Pumpkin-MC/Pumpkin · error

unexpected event

Error message

unexpected event

What it means

This panic fires inside `FromIntoEvent::data_from_event` for `ChunkLoadEvent` when the passed `Event` is not `Event::ChunkLoadEvent`. This impl unwraps the chunk-load payload after the plugin macro pipeline routes by `EVENT_TYPE`; any other variant means events were crossed or the enum was built manually, breaking the routing invariant and panicking.

Solutions

1. Fix the dispatcher so chunk-load handlers receive only `Event::ChunkLoadEvent`.
2. Rebuild both plugin and host against the same API/WIT version.
3. Construct `Event::ChunkLoadEvent(data)` before invoking the handler in a harness.
4. Test each chunk event type round-trips through `data_into_event`/`data_from_event`.

Example fix

// before
Event::ChunkLoadEvent(data) => data,
_ => panic!("unexpected event"),
// after (diagnostic)
Event::ChunkLoadEvent(data) => data,
other => unreachable!("ChunkLoad handler received non-chunk-load event"),

assert!(matches!(event, Event::ChunkLoadEvent(_)), "handler requires Event::ChunkLoadEvent");

fn as_chunk_load(ev: &Event) -> Option<&ChunkLoadEventData> {
    if let Event::ChunkLoadEvent(d) = ev { Some(d) } else { None }
}

// guard before dispatch:
if let Event::ChunkLoadEvent(data) = event { handle(data) } else { log::warn!("non-load event reached chunk-load handler") }

When it happens

Trigger: Sending e.g. `Event::ChunkSaveEvent` to a `ChunkLoadEvent` handler, or calling the generated conversion directly with a mismatched `Event` in custom dispatch code.

Common situations: Custom plugin hosts mapping `EventType::ChunkLoadEvent` to the wrong event; version skew between plugin and host `Event` enums; copy-paste errors registering chunk handlers.

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/488805fe935d3894. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-plugin-api/src/events/world/chunk_load.rs:15

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

use super::super::FromIntoEvent;

/// An event that occurs when a chunk is loaded in a world.
pub struct ChunkLoadEvent;

impl FromIntoEvent for ChunkLoadEvent {
    const EVENT_TYPE: EventType = EventType::ChunkLoadEvent;
    type Data = ChunkLoadEventData;

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

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

View on GitHub (pinned to 8d4639e25a)