Pumpkin-MC/Pumpkin · critical

unexpected event type

Error message

unexpected event type

What it means

The fallback arm of the match in from_wasm_event: any event type other than the expected one reaches `_ => panic!("unexpected event type")`. It signals an internal dispatch bug — the wrong Event variant was passed to a specific event type's converter.

Solutions

1. Verify the event dispatch macro maps each event to its matching ToFromWasmEvent impl
2. Update converters after adding new Event variants
3. Pin plugin and server to the same API version
4. Read the surrounding panic context to identify which converter was mis-dispatched

// dispatch check
fn expects(ev: &Event, want: &str) -> bool { format!("{:?}", ev).starts_with(want) }

fn matches_variant(ev: &Event) -> bool { matches!(ev, Event::BlockFertilizeEvent(_) | Event::BlockMultiPlaceEvent(_)) }

When it happens

Trigger: A converter for one event type (e.g. BlockFertilizeEvent or BlockMultiPlaceEvent) receives a different Event variant than it expects during WASM event conversion.

Common situations: Macro-generated dispatch (crates/pumpkin-api-macros) mismatched with hand-written from_wasm_event impls; new event variant added without updating the converter table; server/plugin version skew.

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

• Cannot construct BlockFertilizeEvent from WASM
• failed to add player resource
• failed to add world resource
• Cannot construct BlockMultiPlaceEvent from WASM
• unexpected event type

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/fee3bc24540f0485. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin/src/plugin/loader/wasm/wasm_host/wit/v0_1/events/block.rs:906

            player,
            changed_blocks,
            cancelled: self.cancelled,
        })
    }

    fn apply_wasm_event(&mut self, event: Event, state: &mut PluginHostState) {
        cleanup_event(&event, state);
        if let Event::BlockFertilizeEvent(data) = event {
            self.cancelled = data.cancelled;
        }
    }

    fn from_wasm_event(event: Event, _state: &mut PluginHostState) -> Self {
        match event {
            Event::BlockFertilizeEvent(_) => {
                panic!("Cannot construct BlockFertilizeEvent from WASM")
            }
            _ => panic!("unexpected event type"),
        }
    }
}

impl ToFromWasmEvent for BlockMultiPlaceEvent {
    fn to_wasm_event(&self, state: &mut PluginHostState) -> Event {
        let player = state
            .add_player(self.player.clone())
            .expect("failed to add player resource");
        let target_world = state
            .add_world(self.world.clone())
            .expect("failed to add world resource");
        let placed_blocks = self
            .placed_blocks
            .iter()
            .map(|(pos, id)| (to_wasm_block_position(*pos), id.as_u16()))
            .collect();
        Event::BlockMultiPlaceEvent(BlockMultiPlaceEventData {

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