Pumpkin-MC/Pumpkin · error

unexpected event type

Error message

unexpected event type

What it means

PacketReceivedEvent::from_wasm_event matches only Event::PacketReceivedEvent (which currently panics as unsupported) and panics with 'unexpected event type' for everything else. Reaching the catch-all means an event of a different kind was dispatched through this converter — a routing invariant violation in the WASM event plumbing.

Solutions

1. Verify the dispatcher maps Event::PacketReceivedEvent exclusively to this converter.
2. Align the plugin's event subscriptions with what the host actually forwards.
3. Update dispatch code whenever the Event enum changes.
4. Downgrade the panic to a logged, recoverable error in host code.

// host side, before calling the converter
assert!(matches!(event, Event::PacketReceivedEvent(_)), "event/converter mismatch");

fn is_packet_received(e: &Event) -> bool { matches!(e, Event::PacketReceivedEvent(_)) }

let out = catch_unwind(|| PacketReceivedEvent::from_wasm_event(event, state))
    .unwrap_or_else(|_| log_and_default());

When it happens

Trigger: The host routes any Event variant other than Event::PacketReceivedEvent (e.g. PacketSentEvent or ServerCommandEvent) into PacketReceivedEvent::from_wasm_event.

Common situations: Dispatch table miswiring after adding new server event variants; plugin subscribed to one event but host delivers another; refactoring changed variant names/order.

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

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/823659910c2c9bd0. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin/src/plugin/loader/wasm/wasm_host/wit/v0_1/events/server.rs:80

    fn apply_wasm_event(&mut self, event: Event, state: &mut PluginHostState) {
        cleanup_event(&event, state);
        if let Event::PacketReceivedEvent(data) = event {
            self.packet_id = data.packet_id;
            self.payload = data.raw_payload.into();
            self.cancelled = data.cancelled;
        }
    }
    fn from_wasm_event(event: Event, _state: &mut PluginHostState) -> Self {
        match event {
            Event::PacketReceivedEvent(_) => {
                // TODO: Implement converting from WIT variant back to raw if needed.
                // For now, we only support cancellation.
                panic!(
                    "Modifying packets from WASM is not yet supported in this simple implementation."
                );
            }
            _ => panic!("unexpected event type"),
        }
    }
}

impl ToFromWasmEvent for PacketSentEvent {
    fn to_wasm_event(&self, state: &mut PluginHostState) -> Event {
        let player_res = state
            .add_player(self.player.clone())
            .expect("failed to add player resource");

        let packet = match self.player.client.as_ref() {
            ClientPlatform::Java(_) => {
                generated_packets::clientbound_java_any_to_wit(self.packet.as_ref())
                    .map_or(ClientboundPacket::Unknown, ClientboundPacket::Java)
            }
            ClientPlatform::Bedrock(_) => {
                generated_packets::clientbound_bedrock_any_to_wit(self.packet.as_ref())
                    .map_or(ClientboundPacket::Unknown, ClientboundPacket::Bedrock)

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