Fix Free Transactions

[distributedstatemachine]

Description

Currently, our runtime does not properly handle fee-free transactions using the pallet_skip_feeless_payment module. This leads to inconsistencies and potential issues with transaction processing, as free transactions now require a fee.. The recent upgrade to Polkadot v1.10 removed the previous functionality, causing a regression in our system. In essence , Pays=No becomes a noop.

Acceptance Criteria

• Integrate the pallet_skip_feeless_payment module into the runtime.
• Define the necessary associated types and implement the required traits for the SkipFeelessPaymentConfig.
• Update the RuntimeEvent enum to include the SkipFeelessPayment variant.
• Ensure that fee-free transactions, including the faucet functionality, are correctly identified and processed.

Tasks

• [ ] Update the runtime's Cargo.toml file to include the pallet-skip-feeless-payment dependency.

• [ ] Implement the pallet_skip_feeless_payment::Config trait for the runtime:

  impl pallet_skip_feeless_payment::Config for Runtime {
    type RuntimeEvent = RuntimeEvent;
  
    fn is_fee_free(call: &Self::RuntimeCall) -> bool {
        // Add logic to determine if a call is fee-free
        // ...
    }
  }

• [ ] Update the RuntimeEvent enum in runtime/src/lib.rs:

  #[derive(Debug, Encode, Decode, PartialEq, Eq, Clone)]
  #[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize))]
  pub enum RuntimeEvent {
    // ...
    SkipFeelessPayment(pallet_skip_feeless_payment::Event<Runtime>),
    // ...
  }

• [ ] Update the construct_runtime! macro to include the SkipFeelessPayment module.
• [ ] Test the changes to ensure fee-free transactions, including the faucet, are correctly processed.

Related Links

• https://docs.rs/pallet-skip-feeless-payment/latest/pallet_skip_feeless_payment/
• https://github.com/paritytech/polkadot-sdk/issues/1725
• https://discord.com/channels/799672011265015819/1237848735195598979

[open-junius]

According to my investigation, the root cause is the account.providers.is_zero() && account.sufficients.is_zero() check added when nonce check in extrinsic extension. We can't fix in via introduce the feeless trait for some extrinsic. Feeless is the machenism in transaction payment pallet, to check accept the transaction or not. But the added check happens before it, the extrinsic fails when check extrinsic extension.

[open-junius]

https://github.com/paritytech/polkadot-sdk/pull/4165/files fix from upstream. which can fix it but we need wait for its merge

[distributedstatemachine]

Closed by https://github.com/opentensor/subtensor/pull/404