Use rpc.account.nextIndex in submittables (#1422)

Author: jacogr

CHANGELOG.md

@@ -1,5 +1,6 @@
 # 0.93.0-beta.x
 
+- In extrinsic submission, use `rpc.account.nextIndex` to retrieve the nonce when available
 - For TypeScript users `api.query.*.*` is now properly typed for default Substrate calls, i.e. `api.query.balances.freeBalance(...)` will return a `Balance` type. Additionally the `api.queryMulti` and `.multi` on queries not allow generic type params.
 - Add `api.rpc.accounts.nextIndex`, `api.rpc.contracts.call` and `api.rpc.rpc.methods` calls. Optional calls (such as account/contracts) is decorated based on the results from `rpc.methods`, so they don't show up on nodes where they are not active.
 - Updated types to support the latest Polkadot/Substrate master changes

packages/api/src/submittable/Submittable.ts

@@ -193,7 +193,9 @@ export default class Submittable<ApiType> extends _Extrinsic implements Submitta
     return combineLatest([
       // if we have a nonce already, don't retrieve the latest, use what is there
       isUndefined(options.nonce)
-        ? this._api.query.system.accountNonce<Index>(address)
+        ? this._api.rpc.account.nextIndex
+          ? this._api.rpc.account.nextIndex(address)
+          : this._api.query.system.accountNonce(address)
         : of(createType('Index', options.nonce)),
       // if we have an era provided already or eraLength is <= 0 (immortal)
       // don't get the latest block, just pass null, handle in mergeMap