feat: Support AppGroups

package/.eslintrc.js

@@ -4,6 +4,5 @@ module.exports = {
   ignorePatterns: ['scripts', 'lib'],
   rules: {
     'prettier/prettier': ['warn'],
-    '@typescript-eslint/consistent-type-imports': 'warn',
   },
 };

package/android/src/main/java/com/mrousavy/mmkv/MmkvPlatformContextModule.java

@@ -1,5 +1,7 @@
 package com.mrousavy.mmkv;
 
+import androidx.annotation.Nullable;
+
 import com.facebook.react.bridge.ReactApplicationContext;
 
 public class MmkvPlatformContextModule extends NativeMmkvPlatformContextSpec {
@@ -14,4 +16,11 @@ public MmkvPlatformContextModule(ReactApplicationContext reactContext) {
     public String getBaseDirectory() {
         return context.getFilesDir().getAbsolutePath() + "/mmkv";
     }
+
+    @Nullable
+    @Override
+    public String getAppGroupDirectory() {
+        // AppGroups do not exist on Android. It's iOS only.
+        return null;
+    }
 }

package/ios/MmkvPlatformContextModule.mm

@@ -24,7 +24,7 @@ - (NSString*)getBaseDirectory {
   NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
 #endif
   NSString* documentPath = (NSString*)[paths firstObject];
-  if ([documentPath length] > 0) {
+  if (documentPath.length > 0) {
     NSString* basePath = [documentPath stringByAppendingPathComponent:@"mmkv"];
     return basePath;
   } else {
@@ -34,4 +34,22 @@ - (NSString*)getBaseDirectory {
   }
 }
 
+- (NSString*)getAppGroupDirectory {
+  NSString* appGroup = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"AppGroup"];
+  if (appGroup == nil) {
+    // No AppGroup set in Info.plist.
+    return nil;
+  }
+  NSURL* groupDir =
+      [[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:appGroup];
+  if (groupDir == nil) {
+    // We have an AppGroup set in Info.plist, but the path is not readable!
+    @throw [NSException exceptionWithName:@"AppGroupNotAccessible"
+                                   reason:@"An AppGroup was set in Info.plist, but it is not "
+                                          @"accessible via NSFileManager!"
+                                 userInfo:@{@"appGroup" : appGroup}];
+  }
+  return groupDir.path;
+}
+
 @end

package/src/MMKV.ts

@@ -4,7 +4,6 @@ import { createMockMMKV } from './createMMKV.mock';
 import { isTest } from './PlatformChecker';
 import type { Configuration } from './NativeMmkv';
 import type { Listener, MMKVInterface, NativeMMKV } from './Types';
-export type { Configuration } from './NativeMmkv';
 
 const onValueChangedListeners = new Map<string, ((key: string) => void)[]>();
 

package/src/NativeMmkv.ts

@@ -42,9 +42,9 @@ export interface Configuration {
    * const temporaryStorage = new MMKV({ path: '/tmp/' })
    * ```
    *
-   * _Notice_: On iOS you can set the AppGroup bundle property to share the same storage between your app and its extensions.
-   * In this case `path` property will be ignored.
-   * See more on MMKV configuration [here](https://github.com/Tencent/MMKV/wiki/iOS_tutorial#configuration).
+   * @note On iOS, if an `AppGroup` is set in `Info.plist` and `path` is `undefined`, MMKV will use the `AppGroup` directory.
+   * App Groups allow you to share MMKV storage between apps, widgets and extensions within the same AppGroup bundle.
+   * For more information, see [the `Configuration` section](https://github.com/Tencent/MMKV/wiki/iOS_tutorial#configuration).
    *
    * @default undefined
    */

package/src/NativeMmkvPlatformContext.ts

@@ -7,6 +7,17 @@ export interface Spec extends TurboModule {
    * Gets the base directory of the documents storage
    */
   getBaseDirectory(): string;
+  /**
+   * Get the App Group directory if it exists, or `undefined` otherwise.
+   *
+   * The App Group directory will be used instead of a custom path to use the same
+   * MMKV instance between the iOS app, Widgets, and other companion apps.
+   *
+   * To set an App Group, add a `AppGroup` field to `Info.plist`
+   *
+   * @platform ios
+   */
+  getAppGroupDirectory(): string | undefined;
 }
 
 let module: Spec | null;

package/src/createMMKV.ts

@@ -1,10 +1,28 @@
-import type { Configuration } from './MMKV';
-import { getMMKVTurboModule } from './NativeMmkv';
+import { Platform } from 'react-native';
+import { getMMKVTurboModule, type Configuration } from './NativeMmkv';
 import type { NativeMMKV } from './Types';
+import { getMMKVPlatformContextTurboModule } from './NativeMmkvPlatformContext';
 
 export const createMMKV = (config: Configuration): NativeMMKV => {
   const module = getMMKVTurboModule();
 
+  if (Platform.OS === 'ios') {
+    if (config.path == null) {
+      try {
+        // If no `path` was supplied, we check if an `AppGroup` was set in Info.plist
+        const appGroupDirectory =
+          getMMKVPlatformContextTurboModule().getAppGroupDirectory();
+        if (appGroupDirectory != null) {
+          // If we have an `AppGroup` in Info.plist, use that as a path.
+          config.path = appGroupDirectory;
+        }
+      } catch (e) {
+        // We cannot throw errors here because it is a sync C++ TurboModule func. idk why.
+        console.error(e);
+      }
+    }
+  }
+
   const instance = module.createMMKV(config);
   if (__DEV__) {
     if (typeof instance !== 'object' || instance == null) {

package/src/createMMKV.web.ts

@@ -1,5 +1,5 @@
 /* global localStorage */
-import type { Configuration } from './MMKV';
+import type { Configuration } from './NativeMmkv';
 import type { NativeMMKV } from './Types';
 import { createTextEncoder } from './createTextEncoder';
 

package/src/hooks.ts

@@ -1,6 +1,6 @@
 import { useRef, useState, useMemo, useCallback, useEffect } from 'react';
-import type { Configuration } from './MMKV';
 import { MMKV } from './MMKV';
+import type { Configuration } from './NativeMmkv';
 
 function isConfigurationEqual(
   left?: Configuration,