fix: preserve i18n and versions in filter method

index.js

@@ -160,10 +160,26 @@ module.exports = class Items extends Array {
    */
   filter(fn) {
     const A = [];
+    const filteredNames = this.i18n ? new Set() : null;
 
     for (const el of this) {
-      if (fn(el)) A.push(el);
+      if (fn(el)) {
+        A.push(el);
+        if (filteredNames) filteredNames.add(el.uniqueName);
+      }
+    }
+
+    if (filteredNames) {
+      const filteredI18n = {};
+      for (const uniqueName of filteredNames) {
+        if (Object.prototype.hasOwnProperty.call(this.i18n, uniqueName)) {
+          filteredI18n[uniqueName] = this.i18n[uniqueName];
+        }
+      }
+      A.i18n = filteredI18n;
     }
+
+    A.versions = this.versions;
     return A;
   }
 

index.mjs

@@ -159,15 +159,31 @@ export default class Items extends Array {
    */
   filter(fn) {
     const A = [];
+    const filteredNames = this.i18n ? new Set() : null;
 
     for (const el of this) {
-      if (fn(el)) A.push(el);
+      if (fn(el)) {
+        A.push(el);
+        if (filteredNames) filteredNames.add(el.uniqueName);
+      }
     }
+
+    if (filteredNames) {
+      const filteredI18n = {};
+      for (const uniqueName of filteredNames) {
+        if (Object.prototype.hasOwnProperty.call(this.i18n, uniqueName)) {
+          filteredI18n[uniqueName] = this.i18n[uniqueName];
+        }
+      }
+      A.i18n = filteredI18n;
+    }
+
+    A.versions = this.versions;
     return A;
   }
 
   /**
-   * @Override Array.prototype.filter
+   * @Override Array.prototype.map
    *
    * See filter override
    */

test/index.spec.mjs

@@ -322,6 +322,30 @@ const test = (base) => {
       const realLength = items.length;
       assert(realLength === items.map((x) => x).length);
     });
+    it('should preserve i18n and versions after filter', async () => {
+      const items = await wrapConstr({ category: ['Pets'], i18n: ['es'] });
+      const filtered = items.filter(() => true);
+      assert.deepStrictEqual(filtered.i18n, items.i18n, 'filter should preserve i18n');
+      assert.deepStrictEqual(filtered.versions, items.versions, 'filter should preserve versions');
+    });
+    it('should filter i18n entries to only matched items', async () => {
+      const items = await wrapConstr({ category: ['Pets'], i18n: ['es'] });
+      const targetUniqueName = items[0]?.uniqueName;
+      const filtered = items.filter((i) => i.uniqueName === targetUniqueName);
+      assert.strictEqual(filtered.length, 1, 'should have exactly one result');
+      assert.ok(filtered.i18n, 'filtered result should have i18n');
+      assert.ok(filtered.i18n[targetUniqueName], 'i18n should contain the matched item');
+      assert.strictEqual(Object.keys(filtered.i18n).length, 1, 'i18n should only contain the matched item');
+    });
+    it('edge case: should ignore i18n entry when is missing from original', async () => {
+      const items = await wrapConstr({ category: ['Pets'], i18n: ['es'] });
+      const targetUniqueName = items[0]?.uniqueName;
+      items.i18n = {}; // simulate missing i18n entries
+      const filtered = items.filter((i) => i.uniqueName === targetUniqueName);
+      assert.strictEqual(filtered.length, 1, 'should have exactly one result');
+      assert.ok(filtered.i18n, 'filtered result should have i18n');
+      assert.strictEqual(Object.keys(filtered.i18n).length, 0, 'i18n should be empty when original is empty');
+    });
     describe('helminth', async () => {
       it('should only have drops', async () => {
         const items = await wrapConstr({ category: ['Warframes'] });