can't construct sr25519 Public key from AuthorityId in pallet but it works in outer node? Same function

Question

I'm retrieving the list of authorities from aura in the pallet like this:

let authorities = pallet_aura::Pallet::<T>::authorities();

this should return a Vec<T::AuthorityId> which is supposedly the same as sp_core::sr25519::Public since AuthorityId in Aura is defined like that here, so I did the following:

authorities.into_iter().map(|id| Public::from_h256(H256::from_slice(id.as_slice())));

I'm doing it this way because for some reason in AuthorityId I don't have access to any method like sp_core::sr25519::Public, (I specifically need the verify method) which is why in the pallet it throws an error:

 no method named `as_slice` found for associated type `<T as pallet_aura::Config>::AuthorityId` in the current scope

now, having said that, in outer node if I call the runtime api authorities() and I try to create sr25519 keys from it, it works:

let authorities= client
    .runtime_api()
    .authorities(&block_id)
    .expect("error");
authorities
    .iter()
    .map(|pubkey| Public::from_h256(H256::from_slice(pubkey.as_slice())))
    .collect()

• why is this happening, even though its completely the same function, Im stuck with AuthorityId` which has literally zero methods? and are there simpler ways to retrieve the Public keys of the current authorities that does not require all this mess?

Ps: I tried importing the trait use sp_core::ByteArray; but it still didn't work.

Answer 1

Check https://github.com/paritytech/substrate/blob/549165727c3b3c14b6f90011085aaebbeff9d7e3/frame/aura/src/lib.rs#LL72-L76C20.

Because it doesn't have a ByteArray trait bound, you can't do that.

But it has a RuntimeAppPublic trait bound.

You can import sp_application_crypto::RuntimeAppPublic and call to_raw_vec() on it.

https://github.com/paritytech/substrate/blob/549165727c3b3c14b6f90011085aaebbeff9d7e3/primitives/application-crypto/src/traits.rs#L127-L128