title: Flutter Internationalization, intl code generation not working
body: <p>I created a new <strong>Flutter project</strong> with <strong>Android Studio</strong>. I'm using <strong>null-safety</strong> and I'm running the application on a physical device yet the <strong>code-generation</strong> is not working, there is no <strong>flutter_gen</strong> folder  inside <strong>.dart_tool</strong> folder just <strong>flutter_build</strong> folder.</p>
  <p>I followed the steps in <a href="https://flutter.dev/docs/development/accessibility-and-localization/internationalization" rel="nofollow noreferrer">Flutter's official Internationalizing documentation</a></p>
  <p>Im not using <a href="https://plugins.jetbrains.com/plugin/13666-flutter-intl" rel="nofollow noreferrer">Flutter Intl</a> plugin because it doesn't support <strong>null-safety</strong> (I'm aware you can make an script to add an old dart version at the top of each generated file as a workaround)</p>
  <p><strong>flutter doctor command output:</strong></p>
  <pre><code>[✓] Flutter (Channel beta, 1.26.0-17.5.pre, on Microsoft Windows [VersiÃ³n 10.0.19042.804], locale es-ES)
      • Flutter version 1.26.0-17.5.pre at &lt;PATH&gt;
      • Framework revision 1fe38dcb5f (3 days ago), 2021-02-10 16:25:47 -0800
      • Engine revision d4453f6018
      • Dart version 2.12.0 (build 2.12.0-259.9.beta)
  
  [✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
      • Android SDK at &lt;PATH&gt;
      • Platform android-30, build-tools 30.0.2
      • Java binary at: &lt;PATH&gt;
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
      • All Android licenses accepted.
  
  [✓] Android Studio (version 4.1.0)
      • Android Studio at &lt;PATH&gt;
      • Flutter plugin can be installed from:
         https://plugins.jetbrains.com/plugin/9212-flutter
      • Dart plugin can be installed from:
         https://plugins.jetbrains.com/plugin/6351-dart
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
  
  [✓] VS Code (version 1.53.2)
      • VS Code at &lt;PATH&gt;
      • Flutter extension version 3.19.0
  
  [✓] Connected device (1 available)
      • &lt;DEVICE&gt; • android-arm • Android 8.1.0 (API 27)
  
  • No issues found!
  </code></pre>
  <p><strong>/pubscpec.yaml:</strong></p>
  <pre class="lang-yaml prettyprint-override"><code>name: example_app
  description: A new Flutter application.
  publish_to: 'none' 
  version: 1.0.0+1
  
  environment:
    sdk: &quot;&gt;=2.12.0-0 &lt;3.0.0&quot;
    
  dependencies:
    flutter:
      sdk: flutter
    flutter_localizations:
      sdk: flutter
    intl: ^0.17.0-nullsafety.2
    cupertino_icons: ^1.0.1
    
  dev_dependencies:
    flutter_test:
      sdk: flutter
    integration_test:
      sdk: flutter
  
  flutter:
    uses-material-design: true
    generate: true
  </code></pre>
  <p><strong>/lib/main.dart:</strong></p>
  <pre class="lang-dart prettyprint-override"><code>import 'package:example_app/ui/screen/home_page.dart';
  import 'package:flutter/material.dart';
  import 'package:flutter_localizations/flutter_localizations.dart';
  // TODO: uncomment the line below after codegen
  // import 'package:flutter_gen/gen_l10n/app_localizations.dart';
  
  void main() {
    runApp(MyApp());
  }
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage('Flutter Demo Home Page'),
        localizationsDelegates: [
          // ... app-specific localization delegate[s] here
          // TODO: uncomment the line below after codegen
          // AppLocalizations.delegate,
          GlobalMaterialLocalizations.delegate,
          GlobalWidgetsLocalizations.delegate,
          GlobalCupertinoLocalizations.delegate,
        ],
        supportedLocales: [
          const Locale('en', ''), // English, no country code
          const Locale('es', ''), // Spanish, no country code
        ],
      );
    }
  }
  </code></pre>
  <p><strong>/lib/l10n.yaml:</strong></p>
  <pre class="lang-yaml prettyprint-override"><code>arb-dir: lib/l10n
  template-arb-file: app_en.arb
  output-localization-file: app_localizations.dart
  </code></pre>
  <p><strong>lib/l10n/app_en.arb</strong></p>
  <pre class="lang-yaml prettyprint-override"><code>{
    &quot;helloWorld&quot;: &quot;Hello World!&quot;
  }
  </code></pre>
  <p><strong>lib/l10n/app_es.arb</strong></p>
  <pre class="lang-yaml prettyprint-override"><code>{
    &quot;helloWorld&quot;: &quot;Hola mundo!&quot;
  }
  </code></pre>