Derive combineLatest order adjustments (#4186)

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

@@ -25,17 +25,20 @@ import { memo } from '../util';
  */
 export function getBlock (instanceId: string, api: ApiInterfaceRx): (hash: Uint8Array | string) => Observable<SignedBlockExtended | undefined> {
   return memo(instanceId, (blockHash: Uint8Array | string): Observable<SignedBlockExtended | undefined> =>
-    api.queryAt(blockHash).pipe(
-      switchMap((queryAt) =>
-        combineLatest([
-          api.rpc.chain.getBlock(blockHash),
-          queryAt.system.events(),
-          queryAt.session
-            ? queryAt.session.validators()
-            : of([])
-        ])
-      ),
-      map(([signedBlock, events, validators]) =>
+    combineLatest([
+      api.rpc.chain.getBlock(blockHash),
+      api.queryAt(blockHash).pipe(
+        switchMap((queryAt) =>
+          combineLatest([
+            queryAt.system.events(),
+            queryAt.session
+              ? queryAt.session.validators()
+              : of([])
+          ])
+        )
+      )
+    ]).pipe(
+      map(([signedBlock, [events, validators]]) =>
         createSignedBlockExtended(api.registry, signedBlock, events, validators)
       ),
       catchError((): Observable<undefined> =>

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

@@ -25,17 +25,18 @@ import { memo } from '../util';
  * console.log(`block #${number} was authored by ${author}`);
  * ```
  */
-export function getHeader (instanceId: string, api: ApiInterfaceRx): (hash: Uint8Array | string) => Observable<HeaderExtended | undefined> {
-  return memo(instanceId, (hash: Uint8Array | string): Observable<HeaderExtended | undefined> =>
-    api.queryAt(hash).pipe(
-      switchMap((queryAt) =>
-        combineLatest([
-          api.rpc.chain.getHeader(hash),
+export function getHeader (instanceId: string, api: ApiInterfaceRx): (blockHash: Uint8Array | string) => Observable<HeaderExtended | undefined> {
+  return memo(instanceId, (blockHash: Uint8Array | string): Observable<HeaderExtended | undefined> =>
+    combineLatest([
+      api.rpc.chain.getHeader(blockHash),
+      api.queryAt(blockHash).pipe(
+        switchMap((queryAt) =>
           queryAt.session
             ? queryAt.session.validators()
             : of([] as AccountId[])
-        ])
-      ),
+        )
+      )
+    ]).pipe(
       map(([header, validators]) =>
         createHeaderExtended(header.registry, header, validators)
       ),

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

@@ -21,15 +21,15 @@ export function subscribeNewBlocks (instanceId: string, api: ApiInterfaceRx): ()
         const blockHash = header.createdAtHash || header.hash;
 
         // we get the block first, setting up the registry
-        return api.queryAt(blockHash).pipe(
-          switchMap((queryAt) =>
-            combineLatest([
-              of(header),
-              api.rpc.chain.getBlock(blockHash),
+        return combineLatest([
+          of(header),
+          api.rpc.chain.getBlock(blockHash),
+          api.queryAt(blockHash).pipe(
+            switchMap((queryAt) =>
               queryAt.system.events()
-            ])
+            )
           )
-        );
+        ]);
       }),
       map(([header, block, events]) =>
         createSignedBlockExtended(block.registry, block, events, header.validators)

packages/api-derive/src/tx/events.ts

@@ -16,13 +16,14 @@ interface Result {
 
 export function events (instanceId: string, api: ApiInterfaceRx): (at: Hash) => Observable<Result> {
   return memo(instanceId, (blockHash: Hash) =>
-    api.queryAt(blockHash).pipe(
-      switchMap((queryAt) =>
-        combineLatest([
-          api.rpc.chain.getBlock(blockHash),
+    combineLatest([
+      api.rpc.chain.getBlock(blockHash),
+      api.queryAt(blockHash).pipe(
+        switchMap((queryAt) =>
           queryAt.system.events()
-        ])
-      ),
+        )
+      )
+    ]).pipe(
       map(([block, events]): Result => ({ block, events }))
     )
   );

packages/api-derive/src/tx/signingInfo.ts

@@ -32,20 +32,23 @@ function nextNonce (api: ApiInterfaceRx, address: string): Observable<Index> {
 
 function signingHeader (api: ApiInterfaceRx): Observable<Header> {
   return combineLatest([
-    api.rpc.chain.getHeader(),
-    api.rpc.chain.getFinalizedHead()
-  ]).pipe(
-    switchMap(([bestHeader, finHash]) =>
-      // retrieve the headers - in the case of the current block, we use the parent
-      // to minimize (not completely remove) the impact that forks do have on the system
-      // (when at genesis, just return the current header as the last known)
-      bestHeader.parentHash.isEmpty
-        ? of([bestHeader, bestHeader])
-        : combineLatest([
-          api.rpc.chain.getHeader(bestHeader.parentHash),
-          api.rpc.chain.getHeader(finHash)
-        ])
+    api.rpc.chain.getHeader().pipe(
+      switchMap((header) =>
+        // check for chains at genesis (until block 1 is produced, e.g. 6s), since
+        // we do need to allow transactions at chain start (also dev/seal chains)
+        header.parentHash.isEmpty
+          ? of(header)
+          // in the case of the current block, we use the parent to minimize the
+          // impact of forks on the system, but not completely remove it
+          : api.rpc.chain.getHeader(header.parentHash)
+      )
     ),
+    api.rpc.chain.getFinalizedHead().pipe(
+      switchMap((hash) =>
+        api.rpc.chain.getHeader(hash)
+      )
+    )
+  ]).pipe(
     map(([current, finalized]) =>
       // determine the hash to use, current when lag > max, else finalized
       current.number.unwrap().sub(finalized.number.unwrap()).gt(MAX_FINALITY_LAG)

packages/api-derive/src/util/approvalFlagsToBools.ts

@@ -8,14 +8,14 @@ import type { ApprovalFlag } from '@polkadot/types/interfaces/elections';
 export function approvalFlagsToBools (flags: Vec<ApprovalFlag> | ApprovalFlag[]): boolean[] {
   const bools: boolean[] = [];
 
-  flags.forEach((flag: ApprovalFlag): void => {
-    const str = flag.toString(2);
+  for (let i = 0; i < flags.length; i++) {
+    const str = flags[i].toString(2);
 
     // read from lowest bit to highest
     for (const bit of str.split('').reverse()) {
       bools.push(!!parseInt(bit, 10));
     }
-  });
+  }
 
   // slice off trailing "false" values, as in substrate
   const lastApproval = bools.lastIndexOf(true);

packages/api-derive/src/util/cacheImpl.ts

@@ -10,10 +10,8 @@ export const deriveMapCache: DeriveCache = {
     mapCache.delete(key);
   },
   forEach: (cb: (key: string, value: any) => void): void => {
-    const entries = mapCache.entries();
-
-    for (const entry in entries) {
-      cb(entry[0], entry[1]);
+    for (const [k, v] of mapCache.entries()) {
+      cb(k, v);
     }
   },
   get: <T = any> (key: string): T | undefined => {