From a003dd8dc2ad50db20c684d5a2b1e748ad339a42 Mon Sep 17 00:00:00 2001
From: Jessica Janiuk <jessicajaniuk@google.com>
Date: Fri, 8 Jul 2022 22:07:52 +0000
Subject: [PATCH] Revert "refactor(router): Simplify the prioritizeGuardValue
 logic" (#46759)

This reverts commit f32fface4763d789a8b7cc4f4489f98be4e1073a.

PR Close #46759
---
 .../src/operators/prioritized_guard_value.ts  | 63 ++++++++++---------
 1 file changed, 34 insertions(+), 29 deletions(-)

diff --git a/packages/router/src/operators/prioritized_guard_value.ts b/packages/router/src/operators/prioritized_guard_value.ts
index 62b5ececcd5..2334841c119 100644
--- a/packages/router/src/operators/prioritized_guard_value.ts
+++ b/packages/router/src/operators/prioritized_guard_value.ts
@@ -7,43 +7,48 @@
  */
 
 import {combineLatest, Observable, OperatorFunction} from 'rxjs';
-import {filter, map, startWith, switchMap, take} from 'rxjs/operators';
+import {filter, map, scan, startWith, switchMap, take} from 'rxjs/operators';
 
 import {UrlTree} from '../url_tree';
+import {isUrlTree} from '../utils/type_guards';
 
-const INITIAL_VALUE = Symbol();
+const INITIAL_VALUE = Symbol('INITIAL_VALUE');
 declare type INTERIM_VALUES = typeof INITIAL_VALUE | boolean | UrlTree;
 
-/**
- * Takes an array of observables and returns the result of the first to emit something other than
- * `true`.
- *
- * If all Observables emit `true`, then this operator emits true.
- * Also note that only the first value of each observable is used.
- */
 export function prioritizedGuardValue():
     OperatorFunction<Observable<boolean|UrlTree>[], boolean|UrlTree> {
   return switchMap(obs => {
     return combineLatest(obs.map(o => o.pipe(take(1), startWith(INITIAL_VALUE as INTERIM_VALUES))))
-        .pipe(
-            map((results: INTERIM_VALUES[]) => {
-              for (const result of results) {
-                if (result === true) {
-                  // If result is true, check the next one
-                  continue;
-                } else if (result === INITIAL_VALUE) {
-                  // If guard has not finished, we need to stop processing.
-                  return INITIAL_VALUE;
-                } else {
-                  // Result finished and was not true. Return the result.
-                  return result;
-                }
-              }
-              // Everything resolved to true. Return true.
-              return true;
-            }),
-            filter((item): item is boolean|UrlTree => item !== INITIAL_VALUE),
-            take(1),
-        );
+               .pipe(
+                   scan(
+                       (acc: INTERIM_VALUES, list: INTERIM_VALUES[]) => {
+                         let isPending = false;
+                         return list.reduce((innerAcc, val, i: number) => {
+                           if (innerAcc !== INITIAL_VALUE) return innerAcc;
+
+                           // Toggle pending flag if any values haven't been set yet
+                           if (val === INITIAL_VALUE) isPending = true;
+
+                           // Any other return values are only valid if we haven't yet hit a pending
+                           // call. This guarantees that in the case of a guard at the bottom of the
+                           // tree that returns a redirect, we will wait for the higher priority
+                           // guard at the top to finish before performing the redirect.
+                           if (!isPending) {
+                             // Early return when we hit a `false` value as that should always
+                             // cancel navigation
+                             if (val === false) return val;
+
+                             if (i === list.length - 1 || isUrlTree(val)) {
+                               return val;
+                             }
+                           }
+
+                           return innerAcc;
+                         }, acc);
+                       },
+                       INITIAL_VALUE),
+                   filter(item => item !== INITIAL_VALUE),
+                   map(item => isUrlTree(item) ? item : item === true),  //
+                   take(1)) as Observable<boolean|UrlTree>;
   });
 }