Expose queryMulti on api (#909)

* Expose queryMulti on api

* Convert contract fees to queryMulti

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

@@ -2,7 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { Observable, combineLatest } from 'rxjs';
+import { Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
 import { ApiInterface$Rx } from '@polkadot/api/types';
 
@@ -12,12 +12,12 @@ import { drr } from '../util/drr';
 
 export function fees (api: ApiInterface$Rx) {
   return (): Observable<DerivedFees> => {
-    return (combineLatest([
-      api.query.balances.creationFee(),
-      api.query.balances.existentialDeposit(),
-      api.query.balances.transactionBaseFee(),
-      api.query.balances.transactionByteFee(),
-      api.query.balances.transferFee()
+    return (api.queryMulti([
+      api.query.balances.creationFee,
+      api.query.balances.existentialDeposit,
+      api.query.balances.transactionBaseFee,
+      api.query.balances.transactionByteFee,
+      api.query.balances.transferFee
     ]) as any as Observable<[BN, BN, BN, BN, BN]>).pipe(
       map(([creationFee, existentialDeposit, transactionBaseFee, transactionByteFee, transferFee]) => ({
         creationFee,

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

@@ -2,43 +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 { ApiInterface$Rx, QueryableStorageFunctionBase } from '@polkadot/api/types';
-import { Codec } from '@polkadot/types/types';
+import { ApiInterface$Rx } from '@polkadot/api/types';
 import { DerivedContractFees } from '../types';
 
 import BN from 'bn.js';
-import { Observable, combineLatest, of } from 'rxjs';
+import { Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
 
 import { drr } from '../util/drr';
 
-// TODO The contracts API is still in flux, so some of these may disappear or re-appear or get replaced. Instead of
-// failing here, do best effort - if something does not exist, return 0 for the specific value. Should be removed
-// when actually stable and no more changes expected
-function nonexistentZero (fn: QueryableStorageFunctionBase<Observable<Codec>, Observable<Codec>>): Observable<BN> {
-  return fn
-    ? fn() as any as Observable<BN>
-    : of(new BN(0));
-}
-
 /**
- * Get the balances for all intentions and their nominators
+ * Retrieves all the contract fees
  */
 export function fees (api: ApiInterface$Rx) {
-  // TODO Once we have muti support for disjointed queries, add here (so we make a single
-  // query for all these to the node).
   return (): Observable<DerivedContractFees> => {
-    return (combineLatest([
-      nonexistentZero(api.query.contract.callBaseFee),
-      nonexistentZero(api.query.contract.contractFee),
-      nonexistentZero(api.query.contract.createBaseFee),
-      nonexistentZero(api.query.contract.creationFee),
-      nonexistentZero(api.query.contract.rentByteFee),
-      nonexistentZero(api.query.contract.rentDepositOffset),
-      nonexistentZero(api.query.contract.transactionBaseFee),
-      nonexistentZero(api.query.contract.transactionByteFee),
-      nonexistentZero(api.query.contract.transferFee),
-      nonexistentZero(api.query.contract.tombstoneDeposit)
+    return (api.queryMulti([
+      api.query.contract.callBaseFee,
+      api.query.contract.contractFee,
+      api.query.contract.createBaseFee,
+      api.query.contract.creationFee,
+      api.query.contract.rentByteFee,
+      api.query.contract.rentDepositOffset,
+      api.query.contract.transactionBaseFee,
+      api.query.contract.transactionByteFee,
+      api.query.contract.transferFee,
+      api.query.contract.tombstoneDeposit
     ]) as any as Observable<Array<BN>>).pipe(
       map(([callBaseFee, contractFee, createBaseFee, creationFee, rentByteFee, rentDepositOffset, transactionBaseFee, transactionByteFee, transferFee, tombstoneDeposit]) => {
         return {