Correct way to catch tx errors

[poka-IT]

I am currently experiencing an issue with handling transaction errors in your library. Specifically, I'm unable to catch errors for transactions.

await author.submitAndWatchExtrinsic(srExtrinsic,
    (data) => log.d('From here: ${data.type} - ${data.value}'));

The problem is that data always indicates a successful blockchain submission, even when the extrinsic fails. Is there a recommended way to catch and handle these transaction errors using your library?

[leonardocustodio]

The extrinsic failing is not an error. The extrinsic was submitted, accepted, and included in a block.
There was no error in there. What you need to do if you want to do something when an extrinsic fails is to watch the extrinsic with the command above and check the extrinsic result. If the result is EXTRINSIC_FAILED, then do whatever you want.

[poka-IT]

I know an extrinsic failing is not an error. The thing is, I don't find a way to get the result you mentionned in your message.

This is part of my my actual code:

  yield TransactionStatusModel(hash: hex.encode(srExtrinsic), state: TransactionState.pending);

  final controller = StreamController<TransactionStatusModel>();

  try {
    final subscription = await authorApi.submitAndWatchExtrinsic(
      srExtrinsic,
      (data) {
        TransactionStatusModel status;
        switch (data.type) {
          case 'future':
          case 'ready':
          case 'broadcast':
            status = TransactionStatusModel(
                hash: hex.encode(srExtrinsic),
                state: TransactionState.pending);
            break;
          case 'inBlock':
            status = TransactionStatusModel(
                hash: hex.encode(srExtrinsic),
                state: TransactionState.inBlock);
            break;
          case 'finalized':
            status = TransactionStatusModel(
              hash: hex.encode(srExtrinsic),
              state: TransactionState.finalized,
            );
            controller.add(status);
            Future.delayed(const Duration(seconds: 3), () {
              controller.add(const TransactionStatusModel.empty());
              controller.close();
            });
            break;

          case 'retracted':
          case 'finalityTimeout':
          case 'usurped':
          case 'dropped':
          case 'invalid':
            status = TransactionStatusModel(
              hash: hex.encode(srExtrinsic),
              state: TransactionState.error,
              errorMessage: data.type,
            );
            break;
          default:
            status = TransactionStatusModel(
              hash: hex.encode(srExtrinsic),
              state: TransactionState.error,
              errorMessage: 'Unknown status: ${data.type}',
            );
        }
        refG.read(transactionStatusProvider.notifier).update(status);
        controller.add(status);
      },
    );

    yield* controller.stream;
    await subscription.cancel();
  } catch (e) {
    log.e('Error during transaction: $e');
    final status = TransactionStatusModel(
      hash: hex.encode(srExtrinsic),
      state: TransactionState.error,
      errorMessage: 'Transaction failed: $e.',
    );
    refG.read(transactionStatusProvider.notifier).update(status);
    controller.addError(status);
    yield* controller.stream;
  } finally {
    await controller.close();
  }
}

I don't understand where to find the EXTRINSIC_FAILED, how to parse the extrinsic result ?