FlutterGen · Mairramer · May 28, 2026 · May 28, 2026 · May 28, 2026 · Aug 28, 2026
@@ -1,3 +1,9 @@
+## 5.16.0
+
+**Feature**
+
+- [#759](https://github.com/FlutterGen/flutter_gen/issues/759) Added `flutter_gen_interface` to allow generated asset classes to implement a shared custom interface for Modular Architectures & Design Systems.
+
 ## 5.15.0
 
 **Feature**

@@ -220,7 +220,9 @@ class $AssetsLottieWrongGen {
   List<String> get values => [dummy, rocketLottieV439];
 }
 
-abstract final class MyAssets {
+class MyAssets {
+  const MyAssets._();
+
   static const String readme = 'README.md';
   static const $AssetsFlareGen flare = $AssetsFlareGen();
   static const $AssetsImagesGen images = $AssetsImagesGen();

@@ -11,7 +11,9 @@
 import 'package:flutter/painting.dart';
 import 'package:flutter/material.dart';
 
-abstract final class MyColorName {
+class MyColorName {
+  MyColorName._();
+
   /// Color: #000000
   static const Color black = Color(0xFF000000);
 

@@ -8,7 +8,9 @@
 // ignore_for_file: type=lint
 // ignore_for_file: deprecated_member_use,directives_ordering,implicit_dynamic_list_literal,unnecessary_import
 
-abstract final class MyFontFamily {
+class MyFontFamily {
+  MyFontFamily._();
+
   /// Font family: Raleway
   static const String raleway = 'Raleway';
 

@@ -56,7 +56,9 @@ class $AssetsUnknownGen {
   List<String> get values => [unknownMimeType];
 }
 
-abstract final class ResAssets {
+class ResAssets {
+  const ResAssets._();
+
   static const String package = 'example_resources';
 
   static const $AssetsImagesGen images = $AssetsImagesGen();

@@ -11,7 +11,9 @@
 import 'package:flutter/painting.dart';
 import 'package:flutter/material.dart';
 
-abstract final class ColorName {
+class ColorName {
+  ColorName._();
+
   /// Color: #000000
   static const Color black = Color(0xFF000000);
 

@@ -22,7 +22,9 @@ class $AssetsImagesGen {
   List<AssetGenImage> get values => [flutter3];
 }
 
-abstract final class GalleryOneAssets {
+class GalleryOneAssets {
+  const GalleryOneAssets._();
+
   static const $AssetsImagesGen images = $AssetsImagesGen();
 }
 

@@ -19,6 +19,8 @@ class $AssetsImagesGen {
   List<String> get values => [dart];
 }
 
-abstract final class GalleryTwoAssets {
+class GalleryTwoAssets {
+  const GalleryTwoAssets._();
+
   static const $AssetsImagesGen images = $AssetsImagesGen();
 }
@@ -4,6 +4,7 @@ packages:
   - packages/command
   - packages/core
   - packages/runner
+  - packages/flutter_gen_interface
   - examples/example
   - examples/example_resources
   - examples/example_workspace
@@ -136,6 +137,7 @@ scripts:
         - flutter_gen
         - flutter_gen_core
         - flutter_gen_runner
+        - flutter_gen_interface
 
   publish:dry:
     run: dart pub publish --dry-run
@@ -147,3 +149,4 @@ scripts:
         - flutter_gen
         - flutter_gen_core
         - flutter_gen_runner
+        - flutter_gen_interface
@@ -77,7 +77,6 @@ Future<String> generateAssets(
       'The value of "flutter/assets:" is incorrect.',
     );
   }
-
   final integrations = <Integration>[
     if (config.flutterGen.integrations.image)
       ImageIntegration(
@@ -165,7 +164,17 @@ Future<String> generateAssets(
 
   final importsBuffer = StringBuffer();
   for (final e in imports.sorted((a, b) => a.import.compareTo(b.import))) {
-    importsBuffer.writeln(import(e));
+    if (e.import ==
+        'package:flutter_gen_interface/flutter_gen_interface.dart') {
+      importsBuffer.writeln(
+        'import \'package:flutter_gen_interface/flutter_gen_interface.dart\';',
+      );
+      importsBuffer.writeln(
+        'export \'package:flutter_gen_interface/flutter_gen_interface.dart\';',
+      );
+    } else {
+      importsBuffer.writeln(import(e));
+    }
   }
 
   final buffer = StringBuffer();

@@ -26,109 +26,13 @@ class ImageIntegration extends Integration {
 
   @override
   List<Import> get requiredImports => const [
-        Import('package:flutter/widgets.dart'),
+        Import(
+          'package:flutter_gen_interface/flutter_gen_interface.dart',
+        ),
       ];
 
   @override
-  String get classOutput => _classDefinition;
-
-  String get _classDefinition => '''class AssetGenImage {
-  const AssetGenImage(
-    this._assetName, {
-    this.size,
-    this.flavors = const {},
-    this.animation,
-  });
-
-  final String _assetName;
-
-${isPackage ? "\n  static const String package = '$packageName';" : ''}
-
-  final Size? size;
-  final Set<String> flavors;
-  final AssetGenImageAnimation? animation;
-
-  Image image({
-    Key? key,
-    AssetBundle? bundle,
-    ImageFrameBuilder? frameBuilder,
-    ImageErrorWidgetBuilder? errorBuilder,
-    String? semanticLabel,
-    bool excludeFromSemantics = false,
-    double? scale,
-    double? width,
-    double? height,
-    Color? color,
-    Animation<double>? opacity,
-    BlendMode? colorBlendMode,
-    BoxFit? fit,
-    AlignmentGeometry alignment = Alignment.center,
-    ImageRepeat repeat = ImageRepeat.noRepeat,
-    Rect? centerSlice,
-    bool matchTextDirection = false,
-    bool gaplessPlayback = true,
-    bool isAntiAlias = false,
-    ${isPackage ? '$deprecationMessagePackage\n' : ''}String? package$packageParameter,
-    FilterQuality filterQuality = FilterQuality.medium,
-    int? cacheWidth,
-    int? cacheHeight,
-  }) {
-    return Image.asset(
-      _assetName,
-      key: key,
-      bundle: bundle,
-      frameBuilder: frameBuilder,
-      errorBuilder: errorBuilder,
-      semanticLabel: semanticLabel,
-      excludeFromSemantics: excludeFromSemantics,
-      scale: scale,
-      width: width,
-      height: height,
-      color: color,
-      opacity: opacity,
-      colorBlendMode: colorBlendMode,
-      fit: fit,
-      alignment: alignment,
-      repeat: repeat,
-      centerSlice: centerSlice,
-      matchTextDirection: matchTextDirection,
-      gaplessPlayback: gaplessPlayback,
-      isAntiAlias: isAntiAlias,
-      package: package,
-      filterQuality: filterQuality,
-      cacheWidth: cacheWidth,
-      cacheHeight: cacheHeight,
-    );
-  }
-
-  ImageProvider provider({
-    AssetBundle? bundle,
-    ${isPackage ? '$deprecationMessagePackage\n' : ''}String? package$packageParameter,
-  }) {
-    return AssetImage(
-      _assetName,
-      bundle: bundle,
-      package: package,
-    );
-  }
-
-  String get path => _assetName;
-
-  String get keyName => $keyName;
-}
-
-class AssetGenImageAnimation {
-  const AssetGenImageAnimation({
-    required this.isAnimation,
-    required this.duration,
-    required this.frames,
-  });
-
-  final bool isAnimation;
-  final Duration duration;
-  final int frames;
-}
-''';
+  String get classOutput => '';
 
   @override
   String get className => 'AssetGenImage';
@@ -157,7 +61,10 @@ class AssetGenImageAnimation {
       final flavors = asset.flavors.map((e) => '\'$e\'').join(', ');
       buffer.write(flavors);
       buffer.write('}');
-      buffer.write(','); // Better formatting.
+      if (!isPackage) buffer.write(','); // Better formatting.
+    }
+    if (isPackage) {
+      buffer.write(', package: \'$packageName\',');
     }
     buffer.write(')');
     return buffer.toString();

@@ -10,10 +10,9 @@ class SvgIntegration extends Integration {
     super.parseMetadata,
   }) : super(packageName);
 
-  String get packageExpression => isPackage ? ' = package' : '';
-
   @override
   List<Import> get requiredImports => const [
+        Import('package:flutter_gen_interface/flutter_gen_interface.dart'),
         Import('package:flutter/widgets.dart'),
         Import('package:flutter/services.dart'),
         Import('package:flutter_svg/flutter_svg.dart', alias: '_svg'),
@@ -23,31 +22,13 @@ class SvgIntegration extends Integration {
   @override
   String get classOutput => _classDefinition;
 
-  String get _classDefinition => '''class SvgGenImage {
-  const SvgGenImage(
-    this._assetName, {
-    this.size,
-    this.flavors = const {},
-  }) : _isVecFormat = false;
-
-  const SvgGenImage.vec(
-    this._assetName, {
-    this.size,
-    this.flavors = const {},
-  }) : _isVecFormat = true;
-
-  final String _assetName;
-  final Size? size;
-  final Set<String> flavors;
-  final bool _isVecFormat;
-
-${isPackage ? "\n  static const String package = '$packageName';" : ''}
-
+  String get _classDefinition =>
+      '''extension SvgGenImageExtension on SvgGenImage {
   _svg.SvgPicture svg({
     Key? key,
     bool matchTextDirection = false,
     AssetBundle? bundle,
-    ${isPackage ? '$deprecationMessagePackage\n' : ''}String? package$packageExpression,
+    ${isPackage ? '$deprecationMessagePackage\n' : ''}String? package,
     double? width,
     double? height,
     BoxFit fit = BoxFit.contain,
@@ -65,17 +46,17 @@ ${isPackage ? "\n  static const String package = '$packageName';" : ''}
     @deprecated bool cacheColorFilter = false,
   }) {
     final _svg.BytesLoader loader;
-    if (_isVecFormat) {
+    if (isVecFormat) {
       loader = _vg.AssetBytesLoader(
-        _assetName,
+        path,
         assetBundle: bundle,
-        packageName: package,
+        packageName: package ?? this.package,
       );
     } else {
       loader = _svg.SvgAssetLoader(
-        _assetName,
+        path,
         assetBundle: bundle,
-        packageName: package,
+        packageName: package ?? this.package,
         theme: theme,
         colorMapper: colorMapper,
       );
@@ -97,10 +78,6 @@ ${isPackage ? "\n  static const String package = '$packageName';" : ''}
       cacheColorFilter: cacheColorFilter,
     );
   }
-
-  String get path => _assetName;
-
-  String get keyName => ${isPackage ? '\'packages/$packageName/\$_assetName\'' : '_assetName'};
 }''';
 
   @override
@@ -127,7 +104,10 @@ ${isPackage ? "\n  static const String package = '$packageName';" : ''}
       final flavors = asset.flavors.map((e) => '\'$e\'').join(', ');
       buffer.write(flavors);
       buffer.write('}');
-      buffer.write(','); // Better formatting.
+      if (!isPackage) buffer.write(','); // Better formatting.
+    }
+    if (isPackage) {
+      buffer.write(', package: \'$packageName\',');
     }
     buffer.write(')');
     return buffer.toString();

@@ -174,20 +174,31 @@ void main() {
         isFalse,
       );
       expect(integration.isConstConstructor, isTrue);
+      expect(
+        integration.classOutput.contains(
+          'extension SvgGenImageExtension on SvgGenImage',
+        ),
+        isTrue,
+      );
       expect(integration.classOutput.contains('String? package,'), isTrue);
 
       final integrationWithPackage = SvgIntegration('package_name');
       expect(
         integrationWithPackage.classOutput.contains(
-          'String? package = package,',
+          "@Deprecated('Do not specify package for a generated library asset')",
         ),
         isTrue,
       );
       expect(
-        integrationWithPackage.classOutput.contains(
-          "static const String package = 'package_name';",
+        integrationWithPackage.classInstantiate(
+          AssetType(
+            rootPath: resPath,
+            path: 'assets/path/dog.svg',
+            flavors: {},
+            transformers: {},
+          ),
         ),
-        isTrue,
+        "SvgGenImage('assets/path/dog.svg', package: 'package_name',)",
       );
     });