✨ Flavored assets (#530)

## What does this change?

Resolves #494 🎯

Generated assets would contain the flavor info specified in the `pubspec.yaml`, but only as a constant not involved with actual flavoring.

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] This change requires a documentation update

README.md

@@ -167,6 +167,18 @@ flutter:
 
 These configurations will generate **`assets.gen.dart`** under the **`lib/gen/`** directory by default.
 
+#### Flavored assets
+
+Flutter supports
+[Conditionally bundling assets based on flavor](https://docs.flutter.dev/deployment/flavors#conditionally-bundling-assets-based-on-flavor).
+Assets are only available with flavors if specified.
+`flutter_gen` will generate the specified `flavors` for assets regardless the current flavor.
+The `flavors` field accessible though `.flavors`, for example:
+
+```dart
+print(MyAssets.images.chip4.flavors); // -> {'extern'}
+```
+
 #### Excluding generating for assets
 
 You can specify `flutter_gen > assets > exclude` using `Glob` patterns to exclude particular assets.

examples/example/lib/gen/assets.gen.dart

@@ -35,6 +35,9 @@ class $AssetsImagesGen {
   /// File path: assets/images/chip2.jpg
   AssetGenImage get chip2 => const AssetGenImage('assets/images/chip2.jpg');
 
+  /// Directory path: assets/images/chip3
+  $AssetsImagesChip3Gen get chip3 => const $AssetsImagesChip3Gen();
+
   /// Directory path: assets/images/chip4
   $AssetsImagesChip4Gen get chip4 => const $AssetsImagesChip4Gen();
 
@@ -142,12 +145,25 @@ class $AssetsUnknownGen {
   List<String> get values => [changelog, readme, unknownMimeType];
 }
 
+class $AssetsImagesChip3Gen {
+  const $AssetsImagesChip3Gen();
+
+  /// File path: assets/images/chip3/chip3.jpg
+  AssetGenImage get chip3 =>
+      const AssetGenImage('assets/images/chip3/chip3.jpg');
+
+  /// List of all assets
+  List<AssetGenImage> get values => [chip3];
+}
+
 class $AssetsImagesChip4Gen {
   const $AssetsImagesChip4Gen();
 
   /// File path: assets/images/chip4/chip4.jpg
-  AssetGenImage get chip4 =>
-      const AssetGenImage('assets/images/chip4/chip4.jpg');
+  AssetGenImage get chip4 => const AssetGenImage(
+        'assets/images/chip4/chip4.jpg',
+        flavors: {'extern'},
+      );
 
   /// List of all assets
   List<AssetGenImage> get values => [chip4];
@@ -202,11 +218,16 @@ class MyAssets {
 }
 
 class AssetGenImage {
-  const AssetGenImage(this._assetName, {this.size = null});
+  const AssetGenImage(
+    this._assetName, {
+    this.size,
+    this.flavors = const {},
+  });
 
   final String _assetName;
 
   final Size? size;
+  final Set<String> flavors;
 
   Image image({
     Key? key,
@@ -280,17 +301,19 @@ class AssetGenImage {
 class SvgGenImage {
   const SvgGenImage(
     this._assetName, {
-    this.size = null,
+    this.size,
+    this.flavors = const {},
   }) : _isVecFormat = false;
 
   const SvgGenImage.vec(
     this._assetName, {
-    this.size = null,
+    this.size,
+    this.flavors = const {},
   }) : _isVecFormat = true;
 
   final String _assetName;
-
   final Size? size;
+  final Set<String> flavors;
   final bool _isVecFormat;
 
   SvgPicture svg({
@@ -313,12 +336,23 @@ class SvgGenImage {
     @deprecated BlendMode colorBlendMode = BlendMode.srcIn,
     @deprecated bool cacheColorFilter = false,
   }) {
+    final BytesLoader loader;
+    if (_isVecFormat) {
+      loader = AssetBytesLoader(
+        _assetName,
+        assetBundle: bundle,
+        packageName: package,
+      );
+    } else {
+      loader = SvgAssetLoader(
+        _assetName,
+        assetBundle: bundle,
+        packageName: package,
+        theme: theme,
+      );
+    }
     return SvgPicture(
-      _isVecFormat
-          ? AssetBytesLoader(_assetName,
-              assetBundle: bundle, packageName: package)
-          : SvgAssetLoader(_assetName,
-              assetBundle: bundle, packageName: package, theme: theme),
+      loader,
       key: key,
       matchTextDirection: matchTextDirection,
       width: width,
@@ -342,9 +376,13 @@ class SvgGenImage {
 }
 
 class FlareGenImage {
-  const FlareGenImage(this._assetName);
+  const FlareGenImage(
+    this._assetName, {
+    this.flavors = const {},
+  });
 
   final String _assetName;
+  final Set<String> flavors;
 
   FlareActor flare({
     String? boundsNode,
@@ -385,9 +423,13 @@ class FlareGenImage {
 }
 
 class RiveGenImage {
-  const RiveGenImage(this._assetName);
+  const RiveGenImage(
+    this._assetName, {
+    this.flavors = const {},
+  });
 
   final String _assetName;
+  final Set<String> flavors;
 
   RiveAnimation rive({
     String? artboard,
@@ -422,9 +464,13 @@ class RiveGenImage {
 }
 
 class LottieGenImage {
-  const LottieGenImage(this._assetName);
+  const LottieGenImage(
+    this._assetName, {
+    this.flavors = const {},
+  });
 
   final String _assetName;
+  final Set<String> flavors;
 
   LottieBuilder lottie({
     Animation<double>? controller,

examples/example/pubspec.yaml

@@ -51,7 +51,6 @@ flutter_gen:
       style: dot-delimiter
 
     exclude:
-      - assets/images/chip3/chip3.jpg
       - assets-extern/*
       - pictures/chip5.jpg
 
@@ -76,7 +75,6 @@ flutter:
     - assets/images/
     - assets/images/chip3/chip3.jpg
     - assets/images/chip3/chip3.jpg # duplicated
-    - assets/images/chip4/
     - assets/images/icons/fuchsia.svg
     - assets/images/icons/kmm.svg
     - assets/images/icons/paint.svg
@@ -91,6 +89,10 @@ flutter:
     - assets/mix/
     - assets-extern/
     - pictures/chip5.jpg
+
+    - path: assets/images/chip4/chip4.jpg
+      flavors:
+        - extern
   fonts:
     - family: Raleway
       fonts:

packages/core/lib/generators/assets_generator.dart

@@ -13,11 +13,13 @@ import 'package:flutter_gen_core/generators/integrations/rive_integration.dart';
 import 'package:flutter_gen_core/generators/integrations/svg_integration.dart';
 import 'package:flutter_gen_core/settings/asset_type.dart';
 import 'package:flutter_gen_core/settings/config.dart';
+import 'package:flutter_gen_core/settings/flavored_asset.dart';
 import 'package:flutter_gen_core/settings/pubspec.dart';
 import 'package:flutter_gen_core/utils/error.dart';
 import 'package:flutter_gen_core/utils/string.dart';
 import 'package:glob/glob.dart';
 import 'package:path/path.dart';
+import 'package:yaml/yaml.dart';
 
 class AssetsGenConfig {
   AssetsGenConfig._(
@@ -41,7 +43,7 @@ class AssetsGenConfig {
   final String rootPath;
   final String _packageName;
   final FlutterGen flutterGen;
-  final List<String> assets;
+  final List<Object> assets;
   final List<Glob> exclude;
 
   String get packageParameterLiteral =>
@@ -194,51 +196,89 @@ String? generatePackageNameForConfig(AssetsGenConfig config) {
   }
 }
 
-/// Returns a list of all releative path assets that are to be considered.
-List<String> _getAssetRelativePathList(
+/// Returns a list of all relative path assets that are to be considered.
+List<FlavoredAsset> _getAssetRelativePathList(
   /// The absolute root path of the assets directory.
   String rootPath,
 
-  /// List of assets as provided the `flutter`.`assets` section in the pubspec.yaml.
-  List<String> assets,
+  /// List of assets as provided the `flutter -> assets`
+  /// section in the pubspec.yaml.
+  List<Object> assets,
 
-  /// List of globs as provided the `flutter_gen`.`assets`.`exclude` section in the pubspec.yaml.
+  /// List of globs as provided the `flutter_gen -> assets -> exclude`
+  /// section in the pubspec.yaml.
   List<Glob> excludes,
 ) {
-  final assetRelativePathList = <String>[];
-  for (final assetName in assets) {
-    final assetAbsolutePath = join(rootPath, assetName);
+  // Normalize.
+  final normalizedAssets = <Object>{...assets.whereType<String>()};
+  final normalizingMap = <String, Set<String>>{};
+  // Resolve flavored assets.
+  for (final map in assets.whereType<YamlMap>()) {
+    final path = (map['path'] as String).trim();
+    final flavors =
+        (map['flavors'] as YamlList?)?.toSet().cast<String>() ?? <String>{};
+    if (normalizingMap.containsKey(path)) {
+      // https://github.com/flutter/flutter/blob/5187cab7bdd434ca74abb45895d17e9fa553678a/packages/flutter_tools/lib/src/asset.dart#L1137-L1139
+      throw StateError(
+        'Multiple assets entries include the file "$path", '
+        'but they specify different lists of flavors.',
+      );
+    }
+    normalizingMap[path] = flavors;
+  }
+  for (final entry in normalizingMap.entries) {
+    normalizedAssets.add(
+      YamlMap.wrap({'path': entry.key, 'flavors': entry.value}),
+    );
+  }
+
+  final assetRelativePathList = <FlavoredAsset>[];
+  for (final asset in normalizedAssets) {
+    final FlavoredAsset tempAsset;
+    if (asset is YamlMap) {
+      tempAsset = FlavoredAsset(path: asset['path'], flavors: asset['flavors']);
+    } else {
+      tempAsset = FlavoredAsset(path: (asset as String).trim());
+    }
+    final assetAbsolutePath = join(rootPath, tempAsset.path);
     if (FileSystemEntity.isDirectorySync(assetAbsolutePath)) {
       assetRelativePathList.addAll(Directory(assetAbsolutePath)
           .listSync()
           .whereType<File>()
-          .map((e) => relative(e.path, from: rootPath))
+          .map(
+            (e) => tempAsset.copyWith(path: relative(e.path, from: rootPath)),
+          )
           .toList());
     } else if (FileSystemEntity.isFileSync(assetAbsolutePath)) {
-      assetRelativePathList.add(relative(assetAbsolutePath, from: rootPath));
+      assetRelativePathList.add(
+        tempAsset.copyWith(path: relative(assetAbsolutePath, from: rootPath)),
+      );
     }
   }
 
   if (excludes.isEmpty) {
     return assetRelativePathList;
   }
-
   return assetRelativePathList
-      .where((file) => !excludes.any((exclude) => exclude.matches(file)))
+      .where((asset) => !excludes.any((exclude) => exclude.matches(asset.path)))
       .toList();
 }
 
 AssetType _constructAssetTree(
-    List<String> assetRelativePathList, String rootPath) {
+  List<FlavoredAsset> assetRelativePathList,
+  String rootPath,
+) {
   // Relative path is the key
   final assetTypeMap = <String, AssetType>{
-    '.': AssetType(rootPath: rootPath, path: '.'),
+    '.': AssetType(rootPath: rootPath, path: '.', flavors: {}),
   };
-  for (final assetPath in assetRelativePathList) {
-    var path = assetPath;
+  for (final asset in assetRelativePathList) {
+    String path = asset.path;
     while (path != '.') {
       assetTypeMap.putIfAbsent(
-          path, () => AssetType(rootPath: rootPath, path: path));
+        path,
+        () => AssetType(rootPath: rootPath, path: path, flavors: asset.flavors),
+      );
       path = dirname(path);
     }
   }
@@ -320,7 +360,8 @@ String _dotDelimiterStyleDefinition(
   final assetsStaticStatements = <_Statement>[];
 
   final assetTypeQueue = ListQueue<AssetType>.from(
-      _constructAssetTree(assetRelativePathList, rootPath).children);
+    _constructAssetTree(assetRelativePathList, rootPath).children,
+  );
 
   while (assetTypeQueue.isNotEmpty) {
     final assetType = assetTypeQueue.removeFirst();
@@ -428,14 +469,20 @@ String _flatStyleDefinition(
   List<Integration> integrations,
   String Function(String) style,
 ) {
-  final statements = _getAssetRelativePathList(
+  final List<FlavoredAsset> paths = _getAssetRelativePathList(
     config.rootPath,
     config.assets,
     config.exclude,
-  )
-      .distinct()
-      .sorted()
-      .map((assetPath) => AssetType(rootPath: config.rootPath, path: assetPath))
+  );
+  paths.sort(((a, b) => a.path.compareTo(b.path)));
+  final statements = paths
+      .map(
+        (assetPath) => AssetType(
+          rootPath: config.rootPath,
+          path: assetPath.path,
+          flavors: assetPath.flavors,
+        ),
+      )
       .mapToUniqueAssetType(style)
       .map(
         (e) => _createAssetTypeStatement(

packages/core/lib/generators/integrations/flare_integration.dart

@@ -17,9 +17,14 @@ class FlareIntegration extends Integration {
   String get classOutput => _classDefinition;
 
   String get _classDefinition => '''class FlareGenImage {
-  const FlareGenImage(this._assetName);
+  const FlareGenImage(
+    this._assetName, {
+    this.flavors = const {},
+  });
 
   final String _assetName;
+  final Set<String> flavors;
+
 ${isPackage ? "\n  static const String package = '$packageName';" : ''}
 
   FlareActor flare({
@@ -63,10 +68,6 @@ ${isPackage ? "\n  static const String package = '$packageName';" : ''}
   @override
   String get className => 'FlareGenImage';
 
-  @override
-  String classInstantiate(AssetType asset) =>
-      'FlareGenImage(\'${asset.posixStylePath}\')';
-
   @override
   bool isSupport(AssetType asset) => asset.extension == '.flr';