What causes "unexpected event" in Pumpkin-MC/Pumpkin?

Register the handler with `EventType::CraftItemEvent` and verify the dispatch route sends only that variant.

unexpected event

Error message

unexpected event

What it means

This panic fires in `data_from_event`, the `Event` trait implementation for `CraftItemEvent`. It matches only `Event::CraftItemEvent(data)`; any other `Event` variant means the dispatcher handed a wrong-type payload to the crafting handler. The library considers this a broken internal invariant and panics with "unexpected event".

Solutions

Register the handler with `EventType::CraftItemEvent` and verify the dispatch route sends only that variant.
When calling manually, wrap data with `CraftItemEvent::data_into_event(data)` first.
Keep pumpkin-plugin-api versions identical across crates and rebuild from clean.
Pre-narrow with `if let Event::CraftItemEvent(data) = event { ... }`.
Return `Option`/`Result` and log instead of panicking.

Example fix

// before
match event {
    Event::CraftItemEvent(data) => data,
    _ => panic!("unexpected event"),
}
// after
match event {
    Event::CraftItemEvent(data) => data,
    _ => log::warn!("CraftItemEvent handler got wrong event"),
    _ => return None,
}

Defensive patterns

Strategy: type-guard

Validate before calling

// Before dispatch
assert_eq!(event.event_type(), EventType::CraftItemEvent, "wrong event routed to CraftItem handler");

Type guard

fn as_craft_item(event: &Event) -> Option<&CraftItemEventData> {
    match event {
        Event::CraftItemEvent(data) => Some(data),
        _ => None,
    }
}

Try / catch

let result = std::panic::catch_unwind(AssertUnwindSafe(|| handler.data_from_event(event)));
if result.is_err() {
    log::error!("CraftItemEvent handler received an unexpected event variant");
}

Prevention

Register the handler with EventType::CraftItemEvent.
Use if-let narrowing instead of blind data_from_event calls.
Always wrap payload data with the type's data_into_event when producing Event values.
Pin identical pumpkin-plugin-api versions across the workspace.
Add a debug_assert in dispatch code comparing event.event_type() to the handler's EVENT_TYPE.

When it happens

Trigger: Dispatching a non-`CraftItemEvent` variant (e.g. `FurnaceExtractEvent`) into `data_from_event`, or registering this handler under a `EventType` other than `CraftItemEvent`.

Common situations: Mismatched handler registration tables, hand-written dispatch where inventory events are conflated, or an upgrade that changed the `Event` enum so the handler's match arm no longer aligns with what's dispatched.

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

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/932f7500f6d65f9e. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-plugin-api/src/events/inventory/craft_item.rs:13

use super::super::FromIntoEvent;
use crate::wit::pumpkin::plugin::event::{CraftItemEventData, Event, EventType};

/// Event triggered when an item is crafted.
pub struct CraftItemEvent;
impl FromIntoEvent for CraftItemEvent {
    const EVENT_TYPE: EventType = EventType::CraftItemEvent;
    type Data = CraftItemEventData;

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

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

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