[BUG] internal/protocol/protocol Protocol.Connect panic error

[danielchang-Z]

In internal/protocol/protocol.go line 187, the protocol object passes a NilPointer as the first parameter to method handleResponse, but the handleResponse method gets the field from the first parameter without any NilPointer checking.

func (p *Protocol) Connect(tr transport.Transport) error {
	p.transport = tr

	tr.SetCloseHandler(func() {
		p.handleClose()
	})

	tr.SetErrorHandler(func(err error) {
		p.handleError(err)
	})

	tr.SetMessageHandler(func(ctx context.Context, message *transport.BaseJsonRpcMessage) {
		switch m := message.Type; {
		case m == transport.BaseMessageTypeJSONRPCRequestType:
			p.handleRequest(ctx, message.JsonRpcRequest)
		case m == transport.BaseMessageTypeJSONRPCNotificationType:
			p.handleNotification(message.JsonRpcNotification)
		case m == transport.BaseMessageTypeJSONRPCResponseType:
			p.handleResponse(message.JsonRpcResponse, nil)
		case m == transport.BaseMessageTypeJSONRPCErrorType:
                         // pass a nil pointer to the method
			p.handleResponse(nil, message.JsonRpcError)
		}
	})

	return tr.Start(context.Background())
}

func (p *Protocol) handleResponse(response *transport.BaseJSONRPCResponse, errResp *transport.BaseJSONRPCError) {
        // get response.Id directly without any checking
	var id = response.Id
	var result interface{}
	var err error

	if errResp != nil {
		id = errResp.Id
		err = fmt.Errorf("RPC error %d: %s", errResp.Error.Code, errResp.Error.Message)
	} else {
		// Parse the response
		result = response.Result
	}

	p.mu.RLock()
	ch := p.responseHandlers[id]
	p.mu.RUnlock()

	if ch != nil {
		ch <- &responseEnvelope{
			response: result,
			err:      err,
		}
	}
}

[ecekyn]

The fix has been released in https://github.com/metoro-io/mcp-golang/releases/tag/v0.13.0.