fix(database, useEmulator): drop multiple calls to useEmulator

guards against case where hot-reload of javascript means state is lost
and second native calls are attempted (and rejected...)

Fixes #5650

Author: mikehardy

packages/database/android/src/main/java/io/invertase/firebase/database/UniversalFirebaseDatabaseCommon.java

@@ -46,9 +46,14 @@ static FirebaseDatabase getDatabaseForApp(String appName, String dbURL) {
     setDatabaseConfig(firebaseDatabase, appName, dbURL);
 
     HashMap emulatorConfig = getEmulatorConfig(appName, dbURL);
-    if (emulatorConfig != null) {
+
+    if (emulatorConfig != null && emulatorConfig.get("configured") == null) {
       firebaseDatabase.useEmulator(
           (String) emulatorConfig.get("host"), (Integer) emulatorConfig.get("port"));
+      // The underlying SDK may only be configured once, but with hot-reloads in the
+      // javascript bundle, javascript cannot hold SDK configuration state. Keep track here
+      // so we only configure once
+      emulatorConfig.put("configured", "true");
     }
 
     return firebaseDatabase;

packages/database/ios/RNFBDatabase/RNFBDatabaseModule.m

@@ -22,6 +22,8 @@
 #import "RNFBDatabaseModule.h"
 #import "RNFBPreferences.h"
 
+static __strong NSMutableDictionary *emulatorSettings;
+
 @implementation RNFBDatabaseModule
 #pragma mark -
 #pragma mark Module Setup
@@ -58,8 +60,22 @@ - (dispatch_queue_t)methodQueue {
                   : (NSString *)dbURL
                   : (nonnull NSString *)host
                   : (NSInteger)port) {
-  [[RNFBDatabaseCommon getDatabaseForApp:firebaseApp dbURL:dbURL] useEmulatorWithHost:host
-                                                                                 port:port];
+  // javascript may hot reload, losing state, and native throws an error if you double-request
+  // so we keep track of useEmulator calls here to avoid calling native twice
+  if (emulatorSettings == nil) {
+    emulatorSettings = [NSMutableDictionary dictionary];
+  }
+
+  NSMutableString *configKey = [firebaseApp.name mutableCopy];
+  if (dbURL != nil && dbURL.length > 0) {
+    [configKey appendString:dbURL];
+  }
+
+  if (!emulatorSettings[configKey]) {
+    [[RNFBDatabaseCommon getDatabaseForApp:firebaseApp dbURL:dbURL] useEmulatorWithHost:host
+                                                                                   port:port];
+    emulatorSettings[configKey] = @YES;
+  }
 }
 
 RCT_EXPORT_METHOD(setPersistenceEnabled