Revert "refactor(core): warn about duplicated keys when using built-in @for (angular#55243)" (angular#55293)

This reverts commit e3696ad.
caused a test failure internally

PR Close angular#55293

Author: atscott

goldens/public-api/core/errors.md

@@ -79,8 +79,6 @@ export const enum RuntimeErrorCode {
     // (undocumented)
     INVALID_SKIP_HYDRATION_HOST = -504,
     // (undocumented)
-    LOOP_TRACK_DUPLICATE_KEYS = 955,
-    // (undocumented)
     MISSING_DOCUMENT = 210,
     // (undocumented)
     MISSING_GENERATED_DEF = 906,

packages/core/src/errors.ts

@@ -124,9 +124,6 @@ export const enum RuntimeErrorCode {
   // Output()
   OUTPUT_REF_DESTROYED = 953,
 
-  // Repeater errors
-  LOOP_TRACK_DUPLICATE_KEYS = 955,
-
   // Runtime dependency tracker errors
   RUNTIME_DEPS_INVALID_IMPORTED_TYPE = 1000,
   RUNTIME_DEPS_ORPHAN_COMPONENT = 1001,

packages/core/src/render3/instructions/control_flow.ts

@@ -9,7 +9,6 @@
 import {setActiveConsumer} from '@angular/core/primitives/signals';
 
 import {TrackByFunction} from '../../change_detection';
-import {formatRuntimeError, RuntimeErrorCode} from '../../errors';
 import {DehydratedContainerView} from '../../hydration/interfaces';
 import {findMatchingDehydratedView} from '../../hydration/views';
 import {assertDefined, assertFunction} from '../../util/assert';
@@ -254,35 +253,6 @@ class LiveCollectionLContainerImpl extends
   }
 }
 
-function detectDuplicateKeys(
-    collection: Iterable<unknown>, trackByFn: TrackByFunction<unknown>): void {
-  const keyToIdx = new Map<unknown, number>();
-  let duplicatedKeysMsg: string[] = [];
-
-  let idx = 0;
-  for (const item of collection) {
-    const key = trackByFn(idx, item);
-
-    if (keyToIdx.has(key)) {
-      const prevIdx = keyToIdx.get(key);
-      duplicatedKeysMsg.push(`key "${key}" at index "${prevIdx}" and "${idx}"`);
-    }
-
-    keyToIdx.set(key, idx++);
-  }
-
-  if (duplicatedKeysMsg.length > 0) {
-    const message = formatRuntimeError(
-        RuntimeErrorCode.LOOP_TRACK_DUPLICATE_KEYS,
-        'The provided track expression resulted in duplicated keys for a given collection. ' +
-            'Adjust the tracking expression such that it uniquely identifies all the items in the collection. ' +
-            'Duplicated keys were: \n' + duplicatedKeysMsg.join(', \n') + '.');
-
-    // tslint:disable-next-line:no-console
-    console.warn(message);
-  }
-}
-
 /**
  * The repeater instruction does update-time diffing of a provided collection (against the
  * collection seen previously) and maps changes in the collection to views structure (by adding,
@@ -308,11 +278,6 @@ export function ɵɵrepeater(collection: Iterable<unknown>|undefined|null): void
       metadata.liveCollection.reset();
     }
 
-    // make sure that tracking expression doesn't result in duplicate keys for a given collection
-    if (ngDevMode && collection != null) {
-      detectDuplicateKeys(collection, metadata.trackByFn);
-    }
-
     const liveCollection = metadata.liveCollection;
     reconcile(liveCollection, collection, metadata.trackByFn);
 

packages/core/test/acceptance/control_flow_for_spec.ts

@@ -273,32 +273,6 @@ describe('control flow - for', () => {
       fixture.detectChanges();
       expect(context).toBe(fixture.componentInstance);
     });
-
-    it('should warn about duplicated keys', () => {
-      @Component({
-        template: `@for (item of items; track item) {{{item}}}`,
-      })
-      class TestComponent {
-        items = ['a', 'b', 'a', 'c', 'a'];
-      }
-
-      spyOn(console, 'warn');
-
-      const fixture = TestBed.createComponent(TestComponent);
-      fixture.detectChanges();
-      expect(fixture.nativeElement.textContent).toBe('abaca');
-      expect(console.warn).toHaveBeenCalledTimes(2);
-      expect(console.warn)
-          .toHaveBeenCalledWith(jasmine.stringContaining(
-              `NG0955: The provided track expression resulted in duplicated keys for a given collection.`));
-      expect(console.warn)
-          .toHaveBeenCalledWith(jasmine.stringContaining(
-              `Adjust the tracking expression such that it uniquely identifies all the items in the collection. `));
-      expect(console.warn)
-          .toHaveBeenCalledWith(jasmine.stringContaining(`key "a" at index "0" and "2"`));
-      expect(console.warn)
-          .toHaveBeenCalledWith(jasmine.stringContaining(`key "a" at index "2" and "4"`));
-    });
   });
 
   describe('list diffing and view operations', () => {