Should we use registerRequestHandler or handle everything in onSessionRequest stream?

[Rimantovas]

Currently I have walletconnect implementation done like in the repository example using registerRequestHandler, but when I checked react-wallet-v2 example, it implemented all request handlers in the onSessionRequest stream. Which is the preferred method or is there no difference?

One thing I found with using registerRequestHandler is that I can't seem to return a valid response back to the dApp. For example, when handling eth_sendTransaction, if the user doesn't approve the request, I can only send back a null transaction hash to produce some sort of error on the dApp's side. If I send anything else, it will handle it as a successful request.

[quetool]

Hello @Rimantovas, thanks for reaching out!

Currently I have walletconnect implementation done like in the repository example using registerRequestHandler, but when I checked react-wallet-v2 example, it implemented all request handlers in the onSessionRequest stream. Which is the preferred method or is there no difference?

Indeed registerRequestHandler is the only way on flutter sdk to support methods from dapp. react-wallet-v2 uses a different approach as it is done with React.JS

One thing I found with using registerRequestHandler is that I can't seem to return a valid response back to the dApp. For example, when handling eth_sendTransaction, if the user doesn't approve the request, I can only send back a null transaction hash to produce some sort of error on the dApp's side. If I send anything else, it will handle it as a successful request.

The proper way to respond with errors AS A WALLET, is to use respondSessionRequest() method from web3wallet instance. You can see the Web way of doing it for guidance as the Flutter doc for that part is wrong https://docs.walletconnect.com/web3wallet/wallet-usage?platform=web#responding-to-session-requests

Here there are error codes everyone should follow https://specs.walletconnect.com/2.0/specs/clients/sign/error-codes

The proper way to capture request errors (such as user rejections) AS A DAPP is by listening to relay messages and parsing it content

For instance:

  _web3App!.core.relayClient.onRelayClientMessage.subscribe(_onRelayMessage);

  void _onRelayMessage(MessageEvent? args) async {
    if (args != null) {
      final payloadString = await _web3App!.core.crypto.decode(
        args.topic,
        args.message,
      );
      final data = jsonDecode(payloadString ?? '{}') as Map<String, dynamic>;
      debugPrint(data.toString());
    }
  }

It's up to the wallets to send the proper message in the proper format and it's up to the dApps to capture them properly.

[quetool]

Hello @Rimantovas! Just looked deepest into Flutter's SDK and you don't have to use respondSessionRequest() if you don't want to. as a wallet, if you want to communicate user rejection to the dapp you just need to return a JsonRpcError. Here it is a simple pseudo-code for personal_sign

Future<dynamic> personalSignHandler(String topic, dynamic parameters) async {
  // Show approval modal
  if (approved) {
    final signature = // => Sign message code
    return signature;
  } else {
    return const JsonRpcError(code: 5001, message: 'User rejected method');
  }
}

[Rimantovas]

Thanks, didn't think of that

[quetool]

Hello @Rimantovas! I was testing out different web-based dapps and it turns out they behave better if flutter answers as follows:

Future<dynamic> personalSignHandler(String topic, dynamic parameters) async {
  // Show approval modal
  if (approved) {
    final signature = // => Sign message code
    return _web3Wallet.respondSessionRequest(
      topic: topic,
        response: JsonRpcResponse(
        id: requestId,
        jsonrpc: '2.0',
        result: '0x$signature',
      ),
    );
  } else {
    return _web3Wallet.respondSessionRequest(
      topic: topic,
        response: JsonRpcResponse(
        id: requestId,
        jsonrpc: '2.0',
        error: const JsonRpcError(code: 5001, message: 'User rejected method',)
      ),
    );
  }
}

I will include this in Web3Wallet documentation for flutter soon.
To be clear, the previous mentioned way is not wrong, it's just some dapps may not handle it properly