fix: Flag store should not access values from prototype. (launchdarkl…

…y#567)

This should be merged after the test organization PR.

packages/shared/sdk-client/__tests__/flag-manager/FlagStore.test.ts

@@ -0,0 +1,60 @@
+import { DefaultFlagStore } from '../../src/flag-manager/FlagStore';
+
+describe('given an empty flag store', () => {
+  let store: DefaultFlagStore;
+
+  beforeEach(() => {
+    store = new DefaultFlagStore();
+  });
+
+  it.each(['unknown', 'toString', 'length'])(
+    'gets undefined for a feature that does not exist',
+    (key) => {
+      expect(store.get(key)).toBeUndefined();
+    },
+  );
+
+  it('can set and get key', () => {
+    store.insertOrUpdate('toString', {
+      version: 1,
+      flag: {
+        version: 1,
+        flagVersion: 1,
+        value: 'test-value',
+        variation: 0,
+        trackEvents: false,
+      },
+    });
+
+    expect(store.get('toString')?.flag.value).toEqual('test-value');
+  });
+
+  it('replaces flags on init', () => {
+    store.insertOrUpdate('potato', {
+      version: 1,
+      flag: {
+        version: 1,
+        flagVersion: 1,
+        value: 'test-value',
+        variation: 0,
+        trackEvents: false,
+      },
+    });
+
+    store.init({
+      newFlag: {
+        version: 1,
+        flag: {
+          version: 1,
+          flagVersion: 1,
+          value: 'new-test-value',
+          variation: 0,
+          trackEvents: false,
+        },
+      },
+    });
+
+    const all = store.getAll();
+    expect(Object.keys(all)).toEqual(['newFlag']);
+  });
+});

packages/shared/sdk-client/src/flag-manager/FlagStore.ts

@@ -31,7 +31,10 @@ export class DefaultFlagStore implements FlagStore {
   }
 
   get(key: string): ItemDescriptor | undefined {
-    return this.flags[key];
+    if (Object.prototype.hasOwnProperty.call(this.flags, key)) {
+      return this.flags[key];
+    }
+    return undefined;
   }
 
   getAll(): { [key: string]: ItemDescriptor } {