(not working) Try having ZulipAsyncStorage class extend AsyncStorage class.

.flowconfig

@@ -32,6 +32,9 @@ node_modules/react-native/Libraries/polyfills/.*
 ; was in this module.
 .*/node_modules/react-native/Libraries/ReactNative/PaperUIManager.js
 
+; Our libdef is more complete, as of 2021-08.
+.*/node_modules/@react-native-async-storage/async-storage.*
+
 [include]
 ; Effectively this line warns Flow that this path might be a symlink
 ; (because the developer might be using `yarn link` to have this point into
@@ -49,7 +52,6 @@ node_modules/react-native/flow/
 ; their autogenerated versions in flow-typed/npm. (Contrast commit 6219e5a23,
 ; where the opposite behavior is exhibited!)
 flow-typed/@sentry/react-native_v1.x.x.js
-flow-typed/@react-native-async-storage/async-storage_v1.x.x.js
 flow-typed/react-native-url-polyfill_vx.x.x.js
 flow-typed/expo-screen-orientation_vx.x.x.js
 

flow-typed/@react-native-async-storage/async-storage_v1.x.x.js

@@ -4,27 +4,25 @@
 declare module '@react-native-async-storage/async-storage' {
   declare type ReadOnlyArrayString = $ReadOnlyArray<string>;
 
-  declare export default {
-    getItem(
+  declare export default class AsyncStorage {
+    static getItem(
       key: string,
       callback?: ?(error: ?Error, result: string | null) => void,
     ): Promise<string | null>,
 
-    setItem(key: string, value: string, callback?: ?(error: ?Error) => void): Promise<null>,
+    static setItem(key: string, value: string, callback?: ?(error: ?Error) => void): Promise<mixed>,
 
-    multiSet(
+    static multiSet(
       keyValuePairs: Array<Array<string>>,
       callback?: ?(errors: ?$ReadOnlyArray<?Error>) => void,
-    ): Promise<null>,
+    ): Promise<mixed>,
 
-    removeItem(key: string, callback?: ?(error: ?Error) => void): Promise<null>,
+    static removeItem(key: string, callback?: ?(error: ?Error) => void): Promise<mixed>,
 
-    getAllKeys(
+    static getAllKeys(
       callback?: ?(error: ?Error, keys: ?ReadOnlyArrayString) => void,
     ): Promise<ReadOnlyArrayString>,
 
-    clear(callback?: ?(error: ?Error) => void): Promise<null>,
-
-    ...
-  };
+    static clear(callback?: ?(error: ?Error) => void): Promise<mixed>,
+  }
 }

jest/jestSetup.js

@@ -91,7 +91,14 @@ jest.mock('react-native-reanimated', () => {
   return Reanimated;
 });
 
-jest.mock('@react-native-async-storage/async-storage', () => mockAsyncStorage);
+jest.mock('@react-native-async-storage/async-storage', () =>
+  // The implementation is a class with static methods `.getItem`, etc.,
+  // whereas `mockAsyncStorage` is just an object with those as properties.
+  // So, simulate the implementation: make the class with a simple class
+  // expression (and give it a name), and give it its statics from
+  // `mockAsyncStorage`.
+  Object.assign(class AsyncStorage {}, mockAsyncStorage),
+);
 
 // Without this, we get lots of these errors on importing the module:
 // `Invariant Violation: Native module cannot be null.`

src/boot/ZulipAsyncStorage.js

@@ -3,9 +3,18 @@ import AsyncStorage from '@react-native-async-storage/async-storage';
 import { NativeModules } from 'react-native';
 import * as logging from '../utils/logging';
 
-export default class ZulipAsyncStorage {
-  static async getItem(key: string) {
-    const item = await AsyncStorage.getItem(key);
+/**
+ * `AsyncStorage`, but with compression on Android.
+ *
+ * See
+ *   https://react-native-async-storage.github.io/async-storage/docs/api
+ * and
+ *   node_modules/@react-native-async-storage/async-storage/src/AsyncStorage.js
+ * for the base class.
+ */
+export default class ZulipAsyncStorage extends AsyncStorage {
+  static async getItem(key: string): Promise<string | null> {
+    const item = await super.getItem(key);
 
     // It's possible that getItem() is called on uncompressed state, for
     // example when a user updates their app from a version without
@@ -46,17 +55,17 @@ export default class ZulipAsyncStorage {
     return item;
   }
 
-  static async setItem(key: string, value: string) {
-    return AsyncStorage.setItem(
+  static async setItem(key: string, value: string): Promise<mixed> {
+    return super.setItem(
       key,
       NativeModules.TextCompressionModule
         ? await NativeModules.TextCompressionModule.compress(value)
         : value,
     );
   }
 
-  static async multiSet(keyValuePairs: Array<Array<string>>) {
-    return AsyncStorage.multiSet(
+  static async multiSet(keyValuePairs: Array<Array<string>>): Promise<mixed> {
+    return super.multiSet(
       NativeModules.TextCompressionModule
         ? await Promise.all(
             keyValuePairs.map(async ([key, value]) => [
@@ -68,9 +77,6 @@ export default class ZulipAsyncStorage {
     );
   }
 
-  static removeItem = AsyncStorage.removeItem;
-
-  static getAllKeys = AsyncStorage.getAllKeys;
-
-  static clear = AsyncStorage.clear;
+  // TODO: `mergeItem`, `multiGet`, and `multiMerge` would need compression
+  //   logic if we used them.
 }

src/boot/store.js

@@ -409,8 +409,6 @@ const reduxPersistConfig: Config = {
 
   // Store data through our own wrapper for AsyncStorage, in particular
   // to get compression.
-  /* $FlowFixMe[incompatible-variance]:
-     https://github.com/rt2zz/redux-persist/issues/823 */
   storage: ZulipAsyncStorage,
   serialize: stringify,
   deserialize: parse,

src/third/redux-persist/index.js.flow

@@ -1,4 +1,5 @@
 // @flow
+import AsyncStorage from '@react-native-async-storage/async-storage'
 
 // redux dependent typing
 declare type Action = Object
@@ -10,17 +11,14 @@ declare type StoreEnhancer = (next: Function) => Function
 type Whitelist = string[]
 type Blacklist = string[]
 
-declare type Storage = {
-  setItem: Function,
-  getItem: Function,
-  removeItem: Function,
-  getAllKeys: Function,
-  ...
-}
 declare type Config = {|
   blacklist?: Blacklist,
   whitelist?: Whitelist,
-  storage?: Storage,
+
+  // Flow's built-in `Class` utility type:
+  //   https://flow.org/en/docs/types/utilities/#toc-class
+  storage?: Class<AsyncStorage>,
+
   serialize?: boolean | Function,
   deserialize?: boolean | Function,
   keyPrefix?: string,