feat: remove .expo extension in favor of generic fallback to legacy native module mechanism (#544)

Author: brentvatne

src/RCTAsyncStorage.expo.js

@@ -1,8 +1,20 @@
-const {NativeModules} = require('react-native');
+const {NativeModules, TurboModuleRegistry} = require('react-native');
+const shouldFallbackToLegacyNativeModule = require('./shouldFallbackToLegacyNativeModule');
 
-const RCTAsyncStorage =
+let RCTAsyncStorage =
   NativeModules.PlatformLocalStorage || // Support for external modules, like react-native-windows
   NativeModules.RNC_AsyncSQLiteDBStorage ||
   NativeModules.RNCAsyncStorage;
 
+if (!RCTAsyncStorage && shouldFallbackToLegacyNativeModule()) {
+  // TurboModuleRegistry falls back to NativeModules so we don't have to try go
+  // assign NativeModules' counterparts if TurboModuleRegistry would resolve
+  // with undefined.
+  if (TurboModuleRegistry) {
+    RCTAsyncStorage = TurboModuleRegistry.get('AsyncSQLiteDBStorage') || TurboModuleRegistry.get('AsyncLocalStorage');
+  } else {
+    RCTAsyncStorage = NativeModules.AsyncSQLiteDBStorage || NativeModules.AsyncLocalStorage;
+  }
+}
+
 export default RCTAsyncStorage;

src/RCTAsyncStorage.js

@@ -0,0 +1,30 @@
+const {NativeModules} = require('react-native');
+
+export default function shouldFallbackToLegacyNativeModule() {
+  const expoConstants =
+    NativeModules.NativeUnimoduleProxy?.modulesConstants?.ExponentConstants;
+
+  if (expoConstants) {
+    /**
+     * In SDK <= 39, appOwnership is defined in managed apps but executionEnvironment is not.
+     * In bare React Native apps using expo-constants, appOwnership is never defined, so
+     * isLegacySdkVersion will be false in that context.
+     */
+    const isLegacySdkVersion = expoConstants.appOwnership && !expoConstants.executionEnvironment;
+
+    /**
+     * Expo managed apps don't include the @react-native-async-storage/async-storage
+     * native modules yet, but the API interface is the same, so we can use the version
+     * exported from React Native still.
+     *
+     * If in future releases (eg: @react-native-async-storage/async-storage >= 2.0.0) this
+     * will likely not be valid anymore, and the package will need to be included in the Expo SDK
+     * to continue to work.
+     */
+    if (isLegacySdkVersion || ['storeClient', 'standalone'].includes(expoConstants.executionEnvironment)) {
+      return true;
+    }
+  }
+
+  return false;
+}

src/shouldFallbackToLegacyNativeModule.js

@@ -4,8 +4,6 @@ title: Installation
 sidebar_label: Installation
 ---
 
-
-
 ### Get library
 
 With npm:
@@ -18,6 +16,11 @@ With Yarn:
 yarn add @react-native-async-storage/async-storage
 ```
 
+With Expo CLI:
+```bash
+expo install @react-native-async-storage/async-storage
+```
+
 ### Link
 
 #### Android & iOS