feat: Make storing to local storage robust (#6139)

Handles non serializable objects like Map and Set and makes the
serialisation/deserialisation process more robust generally.

Closes #
[UNL-322](https://linear.app/unleash/issue/UNL-322/add-types-to-local-storage-and-force-simple-types)

---------

Signed-off-by: andreas-unleash <andreas@getunleash.ai>

frontend/src/utils/storage.test.ts

@@ -53,13 +53,26 @@ Object.defineProperty(window, 'sessionStorage', {
     value: sessionStorageMock,
 });
 
-// Test suite
 describe('localStorage with TTL', () => {
     beforeEach(() => {
         localStorage.clear();
+        sessionStorage.clear();
         vi.useFakeTimers();
     });
 
+    test('object should not be retrievable after TTL expires', () => {
+        const testObject = { name: 'Test', number: 123 };
+        setLocalStorageItem('testObjectKey', testObject, 500000);
+
+        vi.advanceTimersByTime(600000);
+
+        const retrievedObject = getLocalStorageItem<{
+            name: string;
+            number: number;
+        }>('testObjectKey');
+        expect(retrievedObject).toBeUndefined();
+    });
+
     test('item should be retrievable before TTL expires', () => {
         setLocalStorageItem('testKey', 'testValue', 600000);
         expect(getLocalStorageItem('testKey')).toBe('testValue');
@@ -82,47 +95,36 @@ describe('localStorage with TTL', () => {
         }>('testObjectKey');
         expect(retrievedObject).toEqual(testObject);
     });
-
-    test('object should not be retrievable after TTL expires', () => {
-        const testObject = { name: 'Test', number: 123 };
-        setLocalStorageItem('testObjectKey', testObject, 500000);
-
-        vi.advanceTimersByTime(600000);
-
-        const retrievedObject = getLocalStorageItem<{
-            name: string;
-            number: number;
-        }>('testObjectKey');
-        expect(retrievedObject).toBeUndefined();
+    test('should correctly store and retrieve a Map object', () => {
+        const testMap = new Map([
+            ['key1', 'value1'],
+            ['key2', 'value2'],
+        ]);
+        setLocalStorageItem('testMap', testMap);
+        expect(getLocalStorageItem<Map<any, any>>('testMap')).toEqual(testMap);
     });
 
-    test('object should be retrievable before TTL expires in sessionStorage', () => {
-        const testObject = { name: 'TestSession', number: 456 };
-        setSessionStorageItem('testObjectKeySession', testObject, 500000);
-
-        const retrievedObject = getSessionStorageItem<typeof testObject>(
-            'testObjectKeySession',
-        );
-        expect(retrievedObject).toEqual(testObject);
+    test('should correctly store and retrieve a Set object', () => {
+        const testSet = new Set(['value1', 'value2']);
+        setLocalStorageItem('testSet', testSet);
+        expect(getLocalStorageItem<Set<any>>('testSet')).toEqual(testSet);
     });
 
-    test('object should not be retrievable after TTL expires in sessionStorage', () => {
-        const testObject = { name: 'TestSession', number: 456 };
-        setSessionStorageItem('testObjectKeySession', testObject, 500000); // 10 minutes TTL
-
-        vi.advanceTimersByTime(600000);
-
-        const retrievedObject = getSessionStorageItem<typeof testObject>(
-            'testObjectKeySession',
-        );
-        expect(retrievedObject).toBeUndefined();
+    test('should handle nested objects with arrays, Maps, and Sets', () => {
+        const complexObject = {
+            array: [1, 2, 3],
+            map: new Map([['nestedKey', 'nestedValue']]),
+            set: new Set([1, 2, 3]),
+        };
+        setLocalStorageItem('complexObject', complexObject);
+        expect(
+            getLocalStorageItem<typeof complexObject>('complexObject'),
+        ).toEqual(complexObject);
     });
 
-    test('should handle set with any level of nesting', () => {
-        setLocalStorageItem(
-            'testKey',
-            new Set([{ nestedSet: new Set([1, 2]) }]),
-        );
-        expect(getLocalStorageItem('testKey')).toEqual([{ nestedSet: [1, 2] }]);
+    test('sessionStorage item should expire as per TTL', () => {
+        setSessionStorageItem('sessionTTL', 'expiring', 50); // 50ms TTL
+        vi.advanceTimersByTime(60);
+        expect(getSessionStorageItem('sessionTTL')).toBeUndefined();
     });
 });

frontend/src/utils/storage.ts

@@ -3,6 +3,37 @@ type Expirable<T> = {
     expiry: number | null;
 };
 
+function isFunction(value: any): boolean {
+    return typeof value === 'function';
+}
+
+function serializer(key: string, value: any): any {
+    if (isFunction(value)) {
+        console.warn('Unable to store function.');
+        return undefined;
+    }
+    if (value instanceof Map) {
+        return { dataType: 'Map', value: Array.from(value.entries()) };
+    } else if (value instanceof Set) {
+        return { dataType: 'Set', value: Array.from(value) };
+    }
+    return value;
+}
+
+function deserializer(key: string, value: any): any {
+    if (value && value.dataType === 'Map') {
+        return new Map(value.value);
+    } else if (value && value.dataType === 'Set') {
+        return new Set(value.value);
+    }
+    return value;
+}
+
+// Custom replacer for JSON.stringify to handle complex objects
+function customReplacer(key: string, value: any): any {
+    return serializer(key, value);
+}
+
 // Get an item from localStorage.
 // Returns undefined if the browser denies access.
 export function getLocalStorageItem<T>(key: string): T | undefined {
@@ -39,12 +70,7 @@ export function setLocalStorageItem<T>(
                     ? new Date().getTime() + timeToLive
                     : null,
         };
-        window.localStorage.setItem(
-            key,
-            JSON.stringify(item, (_key, value) =>
-                value instanceof Set ? [...value] : value,
-            ),
-        );
+        window.localStorage.setItem(key, JSON.stringify(item, customReplacer));
     } catch (err: unknown) {
         console.warn(err);
     }
@@ -66,9 +92,7 @@ export function setSessionStorageItem<T>(
         };
         window.sessionStorage.setItem(
             key,
-            JSON.stringify(item, (_key, value) =>
-                value instanceof Set ? [...value] : value,
-            ),
+            JSON.stringify(item, customReplacer),
         );
     } catch (err: unknown) {
         console.warn(err);
@@ -97,10 +121,14 @@ export function getSessionStorageItem<T>(key: string): T | undefined {
 
 // Parse an item from localStorage.
 // Returns undefined if the item could not be parsed.
-function parseStoredItem<T>(data: string | null): T | undefined {
+function parseStoredItem<T>(data: string | null): Expirable<T> | undefined {
     try {
-        return data ? JSON.parse(data) : undefined;
+        const item: Expirable<T> = data
+            ? JSON.parse(data, deserializer)
+            : undefined;
+        return item;
     } catch (err: unknown) {
         console.warn(err);
+        return undefined;
     }
 }