Fix errors in find and filter with an empty store (#6265)

* Fix errors in find and filter with an empty store (#6262)

* Fix errors in find and filter with an empty store (#6262)

* fix prettier issues

* add changeset

.changeset/early-birds-taste.md

@@ -0,0 +1,5 @@
+---
+'@graphql-tools/mock': patch
+---
+
+fix errors in find and filter with an empty store

packages/mock/src/MockStore.ts

@@ -192,12 +192,12 @@ export class MockStore implements IMockStore {
 
   filter(key: string, predicate: (val: Entity) => boolean) {
     const entity = this.store[key];
-    return Object.values(entity).filter(predicate);
+    return entity ? Object.values(entity).filter(predicate) : [];
   }
 
   find(key: string, predicate: (val: Entity) => boolean) {
     const entity = this.store[key];
-    return Object.values(entity).find(predicate);
+    return entity ? Object.values(entity).find(predicate) : undefined;
   }
 
   private getImpl<KeyT extends KeyTypeConstraints>(args: GetArgs<KeyT>) {

packages/mock/tests/store.spec.ts

@@ -1,5 +1,5 @@
 import { buildSchema } from 'graphql';
-import { createMockStore } from '../src/index.js';
+import { createMockStore, MockStore } from '../src/index.js';
 import { assertIsRef, Ref } from '../src/types.js';
 import { makeRef } from '../src/utils.js';
 
@@ -626,4 +626,46 @@ describe('MockStore', () => {
     expect(store.get('User', '123', 'name', { format: 'fullName' })).toEqual('Alexandre the Great');
     expect(store.get('User', '123', 'name', { format: 'shortName' })).toEqual('Alex');
   });
+
+  describe('filter method', () => {
+    it('should be able to filter an empty list', () => {
+      const store = new MockStore({ schema });
+      store.set('User', 'user1', { name: 'Ross' });
+      expect(store.filter('User', () => false)).toEqual([]);
+      store.reset();
+      expect(store.filter('User', () => true)).toEqual([]);
+    });
+
+    it('should apply the filter', () => {
+      const store = new MockStore({ schema });
+      store.set('User', 'user1', { name: 'Ross' });
+      store.set('User', 'user2', { name: 'Nico' });
+      expect(store.filter('User', () => true)).toEqual([{ name: 'Ross' }, { name: 'Nico' }]);
+      expect(store.filter('User', ({ name }) => (name as string).startsWith('R'))).toEqual([
+        { name: 'Ross' },
+      ]);
+    });
+  });
+
+  describe('find method', () => {
+    it('should return undefined for an empty store', () => {
+      const store = new MockStore({ schema });
+      expect(store.find('User', () => true)).toBeUndefined();
+    });
+
+    it('should return undefined for a miss', () => {
+      const store = new MockStore({ schema });
+      store.set('User', 'user1', { name: 'Ross' });
+      expect(store.find('User', () => false)).toBeUndefined();
+    });
+
+    it('should return a match', () => {
+      const store = new MockStore({ schema });
+      store.set('User', 'user1', { name: 'Ross' });
+      store.set('User', 'user2', { name: 'Nico' });
+      expect(store.find('User', ({ name }) => (name as string).startsWith('N'))).toEqual({
+        name: 'Nico',
+      });
+    });
+  });
 });