Pumpkin-MC/Pumpkin · critical

Cannot construct BlockFertilizeEvent from WASM

Error message

Cannot construct BlockFertilizeEvent from WASM

What it means

A panic in `BlockFertilizeEvent`'s `from_wasm_event` implementation of the ToFromWasmEvent trait. The host-side event enum contains a BlockFertilizeEvent, which cannot be reconstructed from a WASM-side event representation, so the code intentionally panics — this direction of conversion is unsupported for this event.

Solutions

1. Do not route BlockFertilizeEvent through from_wasm_event; use to_wasm_event only
2. Handle the event natively instead of round-tripping it through WASM
3. Report/implement from_wasm_event support if bidirectional conversion is needed
4. Check plugin/server versions for an unsupported event-flow path

// before conversion
fn convertible_from_wasm(ev: &Event) -> bool { !matches!(ev, Event::BlockFertilizeEvent(_)) }

fn is_block_fertilize(ev: &Event) -> bool { matches!(ev, Event::BlockFertilizeEvent(_)) } // handle natively, never via from_wasm_event

When it happens

Trigger: Host code calls from_wasm_event with Event::BlockFertilizeEvent, i.e. attempting to convert a WASM-originated BlockFertilizeEvent back into the native type for a plugin.

Common situations: Plugin infrastructure routing a fertilizer-use event through the WASM event bridge that only supports native->wasm for this event type; server/plugin version mismatch exercising an unsupported conversion path.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

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

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/cc2f37515d83b3a1. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin/src/plugin/loader/wasm/wasm_host/wit/v0_1/events/block.rs:904

            block_pos: to_wasm_block_position(self.block_pos),
            target_world,
            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()))

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