[flutter_tools] make gallery hot reload 5x faster with one neat trick (#56224)

packages/flutter_tools/lib/src/asset.dart

@@ -74,7 +74,8 @@ class ManifestAssetBundle implements AssetBundle {
   final Map<String, DevFSContent> entries = <String, DevFSContent>{};
 
   // If an asset corresponds to a wildcard directory, then it may have been
-  // updated without changes to the manifest.
+  // updated without changes to the manifest. These are only tracked for
+  // the current project.
   final Map<Uri, Directory> _wildcardDirectories = <Uri, Directory>{};
 
   final LicenseCollector licenseCollector = LicenseCollector(fileSystem: globals.fs);
@@ -203,7 +204,8 @@ class ManifestAssetBundle implements AssetBundle {
         final Map<_Asset, List<_Asset>> packageAssets = _parseAssets(
           packageConfig,
           packageFlutterManifest,
-          wildcardDirectories,
+          // Do not track wildcard directories for dependencies.
+          <Uri>[],
           packageBasePath,
           packageName: package.name,
         );

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

@@ -14,6 +14,7 @@ import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/devfs.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:mockito/mockito.dart';
+import 'package:platform/platform.dart';
 
 import '../src/common.dart';
 import '../src/context.dart';
@@ -223,6 +224,48 @@ assets:
     FileSystem: () => MemoryFileSystem.test(),
     ProcessManager: () => FakeProcessManager.any(),
   });
+
+  testUsingContext('does not track wildcard directories from dependencies', () async {
+    globals.fs.file('.packages').writeAsStringSync(r'''
+example:lib/
+foo:foo/lib/
+''');
+    globals.fs.file(globals.fs.path.join('assets', 'foo', 'bar.txt'))
+      .createSync(recursive: true);
+    globals.fs.file('pubspec.yaml')
+      ..createSync()
+      ..writeAsStringSync(r'''
+name: example
+dependencies:
+  foo: any
+''');
+    globals.fs.file('foo/pubspec.yaml')
+      ..createSync(recursive: true)
+      ..writeAsStringSync(r'''
+name: foo
+
+flutter:
+  assets:
+    - bar/
+''');
+    final AssetBundle bundle = AssetBundleFactory.instance.createBundle();
+    globals.fs.file('foo/bar/fizz.txt').createSync(recursive: true);
+
+    await bundle.build(manifestPath: 'pubspec.yaml');
+
+    expect(bundle.entries, hasLength(4));
+    expect(bundle.needsBuild(manifestPath: 'pubspec.yaml'), false);
+
+    // Does not track dependency's wildcard directories.
+    globals.fs.file(globals.fs.path.join('assets', 'foo', 'bar.txt'))
+      .deleteSync();
+
+    expect(bundle.needsBuild(manifestPath: 'pubspec.yaml'), false);
+  }, overrides: <Type, Generator>{
+    FileSystem: () => MemoryFileSystem.test(),
+    ProcessManager: () => FakeProcessManager.any(),
+    Platform: () => FakePlatform(operatingSystem: 'linux'),
+  });
 }
 
 class MockDirectory extends Mock implements Directory {}