import'package:flutter/material.dart';
import'foo.dart' deferred as foo;
voidmain() {
runApp(constMyApp());
foo.loadLibrary().then((_) =>print(foo.foo()));
}
classMyAppextendsStatelessWidget {
constMyApp({super.key});
// This widget is the root of your application.@overrideWidgetbuild(BuildContext context) {
returnMaterialApp(
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:constMyHomePage(title:'Flutter Demo Home Page'),
);
}
}
classMyHomePageextendsStatefulWidget {
constMyHomePage({super.key, requiredthis.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".finalString title;
@overrideState<MyHomePage> createState() =>_MyHomePageState();
}
class_MyHomePageStateextendsState<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++;
});
}
@overrideWidgetbuild(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.returnScaffold(
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>[
constText(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style:Theme.of(context).textTheme.headlineMedium,
),
],
),
),
floatingActionButton:FloatingActionButton(
onPressed: _incrementCounter,
tooltip:'Increment',
child:constIcon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
Steps to reproduce
With Flutter 3.19.4 generate a new project with
flutter create my_projectNext to main.dart, introduce a new file foo.dart:
In main.dart, import foo as a deferred library and make trivial use of it:
Run
flutter build weband note that build/web/main.dart.js_1.part.js is generatedUpgrade 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
foo.dart
Screenshots or Video
Screenshots / Video demonstration
[Upload media here]
Logs
Logs
Executed command
{flutter -v clean && flutter -v build web && ls -al build/web} 2>&1|pbcopyFlutter 3.19
https://pastebin.com/aLtvFY2c
Flutter 3.20
https://pastebin.com/U7s4MJd7
Flutter Doctor output
Doctor output
Flutter 3.19
Flutter 3.20