Perf/avoid double call

example/lib/network_example.dart

@@ -6,7 +6,7 @@ import 'package:flutter_i18n/loaders/decoders/json_decode_strategy.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 
 class CustomNetworkFileTranslationLoader extends NetworkFileTranslationLoader {
-  CustomNetworkFileTranslationLoader({required baseUri})
+  CustomNetworkFileTranslationLoader(Uri baseUri)
       : super(baseUri: baseUri, decodeStrategies: [JsonDecodeStrategy()]);
 
   @override
@@ -19,7 +19,7 @@ Future main() async {
   WidgetsFlutterBinding.ensureInitialized();
   final FlutterI18nDelegate flutterI18nDelegate = FlutterI18nDelegate(
     translationLoader: CustomNetworkFileTranslationLoader(
-      baseUri: Uri.https("postman-echo.com", "get",
+      Uri.https("postman-echo.com", "get",
           {"title": "Basic network example", "content": "Translated content"}),
     ),
   );

lib/loaders/e2e_file_translation_loader.dart

@@ -2,6 +2,8 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'package:flutter/services.dart';
+import 'package:flutter_i18n/loaders/decoders/base_decode_strategy.dart';
+import 'package:flutter/widgets.dart';
 
 import 'file_translation_loader.dart';
 
@@ -19,12 +21,12 @@ class E2EFileTranslationLoader extends FileTranslationLoader {
   AssetBundle customAssetBundle = _CustomAssetBundle();
 
   E2EFileTranslationLoader(
-      {forcedLocale,
-      fallbackFile = "en",
-      basePath = "assets/flutter_i18n",
-      useCountryCode = false,
-      this.useE2E = true,
-      decodeStrategies})
+      {Locale? forcedLocale,
+      String? fallbackFile = "en",
+      String basePath = "assets/flutter_i18n",
+      bool useCountryCode = false,
+      bool this.useE2E = true,
+      List<BaseDecodeStrategy>? decodeStrategies})
       : super(
             fallbackFile: fallbackFile,
             basePath: basePath,

lib/loaders/file_translation_loader.dart

@@ -14,7 +14,7 @@ import '../utils/message_printer.dart';
 
 /// Loads translation files from JSON, YAML or XML format
 class FileTranslationLoader extends TranslationLoader implements IFileContent {
-  final String fallbackFile;
+  final String? fallbackFile;
   final String basePath;
   final String separator;
   final bool useCountryCode;
@@ -34,22 +34,28 @@ class FileTranslationLoader extends TranslationLoader implements IFileContent {
           ];
 
   FileTranslationLoader(
-      {this.fallbackFile = "en",
-      this.basePath = "assets/flutter_i18n",
-      this.separator = "_",
-      this.useCountryCode = false,
-      this.useScriptCode = false,
-      forcedLocale,
-      decodeStrategies}) {
+      {String? this.fallbackFile = "en",
+      String this.basePath = "assets/flutter_i18n",
+      String this.separator = "_",
+      bool this.useCountryCode = false,
+      bool this.useScriptCode = false,
+      Locale? forcedLocale,
+      List<BaseDecodeStrategy>? decodeStrategies}) {
     this.forcedLocale = forcedLocale;
     this.decodeStrategies = decodeStrategies;
   }
 
   /// Return the translation Map
   Future<Map> load() async {
     _decodedMap = Map();
-    await _loadCurrentTranslation();
-    await _loadFallback();
+    await this._defineLocale();
+    final fileName = composeFileName();
+    _decodedMap.addAll(await _loadTranslation(fileName, false));
+    if (fallbackFile != null && fileName != fallbackFile) {
+      final Map fallbackMap = await _loadTranslation(fallbackFile!, true);
+      _decodedMap = _deepMergeMaps(fallbackMap, _decodedMap);
+      MessagePrinter.debug('Fallback maps have been merged');
+    }
     return _decodedMap;
   }
 
@@ -60,24 +66,19 @@ class FileTranslationLoader extends TranslationLoader implements IFileContent {
         cache: false);
   }
 
-  Future _loadCurrentTranslation() async {
+  Future<Map<dynamic, dynamic>> _loadTranslation(String fileName, bool isFallback) async {
     try {
-      this.locale = locale ?? await findDeviceLocale();
-      MessagePrinter.info("The current locale is ${this.locale}");
-      _decodedMap.addAll(await loadFile(composeFileName()));
+      return await loadFile(fileName);
     } catch (e) {
-      MessagePrinter.debug('Error loading translation $e');
+      MessagePrinter.debug(
+          'Error loading translation${isFallback ? " fallback " : " "}$e');
     }
+    return Map();
   }
 
-  Future _loadFallback() async {
-    try {
-      final Map fallbackMap = await loadFile(fallbackFile);
-      _decodedMap = _deepMergeMaps(fallbackMap, _decodedMap);
-      MessagePrinter.debug('Fallback maps have been merged');
-    } catch (e) {
-      MessagePrinter.debug('Error loading translation fallback $e');
-    }
+  Future _defineLocale() async {
+    this.locale = locale ?? await findDeviceLocale();
+    MessagePrinter.info("The current locale is ${this.locale}");
   }
 
   Map<K, V> _deepMergeMaps<K, V>(

lib/loaders/local_translation_loader.dart

@@ -1,14 +1,16 @@
 import 'dart:io';
 
+import 'package:flutter/widgets.dart';
+import 'package:flutter_i18n/loaders/decoders/base_decode_strategy.dart';
 import 'package:flutter_i18n/loaders/file_translation_loader.dart';
 
 class LocalTranslationLoader extends FileTranslationLoader {
   LocalTranslationLoader(
-      {basePath = "assets/flutter_i18n",
-      useCountryCode = false,
-      useScriptCode = false,
-      forcedLocale,
-      decodeStrategies})
+      {String basePath = "assets/flutter_i18n",
+      bool useCountryCode = false,
+      bool useScriptCode = false,
+      Locale? forcedLocale,
+      List<BaseDecodeStrategy>? decodeStrategies})
       : super(
             basePath: basePath,
             useCountryCode: useCountryCode,

lib/loaders/namespace_file_translation_loader.dart

@@ -1,4 +1,6 @@
 import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_i18n/loaders/decoders/base_decode_strategy.dart';
 import 'package:flutter_i18n/loaders/file_translation_loader.dart';
 import 'package:flutter_i18n/utils/message_printer.dart';
 
@@ -11,14 +13,14 @@ class NamespaceFileTranslationLoader extends FileTranslationLoader {
   Map<dynamic, dynamic> _decodedMap = {};
 
   NamespaceFileTranslationLoader(
-      {required this.namespaces,
-      this.fallbackDir = "en",
-      basePath = "assets/flutter_i18n",
-      separator = "_",
-      useCountryCode = false,
-      useScriptCode = false,
-      forcedLocale,
-      decodeStrategies})
+      {required List<String>? this.namespaces,
+      String this.fallbackDir = "en",
+      String basePath = "assets/flutter_i18n",
+      String separator = "_",
+      bool useCountryCode = false,
+      bool useScriptCode = false,
+      Locale? forcedLocale,
+      List<BaseDecodeStrategy>? decodeStrategies})
       : super(
             basePath: basePath,
             separator: separator,

lib/loaders/network_file_translation_loader.dart

@@ -1,5 +1,7 @@
 import 'dart:async';
 
+import 'package:flutter/widgets.dart';
+import 'package:flutter_i18n/loaders/decoders/base_decode_strategy.dart';
 import 'package:http/http.dart' as http;
 
 import 'file_translation_loader.dart';
@@ -9,13 +11,13 @@ class NetworkFileTranslationLoader extends FileTranslationLoader {
   final Uri baseUri;
 
   NetworkFileTranslationLoader(
-      {required this.baseUri,
-      forcedLocale,
-      fallbackFile = "en",
-      separator = "_",
-      useCountryCode = false,
-      useScriptCode = false,
-      decodeStrategies})
+      {required Uri this.baseUri,
+      Locale? forcedLocale,
+      String fallbackFile = "en",
+      String separator = "_",
+      bool useCountryCode = false,
+      bool useScriptCode = false,
+      List<BaseDecodeStrategy>? decodeStrategies})
       : super(
             fallbackFile: fallbackFile,
             separator: separator,

test/loaders/file_translation_loader_test.dart

@@ -26,9 +26,8 @@ void main() {
 
   test('should deep merge fallback map', () async {
     var instance = FileTranslationLoader(
-      forcedLocale: Locale.fromSubtags(languageCode: "fr"),
-      fallbackFile: "en"
-    );
+        forcedLocale: Locale.fromSubtags(languageCode: "fr"),
+        fallbackFile: "en");
     instance.assetBundle = TestAssetBundleFallbackFrToEn();
 
     var result = await instance.load();
@@ -44,28 +43,50 @@ void main() {
     expect(block["label2"], equals("Bonjour"));
   });
 
+  test('should skip merge fallback map', () async {
+    var instance = FileTranslationLoader(
+        forcedLocale: Locale.fromSubtags(languageCode: "fr"),
+        fallbackFile: null);
+    instance.assetBundle = TestAssetBundleFallbackFrToEn();
+
+    var result = await instance.load();
+
+    expect(result, isMap);
+    expect(result, isNotEmpty);
+    expect(result["title"], equals("flutter_18n_fr"));
+    expect(result["sub_title"], equals(null));
+    var block = result["block"];
+    expect(block, isMap);
+    expect(block, isNotEmpty);
+    expect(block["label1"], equals(null));
+    expect(block["label2"], equals("Bonjour"));
+  });
+
   test('`loadString` should load correct string', () async {
     final instance = TestJsonLoader();
     final result = await instance.loadString("_fileName", "_extension");
     expect(result, contains("_fileName"));
     expect(result, contains("_extension"));
   });
 
-  test('`load` should load correct map from JSON with initial values', () async {
+  test('`load` should load correct map from JSON with initial values',
+      () async {
     final instance = TestJsonLoader();
     final result = await instance.load();
     expect(result["fileName"], "en");
     expect(result["extension"], "json");
   });
 
-  test('`load` should load correct map from YAML with initial values', () async {
+  test('`load` should load correct map from YAML with initial values',
+      () async {
     final instance = TestYamlLoader();
     final result = await instance.load();
     expect(result["fileName"], "en");
     expect(result["extension"], "yaml");
   });
 
-  test('`load` should load correct map from TOML with initial values', () async {
+  test('`load` should load correct map from TOML with initial values',
+      () async {
     final instance = TestTomlLoader();
     final result = await instance.load();
     expect(result["fileName"], "en");

test/test_loader.dart

@@ -1,7 +1,8 @@
+import 'package:flutter/widgets.dart';
 import 'package:flutter_i18n/flutter_i18n.dart';
+import 'package:flutter_i18n/loaders/decoders/toml_decode_strategy.dart';
 import 'package:flutter_i18n/loaders/decoders/xml_decode_strategy.dart';
 import 'package:flutter_i18n/loaders/decoders/yaml_decode_strategy.dart';
-import 'package:flutter_i18n/loaders/decoders/toml_decode_strategy.dart';
 
 Future<String> _loadString(String fileName, String extension) async {
   if (fileName.contains('_en')) {
@@ -31,10 +32,10 @@ Future<String> _loadString(String fileName, String extension) async {
 
 class TestJsonLoader extends FileTranslationLoader {
   TestJsonLoader({
-    forcedLocale,
-    fallbackFile = "en",
-    basePath = "assets/flutter_i18n",
-    useCountryCode = false,
+    Locale? forcedLocale,
+    String fallbackFile = "en",
+    String basePath = "assets/flutter_i18n",
+    bool useCountryCode = false,
   }) : super(
             fallbackFile: fallbackFile,
             basePath: basePath,
@@ -49,10 +50,10 @@ class TestJsonLoader extends FileTranslationLoader {
 
 class TestYamlLoader extends FileTranslationLoader {
   TestYamlLoader({
-    forcedLocale,
-    fallbackFile = "en",
-    basePath = "assets/flutter_i18n",
-    useCountryCode = false,
+    Locale? forcedLocale,
+    String fallbackFile = "en",
+    String basePath = "assets/flutter_i18n",
+    bool useCountryCode = false,
   }) : super(
             fallbackFile: fallbackFile,
             basePath: basePath,
@@ -77,10 +78,10 @@ class TestYamlLoader extends FileTranslationLoader {
 
 class TestTomlLoader extends FileTranslationLoader {
   TestTomlLoader({
-    forcedLocale,
-    fallbackFile = "en",
-    basePath = "assets/flutter_i18n",
-    useCountryCode = false,
+    Locale? forcedLocale,
+    String fallbackFile = "en",
+    String basePath = "assets/flutter_i18n",
+    bool useCountryCode = false,
   }) : super(
       fallbackFile: fallbackFile,
       basePath: basePath,
@@ -105,10 +106,10 @@ class TestTomlLoader extends FileTranslationLoader {
 
 class TestXmlLoader extends FileTranslationLoader {
   TestXmlLoader({
-    forcedLocale,
-    fallbackFile = "en",
-    basePath = "assets/flutter_i18n",
-    useCountryCode = false,
+    Locale? forcedLocale,
+    String fallbackFile = "en",
+    String basePath = "assets/flutter_i18n",
+    bool useCountryCode = false,
   }) : super(
             fallbackFile: fallbackFile,
             basePath: basePath,