How to supply tuple parameters to a dynamic call in subxt

Question

I am struggling to figure out how to supply tuple parameters to a dynamic call in the latest subxt master branch. I know parameters are combinations of Value types.

My current non-working code looks like:

 let call = subxt::dynamic::tx(
        MODULE,
        "create_group",
        vec![
            Value::from_bytes(json.name.as_bytes()),
            Value::unnamed_composite(
                members
                    .into_iter()
                    .map(|(account_id, weight)| {
                        Value::unnamed_composite(vec![
                            Value::from_bytes(account_id),
                            Value::u128(weight.into()),
                        ])
                    })
                    .collect::<Vec<_>>(),
            ),
            Value::u128(json.threshold.into()),
            Value::u128(json.initial_balance),
        ],
    );

The call signature is :

     pub fn create_group(
            origin: OriginFor<T>,
            name: Vec<u8>,
            members: Vec<(T::AccountId, T::MemberCount)>,
            threshold: T::MemberCount,
            initial_balance: <<T as Config>::Currency as Currency<T::AccountId>>::Balance,
        ) -> DispatchResultWithPostInfo {

It compiles but I get the error:

Error encoding from dynamic value: Error at [0].[1]: Cannot encode to type; expected length 2 but got length 32

The auto-generated call works fine, but I am using dynamic calls because I need to be able to pass the call as a parameter to other extrinsics and it appears that that can only be done with dynamic queries.

The autogenerated call that works is:

     let call = borlaug_subxt::tx().groups().create_group(
         json.name.into(),
         members,
         json.threshold,
         json.initial_balance,
    );

And members is a vec of tuples of Account32,u32

Answer 1

Just to give this an answer; this was actually due to a bug in scale-value (see here and here). If you do a cargo update or otherwise ensure that you're using scale-value >= 0.8.1, it should now be fixed.

The value:

Value::unnamed_composite(vec![Value::unnamed_composite(vec![
    Value::u128(20u8.into()),
    Value::u128(30u16.into()),
])]);

Was previously not correctly being encoded into a Vec<(T::AccountId, T::MemberCount)>, but it will be now :)