Generate pallet RPC calls

[ascjones]

It would be nice to generate methods for calling pallet RPC endpoints e.g. contracts_instantiate

This is to avoid having to write code such as this, which at present requires importing or copying the definitions of the request and response types.

In order to do this we would require some metadata to be generated for these calls on the Substrate side.

Once the metadata is available it should be relatively straightforward to generate the rpc calls. Could look something like:

api.rpc().contracts().instantiate(request)

[ascjones]

@athei has pointed out that this should not be restricted to pallet RPCs, that if we have RPC metadata then we can also generate the client code for any "core" rpc methods (see Rpc).

One key distinction is that some "core" rpcs need to be defined up front, particularly author_submitExtrinsic so would need to handle that.

[athei]

The generated type can implement some traits that provide the RPCs that are required for subxt.

[ascjones]

Once we have paritytech/substrate#11648 this can then be all done via state_call. Related use-ink/cargo-contract#701

[niklasad1]

Right, I opened #631 for that not sure if I should close that and rely on this issue.

If you rename it to runtime API calls or something then I'm happy closing #631

[ascjones]

Yours is more detailed/up to date.

Superseded by #631