges the WIT-generated `Event` enum to this event's typed `Data`, trusting that dispatch always pairs event type with matching variant. A mismatch means the dispatch plumbing broke that contract, so the library aborts rather than returning wrong data.

Solutions

1. Match host and pumpkin-plugin-api versions so `EventType::EntitySpawnEvent` maps to `Event::EntitySpawnEvent`
2. Audit dispatch code to route only `EventType::EntitySpawnEvent` to this converter
3. Filter by `EVENT_TYPE` before calling `data_from_event`
4. Return a `Result` or log instead of panicking

Example fix

// before
match event {
    Event::EntitySpawnEvent(data) => data,
    _ => panic!("unexpected event"),
}
// after
match event {
    Event::EntitySpawnEvent(data) => Ok(data),
    _ => Err("unexpected event"),
}

if event.event_type() != EventType::EntitySpawnEvent {
    return; // skip: not an EntitySpawnEvent
}

fn as_entity_spawn(event: &Event) -> Option<&EntitySpawnEventData> {
    match event {
        Event::EntitySpawnEvent(data) => Some(data),
        _ => None,
    }
}

let data = std::panic::catch_unwind(|| EntitySpawnEvent::data_from_event(event))
    .unwrap_or_else(|_| { log::error!("event type mismatch for EntitySpawnEvent"); return; });

When it happens

Trigger: `data_from_event` is invoked with an `Event` that is not `Event::EntitySpawnEvent` — the dispatcher routed a different event to the `EntitySpawnEvent` handler, or the `EventType` tag and `Event` variant disagree due to version skew or unchecked dispatch.

Common situations: Host and plugin API versions out of sync; a custom event bus forwarding raw `Event` values without type checks; `EntitySpawnEvent` registered under the wrong `EventType` after a refactor.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• unexpected event
• unexpected event
• unexpected event
• unexpected event
• unexpected event

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/4be809da539a33b7. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-plugin-api/src/events/entity/entity_spawn.rs:14

use crate::wit::pumpkin::plugin::event::{EntitySpawnEventData, Event, EventType};

use super::super::FromIntoEvent;

/// Event triggered when an entity spawns in the world.
pub struct EntitySpawnEvent;
impl FromIntoEvent for EntitySpawnEvent {
    const EVENT_TYPE: EventType = EventType::EntitySpawnEvent;
    type Data = EntitySpawnEventData;

    fn data_from_event(event: Event) -> Self::Data {
        match event {
            Event::EntitySpawnEvent(data) => data,
            _ => panic!("unexpected event"),
        }
    }

    fn data_into_event(data: Self::Data) -> Event {
        Event::EntitySpawnEvent(data)
    }
}

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