[Web] deferred-loading "part" files not generated in Flutter 3.20.0+ #145653
Description
Steps to reproduce
-
With Flutter 3.19.4 generate a new project with
flutter create my_project -
Next to main.dart, introduce a new file foo.dart:
int foo() => 1;
-
In main.dart, import foo as a deferred library and make trivial use of it:
import 'package:flutter/material.dart'; import 'foo.dart' deferred as foo; // new! void main() { runApp(const MyApp()); foo.loadLibrary().then((_) => print(foo.foo())); // new! } // everything else unchanged from the default main.dart template
-
Run
flutter build weband note that build/web/main.dart.js_1.part.js is generated -
Upgrade to Flutter 3.20.0+
-
Run
flutter clean && flutter build weband note that no *.part.js is generated. When deployed, the built application will fail due to missing the part files.
Expected results
The build/web/*.part.js files should be built as with Flutter 3.19 and earlier.
Actual results
The build/web/*.part.js files are not built.
Code sample
Code sample
main.dart
import 'package:flutter/material.dart';
import 'foo.dart' deferred as foo;
void main() {
runApp(const MyApp());
foo.loadLibrary().then((_) => print(foo.foo()));
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// TRY THIS: Try running your application with "flutter run". You'll see
// the application has a purple toolbar. Then, without quitting the app,
// try changing the seedColor in the colorScheme below to Colors.green
// and then invoke "hot reload" (save your changes or press the "hot
// reload" button in a Flutter-supported IDE, or press "r" if you used
// the command line to start the app).
//
// Notice that the counter didn't reset back to zero; the application
// state is not lost during the reload. To reset the state, use hot
// restart instead.
//
// This works for code too, not just values: Most code changes can be
// tested with just a hot reload.
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
useMaterial3: true,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// TRY THIS: Try changing the color here to a specific color (to
// Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
// change color while the other colors stay the same.
backgroundColor: Theme.of(context).colorScheme.inversePrimary,
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
//
// TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
// action in the IDE, or press "p" in the console), to see the
// wireframe for each widget.
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headlineMedium,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}foo.dart
int foo() => 1;Screenshots or Video
Screenshots / Video demonstration
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Logs
Logs
Executed command
{flutter -v clean && flutter -v build web && ls -al build/web} 2>&1 |pbcopyFlutter 3.19
Flutter 3.20
Flutter Doctor output
Doctor output
Flutter 3.19
Doctor summary (to see all details, run flutter doctor -v):
[!] Flutter (Channel [user-branch], 3.19.4, on macOS 14.4 23E214 darwin-x64, locale en-JP)
! Flutter version 3.19.4 on channel [user-branch] at /Applications/flutter
Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
If that doesn't fix the issue, reinstall Flutter by following instructions at https://flutter.dev/docs/get-started/install.
! Upstream repository unknown source is not a standard remote.
Set environment variable "FLUTTER_GIT_URL" to unknown source to dismiss this error.
[!] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
✗ cmdline-tools component is missing
Run `path/to/sdkmanager --install "cmdline-tools;latest"`
See https://developer.android.com/studio/command-line for more details.
✗ Android license status unknown.
Run `flutter doctor --android-licenses` to accept the SDK licenses.
See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.
[✓] Xcode - develop for iOS and macOS (Xcode 15.3)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2023.2)
[✓] IntelliJ IDEA Community Edition (version 2023.3.5)
[✓] Connected device (4 available)
[✓] Network resources
! Doctor found issues in 2 categories.Flutter 3.20
Doctor summary (to see all details, run flutter doctor -v):
[!] Flutter (Channel [user-branch], 3.20.0-0.0.pre, on macOS 14.4 23E214 darwin-x64, locale en-JP)
! Flutter version 3.20.0-0.0.pre on channel [user-branch] at /Applications/flutter
Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
If that doesn't fix the issue, reinstall Flutter by following instructions at https://flutter.dev/docs/get-started/install.
! Upstream repository unknown source is not a standard remote.
Set environment variable "FLUTTER_GIT_URL" to unknown source to dismiss this error.
[!] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
✗ cmdline-tools component is missing
Run `path/to/sdkmanager --install "cmdline-tools;latest"`
See https://developer.android.com/studio/command-line for more details.
✗ Android license status unknown.
Run `flutter doctor --android-licenses` to accept the SDK licenses.
See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.
[✓] Xcode - develop for iOS and macOS (Xcode 15.3)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2023.2)
[✓] IntelliJ IDEA Community Edition (version 2023.3.5)
[✓] Connected device (4 available)
[✓] Network resources
! Doctor found issues in 2 categories.Metadata
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Building flutter applications with the toolissue is assigned to a domain expert for further triageIt was better in the past than it is nowFound to occur in 3.19Found to occur in 3.21The issue has been confirmed reproducible and is ready to work onWeb applications specificallyIssue is closed as already fixed in a newer versionOwned by Web platform teamAffects the "flutter" command-line tool. See also t: labels.