fix(core): Clear lView from IcuIteratorState when stack is empty to prevent memory leak

mattlewis92 · crisbeto · commit ca3fd7847f60 · 2025-10-27T19:42:21.000+01:00
If a component template contains an icu expression it is being retained until the next change detection cycle for that template. This results in a net retention of only ever a single copy of the given lView but that creates an opportunity for compounding leaks. Change the icu i18n_icu_container_visitor to free the IcuIteratorState retained lView when the stack is empty so that garbage collection can occur when the view is discarded. (cherry picked from commit 59e6489)
diff --git a/packages/core/src/render3/i18n/i18n_icu_container_visitor.ts b/packages/core/src/render3/i18n/i18n_icu_container_visitor.ts
@@ -15,7 +15,7 @@ import {TIcuContainerNode} from '../interfaces/node';
 import {RNode} from '../interfaces/renderer_dom';
 import {LView, TVIEW} from '../interfaces/view';
 
-interface IcuIteratorState {
+export interface IcuIteratorState {
   stack: any[];
   index: number;
   lView?: LView;
@@ -35,7 +35,7 @@ function enterIcu(state: IcuIteratorState, tIcu: TIcu, lView: LView) {
   }
 }
 
-function icuContainerIteratorNext(state: IcuIteratorState): RNode | null {
+export function icuContainerIteratorNext(state: IcuIteratorState): RNode | null {
   if (state.index < state.removes!.length) {
     const removeOpCode = state.removes![state.index++] as number;
     ngDevMode && assertNumber(removeOpCode, 'Expecting OpCode number');
@@ -54,6 +54,8 @@ function icuContainerIteratorNext(state: IcuIteratorState): RNode | null {
     }
   } else {
     if (state.stack.length === 0) {
+      // Clear the lView reference when iteration completes to allow garbage collection
+      state.lView = undefined;
       return null;
     } else {
       state.removes = state.stack.pop();
diff --git a/packages/core/test/render3/i18n/i18n_spec.ts b/packages/core/test/render3/i18n/i18n_spec.ts
@@ -11,6 +11,10 @@ import {
   getTranslationForTemplate,
   i18nStartFirstCreatePass,
 } from '../../../src/render3/i18n/i18n_parse';
+import {
+  icuContainerIteratorNext,
+  IcuIteratorState,
+} from '../../../src/render3/i18n/i18n_icu_container_visitor';
 import {getTIcu} from '../../../src/render3/i18n/i18n_util';
 import {TNodeType} from '../../../src/render3/interfaces/node';
 
@@ -584,6 +588,23 @@ describe('Runtime i18n', () => {
         ],
       });
     });
+
+    it('should clear lView reference when ICU iteration completes', () => {
+      const state: IcuIteratorState = {
+        stack: [],
+        index: 0,
+        removes: [] as any,
+        lView: [] as any, // Mock lView
+      };
+
+      // Call icuContainerIteratorNext with an empty removes array and empty stack
+      // This simulates the end of iteration
+      const result = icuContainerIteratorNext(state);
+
+      expect(result).toBeNull();
+      // Verify that lView should be cleared to allow garbage collection
+      expect(state.lView).toBeUndefined();
+    });
   });
 
   describe(`i18nAttribute`, () => {
