optimize weak cache code

cocos/core/asset-manager/asset-manager.ts

@@ -33,7 +33,7 @@ import { error } from '../platform/debug';
 import { sys } from '../platform/sys';
 import { basename, extname } from '../utils/path';
 import Bundle from './bundle';
-import Cache from './cache';
+import Cache, { ICache } from './cache';
 import CacheManager from './cache-manager';
 import dependUtil from './depend-util';
 import downloader from './downloader';
@@ -161,7 +161,7 @@ export class AssetManager {
      * 已加载 bundle 的集合， 你能通过 {{#crossLink "AssetManager/removeBundle:method"}}{{/crossLink}} 来移除缓存
      *
      */
-    public bundles: Cache<Bundle> = bundles;
+    public bundles: ICache<Bundle> = bundles;
 
     /**
      * @en
@@ -170,7 +170,7 @@ export class AssetManager {
      * @zh
      * 已加载资源的集合， 你能通过 {{#crossLink "AssetManager/releaseAsset:method"}}{{/crossLink}} 来移除缓存
      */
-    public assets: Cache<Asset> = assets;
+    public assets: ICache<Asset> = assets;
 
     public generalImportBase = '';
     public generalNativeBase = '';

cocos/core/asset-manager/cache.ts

@@ -28,6 +28,18 @@
  */
 import { js } from '../utils/js';
 
+export interface ICache<T> {
+    add (key: string, val: T): T;
+    get (key: string): T | undefined | null;
+    has (key: string): boolean;
+    remove (key: string): T | undefined | null;
+    clear (): void;
+    forEach (func: (val: T, key: string) => void): void;
+    find (predicate: (val: T, key: string) => boolean): T | null;
+    readonly count: number;
+    destroy (): void;
+}
+
 /**
  * @en
  * use to cache something
@@ -36,7 +48,7 @@ import { js } from '../utils/js';
  * 用于缓存某些内容
  *
  */
-export default class Cache<T = any> {
+export default class Cache<T = any> implements ICache<T> {
     protected _map: Record<string, T> | null = null;
     protected _count = 0;
 

cocos/core/asset-manager/deprecated.ts

@@ -34,6 +34,7 @@ import { legacyCC } from '../global-exports';
 import { getError, warn, warnID } from '../platform/debug';
 import { macro } from '../platform/macro';
 import { path, removeProperty, replaceProperty } from '../utils';
+import Cache from './cache';
 import assetManager, { AssetManager } from './asset-manager';
 import { resources } from './bundle';
 import dependUtil from './depend-util';
@@ -108,9 +109,17 @@ export class CCLoader {
     public _autoReleaseSetting: Record<string, boolean> = Object.create(null);
     private _parseLoadResArgs = parseLoadResArgs;
 
-    public get _cache () {
-        // @ts-expect-error return private property
-        return assets._map;
+    public get _cache (): Record<string, Asset> {
+        if (assets instanceof Cache) {
+            // @ts-expect-error return private property
+            return assets._map;
+        } else {
+            const map = {};
+            assets.forEach((val, key) => {
+                map[key] = val;
+            });
+            return map;
+        }
     }
 
     /**

cocos/core/asset-manager/pack-manager.ts

@@ -28,10 +28,7 @@
  */
 
 import { ImageAsset, Texture2D } from '../assets';
-import MissingScript from '../components/missing-script';
 import { packCustomObjData, unpackJSONs } from '../data/deserialize';
-// import MissingScript from '../components/missing-script';
-// import { packCustomObjData, unpackJSONs } from '../data/deserialize-compiled';
 import { error, errorID } from '../platform/debug';
 import { js } from '../utils/js';
 import Cache from './cache';

cocos/core/asset-manager/release-manager.ts

@@ -33,8 +33,6 @@ import { Node, Scene } from '../scene-graph';
 import Cache from './cache';
 import dependUtil from './depend-util';
 import { assets, references } from './shared';
-import { ImageAsset } from '../assets/image-asset';
-import { TextureBase } from '../assets/texture-base';
 import { callInNextTick } from '../utils/misc';
 import { js } from '../utils/js';
 

cocos/core/asset-manager/weak-cache.ts

@@ -1,17 +1,16 @@
 import { js } from '../utils/js';
-import Cache from './cache';
+import { ICache } from './cache';
 
 declare class WeakRef<T> {
     constructor (obj: T);
     deref (): T | null;
 }
 
-export default class WeakCache<T> extends Cache<T> {
+export default class WeakCache<T> implements ICache<T> {
     protected _weakMap: Record<string, WeakRef<T>> = {};
 
     constructor (map?: Record<string, T>) {
-        super();
-        this._map = null;
+        if (typeof window.WeakRef === 'undefined') throw new Error('this platform does not support WeakRef!');
         if (map) {
             for (const key in map) {
                 this._weakMap[key] = new WeakRef(map[key]);