Remove double-up-drr (memo vs rpc) (#1541)

* Remove inner memo (no double-up on stringify)

* Validators-specific query

packages/api-derive/src/accounts/idAndIndex.ts

@@ -66,6 +66,6 @@ export const idAndIndex = memo((api: ApiInterfaceRx): (address?: Address | Accou
     indexToIdCall: indexToId(api)
   };
 
-  return memo((address?: Address | AccountId | AccountIndex | string | null): Observable<AccountIdAndIndex> =>
-    retrieve(address, calls).pipe(drr()));
+  return (address?: Address | AccountId | AccountIndex | string | null): Observable<AccountIdAndIndex> =>
+    retrieve(address, calls).pipe(drr());
 }, true);

packages/api-derive/src/accounts/idToIndex.ts

@@ -28,12 +28,12 @@ import { drr, memo } from '../util';
 export const idToIndex = memo((api: ApiInterfaceRx): (accountId: AccountId | string) => Observable<AccountIndex | undefined> => {
   const indexesCall = indexes(api);
 
-  return memo((accountId: AccountId | string): Observable<AccountIndex | undefined> =>
+  return (accountId: AccountId | string): Observable<AccountIndex | undefined> =>
     indexesCall().pipe(
       startWith({}),
       map((indexes: AccountIndexes): AccountIndex | undefined =>
         (indexes || {})[accountId.toString()]
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/accounts/indexToId.ts

@@ -28,7 +28,7 @@ import { drr, memo } from '../util';
 export const indexToId = memo((api: ApiInterfaceRx): (accountIndex: AccountIndex | string) => Observable<AccountId | undefined> => {
   const querySection = api.query.indices || api.query.balances;
 
-  return memo((_accountIndex: AccountIndex | string): Observable<AccountId | undefined> => {
+  return (_accountIndex: AccountIndex | string): Observable<AccountId | undefined> => {
     const accountIndex = _accountIndex instanceof ClassOf('AccountIndex')
       ? _accountIndex
       : createType('AccountIndex', _accountIndex);
@@ -40,5 +40,5 @@ export const indexToId = memo((api: ApiInterfaceRx): (accountIndex: AccountIndex
       ),
       drr()
     );
-  });
+  };
 }, true);

packages/api-derive/src/accounts/indexes.ts

@@ -32,7 +32,7 @@ const enumsetSize = ENUMSET_SIZE.toNumber();
  * ```
  */
 export const indexes = memo((api: ApiInterfaceRx): () => Observable<AccountIndexes> => {
-  return memo((): Observable<AccountIndexes> =>
+  return (): Observable<AccountIndexes> =>
     api.query.indices.nextEnumSet<AccountIndex>().pipe(
       // use the nextEnumSet (which is a counter of the number of sets) to construct
       // a range of values to query [0, 1, 2, ...]. Retrieve the full enum set for the
@@ -54,5 +54,5 @@ export const indexes = memo((api: ApiInterfaceRx): () => Observable<AccountIndex
           return result;
         }, {} as AccountIndexes)),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/accounts/info.ts

@@ -30,7 +30,7 @@ export const info = memo((api: ApiInterfaceRx): (address?: AccountIndex | Accoun
   const idAndIndexCall = idAndIndex(api);
   const nickCall = retrieveNick(api);
 
-  return memo((address?: AccountIndex | AccountId | Address | string | null): Observable<DeriveAccountInfo> =>
+  return (address?: AccountIndex | AccountId | Address | string | null): Observable<DeriveAccountInfo> =>
     idAndIndexCall(address).pipe(
       switchMap(([accountId, accountIndex]): Observable<[DeriveAccountInfo, Option<[Bytes, Balance] & Codec>?]> =>
         combineLatest([
@@ -46,5 +46,5 @@ export const info = memo((api: ApiInterfaceRx): (address?: AccountIndex | Accoun
           : undefined
       })),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/balances/all.ts

@@ -81,7 +81,7 @@ export const all = memo((api: ApiInterfaceRx): (address: AccountIndex | AccountI
   const bestNumberCall = bestNumber(api);
   const infoCall = info(api);
 
-  return memo((address: AccountIndex | AccountId | Address | string): Observable<DerivedBalances> =>
+  return (address: AccountIndex | AccountId | Address | string): Observable<DerivedBalances> =>
     infoCall(address).pipe(
       switchMap(({ accountId }): Observable<Result> =>
         (accountId
@@ -101,5 +101,5 @@ export const all = memo((api: ApiInterfaceRx): (address: AccountIndex | AccountI
       ),
       map(calcBalances),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/balances/fees.ts

@@ -56,7 +56,7 @@ export const fees = memo((api: ApiInterfaceRx): () => Observable<DerivedFees> =>
     ? queryV2
     : queryV1;
 
-  return memo((): Observable<DerivedFees> =>
+  return (): Observable<DerivedFees> =>
     query(api).pipe(
       map(([creationFee, existentialDeposit, transferFee, transactionBaseFee, transactionByteFee]): DerivedFees => ({
         creationFee,
@@ -66,5 +66,5 @@ export const fees = memo((api: ApiInterfaceRx): () => Observable<DerivedFees> =>
         transferFee
       })),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/balances/votingBalances.ts

@@ -12,12 +12,12 @@ import { drr, memo } from '../util';
 import { all } from './all';
 
 export const votingBalances = memo((api: ApiInterfaceRx): (addresses?: (AccountId | AccountIndex | Address | string)[]) => Observable<DerivedBalances[]> => {
-  return memo((addresses?: (AccountId | AccountIndex | Address | string)[]): Observable<DerivedBalances[]> =>
+  return (addresses?: (AccountId | AccountIndex | Address | string)[]): Observable<DerivedBalances[]> =>
     (
       !addresses || !addresses.length
         ? of([] as DerivedBalances[])
         : combineLatest(addresses.map(all(api)))
     ).pipe(
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/balances/votingBalancesNominatorsFor.ts

@@ -17,7 +17,7 @@ import { votingBalances } from './votingBalances';
 export const votingBalancesNominatorsFor = memo((api: ApiInterfaceRx): (address: AccountId | AccountIndex | Address | string) => Observable<DerivedBalances[]> => {
   const infoCall = info(api);
 
-  return memo((address: AccountId | AccountIndex | Address | string): Observable<DerivedBalances[]> =>
+  return (address: AccountId | AccountIndex | Address | string): Observable<DerivedBalances[]> =>
     infoCall(address).pipe(
       switchMap(({ accountId }): Observable<AccountId[]> =>
         accountId
@@ -26,5 +26,5 @@ export const votingBalancesNominatorsFor = memo((api: ApiInterfaceRx): (address:
       ),
       switchMap(votingBalances(api)),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/chain/bestNumber.ts

@@ -23,9 +23,9 @@ import { drr, memo } from '../util';
  * ```
  */
 export const bestNumber = memo((api: ApiInterfaceRx): () => Observable<BlockNumber> => {
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     api.rpc.chain.subscribeNewHeads().pipe(
       map((header): BlockNumber => header.number.unwrap()),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/chain/bestNumberFinalized.ts

@@ -24,9 +24,9 @@ import { drr, memo } from '../util';
  * ```
  */
 export const bestNumberFinalized = memo((api: ApiInterfaceRx): () => Observable<BlockNumber> => {
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     api.rpc.chain.subscribeFinalizedHeads().pipe(
       map((header): BlockNumber => header.number.unwrap()),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/chain/bestNumberLag.ts

@@ -30,7 +30,7 @@ export const bestNumberLag = memo((api: ApiInterfaceRx): () => Observable<BlockN
   const bestNumberCall = bestNumber(api);
   const bestNumberFinalizedCall = bestNumberFinalized(api);
 
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     combineLatest([
       bestNumberCall(),
       bestNumberFinalizedCall()
@@ -39,5 +39,5 @@ export const bestNumberLag = memo((api: ApiInterfaceRx): () => Observable<BlockN
         createType('BlockNumber', bestNumber.sub(bestNumberFinalized))
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/chain/getHeader.ts

@@ -28,7 +28,7 @@ import { drr, memo } from '../util';
  * ```
  */
 export const getHeader = memo((api: ApiInterfaceRx): (hash: Uint8Array | string) => Observable<HeaderExtended | undefined> => {
-  return memo((hash: Uint8Array | string): Observable<HeaderExtended | undefined> =>
+  return (hash: Uint8Array | string): Observable<HeaderExtended | undefined> =>
     combineLatest([
       api.rpc.chain.getHeader(hash),
       api.query.session.validators.at(hash) as Observable<Vec<AccountId>>
@@ -43,5 +43,5 @@ export const getHeader = memo((api: ApiInterfaceRx): (hash: Uint8Array | string)
         of()
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/chain/subscribeNewHeads.ts

@@ -26,7 +26,7 @@ import { drr, memo } from '../util';
  * ```
  */
 export const subscribeNewHeads = memo((api: ApiInterfaceRx): () => Observable<HeaderExtended> => {
-  return memo((): Observable<HeaderExtended> =>
+  return (): Observable<HeaderExtended> =>
     combineLatest([
       api.rpc.chain.subscribeNewHeads(),
       api.query.session.validators<Vec<AccountId>>()
@@ -35,5 +35,5 @@ export const subscribeNewHeads = memo((api: ApiInterfaceRx): () => Observable<He
         new HeaderExtended(header, validators)
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/contracts/fees.ts

@@ -104,7 +104,7 @@ function queryConstants (api: ApiInterfaceRx): Observable<ResultV2> {
  * ```
  */
 export const fees = memo((api: ApiInterfaceRx): () => Observable<DerivedContractFees> => {
-  return memo((): Observable<DerivedContractFees> => {
+  return (): Observable<DerivedContractFees> => {
     if (api.query.contract && !api.query.contract.rentByteFee) {
       return queryV1(api);
     }
@@ -122,5 +122,5 @@ export const fees = memo((api: ApiInterfaceRx): () => Observable<DerivedContract
       ),
       drr()
     );
-  });
+  };
 }, true);

packages/api-derive/src/democracy/referendumInfo.ts

@@ -28,12 +28,11 @@ export function constructInfo (index: BN | number, optionInfo?: Option<Referendu
 }
 
 export const referendumInfo = memo((api: ApiInterfaceRx): (index: BN | number) => Observable<Option<ReferendumInfoExtended>> => {
-  return memo((index: BN | number): Observable<Option<ReferendumInfoExtended>> =>
-    (api.query.democracy.referendumInfoOf<Option<ReferendumInfo>>(index))
-      .pipe(
-        map((optionInfo): Option<ReferendumInfoExtended> =>
-          constructInfo(index, optionInfo)
-        ),
-        drr()
-      ));
+  return (index: BN | number): Observable<Option<ReferendumInfoExtended>> =>
+    api.query.democracy.referendumInfoOf<Option<ReferendumInfo>>(index).pipe(
+      map((optionInfo): Option<ReferendumInfoExtended> =>
+        constructInfo(index, optionInfo)
+      ),
+      drr()
+    );
 }, true);

packages/api-derive/src/democracy/referendumInfos.ts

@@ -15,7 +15,7 @@ import { drr, memo } from '../util';
 import { constructInfo } from './referendumInfo';
 
 export const referendumInfos = memo((api: ApiInterfaceRx): (ids?: (BN | number)[]) => Observable<Option<ReferendumInfoExtended>[]> => {
-  return memo((ids: (BN | number)[] = []): Observable<Option<ReferendumInfoExtended>[]> =>
+  return (ids: (BN | number)[] = []): Observable<Option<ReferendumInfoExtended>[]> =>
     (
       !ids || !ids.length
         ? of([] as Option<ReferendumInfo>[])
@@ -27,5 +27,5 @@ export const referendumInfos = memo((api: ApiInterfaceRx): (ids?: (BN | number)[
         )
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/democracy/referendumVotesFor.ts

@@ -19,7 +19,7 @@ export const referendumVotesFor = memo((api: ApiInterfaceRx): (referendumId: BN
   const votesCall = votes(api);
   const votingBalancesCall = votingBalances(api);
 
-  return memo((referendumId: BN | number): Observable<DerivedReferendumVote[]> =>
+  return (referendumId: BN | number): Observable<DerivedReferendumVote[]> =>
     api.query.democracy.votersFor<Vec<AccountId>>(referendumId).pipe(
       switchMap((votersFor): Observable<[Vec<AccountId>, Vote[], DerivedBalances[]]> =>
         combineLatest([
@@ -36,5 +36,5 @@ export const referendumVotesFor = memo((api: ApiInterfaceRx): (referendumId: BN
         } as unknown as DerivedReferendumVote))
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/democracy/referendums.ts

@@ -17,7 +17,7 @@ import { referendumInfos } from './referendumInfos';
 export const referendums = memo((api: ApiInterfaceRx): () => Observable<Option<ReferendumInfoExtended>[]> => {
   const referendumInfosCall = referendumInfos(api);
 
-  return memo((): Observable<Option<ReferendumInfoExtended>[]> =>
+  return (): Observable<Option<ReferendumInfoExtended>[]> =>
     api.queryMulti<[ReferendumIndex, ReferendumIndex]>([
       api.query.democracy.nextTally,
       api.query.democracy.referendumCount
@@ -32,5 +32,5 @@ export const referendums = memo((api: ApiInterfaceRx): () => Observable<Option<R
           : of([])
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/democracy/votes.ts

@@ -11,7 +11,7 @@ import { ApiInterfaceRx } from '@polkadot/api/types';
 import { drr, memo } from '../util';
 
 export const votes = memo((api: ApiInterfaceRx): (referendumId: BN, accountIds?: AccountId[]) => Observable<Vote[]> => {
-  return memo((referendumId: BN, accountIds: AccountId[] = []): Observable<Vote[]> =>
+  return (referendumId: BN, accountIds: AccountId[] = []): Observable<Vote[]> =>
     (
       !accountIds || !accountIds.length
         ? of([] as Vote[])
@@ -20,5 +20,5 @@ export const votes = memo((api: ApiInterfaceRx): (referendumId: BN, accountIds?:
             [referendumId, accountId]
           )
         )
-    ).pipe(drr()));
+    ).pipe(drr());
 }, true);

packages/api-derive/src/elections/approvalsOf.ts

@@ -24,7 +24,7 @@ import { drr, memo } from '../util';
  * ```
  */
 export const approvalsOf = memo((api: ApiInterfaceRx): (who: AccountId) => Observable<boolean[][]> => {
-  return memo((who: AccountId | string): Observable<boolean[][]> =>
+  return (who: AccountId | string): Observable<boolean[][]> =>
     api.query.elections.nextVoterSet<SetIndex>().pipe(
       switchMap((nextVoterSet: SetIndex): Observable<Vec<ApprovalFlag>[]> =>
         api.query.elections.approvalsOf.multi(
@@ -39,5 +39,5 @@ export const approvalsOf = memo((api: ApiInterfaceRx): (who: AccountId) => Obser
         )
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/elections/approvalsOfAt.ts

@@ -26,9 +26,9 @@ import { drr, memo } from '../util';
  * ```
  */
 export const approvalsOfAt = memo((api: ApiInterfaceRx): (who: AccountId, at: SetIndex) => Observable<boolean[]> => {
-  return memo((who: AccountId | string, at: SetIndex | BN | number): Observable<boolean[]> =>
+  return (who: AccountId | string, at: SetIndex | BN | number): Observable<boolean[]> =>
     api.query.elections.approvalsOf<Vec<ApprovalFlag>>([who.toString(), at]).pipe(
       map((flags: Vec<ApprovalFlag>): boolean[] => approvalFlagsToBools(flags)),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/elections/info.ts

@@ -93,6 +93,6 @@ export const info = memo((api: ApiInterfaceRx): () => Observable<DerivedElection
     ? queryPhragmen
     : queryElections;
 
-  return memo((): Observable<DerivedElectionsInfo> =>
-    query(api).pipe(drr()));
+  return (): Observable<DerivedElectionsInfo> =>
+    query(api).pipe(drr());
 }, true);

packages/api-derive/src/elections/voterPositions.ts

@@ -27,7 +27,7 @@ import { drr, memo } from '../util';
  * ```
  */
 export const voterPositions = memo((api: ApiInterfaceRx): () => Observable<DerivedVoterPositions> => {
-  return memo((): Observable<DerivedVoterPositions> =>
+  return (): Observable<DerivedVoterPositions> =>
     api.query.elections.nextVoterSet<SetIndex>().pipe(
       switchMap((nextVoterSet: SetIndex): Observable<[BN, Vec<Option<AccountId>>[]]> => combineLatest(
         of(api.consts.elections.voterSetSize) as any as Observable<BN>,
@@ -54,5 +54,5 @@ export const voterPositions = memo((api: ApiInterfaceRx): () => Observable<Deriv
         }, {});
       }),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/elections/voters.ts

@@ -28,7 +28,7 @@ import { voterPositions } from './voterPositions';
 export const voters = memo((api: ApiInterfaceRx): () => Observable<Vec<AccountId>> => {
   const voterPositionsCall = voterPositions(api);
 
-  return memo((): Observable<Vec<AccountId>> =>
+  return (): Observable<Vec<AccountId>> =>
     voterPositionsCall().pipe(
       map((voterPositions: DerivedVoterPositions): Vec<AccountId> =>
         createType(
@@ -39,5 +39,5 @@ export const voters = memo((api: ApiInterfaceRx): () => Observable<Vec<AccountId
         )
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/imOnline/receivedHeartbeats.ts

@@ -19,7 +19,7 @@ import { drr, memo } from '../util';
 export const receivedHeartbeats = memo((api: ApiInterfaceRx): () => Observable<DerivedHeartbeats> => {
   const stakingOverviewvCall = stakingOverview(api);
 
-  return memo((): Observable<DerivedHeartbeats> =>
+  return (): Observable<DerivedHeartbeats> =>
     api.query.imOnline && api.query.imOnline.receivedHeartbeats && api.query.imOnline.authoredBlocks
       ? stakingOverviewvCall().pipe(
         switchMap(({ currentIndex, validators }): Observable<[AccountId[], Option<Bytes>[], u32[]]> =>
@@ -41,5 +41,5 @@ export const receivedHeartbeats = memo((api: ApiInterfaceRx): () => Observable<D
         ),
         drr()
       )
-      : of({}));
+      : of({});
 }, true);

packages/api-derive/src/session/eraLength.ts

@@ -14,9 +14,9 @@ import { info } from './info';
 export const eraLength = memo((api: ApiInterfaceRx): () => Observable<BlockNumber> => {
   const infoCall = info(api);
 
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     infoCall().pipe(
       map(({ eraLength }): BlockNumber => eraLength),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/session/eraProgress.ts

@@ -14,9 +14,9 @@ import { info } from './info';
 export const eraProgress = memo((api: ApiInterfaceRx): () => Observable<BlockNumber> => {
   const infoCall = info(api);
 
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     infoCall().pipe(
       map(({ eraProgress }): BlockNumber => eraProgress),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/session/indexes.ts

@@ -13,7 +13,7 @@ import { u32 } from '@polkadot/types';
 import { drr, memo } from '../util';
 
 export const indexes = memo((api: ApiInterfaceRx): () => Observable<DeriveSessionIndexes> => {
-  return memo((): Observable<DeriveSessionIndexes> =>
+  return (): Observable<DeriveSessionIndexes> =>
     api.queryMulti<[SessionIndex, EraIndex, u32]>([
       api.query.session.currentIndex,
       api.query.staking.currentEra,
@@ -23,5 +23,5 @@ export const indexes = memo((api: ApiInterfaceRx): () => Observable<DeriveSessio
         currentIndex, currentEra, validatorCount
       })),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/session/info.ts

@@ -138,6 +138,6 @@ export const info = memo((api: ApiInterfaceRx): () => Observable<DerivedSessionI
       : infoLatestAura // 2.x with Aura (not all info there)
     : infoV1;
 
-  return memo((): Observable<DerivedSessionInfo> =>
-    query(api, calls).pipe(drr()));
+  return (): Observable<DerivedSessionInfo> =>
+    query(api, calls).pipe(drr());
 }, true);

packages/api-derive/src/session/sessionProgress.ts

@@ -14,9 +14,9 @@ import { info } from './info';
 export const sessionProgress = memo((api: ApiInterfaceRx): () => Observable<BlockNumber> => {
   const infoCall = info(api);
 
-  return memo((): Observable<BlockNumber> =>
+  return (): Observable<BlockNumber> =>
     infoCall().pipe(
       map(({ sessionProgress }): BlockNumber => sessionProgress),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/staking/controllers.ts

@@ -16,7 +16,7 @@ import { drr, memo } from '../util';
  * @description From the list of stash accounts, retrieve the list of controllers
  */
 export const controllers = memo((api: ApiInterfaceRx): () => Observable<[AccountId[], Option<AccountId>[]]> => {
-  return memo((): Observable<[AccountId[], Option<AccountId>[]]> =>
+  return (): Observable<[AccountId[], Option<AccountId>[]]> =>
     api.query.staking.validators<[AccountId[]] & Codec>().pipe(
       switchMap(([stashIds]): Observable<[AccountId[], Option<AccountId>[]]> =>
         combineLatest([
@@ -28,5 +28,5 @@ export const controllers = memo((api: ApiInterfaceRx): () => Observable<[Account
         ])
       ),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/staking/info.ts

@@ -232,6 +232,6 @@ export const info = memo((api: ApiInterfaceRx): (_accountId: Uint8Array | string
     ? retrieveV2
     : retrieveV1;
 
-  return memo((accountId: Uint8Array | string): Observable<DerivedStaking> =>
-    query(api, calls, createType('AccountId', accountId)).pipe(drr()));
+  return (accountId: Uint8Array | string): Observable<DerivedStaking> =>
+    query(api, calls, createType('AccountId', accountId)).pipe(drr());
 }, true);

packages/api-derive/src/staking/infoStash.ts

@@ -57,9 +57,9 @@ export const infoStash = memo((api: ApiInterfaceRx): (stashId: AccountId) => Obs
     ? retrieveV2
     : retrieveV1;
 
-  return memo((stashId: AccountId): Observable<DerivedStakingStash> =>
+  return (stashId: AccountId): Observable<DerivedStakingStash> =>
     query(api, stashId).pipe(
       map((result): DerivedStakingStash => parse(stashId, result)),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/staking/overview.ts

@@ -2,32 +2,31 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { AccountId, EraPoints } from '@polkadot/types/interfaces';
+import { EraPoints } from '@polkadot/types/interfaces';
 import { ApiInterfaceRx } from '@polkadot/api/types';
 import { DerivedStakingOverview } from '../types';
 
 import { Observable, combineLatest, of } from 'rxjs';
 import { map, switchMap } from 'rxjs/operators';
-import { createType, Vec } from '@polkadot/types';
+import { createType } from '@polkadot/types';
 
 import { drr, memo } from '../util';
 import { indexes as sessionIndexes } from '../session';
+import { validators } from './validators';
 
 /**
  * @description Retrieve the staking overview, including elected and points earned
  */
 export const overview = memo((api: ApiInterfaceRx): () => Observable<DerivedStakingOverview> => {
   const sessionIndexesCall = sessionIndexes(api);
+  const validatorsCall = validators(api);
 
-  return memo((): Observable<DerivedStakingOverview> =>
+  return (): Observable<DerivedStakingOverview> =>
     combineLatest([
       sessionIndexesCall(),
-      api.queryMulti<[Vec<AccountId>, Vec<AccountId>]>([
-        api.query.session.validators,
-        api.query.staking.currentElected
-      ])
+      validatorsCall()
     ]).pipe(
-      switchMap(([{ currentEra, currentIndex, validatorCount }, [validators, currentElected]]) =>
+      switchMap(([{ currentEra, currentIndex, validatorCount }, { currentElected, validators }]) =>
         combineLatest([
           of({ currentElected, currentEra, currentIndex, validators, validatorCount }),
           // this will change on a per block basis, keep it innermost (and it needs eraIndex)
@@ -40,5 +39,5 @@ export const overview = memo((api: ApiInterfaceRx): () => Observable<DerivedStak
         currentElected, currentEra, currentIndex, eraPoints, validators, validatorCount
       })),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/staking/recentlyOffline.ts

@@ -36,7 +36,7 @@ function expandDerived (recentlyOffline: OfflineResult): DerivedRecentlyOffline
  * @description Retrieve a keyed record of accounts recently reported to be offline
  */
 export const recentlyOffline = memo((api: ApiInterfaceRx): () => Observable<DerivedRecentlyOffline> => {
-  return memo((): Observable<DerivedRecentlyOffline> =>
+  return (): Observable<DerivedRecentlyOffline> =>
     (
       // TODO recentlyOffline  has been dropped for 2.x and replaced, figure out the
       // replacement as actually use and implement it
@@ -46,5 +46,5 @@ export const recentlyOffline = memo((api: ApiInterfaceRx): () => Observable<Deri
     ).pipe(
       map(expandDerived),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/staking/validators.ts

@@ -4,22 +4,26 @@
 
 import { AccountId } from '@polkadot/types/interfaces';
 import { ApiInterfaceRx } from '@polkadot/api/types';
+import { DeriveStakingValidators } from '../types';
 
 import { Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
+import { Vec } from '@polkadot/types';
 
 import { drr, memo } from '../util';
-import { overview } from './overview';
 
 /**
  * @description Retrieve latest list of validators
  */
-export const validators = memo((api: ApiInterfaceRx): () => Observable<AccountId[]> => {
-  const overviewCall = overview(api);
-
-  return memo((): Observable<AccountId[]> =>
-    overviewCall().pipe(
-      map(({ validators }): AccountId[] => validators),
+export const validators = memo((api: ApiInterfaceRx): () => Observable<DeriveStakingValidators> => {
+  return (): Observable<DeriveStakingValidators> =>
+    api.queryMulti<[Vec<AccountId>, Vec<AccountId>]>([
+      api.query.session.validators,
+      api.query.staking.currentElected
+    ]).pipe(
+      map(([validators, currentElected]): DeriveStakingValidators => ({
+        currentElected, validators
+      })),
       drr()
-    ));
+    );
 }, true);

packages/api-derive/src/types.ts

@@ -115,6 +115,11 @@ export interface DerivedStakingOnlineStatus {
   }[];
 }
 
+export interface DeriveStakingValidators {
+  currentElected: AccountId[];
+  validators: AccountId[];
+}
+
 export interface DerivedStakingStash {
   controllerId?: AccountId;
   nominators?: AccountId[];