how to decode extrinsic data inside a pallet | Frontier

Question

i have a pallet that prints extrinsic data (bytes and hex) of every extrinsic inside every block, how can i print it like an human readable object ("from", "to" ecc..)?

that's my pallet code:

#[frame_support::pallet]
pub mod pallet_custom {
    use frame_support::pallet_prelude::*;
    use frame_system::pallet_prelude::*;
    use sp_runtime::generic::UncheckedExtrinsic;
    
    #[pallet::pallet]
    pub struct Pallet<T>(_);

    #[pallet::config]
    pub trait Config: frame_system::Config {}


    #[pallet::call]
    impl<T: Config> Pallet<T> {
        // Aggiungi le funzioni di chiamata qui
    }

    #[pallet::hooks]
    impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
        fn on_finalize(block_number: BlockNumberFor<T>) {
            log::info!("🇮🇹 on_finalize | Block number is {:?}", block_number);

            let total_block_transactions_count = frame_system::Pallet::<T>::extrinsic_count();
            log::info!("🇮🇹 on_finalize | Extrinsic count is {:?}", total_block_transactions_count);

            for i in 0..total_block_transactions_count {
                let transactions_data = frame_system::Pallet::<T>::extrinsic_data(i);
                log::info!("🇮🇹 on_finalize | Extrinsic data {:?} is {:?}", i, transactions_data);
              
                // convert the transaction data to hex string
                let transactions_data_hex = hex::encode(transactions_data.clone());
                log::info!("🇮🇹 on_finalize | Extrinsic data hex {:?} is {:?}", i, transactions_data_hex);

            

            }
        }

        fn offchain_worker(block_number: BlockNumberFor<T>) {
            log::info!("🇮🇹 offchain_worker | Block number is {:?}", block_number);
        }
    }
}

I hope to read something like:

{from: "0x94..", to: "0x4a9...", value: 0, data: "0x39c...."}

i receive something like:

0xe50184f24ff3a9cf04c71dbc94d0b566f7a27b94566cac48ddbb2036e1a0b045ce62ce71741ef06493cc58a03056adc3026a04ecb471dd3cd433087417721f1d4f716acc03d2cfda9b5cde20dbefaeafa6ce79ef25fbdf00350000000403798d4ba9baf0064ec19eb4f0a1a45785ae9d6dfc130000e8890423c78a

Answer 1

The question is not very clear which line of code that you expect it to print out because I don't find any code related to your expected output. But I assume these lines are what you expect

// convert the transaction data to hex string
let transactions_data_hex = hex::encode(transactions_data.clone());
log::info!("🇮🇹 on_finalize | Extrinsic data hex {:?} is {:?}", i, transactions_data_hex);

If so, then I don't think hex encoding the byte vector of transaction data is a right way to do. Can you give a try?

let extrinsic = sp_runtime::generic::UncheckedExtrinsic::decode(&mut input);

Reference: https://paritytech.github.io/polkadot-sdk/master/sp_runtime/generic/struct.UncheckedExtrinsic.html#impl-Decode-for-UncheckedExtrinsic%3CAddress,+Call,+Signature,+Extra%3E

The expected output would be

pub struct UncheckedExtrinsic<Address, Call, Signature, Extra>
where
    Extra: SignedExtension,
{
    pub signature: Option<(Address, Signature, Extra)>,
    pub function: Call,
}