From bc85551bfce735493054489acb31426b4875e602 Mon Sep 17 00:00:00 2001
From: Andrew Scott <atscott@google.com>
Date: Mon, 22 Jan 2024 09:12:44 -0800
Subject: [PATCH] fix(router): revert commit that replaced `last` helper with
 native `Array.at(-1)` (#54021)

While `Array.at` is technically supported in all browsers we officially
support, the change was needlessly breaking without any real benefit.

PR Close #54021
---
 .../core/test/bundling/router/bundle.golden_symbols.json   | 3 +++
 packages/router/src/create_url_tree.ts                     | 4 ++--
 packages/router/src/utils/collection.ts                    | 7 +++++++
 packages/router/src/utils/config_matching.ts               | 3 ++-
 4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/packages/core/test/bundling/router/bundle.golden_symbols.json b/packages/core/test/bundling/router/bundle.golden_symbols.json
index b3c9d87c001..10629a5ad93 100644
--- a/packages/core/test/bundling/router/bundle.golden_symbols.json
+++ b/packages/core/test/bundling/router/bundle.golden_symbols.json
@@ -1583,6 +1583,9 @@
   {
     "name": "last"
   },
+  {
+    "name": "last3"
+  },
   {
     "name": "lastNodeWasCreated"
   },
diff --git a/packages/router/src/create_url_tree.ts b/packages/router/src/create_url_tree.ts
index 42ef1222693..361c2e52a76 100644
--- a/packages/router/src/create_url_tree.ts
+++ b/packages/router/src/create_url_tree.ts
@@ -12,7 +12,7 @@ import {RuntimeErrorCode} from './errors';
 import {ActivatedRouteSnapshot} from './router_state';
 import {Params, PRIMARY_OUTLET} from './shared';
 import {createRoot, squashSegmentGroup, UrlSegment, UrlSegmentGroup, UrlTree} from './url_tree';
-import {shallowEqual} from './utils/collection';
+import {last, shallowEqual} from './utils/collection';
 
 
 /**
@@ -187,7 +187,7 @@ class Navigation {
     }
 
     const cmdWithOutlet = commands.find(isCommandWithOutlets);
-    if (cmdWithOutlet && cmdWithOutlet !== commands.at(-1)) {
+    if (cmdWithOutlet && cmdWithOutlet !== last(commands)) {
       throw new RuntimeError(
           RuntimeErrorCode.MISPLACED_OUTLETS_COMMAND,
           (typeof ngDevMode === 'undefined' || ngDevMode) &&
diff --git a/packages/router/src/utils/collection.ts b/packages/router/src/utils/collection.ts
index 7be405ec8d1..b6cd8ec59aa 100644
--- a/packages/router/src/utils/collection.ts
+++ b/packages/router/src/utils/collection.ts
@@ -57,6 +57,13 @@ export function equalArraysOrString(a: string|string[], b: string|string[]) {
   }
 }
 
+/**
+ * Return the last element of an array.
+ */
+export function last<T>(a: T[]): T|null {
+  return a.length > 0 ? a[a.length - 1] : null;
+}
+
 export function wrapIntoObservable<T>(value: T|Promise<T>|Observable<T>): Observable<T> {
   if (isObservable(value)) {
     return value;
diff --git a/packages/router/src/utils/config_matching.ts b/packages/router/src/utils/config_matching.ts
index 25b5b6a1e6c..14e81364084 100644
--- a/packages/router/src/utils/config_matching.ts
+++ b/packages/router/src/utils/config_matching.ts
@@ -15,6 +15,7 @@ import {runCanMatchGuards} from '../operators/check_guards';
 import {defaultUrlMatcher, PRIMARY_OUTLET} from '../shared';
 import {UrlSegment, UrlSegmentGroup, UrlSerializer} from '../url_tree';
 
+import {last} from './collection';
 import {getOrCreateRouteInjectorIfNeeded, getOutlet} from './config';
 
 export interface MatchResult {
@@ -95,7 +96,7 @@ export function match(
 function createWildcardMatchResult(segments: UrlSegment[]): MatchResult {
   return {
     matched: true,
-    parameters: segments.at(-1)?.parameters ?? {},
+    parameters: segments.length > 0 ? last(segments)!.parameters : {},
     consumedSegments: segments,
     remainingSegments: [],
     positionalParamSegments: {},