Free sudo calls?

[justintim-es]

Dear substrate,
I don't know if it should work this way, but when we use ensure_root and
call our extrinsic

await api.tx.sudo.sudo(api.tx.access.access('5CiKbPQtCW6X6oFpsLLJ8vSUEzqSYnUkWuoqkp41iDevMBK6', [1,2])).signAndSend(pair)

we have to pay some fee eventhough we have the following weigth annotation

#[weight = (100_000, DispatchClass::Normal, Pays::No)]

Is it possible for sudo calls to be free as well?

[gui1117]

sudo should already be free when the extrinsic is successful (i.e. signed by sudo) as it returns Pays::No:

		fn sudo(origin, call: Box<<T as Trait>::Call>) -> DispatchResultWithPostInfo {
			// This is a public call, so we ensure that the origin is some signed account.
			let sender = ensure_signed(origin)?;
			ensure!(sender == Self::key(), Error::<T>::RequireSudo);

			let res = call.dispatch_bypass_filter(frame_system::RawOrigin::Root.into());
			Self::deposit_event(RawEvent::Sudid(res.map(|_| ()).map_err(|e| e.error)));
			// Sudo user does not pay a fee.
			Ok(Pays::No.into())
		}

What is exactly your sudo extrinsic ?
also the current sudo does not pay fee only if the extrinsic is successful, that means that the signer must be able to pay the fee for the transaction to be valid (in case the transaction is not successful).

but indeed the following pattern

#[weight = (100_000, DispatchClass::Normal, Pays::No)]

shouldn't require the signer to be able to pay the fee (because no matter what he won't pay for it), is this your issue ?

EDIT: note that #[weight = (100_000, DispatchClass::Normal, Pays::No)] looks dangerous as someone could potentially send a lot of transaction for free just to fill the block, no ?
I guess in this case better to use ValidateUnsigned which will make use of pre_dispatch in order to avoid including invalid transaction. 🤔

[justintim-es]

Yeah exactly because of ensure_root instead of ensure_signed inside of the function body with the following annotation
#[weight = (100_000, DispatchClass::Normal, Pays::No)] it charges a fee of +- 250000000 instead of nothing using rc-4

[shawntabrizi]

@noahsalvadordenjo this is solved in the latest versions of Substrate: #6749

There is not much we can do about RC-4 I think, but you should get the expected behavior moving forward.

[gui1117]

(note I closed because I couldn't reproduced on rc-6 and shawn says it was fixed, if you still have issue, feel free to reopen)

[justintim-es]

couldn't reproduce as well