fix: use shareReplay for inflight requests (#11810)

packages/puppeteer-core/src/api/Page.ts

@@ -19,11 +19,13 @@ import {
   map,
   merge,
   mergeMap,
+  mergeScan,
   of,
-  race,
   raceWith,
+  ReplaySubject,
   startWith,
   switchMap,
+  take,
   takeUntil,
   timer,
   type Observable,
@@ -604,8 +606,7 @@ export abstract class Page extends EventEmitter<PageEvents> {
 
   #requestHandlers = new WeakMap<Handler<HTTPRequest>, Handler<HTTPRequest>>();
 
-  #requestsInFlight = 0;
-  #inflight$: Observable<number>;
+  #inflight$ = new ReplaySubject<number>(1);
 
   /**
    * @internal
@@ -613,39 +614,37 @@ export abstract class Page extends EventEmitter<PageEvents> {
   constructor() {
     super();
 
-    this.#inflight$ = fromEmitterEvent(this, PageEvent.Request).pipe(
-      takeUntil(fromEmitterEvent(this, PageEvent.Close)),
-      mergeMap(request => {
-        return concat(
-          of(1),
-          race(
-            fromEmitterEvent(this, PageEvent.Response).pipe(
-              filter(response => {
-                return response.request()._requestId === request._requestId;
-              })
-            ),
-            fromEmitterEvent(this, PageEvent.RequestFailed).pipe(
-              filter(failure => {
-                return failure._requestId === request._requestId;
-              })
-            ),
-            fromEmitterEvent(this, PageEvent.RequestFinished).pipe(
-              filter(success => {
-                return success._requestId === request._requestId;
+    fromEmitterEvent(this, PageEvent.Request)
+      .pipe(
+        mergeMap(originalRequest => {
+          return concat(
+            of(1),
+            merge(
+              fromEmitterEvent(this, PageEvent.RequestFailed),
+              fromEmitterEvent(this, PageEvent.RequestFinished),
+              fromEmitterEvent(this, PageEvent.Response).pipe(
+                map(response => {
+                  return response.request();
+                })
+              )
+            ).pipe(
+              filter(request => {
+                return request._requestId === originalRequest._requestId;
+              }),
+              take(1),
+              map(() => {
+                return -1;
               })
             )
-          ).pipe(
-            map(() => {
-              return -1;
-            })
-          )
-        );
-      })
-    );
-
-    this.#inflight$.subscribe(count => {
-      this.#requestsInFlight += count;
-    });
+          );
+        }),
+        mergeScan((acc, addend) => {
+          return of(acc + addend);
+        }, 0),
+        takeUntil(fromEmitterEvent(this, PageEvent.Close)),
+        startWith(0)
+      )
+      .subscribe(this.#inflight$);
   }
 
   /**
@@ -1776,13 +1775,11 @@ export abstract class Page extends EventEmitter<PageEvents> {
     } = options;
 
     return this.#inflight$.pipe(
-      startWith(this.#requestsInFlight),
-      switchMap(() => {
-        if (this.#requestsInFlight > concurrency) {
+      switchMap(inflight => {
+        if (inflight > concurrency) {
           return EMPTY;
-        } else {
-          return timer(idleTime);
         }
+        return timer(idleTime);
       }),
       map(() => {}),
       raceWith(

packages/puppeteer-core/third_party/rxjs/rxjs.ts

@@ -22,8 +22,10 @@ export {
   ignoreElements,
   lastValueFrom,
   map,
+  ReplaySubject,
   merge,
   mergeMap,
+  mergeScan,
   NEVER,
   noop,
   Observable,
@@ -34,6 +36,7 @@ export {
   retry,
   startWith,
   switchMap,
+  take,
   takeUntil,
   tap,
   throwIfEmpty,