Trait HostCallBridge 

pub trait HostCallBridge {
    // Required method
    fn dispatch(
        &self,
        capability: &str,
        operation: &str,
        params: &BTreeMap<String, VmValue>,
    ) -> Result<Option<VmValue>, VmError>;
}

Embedder-supplied bridge for host_call ops.

Embedders (debug adapters, CLIs, IDE hosts) implement this trait to satisfy capability/operation pairs that harn-vm itself doesn’t know how to handle. Returning Ok(None) means “I don’t handle this op — fall through to the built-in fallbacks (env-derived defaults, then the unsupported operation error)”. Ok(Some(value)) is the result; Err(VmError::Thrown(_)) surfaces as a Harn exception.

The trait is intentionally synchronous. Bridges that need async I/O (e.g. DAP reverse requests) should drive their own runtime or use a blocking channel — see harn-dap’s DapHostBridge for the canonical pattern. Sync keeps the boundary simple and avoids forcing the entire dispatch path into an opaque future.

Required Methods

fn dispatch( &self, capability: &str, operation: &str, params: &BTreeMap<String, VmValue>, ) -> Result<Option<VmValue>, VmError>

Implementors