Use asyncScheduler for all derives (#2043)

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

@@ -4,10 +4,9 @@
 
 import { BlockNumber } from '@polkadot/types/interfaces';
 
-import { Observable, combineLatest } from 'rxjs';
-import { map } from 'rxjs/operators';
+import { Observable, asyncScheduler, combineLatest } from 'rxjs';
+import { map, observeOn } from 'rxjs/operators';
 import { ApiInterfaceRx } from '@polkadot/api/types';
-import { createType } from '@polkadot/types';
 
 import { memo } from '../util';
 
@@ -30,8 +29,9 @@ export function bestNumberLag (api: ApiInterfaceRx): () => Observable<BlockNumbe
       api.derive.chain.bestNumber(),
       api.derive.chain.bestNumberFinalized()
     ]).pipe(
+      observeOn(asyncScheduler),
       map(([bestNumber, bestNumberFinalized]): BlockNumber =>
-        createType(api.registry, 'BlockNumber', bestNumber.sub(bestNumberFinalized))
+        api.registry.createType('BlockNumber', bestNumber.sub(bestNumberFinalized))
       )
     ));
 }

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

@@ -4,8 +4,8 @@
 
 import { ApiInterfaceRx } from '@polkadot/api/types';
 
-import { Observable, combineLatest, of } from 'rxjs';
-import { catchError, map } from 'rxjs/operators';
+import { Observable, asyncScheduler, combineLatest, of } from 'rxjs';
+import { catchError, map, observeOn } from 'rxjs/operators';
 
 import { HeaderExtended } from '../type';
 import { memo } from '../util';
@@ -32,6 +32,7 @@ export function getHeader (api: ApiInterfaceRx): (hash: Uint8Array | string) =>
         ? api.query.session.validators.at(hash)
         : of([])
     ]).pipe(
+      observeOn(asyncScheduler),
       map(([header, validators]): HeaderExtended =>
         new HeaderExtended(api.registry, header, validators)
       ),

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

@@ -4,8 +4,8 @@
 
 import { ApiInterfaceRx } from '@polkadot/api/types';
 
-import { Observable, combineLatest, of } from 'rxjs';
-import { map } from 'rxjs/operators';
+import { Observable, asyncScheduler, combineLatest, of } from 'rxjs';
+import { map, observeOn } from 'rxjs/operators';
 
 import { HeaderExtended } from '../type';
 import { memo } from '../util';
@@ -31,6 +31,7 @@ export function subscribeNewHeads (api: ApiInterfaceRx): () => Observable<Header
         ? api.query.session.validators()
         : of([])
     ]).pipe(
+      observeOn(asyncScheduler),
       map(([header, validators]): HeaderExtended =>
         new HeaderExtended(api.registry, header, validators)
       )