Allow unserialised data to be written to store

src/Storage.ts

@@ -5,7 +5,7 @@ import {
 } from './types';
 
 export default class Storage<T> {
-  storage: PersistentStorage;
+  storage: PersistentStorage<PersistedData<T>>;
   key: string;
 
   constructor(options: ApolloPersistOptions<T>) {
@@ -20,7 +20,7 @@ export default class Storage<T> {
   }
 
   async write(data: PersistedData<T>): Promise<void> {
-    await this.storage.setItem(this.key, data.toString());
+    await this.storage.setItem(this.key, data);
   }
 
   async purge(): Promise<void> {

src/__tests__/Storage.ts

@@ -12,4 +12,22 @@ describe('Storage', () => {
     await storage.purge();
     await expect(storage.read()).resolves.toBe(undefined);
   });
+
+  describe('when data is an object', () => {
+    it ('writes an object to persistent storage', async () => {
+      const obj = {
+        yo: 'yo yo'
+      }
+
+      await expect(storage.write(obj)).resolves.toBe(undefined);
+      await expect(storage.read()).resolves.toBe(obj);
+    })
+  })  
+
+  describe('when data is a string', () => {
+    it ('writes a string to persistent storage', async () => {
+      await expect(storage.write('yo yo yo')).resolves.toBe(undefined);
+      await expect(storage.read()).resolves.toBe('yo yo yo');
+    })
+  })
 });

src/storageWrappers/AsyncStorageWrapper.ts

@@ -12,7 +12,7 @@ import { PersistentStorage } from '../types';
  * });
  *
  */
-export class AsyncStorageWrapper implements PersistentStorage {
+export class AsyncStorageWrapper implements PersistentStorage<string> {
   // Actual type definition: https://github.com/react-native-async-storage/async-storage/blob/master/types/index.d.ts
   private storage;
 

src/storageWrappers/IonicStorageWrapper.ts

@@ -1,6 +1,6 @@
 import { PersistentStorage } from '../types';
 
-export class IonicStorageWrapper implements PersistentStorage {
+export class IonicStorageWrapper implements PersistentStorage<string> {
   // Actual type definition: https://github.com/ionic-team/ionic-storage/blob/main/src/storage.ts#L102
   private storage;
 

src/storageWrappers/LocalForageWrapper.ts

@@ -1,6 +1,6 @@
 import { PersistentStorage } from '../types';
 
-export class LocalForageWrapper implements PersistentStorage {
+export class LocalForageWrapper implements PersistentStorage<string | object> {
   // Actual type definition: https://github.com/localForage/localForage/blob/master/typings/localforage.d.ts#L17
   private storage;
 

src/storageWrappers/LocalStorageWrapper.ts

@@ -1,6 +1,6 @@
 import { PersistentStorage } from '../types';
 
-export class LocalStorageWrapper implements PersistentStorage {
+export class LocalStorageWrapper implements PersistentStorage<string> {
   // Actual type definition: https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.d.ts#L15286
   private storage;
 

src/storageWrappers/MMKVStorageWrapper.ts

@@ -11,7 +11,7 @@ import { PersistentStorage } from '../types';
  * });
  *
  */
-export class MMKVStorageWrapper implements PersistentStorage {
+export class MMKVStorageWrapper implements PersistentStorage<string> {
   // Actual type definition: https://github.com/ammarahm-ed/react-native-mmkv-storage/blob/master/index.d.ts#L27
   private storage;
 

src/storageWrappers/SessionStorageWrapper.ts

@@ -1,6 +1,6 @@
 import { PersistentStorage } from '../types';
 
-export class SessionStorageWrapper implements PersistentStorage {
+export class SessionStorageWrapper implements PersistentStorage<string> {
   // Actual type definition: https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.d.ts#L15286
   private storage;
 

src/types/index.ts

@@ -10,15 +10,15 @@ export type TriggerFunction = (persist: () => void) => TriggerUninstallFunction;
 
 export type PersistedData<T> = T | string | null;
 
-export interface PersistentStorage {
-  getItem: (key: string) => string | null | Promise<string | null>;
-  setItem: (key: string, value: string) => void | Promise<void>;
-  removeItem: (key: string) => void | Promise<void>;
+export interface PersistentStorage<T> {
+  getItem: (key: string) => Promise<T | null> | T | null;
+  setItem: (key: string, value: T) => Promise<T> | Promise<void> | void | T;
+  removeItem: (key: string) => Promise<T> | Promise<void> | void;
 }
 
 export interface ApolloPersistOptions<TSerialized> {
   cache: ApolloCache<TSerialized>;
-  storage: PersistentStorage;
+  storage: PersistentStorage<PersistedData<TSerialized>>;
   trigger?: 'write' | 'background' | TriggerFunction | false;
   debounce?: number;
   key?: string;