Speed up first asset load by encoding asset manifest in binary rather than JSON (#113637)

dev/benchmarks/microbenchmarks/lib/foundation/decode_and_parse_asset_manifest.dart

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 import 'dart:convert';
+import 'dart:typed_data';
 
-import 'package:flutter/foundation.dart';
-import 'package:flutter/services.dart' show PlatformAssetBundle;
+import 'package:flutter/services.dart' show PlatformAssetBundle, StandardMessageCodec;
 import 'package:flutter/widgets.dart';
 
 import '../common.dart';
@@ -18,16 +18,14 @@ void main() async {
   final BenchmarkResultPrinter printer = BenchmarkResultPrinter();
   WidgetsFlutterBinding.ensureInitialized();
   final Stopwatch watch = Stopwatch();
-  final PlatformAssetBundle bundle = PlatformAssetBundle();
 
-  final ByteData assetManifestBytes = await bundle.load('money_asset_manifest.json');
+  final ByteData assetManifest = await loadAssetManifest();
+
   watch.start();
   for (int i = 0; i < _kNumIterations; i++) {
-    bundle.clear();
-    final String json = utf8.decode(assetManifestBytes.buffer.asUint8List());
-    // This is a test, so we don't need to worry about this rule.
+    // This is effectively a test.
     // ignore: invalid_use_of_visible_for_testing_member
-    await AssetImage.manifestParser(json);
+    AssetImage.parseAssetManifest(assetManifest);
   }
   watch.stop();
 
@@ -40,3 +38,49 @@ void main() async {
 
   printer.printToStdout();
 }
+
+final RegExp _extractRatioRegExp = RegExp(r'/?(\d+(\.\d*)?)x$');
+
+Future<ByteData> loadAssetManifest() async {
+  double parseScale(String key) {
+    final Uri assetUri = Uri.parse(key);
+    String directoryPath = '';
+    if (assetUri.pathSegments.length > 1) {
+      directoryPath = assetUri.pathSegments[assetUri.pathSegments.length - 2];
+    }
+    final Match? match = _extractRatioRegExp.firstMatch(directoryPath);
+    if (match != null && match.groupCount > 0) {
+      return double.parse(match.group(1)!);
+    }
+    return 1.0;
+  }
+
+  final Map<String, dynamic> result = <String, dynamic>{};
+  final PlatformAssetBundle bundle = PlatformAssetBundle();
+
+  // For the benchmark, we use the older JSON format and then convert it to the modern binary format.
+  final ByteData jsonAssetManifestBytes = await bundle.load('money_asset_manifest.json');
+  final String jsonAssetManifest = utf8.decode(jsonAssetManifestBytes.buffer.asUint8List());
+
+  final Map<String, dynamic> assetManifest = json.decode(jsonAssetManifest) as Map<String, dynamic>;
+
+  for (final MapEntry<String, dynamic> manifestEntry in assetManifest.entries) {
+    final List<dynamic> resultVariants = <dynamic>[];
+    final List<String> entries = (manifestEntry.value as List<dynamic>).cast<String>();
+    for (final String variant in entries) {
+      if (variant == manifestEntry.key) {
+        // With the newer binary format, don't include the main asset in it's
+        // list of variants. This reduces parsing time at runtime.
+        continue;
+      }
+      final Map<String, dynamic> resultVariant = <String, dynamic>{};
+      final double variantDevicePixelRatio = parseScale(variant);
+      resultVariant['asset'] = variant;
+      resultVariant['dpr'] = variantDevicePixelRatio;
+      resultVariants.add(resultVariant);
+    }
+    result[manifestEntry.key] = resultVariants;
+  }
+
+  return const StandardMessageCodec().encodeMessage(result)!;
+}

dev/integration_tests/flutter_gallery/test/example_code_parser_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter/services.dart';
 import 'package:flutter_gallery/gallery/example_code_parser.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -58,4 +60,9 @@ class TestAssetBundle extends AssetBundle {
 
   @override
   String toString() => '$runtimeType@$hashCode()';
+
+  @override
+  Future<T> loadStructuredBinaryData<T>(String key, FutureOr<T> Function(ByteData data) parser) async {
+    return parser(await load(key));
+  }
 }

packages/flutter/lib/src/painting/image_resolution.dart

@@ -11,7 +11,8 @@ import 'package:flutter/services.dart';
 
 import 'image_provider.dart';
 
-const String _kAssetManifestFileName = 'AssetManifest.json';
+const String _kLegacyAssetManifestFilename = 'AssetManifest.json';
+const String _kAssetManifestFilename = 'AssetManifest.bin';
 
 /// A screen with a device-pixel ratio strictly less than this value is
 /// considered a low-resolution screen (typically entry-level to mid-range
@@ -284,18 +285,45 @@ class AssetImage extends AssetBundleImageProvider {
     Completer<AssetBundleImageKey>? completer;
     Future<AssetBundleImageKey>? result;
 
-    chosenBundle.loadStructuredData<Map<String, List<String>>?>(_kAssetManifestFileName, manifestParser).then<void>(
-      (Map<String, List<String>>? manifest) {
-        final String chosenName = _chooseVariant(
+    Future<_AssetManifest> loadJsonAssetManifest() {
+      Future<_AssetManifest> parseJson(String data) {
+        final _AssetManifest parsed = _LegacyAssetManifest.fromJsonString(data);
+        return SynchronousFuture<_AssetManifest>(parsed);
+      }
+      return chosenBundle.loadStructuredData(_kLegacyAssetManifestFilename, parseJson);
+    }
+
+    // TODO(andrewkolos): Once google3 and google-fonts-flutter are migrated
+    // away from using AssetManifest.json, remove all references to it.
+    // See https://github.com/flutter/flutter/issues/114913.
+    Future<_AssetManifest>? manifest;
+
+    // Since AssetBundle load calls can be synchronous (e.g. in the case of tests),
+    // it is not sufficient to only use catchError/onError or the onError parameter
+    // of Future.then--we also have to use a synchronous try/catch. Once google3
+    // tooling starts producing AssetManifest.bin, this block can be removed.
+    try {
+      manifest = chosenBundle.loadStructuredBinaryData(_kAssetManifestFilename, _AssetManifestBin.fromStandardMessageCodecMessage);
+    } catch (error) {
+      manifest = loadJsonAssetManifest();
+    }
+
+    manifest
+      // To understand why we use this no-op `then` instead of `catchError`/`onError`,
+      // see https://github.com/flutter/flutter/issues/115601
+      .then((_AssetManifest manifest) => manifest,
+          onError: (Object? error, StackTrace? stack) => loadJsonAssetManifest())
+      .then((_AssetManifest manifest) {
+        final List<_AssetVariant> candidateVariants = manifest.getVariants(keyName);
+        final _AssetVariant chosenVariant = _chooseVariant(
           keyName,
           configuration,
-          manifest == null ? null : manifest[keyName],
-        )!;
-        final double chosenScale = _parseScale(chosenName);
+          candidateVariants,
+        );
         final AssetBundleImageKey key = AssetBundleImageKey(
           bundle: chosenBundle,
-          name: chosenName,
-          scale: chosenScale,
+          name: chosenVariant.asset,
+          scale: chosenVariant.devicePixelRatio,
         );
         if (completer != null) {
           // We already returned from this function, which means we are in the
@@ -309,14 +337,15 @@ class AssetImage extends AssetBundleImageProvider {
           // ourselves.
           result = SynchronousFuture<AssetBundleImageKey>(key);
         }
-      },
-    ).catchError((Object error, StackTrace stack) {
-      // We had an error. (This guarantees we weren't called synchronously.)
-      // Forward the error to the caller.
-      assert(completer != null);
-      assert(result == null);
-      completer!.completeError(error, stack);
-    });
+      })
+      .onError((Object error, StackTrace stack) {
+        // We had an error. (This guarantees we weren't called synchronously.)
+        // Forward the error to the caller.
+        assert(completer != null);
+        assert(result == null);
+        completer!.completeError(error, stack);
+      });
+
     if (result != null) {
       // The code above ran synchronously, and came up with an answer.
       // Return the SynchronousFuture that we created above.
@@ -328,35 +357,29 @@ class AssetImage extends AssetBundleImageProvider {
     return completer.future;
   }
 
-  /// Parses the asset manifest string into a strongly-typed map.
+  /// Parses the asset manifest's file contents into it's Dart representation.
   @visibleForTesting
-  static Future<Map<String, List<String>>?> manifestParser(String? jsonData) {
-    if (jsonData == null) {
-      return SynchronousFuture<Map<String, List<String>>?>(null);
-    }
-    // TODO(ianh): JSON decoding really shouldn't be on the main thread.
-    final Map<String, dynamic> parsedJson = json.decode(jsonData) as Map<String, dynamic>;
-    final Iterable<String> keys = parsedJson.keys;
-    final Map<String, List<String>> parsedManifest = <String, List<String>> {
-      for (final String key in keys) key: List<String>.from(parsedJson[key] as List<dynamic>),
-    };
-    // TODO(ianh): convert that data structure to the right types.
-    return SynchronousFuture<Map<String, List<String>>?>(parsedManifest);
+  // Return type is set to Object?, because the specific type is private.
+  static Object? parseAssetManifest(ByteData bytes) {
+    return _AssetManifestBin.fromStandardMessageCodecMessage(bytes);
   }
 
-  String? _chooseVariant(String main, ImageConfiguration config, List<String>? candidates) {
-    if (config.devicePixelRatio == null || candidates == null || candidates.isEmpty) {
-      return main;
+  _AssetVariant _chooseVariant(String mainAssetKey, ImageConfiguration config, List<_AssetVariant> candidateVariants) {
+    final _AssetVariant mainAsset = _AssetVariant(asset: mainAssetKey,
+      devicePixelRatio: _naturalResolution);
+    if (config.devicePixelRatio == null || candidateVariants.isEmpty) {
+      return mainAsset;
     }
-    // TODO(ianh): Consider moving this parsing logic into _manifestParser.
-    final SplayTreeMap<double, String> mapping = SplayTreeMap<double, String>();
-    for (final String candidate in candidates) {
-      mapping[_parseScale(candidate)] = candidate;
+    final SplayTreeMap<double, _AssetVariant> candidatesByDevicePixelRatio =
+      SplayTreeMap<double, _AssetVariant>();
+    for (final _AssetVariant candidate in candidateVariants) {
+      candidatesByDevicePixelRatio[candidate.devicePixelRatio] = candidate;
     }
+    candidatesByDevicePixelRatio.putIfAbsent(_naturalResolution, () => mainAsset);
     // TODO(ianh): implement support for config.locale, config.textDirection,
     // config.size, config.platform (then document this over in the Image.asset
     // docs)
-    return _findBestVariant(mapping, config.devicePixelRatio!);
+    return _findBestVariant(candidatesByDevicePixelRatio, config.devicePixelRatio!);
   }
 
   // Returns the "best" asset variant amongst the available `candidates`.
@@ -371,17 +394,17 @@ class AssetImage extends AssetBundleImageProvider {
   //   lowest key higher than `value`.
   // - If the screen has high device pixel ratio, choose the variant with the
   //   key nearest to `value`.
-  String? _findBestVariant(SplayTreeMap<double, String> candidates, double value) {
-    if (candidates.containsKey(value)) {
-      return candidates[value]!;
+  _AssetVariant _findBestVariant(SplayTreeMap<double, _AssetVariant> candidatesByDpr, double value) {
+    if (candidatesByDpr.containsKey(value)) {
+      return candidatesByDpr[value]!;
     }
-    final double? lower = candidates.lastKeyBefore(value);
-    final double? upper = candidates.firstKeyAfter(value);
+    final double? lower = candidatesByDpr.lastKeyBefore(value);
+    final double? upper = candidatesByDpr.firstKeyAfter(value);
     if (lower == null) {
-      return candidates[upper];
+      return candidatesByDpr[upper]!;
     }
     if (upper == null) {
-      return candidates[lower];
+      return candidatesByDpr[lower]!;
     }
 
     // On screens with low device-pixel ratios the artifacts from upscaling
@@ -389,20 +412,116 @@ class AssetImage extends AssetBundleImageProvider {
     // ratios because the physical pixels are larger. Choose the higher
     // resolution image in that case instead of the nearest one.
     if (value < _kLowDprLimit || value > (lower + upper) / 2) {
-      return candidates[upper];
+      return candidatesByDpr[upper]!;
     } else {
-      return candidates[lower];
+      return candidatesByDpr[lower]!;
     }
   }
 
+  @override
+  bool operator ==(Object other) {
+    if (other.runtimeType != runtimeType) {
+      return false;
+    }
+    return other is AssetImage
+        && other.keyName == keyName
+        && other.bundle == bundle;
+  }
+
+  @override
+  int get hashCode => Object.hash(keyName, bundle);
+
+  @override
+  String toString() => '${objectRuntimeType(this, 'AssetImage')}(bundle: $bundle, name: "$keyName")';
+}
+
+/// Centralizes parsing and typecasting of the contents of the asset manifest file,
+/// which is generated by the flutter tool at build time.
+abstract class _AssetManifest {
+  List<_AssetVariant> getVariants(String key);
+}
+
+/// Parses the binary asset manifest into a data structure that's easier to work with.
+///
+/// The asset manifest is a map of asset files to a list of objects containing
+/// information about variants of that asset.
+///
+/// The entries with each variant object are:
+///  - "asset": the location of this variant to load it from.
+///  - "dpr": The device-pixel-ratio that the asset is best-suited for.
+///
+/// New fields could be added to this object schema to support new asset variation
+/// features, such as themes, locale/region support, reading directions, and so on.
+class _AssetManifestBin implements _AssetManifest {
+  _AssetManifestBin(Map<Object?, Object?> standardMessageData): _data = standardMessageData;
+
+  factory _AssetManifestBin.fromStandardMessageCodecMessage(ByteData message) {
+    final Object? data = const StandardMessageCodec().decodeMessage(message);
+    return _AssetManifestBin(data! as Map<Object?, Object?>);
+  }
+
+  final Map<Object?, Object?> _data;
+  final Map<String, List<_AssetVariant>> _typeCastedData = <String, List<_AssetVariant>>{};
+
+  @override
+  List<_AssetVariant> getVariants(String key) {
+    // We lazily delay typecasting to prevent a performance hiccup when parsing
+    // large asset manifests.
+    if (!_typeCastedData.containsKey(key)) {
+      _typeCastedData[key] = ((_data[key] ?? <Object?>[]) as List<Object?>)
+        .cast<Map<Object?, Object?>>()
+        .map(_AssetVariant.fromManifestData)
+        .toList();
+    }
+    return _typeCastedData[key]!;
+  }
+}
+
+class _LegacyAssetManifest implements _AssetManifest {
+  _LegacyAssetManifest({
+    required this.manifest,
+  });
+
+  factory _LegacyAssetManifest.fromJsonString(String jsonString) {
+    List<_AssetVariant> adaptLegacyVariantList(String mainAsset, List<String> variants) {
+      return variants
+        .map((String variant) =>
+          _AssetVariant(asset: variant, devicePixelRatio: _parseScale(mainAsset, variant)))
+        .toList();
+    }
+
+    if (jsonString == null) {
+      return _LegacyAssetManifest(manifest: <String, List<_AssetVariant>>{});
+    }
+    final Map<String, Object?> parsedJson = json.decode(jsonString) as Map<String, dynamic>;
+    final Iterable<String> keys = parsedJson.keys;
+    final Map<String, List<String>> parsedManifest = <String, List<String>> {
+      for (final String key in keys) key: List<String>.from(parsedJson[key]! as List<dynamic>),
+    };
+    final Map<String, List<_AssetVariant>> manifestWithParsedVariants =
+      parsedManifest.map((String asset, List<String> variants) =>
+        MapEntry<String, List<_AssetVariant>>(asset, adaptLegacyVariantList(asset, variants)));
+
+    return _LegacyAssetManifest(manifest: manifestWithParsedVariants);
+  }
+
+  final Map<String, List<_AssetVariant>> manifest;
+
   static final RegExp _extractRatioRegExp = RegExp(r'/?(\d+(\.\d*)?)x$');
+  static const double _naturalResolution = 1.0;
+
+  @override
+  List<_AssetVariant> getVariants(String key) {
+    return manifest[key] ?? const <_AssetVariant>[];
+  }
 
-  double _parseScale(String key) {
-    if (key == assetName) {
+  static double _parseScale(String mainAsset, String variant) {
+    // The legacy asset manifest includes the main asset within its variant list.
+    if (mainAsset == variant) {
       return _naturalResolution;
     }
 
-    final Uri assetUri = Uri.parse(key);
+    final Uri assetUri = Uri.parse(variant);
     String directoryPath = '';
     if (assetUri.pathSegments.length > 1) {
       directoryPath = assetUri.pathSegments[assetUri.pathSegments.length - 2];
@@ -412,22 +531,23 @@ class AssetImage extends AssetBundleImageProvider {
     if (match != null && match.groupCount > 0) {
       return double.parse(match.group(1)!);
     }
+
     return _naturalResolution; // i.e. default to 1.0x
   }
+}
 
-  @override
-  bool operator ==(Object other) {
-    if (other.runtimeType != runtimeType) {
-      return false;
-    }
-    return other is AssetImage
-        && other.keyName == keyName
-        && other.bundle == bundle;
-  }
+class _AssetVariant {
+  _AssetVariant({
+    required this.asset,
+    required this.devicePixelRatio,
+  });
 
-  @override
-  int get hashCode => Object.hash(keyName, bundle);
+  factory _AssetVariant.fromManifestData(Object data) {
+    final Map<Object?, Object?> asStructuredData = data as Map<Object?, Object?>;
+    return _AssetVariant(asset: asStructuredData['asset']! as String,
+      devicePixelRatio: asStructuredData['dpr']! as double);
+  }
 
-  @override
-  String toString() => '${objectRuntimeType(this, 'AssetImage')}(bundle: $bundle, name: "$keyName")';
+  final double devicePixelRatio;
+  final String asset;
 }

packages/flutter/lib/src/services/asset_bundle.dart

@@ -96,12 +96,25 @@ abstract class AssetBundle {
   }
 
   /// Retrieve a string from the asset bundle, parse it with the given function,
-  /// and return the function's result.
+  /// and return that function's result.
   ///
   /// Implementations may cache the result, so a particular key should only be
   /// used with one parser for the lifetime of the asset bundle.
   Future<T> loadStructuredData<T>(String key, Future<T> Function(String value) parser);
 
+  /// Retrieve [ByteData] from the asset bundle, parse it with the given function,
+  /// and return that function's result.
+  ///
+  /// Implementations may cache the result, so a particular key should only be
+  /// used with one parser for the lifetime of the asset bundle.
+  Future<T> loadStructuredBinaryData<T>(String key, FutureOr<T> Function(ByteData data) parser) async {
+    final ByteData data = await load(key);
+    if (data == null) {
+      throw FlutterError('Unable to load asset: $key');
+    }
+    return parser(data);
+  }
+
   /// If this is a caching asset bundle, and the given key describes a cached
   /// asset, then evict the asset from the cache so that the next time it is
   /// loaded, the cache will be reread from the asset bundle.
@@ -156,6 +169,18 @@ class NetworkAssetBundle extends AssetBundle {
     return parser(await loadString(key));
   }
 
+  /// Retrieve [ByteData] from the asset bundle, parse it with the given function,
+  /// and return the function's result.
+  ///
+  /// The result is not cached. The parser is run each time the resource is
+  /// fetched.
+  @override
+  Future<T> loadStructuredBinaryData<T>(String key, FutureOr<T> Function(ByteData data) parser) async {
+    assert(key != null);
+    assert(parser != null);
+    return parser(await load(key));
+  }
+
   // TODO(ianh): Once the underlying network logic learns about caching, we
   // should implement evict().
 
@@ -175,6 +200,7 @@ abstract class CachingAssetBundle extends AssetBundle {
   // TODO(ianh): Replace this with an intelligent cache, see https://github.com/flutter/flutter/issues/3568
   final Map<String, Future<String>> _stringCache = <String, Future<String>>{};
   final Map<String, Future<dynamic>> _structuredDataCache = <String, Future<dynamic>>{};
+  final Map<String, Future<dynamic>> _structuredBinaryDataCache = <String, Future<dynamic>>{};
 
   @override
   Future<String> loadString(String key, { bool cache = true }) {
@@ -225,16 +251,69 @@ abstract class CachingAssetBundle extends AssetBundle {
     return completer.future;
   }
 
+  /// Retrieve bytedata from the asset bundle, parse it with the given function,
+  /// and return the function's result.
+  ///
+  /// The result of parsing the bytedata is cached (the bytedata itself is not).
+  /// For any given `key`, the `parser` is only run the first time.
+  ///
+  /// Once the value has been parsed, the future returned by this function for
+  /// subsequent calls will be a [SynchronousFuture], which resolves its
+  /// callback synchronously.
+  @override
+  Future<T> loadStructuredBinaryData<T>(String key, FutureOr<T> Function(ByteData data) parser) {
+    assert(key != null);
+    assert(parser != null);
+
+    if (_structuredBinaryDataCache.containsKey(key)) {
+      return _structuredBinaryDataCache[key]! as Future<T>;
+    }
+
+    // load can return a SynchronousFuture in certain cases, like in the
+    // flutter_test framework. So, we need to support both async and sync flows.
+    Completer<T>? completer; // For async flow.
+    SynchronousFuture<T>? result; // For sync flow.
+
+    load(key)
+      .then<T>(parser)
+      .then<void>((T value) {
+        result = SynchronousFuture<T>(value);
+        if (completer != null) {
+          // The load and parse operation ran asynchronously. We already returned
+          // from the loadStructuredBinaryData function and therefore the caller
+          // was given the future of the completer.
+          completer.complete(value);
+        }
+      }, onError: (Object err, StackTrace? stack) {
+        completer!.completeError(err, stack);
+      });
+
+    if (result != null) {
+      // The above code ran synchronously. We can synchronously return the result.
+      _structuredBinaryDataCache[key] = result!;
+      return result!;
+    }
+
+    // Since the above code is being run asynchronously and thus hasn't run its
+    // `then` handler yet, we'll return a completer that will be completed
+    // when the handler does run.
+    completer = Completer<T>();
+    _structuredBinaryDataCache[key] = completer.future;
+    return completer.future;
+  }
+
   @override
   void evict(String key) {
     _stringCache.remove(key);
     _structuredDataCache.remove(key);
+    _structuredBinaryDataCache.remove(key);
   }
 
   @override
   void clear() {
     _stringCache.clear();
     _structuredDataCache.clear();
+    _structuredBinaryDataCache.clear();
   }
 
   @override
@@ -276,7 +355,7 @@ class PlatformAssetBundle extends CachingAssetBundle {
     bool debugUsePlatformChannel = false;
     assert(() {
       // dart:io is safe to use here since we early return for web
-      // above. If that code is changed, this needs to be gaurded on
+      // above. If that code is changed, this needs to be guarded on
       // web presence. Override how assets are loaded in tests so that
       // the old loader behavior that allows tests to load assets from
       // the current package using the package prefix.

packages/flutter/test/painting/image_resolution_test.dart

@@ -13,18 +13,14 @@ import 'package:flutter_test/flutter_test.dart';
 class TestAssetBundle extends CachingAssetBundle {
   TestAssetBundle(this._assetBundleMap);
 
-  final Map<String, List<String>> _assetBundleMap;
+  final Map<String, List<Map<dynamic, dynamic>>> _assetBundleMap;
 
   Map<String, int> loadCallCount = <String, int>{};
 
-  String get _assetBundleContents {
-    return json.encode(_assetBundleMap);
-  }
-
   @override
   Future<ByteData> load(String key) async {
-    if (key == 'AssetManifest.json') {
-      return ByteData.view(Uint8List.fromList(const Utf8Encoder().convert(_assetBundleContents)).buffer);
+    if (key == 'AssetManifest.bin') {
+      return const StandardMessageCodec().encodeMessage(_assetBundleMap)!;
     }
 
     loadCallCount[key] = loadCallCount[key] ?? 0 + 1;
@@ -42,12 +38,71 @@ class TestAssetBundle extends CachingAssetBundle {
   }
 }
 
+class BundleWithoutAssetManifestBin extends CachingAssetBundle {
+  BundleWithoutAssetManifestBin(this._legacyAssetBundleMap);
+
+  final Map<dynamic, List<String>> _legacyAssetBundleMap;
+
+  Map<String, int> loadCallCount = <String, int>{};
+
+  @override
+  Future<ByteData> load(String key) async {
+    ByteData testByteData(double scale) => ByteData(8)..setFloat64(0, scale);
+
+    if (key == 'AssetManifest.bin') {
+      throw FlutterError('AssetManifest.bin was not found.');
+    }
+    if (key == 'AssetManifest.json') {
+      return ByteData.view(Uint8List.fromList(const Utf8Encoder().convert(json.encode(_legacyAssetBundleMap))).buffer);
+    }
+    switch (key) {
+      case 'assets/image.png':
+        return testByteData(1.0); // see "...with a main asset and a 1.0x asset"
+      case 'assets/2.0x/image.png':
+        return testByteData(1.5);
+    }
+
+    throw FlutterError('Unexpected key: $key');
+  }
+
+  @override
+  Future<ui.ImmutableBuffer> loadBuffer(String key) async {
+    final ByteData data = await load(key);
+    return ui.ImmutableBuffer.fromUint8List(data.buffer.asUint8List());
+  }
+}
+
 void main() {
+
+  // TODO(andrewkolos): Once google3 is migrated away from using AssetManifest.json,
+  // remove all references to it. See https://github.com/flutter/flutter/issues/114913.
+  test('AssetBundle falls back to using AssetManifest.json if AssetManifest.bin cannot be found.', () async {
+    const String assetPath = 'assets/image.png';
+    final Map<dynamic, List<String>> assetBundleMap = <dynamic, List<String>>{};
+    assetBundleMap[assetPath] = <String>[];
+    final AssetImage assetImage = AssetImage(assetPath, bundle: BundleWithoutAssetManifestBin(assetBundleMap));
+    final AssetBundleImageKey key = await assetImage.obtainKey(ImageConfiguration.empty);
+    expect(key.name, assetPath);
+    expect(key.scale, 1.0);
+  });
+
+  test('When using AssetManifest.json, on a high DPR device, a high dpr variant is selected.', () async {
+    const String assetPath = 'assets/image.png';
+    const String asset2xPath = 'assets/2.0x/image.png';
+    final Map<dynamic, List<String>> assetBundleMap = <dynamic, List<String>>{};
+    assetBundleMap[assetPath] = <String>[asset2xPath];
+    final AssetImage assetImage = AssetImage(assetPath, bundle: BundleWithoutAssetManifestBin(assetBundleMap));
+    final AssetBundleImageKey key = await assetImage.obtainKey(const ImageConfiguration(devicePixelRatio: 2.0));
+    expect(key.name, asset2xPath);
+    expect(key.scale, 2.0);
+  });
+
   group('1.0 scale device tests', () {
     void buildAndTestWithOneAsset(String mainAssetPath) {
-      final Map<String, List<String>> assetBundleMap = <String, List<String>>{};
+      final Map<String, List<Map<dynamic, dynamic>>> assetBundleMap =
+        <String, List<Map<dynamic, dynamic>>>{};
 
-      assetBundleMap[mainAssetPath] = <String>[];
+      assetBundleMap[mainAssetPath] = <Map<dynamic,dynamic>>[];
 
       final AssetImage assetImage = AssetImage(
         mainAssetPath,
@@ -93,10 +148,13 @@ void main() {
       const String mainAssetPath = 'assets/normalFolder/normalFile.png';
       const String variantPath = 'assets/normalFolder/3.0x/normalFile.png';
 
-      final Map<String, List<String>> assetBundleMap =
-      <String, List<String>>{};
+      final Map<String, List<Map<dynamic, dynamic>>> assetBundleMap =
+        <String, List<Map<dynamic, dynamic>>>{};
 
-      assetBundleMap[mainAssetPath] = <String>[mainAssetPath, variantPath];
+      final Map<dynamic, dynamic> mainAssetVariantManifestEntry = <dynamic, dynamic>{};
+      mainAssetVariantManifestEntry['asset'] = variantPath;
+      mainAssetVariantManifestEntry['dpr'] = 3.0;
+      assetBundleMap[mainAssetPath] = <Map<dynamic, dynamic>>[mainAssetVariantManifestEntry];
 
       final TestAssetBundle testAssetBundle = TestAssetBundle(assetBundleMap);
 
@@ -123,10 +181,10 @@ void main() {
     test('When high-res device and high-res asset not present in bundle then return main variant', () {
       const String mainAssetPath = 'assets/normalFolder/normalFile.png';
 
-      final Map<String, List<String>> assetBundleMap =
-      <String, List<String>>{};
+      final Map<String, List<Map<dynamic, dynamic>>> assetBundleMap =
+        <String, List<Map<dynamic, dynamic>>>{};
 
-      assetBundleMap[mainAssetPath] = <String>[mainAssetPath];
+      assetBundleMap[mainAssetPath] = <Map<dynamic, dynamic>>[];
 
       final TestAssetBundle testAssetBundle = TestAssetBundle(assetBundleMap);
 
@@ -156,16 +214,18 @@ void main() {
     const String mainAssetPath = 'assets/normalFolder/normalFile.png';
     const String variantPath = 'assets/normalFolder/3.0x/normalFile.png';
 
-
     void buildBundleAndTestVariantLogic(
       double deviceRatio,
       double chosenAssetRatio,
       String expectedAssetPath,
     ) {
-      final Map<String, List<String>> assetBundleMap =
-      <String, List<String>>{};
+      final Map<String, List<Map<dynamic, dynamic>>> assetBundleMap =
+        <String, List<Map<dynamic, dynamic>>>{};
 
-      assetBundleMap[mainAssetPath] = <String>[mainAssetPath, variantPath];
+      final Map<dynamic, dynamic> mainAssetVariantManifestEntry = <dynamic, dynamic>{};
+      mainAssetVariantManifestEntry['asset'] = variantPath;
+      mainAssetVariantManifestEntry['dpr'] = 3.0;
+      assetBundleMap[mainAssetPath] = <Map<dynamic, dynamic>>[mainAssetVariantManifestEntry];
 
       final TestAssetBundle testAssetBundle = TestAssetBundle(assetBundleMap);
 

packages/flutter/test/services/asset_bundle_test.dart

@@ -9,14 +9,14 @@ import 'package:flutter/painting.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-class TestAssetBundle extends CachingAssetBundle {
+class _TestAssetBundle extends CachingAssetBundle {
   Map<String, int> loadCallCount = <String, int>{};
 
   @override
   Future<ByteData> load(String key) async {
     loadCallCount[key] = loadCallCount[key] ?? 0 + 1;
-    if (key == 'AssetManifest.json') {
-      return ByteData.view(Uint8List.fromList(const Utf8Encoder().convert('{"one": ["one"]}')).buffer);
+    if (key == 'AssetManifest.bin') {
+      return const StandardMessageCodec().encodeMessage(json.decode('{"one":[]}'))!;
     }
 
     if (key == 'one') {
@@ -30,7 +30,7 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
   test('Caching asset bundle test', () async {
-    final TestAssetBundle bundle = TestAssetBundle();
+    final _TestAssetBundle bundle = _TestAssetBundle();
 
     final ByteData assetData = await bundle.load('one');
     expect(assetData.getInt8(0), equals(49));
@@ -53,7 +53,7 @@ void main() {
 
   test('AssetImage.obtainKey succeeds with ImageConfiguration.empty', () async {
     // This is a regression test for https://github.com/flutter/flutter/issues/12392
-    final AssetImage assetImage = AssetImage('one', bundle: TestAssetBundle());
+    final AssetImage assetImage = AssetImage('one', bundle: _TestAssetBundle());
     final AssetBundleImageKey key = await assetImage.obtainKey(ImageConfiguration.empty);
     expect(key.name, 'one');
     expect(key.scale, 1.0);

packages/flutter/test/widgets/image_resolution_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 @TestOn('!chrome')
+import 'dart:convert';
 import 'dart:ui' as ui show Image;
 
 import 'package:flutter/foundation.dart';
@@ -16,27 +17,32 @@ import '../image_data.dart';
 ByteData testByteData(double scale) => ByteData(8)..setFloat64(0, scale);
 double scaleOf(ByteData data) => data.getFloat64(0);
 
-const String testManifest = '''
+final Map<dynamic, dynamic> testManifest = json.decode('''
 {
   "assets/image.png" : [
-    "assets/image.png",
-    "assets/1.5x/image.png",
-    "assets/2.0x/image.png",
-    "assets/3.0x/image.png",
-    "assets/4.0x/image.png"
+    {"asset": "assets/1.5x/image.png", "dpr": 1.5},
+    {"asset": "assets/2.0x/image.png", "dpr": 2.0},
+    {"asset": "assets/3.0x/image.png", "dpr": 3.0},
+    {"asset": "assets/4.0x/image.png", "dpr": 4.0}
   ]
 }
-''';
+''') as Map<dynamic, dynamic>;
 
 class TestAssetBundle extends CachingAssetBundle {
-  TestAssetBundle({ this.manifest = testManifest });
 
-  final String manifest;
+  TestAssetBundle({ required Map<dynamic, dynamic> manifest }) {
+    this.manifest = const StandardMessageCodec().encodeMessage(manifest)!;
+  }
+
+  late final ByteData manifest;
 
   @override
   Future<ByteData> load(String key) {
     late ByteData data;
     switch (key) {
+      case 'AssetManifest.bin':
+        data = manifest;
+        break;
       case 'assets/image.png':
         data = testByteData(1.0);
         break;
@@ -59,14 +65,6 @@ class TestAssetBundle extends CachingAssetBundle {
     return SynchronousFuture<ByteData>(data);
   }
 
-  @override
-  Future<String> loadString(String key, { bool cache = true }) {
-    if (key == 'AssetManifest.json') {
-      return SynchronousFuture<String>(manifest);
-    }
-    return SynchronousFuture<String>('');
-  }
-
   @override
   String toString() => '${describeIdentity(this)}()';
 }
@@ -106,7 +104,7 @@ Widget buildImageAtRatio(String imageName, Key key, double ratio, bool inferSize
       devicePixelRatio: ratio,
     ),
     child: DefaultAssetBundle(
-      bundle: bundle ?? TestAssetBundle(),
+      bundle: bundle ?? TestAssetBundle(manifest: testManifest),
       child: Center(
         child: inferSize ?
           Image(
@@ -259,46 +257,21 @@ void main() {
     expect(getRenderImage(tester, key).scale, 4.0);
   });
 
-  testWidgets('Image for device pixel ratio 1.0, with no main asset', (WidgetTester tester) async {
-    const String manifest = '''
-    {
-      "assets/image.png" : [
-        "assets/1.5x/image.png",
-        "assets/2.0x/image.png",
-        "assets/3.0x/image.png",
-        "assets/4.0x/image.png"
-      ]
-    }
-    ''';
-    final AssetBundle bundle = TestAssetBundle(manifest: manifest);
-
-    const double ratio = 1.0;
-    Key key = GlobalKey();
-    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false, images, bundle));
-    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
-    expect(getRenderImage(tester, key).scale, 1.5);
-    key = GlobalKey();
-    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true, images, bundle));
-    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
-    expect(getRenderImage(tester, key).scale, 1.5);
-  });
-
   testWidgets('Image for device pixel ratio 1.0, with a main asset and a 1.0x asset', (WidgetTester tester) async {
     // If both a main asset and a 1.0x asset are specified, then prefer
     // the 1.0x asset.
 
-    const String manifest = '''
+    final Map<dynamic, dynamic> manifest = json.decode('''
     {
       "assets/image.png" : [
-        "assets/image.png",
-        "assets/1.0x/image.png",
-        "assets/1.5x/image.png",
-        "assets/2.0x/image.png",
-        "assets/3.0x/image.png",
-        "assets/4.0x/image.png"
+        {"asset": "assets/1.0x/image.png", "dpr":1.0},
+        {"asset": "assets/1.5x/image.png", "dpr":1.5},
+        {"asset": "assets/2.0x/image.png", "dpr":2.0},
+        {"asset": "assets/3.0x/image.png", "dpr":3.0},
+        {"asset": "assets/4.0x/image.png", "dpr":4.0}
       ]
     }
-    ''';
+    ''') as Map<dynamic, dynamic>;
     final AssetBundle bundle = TestAssetBundle(manifest: manifest);
 
     const double ratio = 1.0;
@@ -337,14 +310,13 @@ void main() {
   // if higher resolution assets are not available we will pick the best
   // available.
   testWidgets('Low-resolution assets', (WidgetTester tester) async {
-    final AssetBundle bundle = TestAssetBundle(manifest: '''
+    final AssetBundle bundle = TestAssetBundle(manifest: json.decode('''
       {
         "assets/image.png" : [
-          "assets/image.png",
-          "assets/1.5x/image.png"
+          {"asset": "assets/1.5x/image.png", "dpr": 1.5}
         ]
       }
-    ''');
+    ''') as Map<dynamic, dynamic>);
 
     Future<void> testRatio({required double ratio, required double expectedScale}) async {
       Key key = GlobalKey();

packages/flutter_tools/lib/src/asset.dart

@@ -2,8 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:typed_data';
+
 import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 import 'base/context.dart';
 import 'base/deferred_component.dart';
@@ -136,6 +139,9 @@ class ManifestAssetBundle implements AssetBundle {
        _splitDeferredAssets = splitDeferredAssets,
        _licenseCollector = LicenseCollector(fileSystem: fileSystem);
 
+  // We assume the main asset is designed for a device pixel ratio of 1.0
+  static const double _defaultResolution = 1.0;
+
   final Logger _logger;
   final FileSystem _fileSystem;
   final LicenseCollector _licenseCollector;
@@ -161,7 +167,8 @@ class ManifestAssetBundle implements AssetBundle {
 
   DateTime? _lastBuildTimestamp;
 
-  static const String _kAssetManifestJson = 'AssetManifest.json';
+  static const String _kAssetManifestBinFileName = 'AssetManifest.bin';
+  static const String _kAssetManifestJsonFileName = 'AssetManifest.json';
   static const String _kNoticeFile = 'NOTICES';
   // Comically, this can't be name with the more common .gz file extension
   // because when it's part of an AAR and brought into another APK via gradle,
@@ -229,8 +236,13 @@ class ManifestAssetBundle implements AssetBundle {
     // device.
     _lastBuildTimestamp = DateTime.now();
     if (flutterManifest.isEmpty) {
-      entries[_kAssetManifestJson] = DevFSStringContent('{}');
-      entryKinds[_kAssetManifestJson] = AssetKind.regular;
+      entries[_kAssetManifestJsonFileName] = DevFSStringContent('{}');
+      entryKinds[_kAssetManifestJsonFileName] = AssetKind.regular;
+      final ByteData emptyAssetManifest =
+        const StandardMessageCodec().encodeMessage(<dynamic, dynamic>{})!;
+      entries[_kAssetManifestBinFileName] =
+        DevFSByteContent(emptyAssetManifest.buffer.asUint8List(0, emptyAssetManifest.lengthInBytes));
+      entryKinds[_kAssetManifestBinFileName] = AssetKind.regular;
       return 0;
     }
 
@@ -426,7 +438,11 @@ class ManifestAssetBundle implements AssetBundle {
       _wildcardDirectories[uri] ??= _fileSystem.directory(uri);
     }
 
-    final DevFSStringContent assetManifest  = _createAssetManifest(assetVariants, deferredComponentsAssetVariants);
+    final Map<String, List<String>> assetManifest =
+      _createAssetManifest(assetVariants, deferredComponentsAssetVariants);
+    final DevFSStringContent assetManifestJson = DevFSStringContent(json.encode(assetManifest));
+    final DevFSByteContent assetManifestBinary = _createAssetManifestBinary(assetManifest);
+
     final DevFSStringContent fontManifest = DevFSStringContent(json.encode(fonts));
     final LicenseResult licenseResult = _licenseCollector.obtainLicenses(packageConfig, additionalLicenseFiles);
     if (licenseResult.errorMessages.isNotEmpty) {
@@ -450,7 +466,8 @@ class ManifestAssetBundle implements AssetBundle {
         _fileSystem.file('DOES_NOT_EXIST_RERUN_FOR_WILDCARD$suffix').absolute);
     }
 
-    _setIfChanged(_kAssetManifestJson, assetManifest, AssetKind.regular);
+    _setIfChanged(_kAssetManifestJsonFileName, assetManifestJson, AssetKind.regular);
+    _setIfChanged(_kAssetManifestBinFileName, assetManifestBinary, AssetKind.regular);
     _setIfChanged(kFontManifestJson, fontManifest, AssetKind.regular);
     _setLicenseIfChanged(licenseResult.combinedLicenses, targetPlatform);
     return 0;
@@ -459,17 +476,31 @@ class ManifestAssetBundle implements AssetBundle {
   @override
   List<File> additionalDependencies = <File>[];
 
-  void _setIfChanged(String key, DevFSStringContent content, AssetKind assetKind) {
-    if (!entries.containsKey(key)) {
-      entries[key] = content;
-      entryKinds[key] = assetKind;
-      return;
+  void _setIfChanged(String key, DevFSContent content, AssetKind assetKind) {
+    bool areEqual(List<int> o1, List<int> o2) {
+      if (o1.length != o2.length) {
+        return false;
+      }
+
+      for (int index = 0; index < o1.length; index++) {
+        if (o1[index] != o2[index]) {
+          return false;
+        }
+      }
+
+      return true;
     }
-    final DevFSStringContent? oldContent = entries[key] as DevFSStringContent?;
-    if (oldContent?.string != content.string) {
-      entries[key] = content;
-      entryKinds[key] = assetKind;
+
+    final DevFSContent? oldContent = entries[key];
+    // In the case that the content is unchanged, we want to avoid an overwrite
+    // as the isModified property may be reset to true,
+    if (oldContent is DevFSByteContent && content is DevFSByteContent &&
+        areEqual(oldContent.bytes, content.bytes)) {
+      return;
     }
+
+    entries[key] = content;
+    entryKinds[key] = assetKind;
   }
 
   void _setLicenseIfChanged(
@@ -621,14 +652,14 @@ class ManifestAssetBundle implements AssetBundle {
     return deferredComponentsAssetVariants;
   }
 
-  DevFSStringContent _createAssetManifest(
+  Map<String, List<String>> _createAssetManifest(
     Map<_Asset, List<_Asset>> assetVariants,
     Map<String, Map<_Asset, List<_Asset>>> deferredComponentsAssetVariants
   ) {
-    final Map<String, List<String>> jsonObject = <String, List<String>>{};
-    final Map<_Asset, List<String>> jsonEntries = <_Asset, List<String>>{};
+    final Map<String, List<String>> manifest = <String, List<String>>{};
+    final Map<_Asset, List<String>> entries = <_Asset, List<String>>{};
     assetVariants.forEach((_Asset main, List<_Asset> variants) {
-      jsonEntries[main] = <String>[
+      entries[main] = <String>[
         for (final _Asset variant in variants)
           variant.entryUri.path,
       ];
@@ -636,26 +667,69 @@ class ManifestAssetBundle implements AssetBundle {
     if (deferredComponentsAssetVariants != null) {
       for (final Map<_Asset, List<_Asset>> componentAssets in deferredComponentsAssetVariants.values) {
         componentAssets.forEach((_Asset main, List<_Asset> variants) {
-          jsonEntries[main] = <String>[
+          entries[main] = <String>[
             for (final _Asset variant in variants)
               variant.entryUri.path,
           ];
         });
       }
     }
-    final List<_Asset> sortedKeys = jsonEntries.keys.toList()
+    final List<_Asset> sortedKeys = entries.keys.toList()
         ..sort((_Asset left, _Asset right) => left.entryUri.path.compareTo(right.entryUri.path));
     for (final _Asset main in sortedKeys) {
       final String decodedEntryPath = Uri.decodeFull(main.entryUri.path);
-      final List<String> rawEntryVariantsPaths = jsonEntries[main]!;
+      final List<String> rawEntryVariantsPaths = entries[main]!;
       final List<String> decodedEntryVariantPaths = rawEntryVariantsPaths
         .map((String value) => Uri.decodeFull(value))
         .toList();
-      jsonObject[decodedEntryPath] = decodedEntryVariantPaths;
+      manifest[decodedEntryPath] = decodedEntryVariantPaths;
+    }
+    return manifest;
+  }
+
+  DevFSByteContent _createAssetManifestBinary(
+    Map<String, List<String>> assetManifest
+  ) {
+    double parseScale(String key) {
+      final Uri assetUri = Uri.parse(key);
+      String directoryPath = '';
+      if (assetUri.pathSegments.length > 1) {
+        directoryPath = assetUri.pathSegments[assetUri.pathSegments.length - 2];
+      }
+
+      final Match? match = _extractRatioRegExp.firstMatch(directoryPath);
+      if (match != null && match.groupCount > 0) {
+        return double.parse(match.group(1)!);
+      }
+      return _defaultResolution;
+    }
+
+    final Map<String, dynamic> result = <String, dynamic>{};
+
+    for (final MapEntry<String, dynamic> manifestEntry in assetManifest.entries) {
+      final List<dynamic> resultVariants = <dynamic>[];
+      final List<String> entries = (manifestEntry.value as List<dynamic>).cast<String>();
+      for (final String variant in entries) {
+        if (variant == manifestEntry.key) {
+          // With the newer binary format, don't include the main asset in it's
+          // list of variants. This reduces parsing time at runtime.
+          continue;
+        }
+        final Map<String, dynamic> resultVariant = <String, dynamic>{};
+        final double variantDevicePixelRatio = parseScale(variant);
+        resultVariant['asset'] = variant;
+        resultVariant['dpr'] = variantDevicePixelRatio;
+        resultVariants.add(resultVariant);
+      }
+      result[manifestEntry.key] = resultVariants;
     }
-    return DevFSStringContent(json.encode(jsonObject));
+
+    final ByteData message = const StandardMessageCodec().encodeMessage(result)!;
+    return DevFSByteContent(message.buffer.asUint8List(0, message.lengthInBytes));
   }
 
+  static final RegExp _extractRatioRegExp = RegExp(r'/?(\d+(\.\d*)?)x$');
+
   /// Prefixes family names and asset paths of fonts included from packages with
   /// 'packages/<package_name>'
   List<Font> _parsePackageFonts(

packages/flutter_tools/pubspec.yaml

@@ -57,6 +57,8 @@ dependencies:
 
   vm_service: 9.4.0
 
+  standard_message_codec: 0.0.1+3
+
   _fe_analyzer_shared: 50.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   analyzer: 5.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   boolean_selector: 2.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
@@ -88,7 +90,6 @@ dependencies:
   watcher: 1.0.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
 
 dev_dependencies:
-  collection: 1.17.0
   file_testing: 3.0.0
   pubspec_parse: 1.2.1
 
@@ -97,9 +98,10 @@ dev_dependencies:
   json_annotation: 4.7.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   node_preamble: 2.0.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   test: 1.22.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
+  collection: 1.17.0
 
 dartdoc:
   # Exclude this package from the hosted API docs.
   nodoc: true
 
-# PUBSPEC CHECKSUM: 65eb
+# PUBSPEC CHECKSUM: 408d

packages/flutter_tools/test/general.shard/android/deferred_components_gen_snapshot_validator_test.dart

@@ -220,7 +220,7 @@ loading-units-spelled-wrong:
     expect(logger.statusText, contains('Errors checking the following files:'));
     expect(logger.statusText, contains("Invalid loading units yaml file, 'loading-units' entry did not exist."));
 
-    expect(logger.statusText.contains('Previously existing loading units no longer exist:\n\n  LoadingUnit 2\n    Libraries:\n    - lib1\n'), false);
+    expect(logger.statusText, isNot(contains('Previously existing loading units no longer exist:\n\n  LoadingUnit 2\n    Libraries:\n    - lib1\n')));
   });
 
   testWithoutContext('loadingUnitCache validator detects malformed file: not a list', () async {
@@ -382,7 +382,7 @@ loading-units:
     validator.displayResults();
     validator.attemptToolExit();
 
-    expect(logger.statusText.contains('Errors checking the following files:'), false);
+    expect(logger.statusText, isNot(contains('Errors checking the following files:')));
   });
 
   testWithoutContext('androidStringMapping modifies strings file', () async {
@@ -448,9 +448,10 @@ loading-units:
       .childDirectory('main')
       .childFile('AndroidManifest.xml');
     expect(manifestOutput.existsSync(), true);
-    expect(manifestOutput.readAsStringSync().contains('<meta-data android:name="io.flutter.embedding.engine.deferredcomponents.DeferredComponentManager.loadingUnitMapping" android:value="3:component1,2:component2,4:component2"/>'), true);
-    expect(manifestOutput.readAsStringSync().contains('android:value="invalidmapping"'), false);
-    expect(manifestOutput.readAsStringSync().contains("<!-- Don't delete the meta-data below."), true);
+    final String manifestOutputString = manifestOutput.readAsStringSync();
+    expect(manifestOutputString, contains('<meta-data android:name="io.flutter.embedding.engine.deferredcomponents.DeferredComponentManager.loadingUnitMapping" android:value="3:component1,2:component2,4:component2"/>'));
+    expect(manifestOutputString, isNot(contains('android:value="invalidmapping"')));
+    expect(manifestOutputString, contains("<!-- Don't delete the meta-data below."));
   });
 
   testWithoutContext('androidStringMapping adds mapping when no existing mapping', () async {
@@ -695,8 +696,8 @@ loading-units:
       .childDirectory('main')
       .childFile('AndroidManifest.xml');
     expect(manifestOutput.existsSync(), true);
-    expect(manifestOutput.readAsStringSync().contains('<meta-data android:name="io.flutter.embedding.engine.deferredcomponents.DeferredComponentManager.loadingUnitMapping" android:value="3:component1,2:component2,4:component2"/>'), true);
-    expect(manifestOutput.readAsStringSync().contains(RegExp(r'android:value[\s\n]*=[\s\n]*"invalidmapping"')), false);
-    expect(manifestOutput.readAsStringSync().contains("<!-- Don't delete the meta-data below."), true);
+    expect(manifestOutput.readAsStringSync(), contains('<meta-data android:name="io.flutter.embedding.engine.deferredcomponents.DeferredComponentManager.loadingUnitMapping" android:value="3:component1,2:component2,4:component2"/>'));
+    expect(manifestOutput.readAsStringSync(), isNot(contains(RegExp(r'android:value[\s\n]*=[\s\n]*"invalidmapping"'))));
+    expect(manifestOutput.readAsStringSync(), contains("<!-- Don't delete the meta-data below."));
   });
 }

packages/flutter_tools/test/general.shard/asset_bundle_package_fonts_test.dart

@@ -111,8 +111,9 @@ $fontsSection
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
-      expect(bundle.entries.containsKey('FontManifest.json'), isTrue);
+      expect(bundle.entries.keys, containsAll(
+        <String>['AssetManifest.bin', 'AssetManifest.json', 'FontManifest.json', 'NOTICES.Z']
+      ));
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
       ProcessManager: () => FakeProcessManager.any(),

packages/flutter_tools/test/general.shard/asset_bundle_package_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
@@ -11,6 +12,7 @@ import 'package:flutter_tools/src/asset.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 
 import 'package:flutter_tools/src/globals.dart' as globals;
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 import '../src/common.dart';
 import '../src/context.dart';
@@ -24,6 +26,7 @@ void main() {
     // rolls into Flutter.
     return path.replaceAll('/', globals.fs.path.separator);
   }
+
   void writePubspecFile(String path, String name, { List<String>? assets }) {
     String assetsSection;
     if (assets == null) {
@@ -60,37 +63,6 @@ $assetsSection
       ..writeAsStringSync(packages);
   }
 
-  Future<void> buildAndVerifyAssets(
-    List<String> assets,
-    List<String> packages,
-    String? expectedAssetManifest, {
-    bool expectExists = true,
-  }) async {
-    final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-    await bundle.build(packagesPath: '.packages');
-
-    for (final String packageName in packages) {
-      for (final String asset in assets) {
-        final String entryKey = Uri.encodeFull('packages/$packageName/$asset');
-        expect(bundle.entries.containsKey(entryKey), expectExists,
-          reason: 'Cannot find key on bundle: $entryKey');
-        if (expectExists) {
-          expect(
-            utf8.decode(await bundle.entries[entryKey]!.contentsAsBytes()),
-            asset,
-          );
-        }
-      }
-    }
-
-    if (expectExists) {
-      expect(
-        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
-        expectedAssetManifest,
-      );
-    }
-  }
-
   void writeAssets(String path, List<String> assets) {
     for (final String asset in assets) {
       final String fullPath = fixPath(globals.fs.path.join(path, asset));
@@ -101,182 +73,391 @@ $assetsSection
     }
   }
 
-  late FileSystem testFileSystem;
-
-  setUp(() async {
-    testFileSystem = MemoryFileSystem(
-      style: globals.platform.isWindows
-        ? FileSystemStyle.windows
-        : FileSystemStyle.posix,
-    );
-    testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
-  });
-
-  group('AssetBundle assets from packages', () {
-    testUsingContext('No assets are bundled when the package has no assets', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-      writePubspecFile('p/p/pubspec.yaml', 'test_package');
-
+  // TODO(andrewkolos): Delete this group once we stop producing AssetManifest.json
+  // as part of build.
+  group('Legacy asset manifest (AssetManifest.json)', () {
+    Future<void> buildAndVerifyAssets(
+      List<String> assets,
+      List<String> packages,
+      String? expectedAssetManifest, {
+      bool expectExists = true,
+    }) async {
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
-      const String expectedAssetManifest = '{}';
-      expect(
-        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
-        expectedAssetManifest,
-      );
-      expect(
-        utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
-        '[]',
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
-
-    testUsingContext('No assets are bundled when the package has an asset that is not listed', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-      writePubspecFile('p/p/pubspec.yaml', 'test_package');
-
-      final List<String> assets = <String>['a/foo'];
-      writeAssets('p/p/', assets);
-
-      final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(packagesPath: '.packages');
-      expect(bundle.entries.length, 3); // LICENSE, AssetManifest, FontManifest
-      const String expectedAssetManifest = '{}';
-      expect(
-        utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
-        expectedAssetManifest,
-      );
-      expect(
-        utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
-        '[]',
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
-
-    testUsingContext('One asset is bundled when the package has and lists one '
-      'asset its pubspec', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assets = <String>['a/foo'];
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assets,
-      );
-
-      writeAssets('p/p/', assets);
-
-      const String expectedAssetManifest = '{"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo"]}';
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
-
-    testUsingContext('One asset is bundled when the package has one asset, '
-      "listed in the app's pubspec", () async {
-      final List<String> assetEntries = <String>['packages/test_package/a/foo'];
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-        assets: assetEntries,
-      );
-      writePackagesFile('test_package:p/p/lib/');
-      writePubspecFile('p/p/pubspec.yaml', 'test_package');
-
-      final List<String> assets = <String>['a/foo'];
-      writeAssets('p/p/lib/', assets);
-
-      const String expectedAssetManifest = '{"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo"]}';
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
 
-    testUsingContext('One asset and its variant are bundled when the package '
-      'has an asset and a variant, and lists the asset in its pubspec', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: <String>['a/foo', 'a/bar'],
-      );
+      for (final String packageName in packages) {
+        for (final String asset in assets) {
+          final String entryKey = Uri.encodeFull('packages/$packageName/$asset');
+          expect(bundle.entries.containsKey(entryKey), expectExists,
+            reason: 'Cannot find key on bundle: $entryKey');
+          if (expectExists) {
+            expect(
+              utf8.decode(await bundle.entries[entryKey]!.contentsAsBytes()),
+              asset,
+            );
+          }
+        }
+      }
 
-      final List<String> assets = <String>['a/foo', 'a/2x/foo', 'a/bar'];
-      writeAssets('p/p/', assets);
+      if (expectExists) {
+        expect(
+          utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
+          expectedAssetManifest,
+        );
+      }
+    }
 
-      const String expectedManifest = '{'
-          '"packages/test_package/a/bar":'
-          '["packages/test_package/a/bar"],'
-          '"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo","packages/test_package/a/2x/foo"]'
-          '}';
+    late FileSystem testFileSystem;
 
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package'],
-        expectedManifest,
+    setUp(() async {
+      testFileSystem = MemoryFileSystem(
+        style: globals.platform.isWindows
+          ? FileSystemStyle.windows
+          : FileSystemStyle.posix,
       );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+      testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
     });
 
-    testUsingContext('One asset and its variant are bundled when the package '
-      'has an asset and a variant, and the app lists the asset in its pubspec', () async {
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-        assets: <String>['packages/test_package/a/foo'],
-      );
-      writePackagesFile('test_package:p/p/lib/');
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-      );
-
-      final List<String> assets = <String>['a/foo', 'a/2x/foo'];
-      writeAssets('p/p/lib/', assets);
-
-      const String expectedManifest = '{"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo","packages/test_package/a/2x/foo"]}';
-
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package'],
-        expectedManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from packages', () {
+      testUsingContext('No assets are bundled when the package has no assets', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+        expect(bundle.entries.keys, unorderedEquals(
+          <String>['AssetManifest.bin', 'AssetManifest.json', 'FontManifest.json', 'NOTICES.Z']
+        ));
+        const String expectedAssetManifest = '{}';
+        expect(
+          utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
+          expectedAssetManifest,
+        );
+        expect(
+          utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
+          '[]',
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('No assets are bundled when the package has an asset that is not listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final List<String> assets = <String>['a/foo'];
+        writeAssets('p/p/', assets);
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+        expect(bundle.entries.keys, unorderedEquals(
+          <String>['AssetManifest.bin', 'AssetManifest.json', 'FontManifest.json', 'NOTICES.Z']
+        ));
+        const String expectedAssetManifest = '{}';
+        expect(
+          utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
+          expectedAssetManifest,
+        );
+        expect(
+          utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
+          '[]',
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the package has and lists one '
+        'asset its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assets,
+        );
+
+        writeAssets('p/p/', assets);
+
+        const String expectedAssetManifest = '{"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo"]}';
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the package has one asset, '
+        "listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>['packages/test_package/a/foo'];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final List<String> assets = <String>['a/foo'];
+        writeAssets('p/p/lib/', assets);
+
+        const String expectedAssetManifest = '{"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo"]}';
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset and its variant are bundled when the package '
+        'has an asset and a variant, and lists the asset in its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['a/foo', 'a/bar'],
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo', 'a/bar'];
+        writeAssets('p/p/', assets);
+
+        const String expectedManifest = '{'
+            '"packages/test_package/a/bar":'
+            '["packages/test_package/a/bar"],'
+            '"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo","packages/test_package/a/2x/foo"]'
+            '}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset and its variant are bundled when the package '
+        'has an asset and a variant, and the app lists the asset in its pubspec', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: <String>['packages/test_package/a/foo'],
+        );
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/lib/', assets);
+
+        const String expectedManifest = '{"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo","packages/test_package/a/2x/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when the package has and lists '
+        'two assets in its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo', 'a/bar'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assets,
+        );
+
+        writeAssets('p/p/', assets);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
+            '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext("Two assets are bundled when the package has two assets, listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>[
+          'packages/test_package/a/foo',
+          'packages/test_package/a/bar',
+        ];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo', 'a/bar'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+
+        writeAssets('p/p/lib/', assets);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
+            '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when two packages each have and list an asset their pubspec', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['a/foo'],
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+          assets: <String>['a/foo'],
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/', assets);
+        writeAssets('p2/p/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo","packages/test_package/a/2x/foo"],'
+            '"packages/test_package2/a/foo":'
+            '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package', 'test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext("Two assets are bundled when two packages each have an asset, listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>[
+          'packages/test_package/a/foo',
+          'packages/test_package2/a/foo',
+        ];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/lib/', assets);
+        writeAssets('p2/p/lib/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":'
+            '["packages/test_package/a/foo","packages/test_package/a/2x/foo"],'
+            '"packages/test_package2/a/foo":'
+            '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package', 'test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the app depends on a package, '
+        'listing in its pubspec an asset from another package', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['packages/test_package2/a/foo'],
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p2/p/lib/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package2/a/foo":'
+            '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
 
-    testUsingContext('Two assets are bundled when the package has and lists '
-      'two assets in its pubspec', () async {
+    testUsingContext('Asset paths can contain URL reserved characters', () async {
       writePubspecFile('pubspec.yaml', 'test');
       writePackagesFile('test_package:p/p/lib/');
 
-      final List<String> assets = <String>['a/foo', 'a/bar'];
+      final List<String> assets = <String>['a/foo', 'a/foo [x]'];
       writePubspecFile(
         'p/p/pubspec.yaml',
         'test_package',
@@ -285,8 +466,8 @@ $assetsSection
 
       writeAssets('p/p/', assets);
       const String expectedAssetManifest =
-          '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
-          '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
+          '{"packages/test_package/a/foo":["packages/test_package/a/foo"],'
+          '"packages/test_package/a/foo [x]":["packages/test_package/a/foo [x]"]}';
 
       await buildAndVerifyAssets(
         assets,
@@ -295,283 +476,584 @@ $assetsSection
       );
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+        ProcessManager: () => FakeProcessManager.any(),
     });
 
-    testUsingContext("Two assets are bundled when the package has two assets, listed in the app's pubspec", () async {
-      final List<String> assetEntries = <String>[
-        'packages/test_package/a/foo',
-        'packages/test_package/a/bar',
-      ];
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-         assets: assetEntries,
-      );
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assets = <String>['a/foo', 'a/bar'];
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-      );
-
-      writeAssets('p/p/lib/', assets);
-      const String expectedAssetManifest =
-          '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
-          '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
-
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from scanned paths', () {
+      testUsingContext('Two assets are bundled when scanning their directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'a/bar'];
+        final List<String> assetsOnManifest = <String>['a/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetsOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
+            '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when listing one and scanning second directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'abc/bar'];
+        final List<String> assetOnManifest = <String>['a/foo', 'abc/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":["packages/test_package/a/foo"],'
+            '"packages/test_package/abc/bar":["packages/test_package/abc/bar"]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled with variant, scanning wrong directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo','a/b/foo','a/bar'];
+        final List<String> assetOnManifest = <String>['a','a/bar']; // can't list 'a' as asset, should be 'a/'
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+
+        expect(bundle.entries['AssetManifest.bin'], isNull,
+          reason: 'Invalid pubspec.yaml should not generate AssetManifest.bin'  );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
 
-    testUsingContext('Two assets are bundled when two packages each have and list an asset their pubspec', () async {
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-      );
-      writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: <String>['a/foo'],
-      );
-      writePubspecFile(
-        'p2/p/pubspec.yaml',
-        'test_package2',
-        assets: <String>['a/foo'],
-      );
-
-      final List<String> assets = <String>['a/foo', 'a/2x/foo'];
-      writeAssets('p/p/', assets);
-      writeAssets('p2/p/', assets);
-
-      const String expectedAssetManifest =
-          '{"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo","packages/test_package/a/2x/foo"],'
-          '"packages/test_package2/a/foo":'
-          '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
-
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package', 'test_package2'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
-
-    testUsingContext("Two assets are bundled when two packages each have an asset, listed in the app's pubspec", () async {
-      final List<String> assetEntries = <String>[
-        'packages/test_package/a/foo',
-        'packages/test_package2/a/foo',
-      ];
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-        assets: assetEntries,
-      );
-      writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-      );
-      writePubspecFile(
-        'p2/p/pubspec.yaml',
-        'test_package2',
-      );
-
-      final List<String> assets = <String>['a/foo', 'a/2x/foo'];
-      writeAssets('p/p/lib/', assets);
-      writeAssets('p2/p/lib/', assets);
-
-      const String expectedAssetManifest =
-          '{"packages/test_package/a/foo":'
-          '["packages/test_package/a/foo","packages/test_package/a/2x/foo"],'
-          '"packages/test_package2/a/foo":'
-          '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
-
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package', 'test_package2'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
-
-    testUsingContext('One asset is bundled when the app depends on a package, '
-      'listing in its pubspec an asset from another package', () async {
-      writePubspecFile(
-        'pubspec.yaml',
-        'test',
-      );
-      writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: <String>['packages/test_package2/a/foo'],
-      );
-      writePubspecFile(
-        'p2/p/pubspec.yaml',
-        'test_package2',
-      );
-
-      final List<String> assets = <String>['a/foo', 'a/2x/foo'];
-      writeAssets('p2/p/lib/', assets);
-
-      const String expectedAssetManifest =
-          '{"packages/test_package2/a/foo":'
-          '["packages/test_package2/a/foo","packages/test_package2/a/2x/foo"]}';
-
-      await buildAndVerifyAssets(
-        assets,
-        <String>['test_package2'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from scanned paths with MemoryFileSystem', () {
+      testUsingContext('One asset is bundled with variant, scanning directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo','a/2x/foo'];
+        final List<String> assetOnManifest = <String>['a/',];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":["packages/test_package/a/foo","packages/test_package/a/2x/foo"]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('No asset is bundled with variant, no assets or directories are listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'a/2x/foo'];
+        final List<String> assetOnManifest = <String>[];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest = '{}';
+
+        await buildAndVerifyAssets(
+          assetOnManifest,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Expect error generating manifest, wrong non-existing directory is listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetOnManifest = <String>['c/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        await buildAndVerifyAssets(
+          assetOnManifest,
+          <String>['test_package'],
+          null,
+          expectExists: false,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
   });
+  group('Current asset manifest (AssetManifest.bin)', () {
+    Future<String> extractAssetManifestFromBundleAsJson(AssetBundle bundle) async {
+      final List<int> manifestBytes = await bundle.entries['AssetManifest.bin']!.contentsAsBytes();
+      return json.encode(const StandardMessageCodec().decodeMessage(
+        ByteData.sublistView(Uint8List.fromList(manifestBytes))
+      ));
+    }
 
-  testUsingContext('Asset paths can contain URL reserved characters', () async {
-    writePubspecFile('pubspec.yaml', 'test');
-    writePackagesFile('test_package:p/p/lib/');
-
-    final List<String> assets = <String>['a/foo', 'a/foo [x]'];
-    writePubspecFile(
-      'p/p/pubspec.yaml',
-      'test_package',
-      assets: assets,
-    );
-
-    writeAssets('p/p/', assets);
-    const String expectedAssetManifest =
-        '{"packages/test_package/a/foo":["packages/test_package/a/foo"],'
-        '"packages/test_package/a/foo [x]":["packages/test_package/a/foo [x]"]}';
-
-    await buildAndVerifyAssets(
-      assets,
-      <String>['test_package'],
-      expectedAssetManifest,
-    );
-  }, overrides: <Type, Generator>{
-    FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-  });
-
-  group('AssetBundle assets from scanned paths', () {
-    testUsingContext('Two assets are bundled when scanning their directory', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assetsOnDisk = <String>['a/foo', 'a/bar'];
-      final List<String> assetsOnManifest = <String>['a/'];
-
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assetsOnManifest,
-      );
-
-      writeAssets('p/p/', assetsOnDisk);
-      const String expectedAssetManifest =
-          '{"packages/test_package/a/bar":["packages/test_package/a/bar"],'
-          '"packages/test_package/a/foo":["packages/test_package/a/foo"]}';
+    Future<void> buildAndVerifyAssets(
+      List<String> assets,
+      List<String> packages,
+      String? expectedAssetManifest, {
+      bool expectExists = true,
+    }) async {
+      final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+      await bundle.build(packagesPath: '.packages');
 
-      await buildAndVerifyAssets(
-        assetsOnDisk,
-        <String>['test_package'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
-    });
+      for (final String packageName in packages) {
+        for (final String asset in assets) {
+          final String entryKey = Uri.encodeFull('packages/$packageName/$asset');
+          expect(bundle.entries.containsKey(entryKey), expectExists,
+            reason: 'Cannot find key on bundle: $entryKey');
+          if (expectExists) {
+            expect(
+              utf8.decode(await bundle.entries[entryKey]!.contentsAsBytes()),
+              asset,
+            );
+          }
+        }
+      }
 
-    testUsingContext('Two assets are bundled when listing one and scanning second directory', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
+      if (expectExists) {
+        final String actualAssetManifest = await extractAssetManifestFromBundleAsJson(bundle);
+        expect(
+          actualAssetManifest,
+          expectedAssetManifest,
+        );
+      }
+    }
 
-      final List<String> assetsOnDisk = <String>['a/foo', 'abc/bar'];
-      final List<String> assetOnManifest = <String>['a/foo', 'abc/'];
+    void writeAssets(String path, List<String> assets) {
+      for (final String asset in assets) {
+        final String fullPath = fixPath(globals.fs.path.join(path, asset));
 
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assetOnManifest,
-      );
+        globals.fs.file(fullPath)
+          ..createSync(recursive: true)
+          ..writeAsStringSync(asset);
+      }
+    }
 
-      writeAssets('p/p/', assetsOnDisk);
-      const String expectedAssetManifest =
-          '{"packages/test_package/a/foo":["packages/test_package/a/foo"],'
-          '"packages/test_package/abc/bar":["packages/test_package/abc/bar"]}';
+    late FileSystem testFileSystem;
 
-      await buildAndVerifyAssets(
-        assetsOnDisk,
-        <String>['test_package'],
-        expectedAssetManifest,
+    setUp(() async {
+      testFileSystem = MemoryFileSystem(
+        style: globals.platform.isWindows
+          ? FileSystemStyle.windows
+          : FileSystemStyle.posix,
       );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+      testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
     });
 
-    testUsingContext('One asset is bundled with variant, scanning wrong directory', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assetsOnDisk = <String>['a/foo','a/b/foo','a/bar'];
-      final List<String> assetOnManifest = <String>['a','a/bar']; // can't list 'a' as asset, should be 'a/'
-
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assetOnManifest,
-      );
-
-      writeAssets('p/p/', assetsOnDisk);
-
-      final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
-      await bundle.build(packagesPath: '.packages');
-
-      expect(bundle.entries['AssetManifest.json'], isNull,
-        reason: 'Invalid pubspec.yaml should not generate AssetManifest.json'  );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from packages', () {
+      testUsingContext('No assets are bundled when the package has no assets', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+        expect(bundle.entries.keys, unorderedEquals(
+          <String>['AssetManifest.bin', 'AssetManifest.json', 'FontManifest.json', 'NOTICES.Z']
+        ));
+        final String actualAssetManifest = await extractAssetManifestFromBundleAsJson(bundle);
+        const String expectedAssetManifest = '{}';
+        expect(
+          actualAssetManifest,
+          expectedAssetManifest,
+        );
+        expect(
+          utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
+          '[]',
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('No assets are bundled when the package has an asset that is not listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final List<String> assets = <String>['a/foo'];
+        writeAssets('p/p/', assets);
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+        expect(bundle.entries.keys, unorderedEquals(
+          <String>['AssetManifest.bin', 'AssetManifest.json', 'FontManifest.json', 'NOTICES.Z']
+        ));
+        final String actualAssetManifest = await extractAssetManifestFromBundleAsJson(bundle);
+        const String expectedAssetManifest = '{}';
+        expect(
+          actualAssetManifest,
+          expectedAssetManifest,
+        );
+        expect(
+          utf8.decode(await bundle.entries['FontManifest.json']!.contentsAsBytes()),
+          '[]',
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the package has and lists one '
+        'asset its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assets,
+        );
+
+        writeAssets('p/p/', assets);
+
+        const String expectedAssetManifest = '{"packages/test_package/a/foo":'
+            '[]}';
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the package has one asset, '
+        "listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>['packages/test_package/a/foo'];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile('p/p/pubspec.yaml', 'test_package');
+
+        final List<String> assets = <String>['a/foo'];
+        writeAssets('p/p/lib/', assets);
+
+        const String expectedAssetManifest = '{"packages/test_package/a/foo":[]}';
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset and its variant are bundled when the package '
+        'has an asset and a variant, and lists the asset in its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['a/foo', 'a/bar'],
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo', 'a/bar'];
+        writeAssets('p/p/', assets);
+
+        const String expectedManifest = '{'
+            '"packages/test_package/a/bar":[],'
+            '"packages/test_package/a/foo":['
+              '{"asset":"packages/test_package/a/2x/foo","dpr":2.0}]'
+            '}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset and its variant are bundled when the package '
+        'has an asset and a variant, and the app lists the asset in its pubspec', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: <String>['packages/test_package/a/foo'],
+        );
+        writePackagesFile('test_package:p/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/lib/', assets);
+
+        const String expectedManifest = '{"packages/test_package/a/foo":'
+            '[{"asset":"packages/test_package/a/2x/foo","dpr":2.0}]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when the package has and lists '
+        'two assets in its pubspec', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo', 'a/bar'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assets,
+        );
+
+        writeAssets('p/p/', assets);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":[],'
+            '"packages/test_package/a/foo":[]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext("Two assets are bundled when the package has two assets, listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>[
+          'packages/test_package/a/foo',
+          'packages/test_package/a/bar',
+        ];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assets = <String>['a/foo', 'a/bar'];
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+
+        writeAssets('p/p/lib/', assets);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":[],'
+            '"packages/test_package/a/foo":[]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when two packages each have and list an asset their pubspec', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['a/foo'],
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+          assets: <String>['a/foo'],
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/', assets);
+        writeAssets('p2/p/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":'
+            '[{"asset":"packages/test_package/a/2x/foo","dpr":2.0}],'
+            '"packages/test_package2/a/foo":'
+            '[{"asset":"packages/test_package2/a/2x/foo","dpr":2.0}]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package', 'test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext("Two assets are bundled when two packages each have an asset, listed in the app's pubspec", () async {
+        final List<String> assetEntries = <String>[
+          'packages/test_package/a/foo',
+          'packages/test_package2/a/foo',
+        ];
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+          assets: assetEntries,
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p/p/lib/', assets);
+        writeAssets('p2/p/lib/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":'
+            '[{"asset":"packages/test_package/a/2x/foo","dpr":2.0}],'
+            '"packages/test_package2/a/foo":'
+            '[{"asset":"packages/test_package2/a/2x/foo","dpr":2.0}]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package', 'test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled when the app depends on a package, '
+        'listing in its pubspec an asset from another package', () async {
+        writePubspecFile(
+          'pubspec.yaml',
+          'test',
+        );
+        writePackagesFile('test_package:p/p/lib/\ntest_package2:p2/p/lib/');
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: <String>['packages/test_package2/a/foo'],
+        );
+        writePubspecFile(
+          'p2/p/pubspec.yaml',
+          'test_package2',
+        );
+
+        final List<String> assets = <String>['a/foo', 'a/2x/foo'];
+        writeAssets('p2/p/lib/', assets);
+
+        const String expectedAssetManifest =
+            '{"packages/test_package2/a/foo":'
+            '[{"asset":"packages/test_package2/a/2x/foo","dpr":2.0}]}';
+
+        await buildAndVerifyAssets(
+          assets,
+          <String>['test_package2'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
-  });
 
-  group('AssetBundle assets from scanned paths with MemoryFileSystem', () {
-    testUsingContext('One asset is bundled with variant, scanning directory', () async {
+    testUsingContext('Asset paths can contain URL reserved characters', () async {
       writePubspecFile('pubspec.yaml', 'test');
       writePackagesFile('test_package:p/p/lib/');
 
-      final List<String> assetsOnDisk = <String>['a/foo','a/2x/foo'];
-      final List<String> assetOnManifest = <String>['a/',];
-
+      final List<String> assets = <String>['a/foo', 'a/foo [x]'];
       writePubspecFile(
         'p/p/pubspec.yaml',
         'test_package',
-        assets: assetOnManifest,
+        assets: assets,
       );
 
-      writeAssets('p/p/', assetsOnDisk);
+      writeAssets('p/p/', assets);
       const String expectedAssetManifest =
-          '{"packages/test_package/a/foo":["packages/test_package/a/foo","packages/test_package/a/2x/foo"]}';
+          '{"packages/test_package/a/foo":[],'
+          '"packages/test_package/a/foo [x]":[]}';
 
       await buildAndVerifyAssets(
-        assetsOnDisk,
+        assets,
         <String>['test_package'],
         expectedAssetManifest,
       );
@@ -580,53 +1062,165 @@ $assetsSection
       ProcessManager: () => FakeProcessManager.any(),
     });
 
-    testUsingContext('No asset is bundled with variant, no assets or directories are listed', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assetsOnDisk = <String>['a/foo', 'a/2x/foo'];
-      final List<String> assetOnManifest = <String>[];
-
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assetOnManifest,
-      );
-
-      writeAssets('p/p/', assetsOnDisk);
-      const String expectedAssetManifest = '{}';
-
-      await buildAndVerifyAssets(
-        assetOnManifest,
-        <String>['test_package'],
-        expectedAssetManifest,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from scanned paths', () {
+      testUsingContext('Two assets are bundled when scanning their directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'a/bar'];
+        final List<String> assetsOnManifest = <String>['a/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetsOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/bar":[],'
+            '"packages/test_package/a/foo":[]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Two assets are bundled when listing one and scanning second directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'abc/bar'];
+        final List<String> assetOnManifest = <String>['a/foo', 'abc/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":[],'
+            '"packages/test_package/abc/bar":[]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('One asset is bundled with variant, scanning wrong directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo','a/b/foo','a/bar'];
+        final List<String> assetOnManifest = <String>['a','a/bar']; // can't list 'a' as asset, should be 'a/'
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+
+        final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+        await bundle.build(packagesPath: '.packages');
+
+        expect(bundle.entries['AssetManifest.bin'], isNull,
+          reason: 'Invalid pubspec.yaml should not generate AssetManifest.bin'  );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
 
-    testUsingContext('Expect error generating manifest, wrong non-existing directory is listed', () async {
-      writePubspecFile('pubspec.yaml', 'test');
-      writePackagesFile('test_package:p/p/lib/');
-
-      final List<String> assetOnManifest = <String>['c/'];
-
-      writePubspecFile(
-        'p/p/pubspec.yaml',
-        'test_package',
-        assets: assetOnManifest,
-      );
-
-      await buildAndVerifyAssets(
-        assetOnManifest,
-        <String>['test_package'],
-        null,
-        expectExists: false,
-      );
-    }, overrides: <Type, Generator>{
-      FileSystem: () => testFileSystem,
-      ProcessManager: () => FakeProcessManager.any(),
+    group('AssetBundle assets from scanned paths with MemoryFileSystem', () {
+      testUsingContext('One asset is bundled with variant, scanning directory', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo','a/2x/foo'];
+        final List<String> assetOnManifest = <String>['a/',];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest =
+            '{"packages/test_package/a/foo":[{"asset":"packages/test_package/a/2x/foo","dpr":2.0}]}';
+
+        await buildAndVerifyAssets(
+          assetsOnDisk,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('No asset is bundled with variant, no assets or directories are listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetsOnDisk = <String>['a/foo', 'a/2x/foo'];
+        final List<String> assetOnManifest = <String>[];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        writeAssets('p/p/', assetsOnDisk);
+        const String expectedAssetManifest = '{}';
+
+        await buildAndVerifyAssets(
+          assetOnManifest,
+          <String>['test_package'],
+          expectedAssetManifest,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('Expect error generating manifest, wrong non-existing directory is listed', () async {
+        writePubspecFile('pubspec.yaml', 'test');
+        writePackagesFile('test_package:p/p/lib/');
+
+        final List<String> assetOnManifest = <String>['c/'];
+
+        writePubspecFile(
+          'p/p/pubspec.yaml',
+          'test_package',
+          assets: assetOnManifest,
+        );
+
+        await buildAndVerifyAssets(
+          assetOnManifest,
+          <String>['test_package'],
+          null,
+          expectExists: false,
+        );
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
     });
   });
 }

packages/flutter_tools/test/general.shard/asset_bundle_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
@@ -13,6 +14,7 @@ import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/bundle_builder.dart';
 import 'package:flutter_tools/src/devfs.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 import '../src/common.dart';
 import '../src/context.dart';
@@ -48,11 +50,16 @@ void main() {
 
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      expect(bundle.entries.length, 1);
-      const String expectedAssetManifest = '{}';
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json', 'AssetManifest.bin']));
+      const String expectedJsonAssetManifest = '{}';
       expect(
         utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes()),
-        expectedAssetManifest,
+        expectedJsonAssetManifest,
+      );
+      const String expectedBinAssetManifest = '{}';
+      expect(
+        await _extractBinAssetManifestFromBundleAsJson(bundle),
+        expectedBinAssetManifest
       );
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
@@ -72,12 +79,8 @@ flutter:
 ''');
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt']));
       expect(bundle.needsBuild(), false);
 
       // Simulate modifying the files by updating the filestat time manually.
@@ -87,13 +90,9 @@ flutter:
 
       expect(bundle.needsBuild(), true);
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      //  - assets/foo/fizz.txt
-      expect(bundle.entries.length, 5);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt',
+        'assets/foo/fizz.txt']));
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
       ProcessManager: () => FakeProcessManager.any(),
@@ -112,12 +111,8 @@ flutter:
       globals.fs.file('.packages').createSync();
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt']));
       expect(bundle.needsBuild(), false);
 
       // Delete the wildcard directory and update pubspec file.
@@ -138,12 +133,8 @@ name: example''')
       // supporting file deletion.
       expect(bundle.needsBuild(), true);
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt']));
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
       ProcessManager: () => FakeProcessManager.any(),
@@ -166,12 +157,8 @@ flutter:
       globals.fs.file('.packages').createSync();
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt']));
       expect(bundle.needsBuild(), false);
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
@@ -203,12 +190,8 @@ flutter:
         splitDeferredAssets: true,
       ).createBundle();
       await bundle.build(packagesPath: '.packages', deferredComponentsEnabled: true);
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z', 'assets/foo/bar.txt']));
       expect(bundle.deferredComponentsEntries.length, 1);
       expect(bundle.deferredComponentsEntries['component1']!.length, 2);
       expect(bundle.needsBuild(), false);
@@ -237,12 +220,9 @@ flutter:
 ''');
       final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
       await bundle.build(packagesPath: '.packages');
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 6);
+      expect(bundle.entries.keys, unorderedEquals(<String>['assets/foo/bar.txt',
+        'assets/bar/barbie.txt', 'assets/wild/dash.txt', 'AssetManifest.json',
+        'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z']));
       expect(bundle.deferredComponentsEntries.isEmpty, true);
       expect(bundle.needsBuild(), false);
     }, overrides: <Type, Generator>{
@@ -275,14 +255,11 @@ flutter:
         splitDeferredAssets: true,
       ).createBundle();
       await bundle.build(packagesPath: '.packages', deferredComponentsEnabled: true);
-      // Expected assets:
-      //  - asset manifest
-      //  - font manifest
-      //  - license file
-      //  - assets/foo/bar.txt
-      expect(bundle.entries.length, 4);
-      expect(bundle.deferredComponentsEntries.length, 1);
-      expect(bundle.deferredComponentsEntries['component1']!.length, 2);
+      expect(bundle.entries.keys, unorderedEquals(<String>['assets/foo/bar.txt',
+        'AssetManifest.json', 'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z']));
+      expect(bundle.deferredComponentsEntries.keys, unorderedEquals(<String>['component1']));
+      expect(bundle.deferredComponentsEntries['component1']!.keys,
+        unorderedEquals(<String>['assets/bar/barbie.txt', 'assets/wild/dash.txt']));
       expect(bundle.needsBuild(), false);
 
       // Simulate modifying the files by updating the filestat time manually.
@@ -293,9 +270,13 @@ flutter:
       expect(bundle.needsBuild(), true);
       await bundle.build(packagesPath: '.packages', deferredComponentsEnabled: true);
 
-      expect(bundle.entries.length, 4);
+      expect(bundle.entries.keys, unorderedEquals(<String>['assets/foo/bar.txt',
+        'AssetManifest.json', 'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z']));
       expect(bundle.deferredComponentsEntries.length, 1);
-      expect(bundle.deferredComponentsEntries['component1']!.length, 3);
+      expect(bundle.deferredComponentsEntries['component1']!.keys,
+        unorderedEquals(<String>['assets/bar/barbie.txt', 'assets/wild/dash.txt',
+        'assets/wild/fizz.txt']));
+
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
       ProcessManager: () => FakeProcessManager.any(),
@@ -335,7 +316,8 @@ assets:
     final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
     await bundle.build(packagesPath: '.packages');
 
-    final DevFSStringContent? assetManifest = bundle.entries['AssetManifest.json']
+    final DevFSContent? assetManifestBin = bundle.entries['AssetManifest.bin'];
+    final DevFSStringContent? assetManifestJson = bundle.entries['AssetManifest.json']
       as DevFSStringContent?;
     final DevFSStringContent? fontManifest = bundle.entries['FontManifest.json']
       as DevFSStringContent?;
@@ -344,7 +326,8 @@ assets:
 
     await bundle.build(packagesPath: '.packages');
 
-    expect(assetManifest, bundle.entries['AssetManifest.json']);
+    expect(assetManifestBin, bundle.entries['AssetManifest.bin']);
+    expect(assetManifestJson, bundle.entries['AssetManifest.json']);
     expect(fontManifest, bundle.entries['FontManifest.json']);
     expect(license, bundle.entries['NOTICES']);
   }, overrides: <Type, Generator>{
@@ -639,7 +622,8 @@ flutter:
 
     await bundle.build(packagesPath: '.packages');
 
-    expect(bundle.entries, hasLength(4));
+    expect(bundle.entries.keys, unorderedEquals(<String>['packages/foo/bar/fizz.txt',
+    'AssetManifest.json', 'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z']));
     expect(bundle.needsBuild(), false);
 
     // Does not track dependency's wildcard directories.
@@ -739,6 +723,7 @@ flutter:
     expect(await bundle.build(packagesPath: '.packages'), 0);
     expect((bundle.entries['FontManifest.json']! as DevFSStringContent).string, '[]');
     expect((bundle.entries['AssetManifest.json']! as DevFSStringContent).string, '{}');
+    expect(await _extractBinAssetManifestFromBundleAsJson(bundle), '{}');
     expect(testLogger.errorText, contains(
       'package:foo has `uses-material-design: true` set'
     ));
@@ -774,7 +759,8 @@ flutter:
     final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
 
     expect(await bundle.build(packagesPath: '.packages'), 0);
-    expect(bundle.entries.length, 4);
+    expect(bundle.entries.keys, unorderedEquals(<String>['assets/foo.txt',
+      'AssetManifest.json', 'AssetManifest.bin', 'FontManifest.json', 'NOTICES.Z']));
   }, overrides: <Type, Generator>{
     FileSystem: () => MemoryFileSystem.test(),
     ProcessManager: () => FakeProcessManager.any(),
@@ -812,9 +798,17 @@ flutter:
     // The assets from deferred components and regular assets
     // are both included in alphabetical order
     expect((bundle.entries['AssetManifest.json']! as DevFSStringContent).string, '{"assets/apple.jpg":["assets/apple.jpg"],"assets/bar.jpg":["assets/bar.jpg"],"assets/foo.jpg":["assets/foo.jpg"],"assets/zebra.jpg":["assets/zebra.jpg"]}');
+    expect(await _extractBinAssetManifestFromBundleAsJson(bundle), '{"assets/apple.jpg":[],"assets/bar.jpg":[],"assets/foo.jpg":[],"assets/zebra.jpg":[]}');
   }, overrides: <Type, Generator>{
     FileSystem: () => MemoryFileSystem.test(),
     ProcessManager: () => FakeProcessManager.any(),
     Platform: () => FakePlatform(),
   });
 }
+
+Future<String> _extractBinAssetManifestFromBundleAsJson(AssetBundle bundle) async {
+  final List<int> manifestBytes = await bundle.entries['AssetManifest.bin']!.contentsAsBytes();
+  return json.encode(const StandardMessageCodec().decodeMessage(
+    ByteData.sublistView(Uint8List.fromList(manifestBytes))
+  ));
+}

packages/flutter_tools/test/general.shard/asset_bundle_variant_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
@@ -15,209 +16,418 @@ import 'package:flutter_tools/src/base/user_messages.dart';
 import 'package:flutter_tools/src/cache.dart';
 
 import 'package:flutter_tools/src/project.dart';
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 import '../src/common.dart';
 
 void main() {
 
-  Future<Map<String, List<String>>> extractAssetManifestFromBundle(ManifestAssetBundle bundle) async {
-    final String manifestJson = utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes());
-    final Map<String, dynamic> parsedJson = json.decode(manifestJson) as Map<String, dynamic>;
-    final Iterable<String> keys = parsedJson.keys;
-    final Map<String, List<String>> parsedManifest = <String, List<String>> {
-      for (final String key in keys) key: List<String>.from(parsedJson[key] as List<dynamic>),
-    };
-    return parsedManifest;
-  }
-
-  group('AssetBundle asset variants (with Unix-style paths)', () {
-    late Platform platform;
-    late FileSystem fs;
-
-    setUp(() {
-      platform = FakePlatform();
-      fs = MemoryFileSystem.test();
-      Cache.flutterRoot = Cache.defaultFlutterRoot(
-        platform: platform,
-        fileSystem: fs,
-        userMessages: UserMessages()
-      );
-
-      fs.file('.packages').createSync();
-
-      fs.file('pubspec.yaml').writeAsStringSync(
-'''
-name: test
-dependencies:
+  // TODO(andrewkolos): Delete this group once we stop producing AssetManifest.json
+  // as part of build.
+  group('Legacy asset manifest (AssetManifest.json)', () {
+    Future<Map<String, List<String>>> extractAssetManifestFromBundle(ManifestAssetBundle bundle) async {
+      final String manifestJson = utf8.decode(await bundle.entries['AssetManifest.json']!.contentsAsBytes());
+      final Map<String, dynamic> parsedJson = json.decode(manifestJson) as Map<String, dynamic>;
+      final Iterable<String> keys = parsedJson.keys;
+      final Map<String, List<String>> parsedManifest = <String, List<String>> {
+        for (final String key in keys) key: List<String>.from(parsedJson[key] as List<dynamic>),
+      };
+      return parsedManifest;
+    }
+
+    group('AssetBundle asset variants (with Unix-style paths)', () {
+      late Platform platform;
+      late FileSystem fs;
+
+      setUp(() {
+        platform = FakePlatform();
+        fs = MemoryFileSystem.test();
+        Cache.flutterRoot = Cache.defaultFlutterRoot(
+          platform: platform,
+          fileSystem: fs,
+          userMessages: UserMessages()
+        );
+
+        fs.file('.packages').createSync();
+
+        fs.file('pubspec.yaml').writeAsStringSync(
+  '''
+  name: test
+  dependencies:
+    flutter:
+      sdk: flutter
   flutter:
-    sdk: flutter
-flutter:
-  assets:
-    - assets/
-'''
-      );
+    assets:
+      - assets/
+  '''
+        );
+      });
+
+      testWithoutContext('Only images in folders named with device pixel ratios (e.g. 2x, 3.0x) should be considered as variants of other images', () async {
+        const String image = 'assets/image.jpg';
+        const String image2xVariant = 'assets/2x/image.jpg';
+        const String imageNonVariant = 'assets/notAVariant/image.jpg';
+
+        final List<String> assets = <String>[
+          image,
+          image2xVariant,
+          imageNonVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
+
+        expect(manifest, hasLength(2));
+        expect(manifest[image], equals(<String>[image, image2xVariant]));
+        expect(manifest[imageNonVariant], equals(<String>[imageNonVariant]));
+      });
+
+      testWithoutContext('Asset directories are recursively searched for assets', () async {
+        const String topLevelImage = 'assets/image.jpg';
+        const String secondLevelImage = 'assets/folder/secondLevel.jpg';
+        const String secondLevel2xVariant = 'assets/folder/2x/secondLevel.jpg';
+
+        final List<String> assets = <String>[
+          topLevelImage,
+          secondLevelImage,
+          secondLevel2xVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
+        expect(manifest, hasLength(2));
+        expect(manifest[topLevelImage], equals(<String>[topLevelImage]));
+        expect(manifest[secondLevelImage], equals(<String>[secondLevelImage, secondLevel2xVariant]));
+      });
+
+      testWithoutContext('Asset paths should never be URI-encoded', () async {
+        const String image = 'assets/normalFolder/i have URI-reserved_characters.jpg';
+        const String imageVariant = 'assets/normalFolder/3x/i have URI-reserved_characters.jpg';
+
+        final List<String> assets = <String>[
+          image,
+          imageVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
+        expect(manifest, hasLength(1));
+        expect(manifest[image], equals(<String>[image, imageVariant]));
+      });
     });
 
-    testWithoutContext('Only images in folders named with device pixel ratios (e.g. 2x, 3.0x) should be considered as variants of other images', () async {
-      const String image = 'assets/image.jpg';
-      const String image2xVariant = 'assets/2x/image.jpg';
-      const String imageNonVariant = 'assets/notAVariant/image.jpg';
-
-      final List<String> assets = <String>[
-        image,
-        image2xVariant,
-        imageNonVariant
-      ];
-
-      for (final String asset in assets) {
-        final File assetFile = fs.file(asset);
-        assetFile.createSync(recursive: true);
-        assetFile.writeAsStringSync(asset);
-      }
-
-      final ManifestAssetBundle bundle = ManifestAssetBundle(
-        logger: BufferLogger.test(),
-        fileSystem: fs,
-        platform: platform,
-      );
-
-      await bundle.build(
-        packagesPath: '.packages',
-        flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
-      );
-
-      final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
-
-      expect(manifest, hasLength(2));
-      expect(manifest[image], equals(<String>[image, image2xVariant]));
-      expect(manifest[imageNonVariant], equals(<String>[imageNonVariant]));
-    });
 
-    testWithoutContext('Asset directories are recursively searched for assets', () async {
-      const String topLevelImage = 'assets/image.jpg';
-      const String secondLevelImage = 'assets/folder/secondLevel.jpg';
-      const String secondLevel2xVariant = 'assets/folder/2x/secondLevel.jpg';
-
-      final List<String> assets = <String>[
-        topLevelImage,
-        secondLevelImage,
-        secondLevel2xVariant
-      ];
-
-      for (final String asset in assets) {
-        final File assetFile = fs.file(asset);
-        assetFile.createSync(recursive: true);
-        assetFile.writeAsStringSync(asset);
-      }
-
-      final ManifestAssetBundle bundle = ManifestAssetBundle(
-        logger: BufferLogger.test(),
-        fileSystem: fs,
-        platform: platform,
-      );
-
-      await bundle.build(
-        packagesPath: '.packages',
-        flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
-      );
-
-      final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
-      expect(manifest, hasLength(2));
-      expect(manifest[topLevelImage], equals(<String>[topLevelImage]));
-      expect(manifest[secondLevelImage], equals(<String>[secondLevelImage, secondLevel2xVariant]));
-    });
+    group('AssetBundle asset variants (with Windows-style filepaths)', () {
+      late final Platform platform;
+      late final FileSystem fs;
+
+      setUp(() {
+        platform = FakePlatform(operatingSystem: 'windows');
+        fs = MemoryFileSystem.test(style: FileSystemStyle.windows);
+        Cache.flutterRoot = Cache.defaultFlutterRoot(
+          platform: platform,
+          fileSystem: fs,
+          userMessages: UserMessages()
+        );
 
-    testWithoutContext('Asset paths should never be URI-encoded', () async {
-      const String image = 'assets/normalFolder/i have URI-reserved_characters.jpg';
-      const String imageVariant = 'assets/normalFolder/3x/i have URI-reserved_characters.jpg';
-
-      final List<String> assets = <String>[
-        image,
-        imageVariant
-      ];
-
-      for (final String asset in assets) {
-        final File assetFile = fs.file(asset);
-        assetFile.createSync(recursive: true);
-        assetFile.writeAsStringSync(asset);
-      }
-
-      final ManifestAssetBundle bundle = ManifestAssetBundle(
-        logger: BufferLogger.test(),
-        fileSystem: fs,
-        platform: platform,
-      );
-
-      await bundle.build(
-        packagesPath: '.packages',
-        flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
-      );
-
-      final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
-      expect(manifest, hasLength(1));
-      expect(manifest[image], equals(<String>[image, imageVariant]));
+        fs.file('.packages').createSync();
+
+        fs.file('pubspec.yaml').writeAsStringSync(
+  '''
+  name: test
+  dependencies:
+    flutter:
+      sdk: flutter
+  flutter:
+    assets:
+      - assets/
+  '''
+        );
+      });
+
+      testWithoutContext('Variant detection works with windows-style filepaths', () async {
+        const List<String> assets = <String>[
+          r'assets\foo.jpg',
+          r'assets\2x\foo.jpg',
+          r'assets\somewhereElse\bar.jpg',
+          r'assets\somewhereElse\2x\bar.jpg',
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
+
+        expect(manifest, hasLength(2));
+        expect(manifest['assets/foo.jpg'], equals(<String>['assets/foo.jpg', 'assets/2x/foo.jpg']));
+        expect(manifest['assets/somewhereElse/bar.jpg'], equals(<String>['assets/somewhereElse/bar.jpg', 'assets/somewhereElse/2x/bar.jpg']));
+      });
     });
   });
 
+  group('Current asset manifest (AssetManifest.bin)', () {
+    Future<String> extractAssetManifestFromBundleAsJson(ManifestAssetBundle bundle) async {
+      final List<int> manifestBytes = await bundle.entries['AssetManifest.bin']!.contentsAsBytes();
+      return json.encode(const StandardMessageCodec().decodeMessage(
+        ByteData.sublistView(Uint8List.fromList(manifestBytes))
+      ));
+    }
+
+    group('AssetBundle asset variants (with Unix-style paths)', () {
+      late Platform platform;
+      late FileSystem fs;
+
+      setUp(() {
+        platform = FakePlatform();
+        fs = MemoryFileSystem.test();
+        Cache.flutterRoot = Cache.defaultFlutterRoot(
+          platform: platform,
+          fileSystem: fs,
+          userMessages: UserMessages()
+        );
+
+        fs.file('.packages').createSync();
+
+        fs.file('pubspec.yaml').writeAsStringSync(
+  '''
+  name: test
+  dependencies:
+    flutter:
+      sdk: flutter
+  flutter:
+    assets:
+      - assets/
+  '''
+        );
+      });
+
+      testWithoutContext('Only images in folders named with device pixel ratios (e.g. 2x, 3.0x) should be considered as variants of other images', () async {
+        const String image = 'assets/image.jpg';
+        const String image2xVariant = 'assets/2x/image.jpg';
+        const String imageNonVariant = 'assets/notAVariant/image.jpg';
+
+        final List<String> assets = <String>[
+          image,
+          image2xVariant,
+          imageNonVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        const String expectedManifest = '{"$image":[{"asset":"$image2xVariant","dpr":2.0}],'
+          '"$imageNonVariant":[]}';
+
+        final String manifest = await extractAssetManifestFromBundleAsJson(bundle);
+        expect(manifest, equals(expectedManifest));
+      });
+
+      testWithoutContext('Asset directories are recursively searched for assets', () async {
+        const String topLevelImage = 'assets/image.jpg';
+        const String secondLevelImage = 'assets/folder/secondLevel.jpg';
+        const String secondLevel2xVariant = 'assets/folder/2x/secondLevel.jpg';
+
+        final List<String> assets = <String>[
+          topLevelImage,
+          secondLevelImage,
+          secondLevel2xVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        const String expectedManifest = '{'
+          '"$secondLevelImage":[{"asset":"$secondLevel2xVariant","dpr":2.0}],'
+          '"$topLevelImage":[]'
+        '}';
+
+        final String manifest = await extractAssetManifestFromBundleAsJson(bundle);
+        expect(manifest, equals(expectedManifest));
+      });
+
+      testWithoutContext('Asset paths should never be URI-encoded', () async {
+        const String image = 'assets/normalFolder/i have URI-reserved_characters.jpg';
+        const String imageVariant = 'assets/normalFolder/3x/i have URI-reserved_characters.jpg';
+
+        final List<String> assets = <String>[
+          image,
+          imageVariant
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        const String expectedManifest = '{"$image":[{"asset":"$imageVariant","dpr":3.0}]}';
+
+        final String manifest = await extractAssetManifestFromBundleAsJson(bundle);
+        expect(manifest, equals(expectedManifest));
+      });
+    });
 
-  group('AssetBundle asset variants (with Windows-style filepaths)', () {
-    late final Platform platform;
-    late final FileSystem fs;
 
-    setUp(() {
-      platform = FakePlatform(operatingSystem: 'windows');
-      fs = MemoryFileSystem.test(style: FileSystemStyle.windows);
-      Cache.flutterRoot = Cache.defaultFlutterRoot(
-        platform: platform,
-        fileSystem: fs,
-        userMessages: UserMessages()
-      );
+    group('AssetBundle asset variants (with Windows-style filepaths)', () {
+      late final Platform platform;
+      late final FileSystem fs;
 
-      fs.file('.packages').createSync();
+      setUp(() {
+        platform = FakePlatform(operatingSystem: 'windows');
+        fs = MemoryFileSystem.test(style: FileSystemStyle.windows);
+        Cache.flutterRoot = Cache.defaultFlutterRoot(
+          platform: platform,
+          fileSystem: fs,
+          userMessages: UserMessages()
+        );
 
-      fs.file('pubspec.yaml').writeAsStringSync(
-'''
-name: test
-dependencies:
-  flutter:
-    sdk: flutter
-flutter:
-  assets:
-    - assets/
-'''
-      );
-    });
+        fs.file('.packages').createSync();
 
-    testWithoutContext('Variant detection works with windows-style filepaths', () async {
-      const List<String> assets = <String>[
-        r'assets\foo.jpg',
-        r'assets\2x\foo.jpg',
-        r'assets\somewhereElse\bar.jpg',
-        r'assets\somewhereElse\2x\bar.jpg',
-      ];
-
-      for (final String asset in assets) {
-        final File assetFile = fs.file(asset);
-        assetFile.createSync(recursive: true);
-        assetFile.writeAsStringSync(asset);
-      }
-
-      final ManifestAssetBundle bundle = ManifestAssetBundle(
-        logger: BufferLogger.test(),
-        fileSystem: fs,
-        platform: platform,
-      );
-
-      await bundle.build(
-        packagesPath: '.packages',
-        flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
-      );
-
-      final Map<String, List<String>> manifest = await extractAssetManifestFromBundle(bundle);
-
-      expect(manifest, hasLength(2));
-      expect(manifest['assets/foo.jpg'], equals(<String>['assets/foo.jpg', 'assets/2x/foo.jpg']));
-      expect(manifest['assets/somewhereElse/bar.jpg'], equals(<String>['assets/somewhereElse/bar.jpg', 'assets/somewhereElse/2x/bar.jpg']));
+        fs.file('pubspec.yaml').writeAsStringSync(
+  '''
+  name: test
+  dependencies:
+    flutter:
+      sdk: flutter
+  flutter:
+    assets:
+      - assets/
+  '''
+        );
+      });
+
+      testWithoutContext('Variant detection works with windows-style filepaths', () async {
+        const List<String> assets = <String>[
+          r'assets\foo.jpg',
+          r'assets\2x\foo.jpg',
+          r'assets\somewhereElse\bar.jpg',
+          r'assets\somewhereElse\2x\bar.jpg',
+        ];
+
+        for (final String asset in assets) {
+          final File assetFile = fs.file(asset);
+          assetFile.createSync(recursive: true);
+          assetFile.writeAsStringSync(asset);
+        }
+
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: BufferLogger.test(),
+          fileSystem: fs,
+          platform: platform,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject:  FlutterProject.fromDirectoryTest(fs.currentDirectory),
+        );
+
+        const String expectedManifest = '{"assets/foo.jpg":[{"asset":"assets/2x/foo.jpg","dpr":2.0}],'
+        '"assets/somewhereElse/bar.jpg":[{"asset":"assets/somewhereElse/2x/bar.jpg","dpr":2.0}]}';
+
+        final String manifest = await extractAssetManifestFromBundleAsJson(bundle);
+        expect(manifest, equals(expectedManifest));
+      });
     });
   });
 }