Don't build native assets in `flutter build bundle` (#136641)

Closes: https://github.com/flutter/flutter/issues/136547

packages/flutter_tools/lib/src/build_info.dart

@@ -967,6 +967,20 @@ const String kSdkRoot = 'SdkRoot';
 /// Whether to enable Dart obfuscation and where to save the symbol map.
 const String kDartObfuscation = 'DartObfuscation';
 
+/// Whether to enable Native Assets.
+///
+/// If true, native assets are built and the mapping for native assets lookup
+/// at runtime is embedded in the kernel file.
+///
+/// If false, native assets are not built, and an empty mapping is embedded in
+/// the kernel file. Used for targets that trigger kernel builds but
+/// are not OS/architecture specific.
+///
+/// Supported values are 'true' and 'false'.
+///
+/// Defaults to 'true'.
+const String kNativeAssets = 'NativeAssets';
+
 /// An output directory where one or more code-size measurements may be written.
 const String kCodeSizeDirectory = 'CodeSizeDirectory';
 

packages/flutter_tools/lib/src/build_system/targets/native_assets.dart

@@ -48,14 +48,20 @@ class NativeAssets extends Target {
 
   @override
   Future<void> build(Environment environment) async {
+    final String? nativeAssetsEnvironment = environment.defines[kNativeAssets];
+    final List<Uri> dependencies;
+    final FileSystem fileSystem = environment.fileSystem;
+    final File nativeAssetsFile = environment.buildDir.childFile('native_assets.yaml');
+    if (nativeAssetsEnvironment == 'false') {
+      dependencies = <Uri>[];
+      await writeNativeAssetsYaml(<Asset>[], environment.buildDir.uri, fileSystem);
+    } else {
       final String? targetPlatformEnvironment = environment.defines[kTargetPlatform];
       if (targetPlatformEnvironment == null) {
         throw MissingDefineException(kTargetPlatform, name);
       }
       final TargetPlatform targetPlatform = getTargetPlatformForName(targetPlatformEnvironment);
-
       final Uri projectUri = environment.projectDir.uri;
-    final FileSystem fileSystem = environment.fileSystem;
       final File packagesFile = fileSystem
           .directory(projectUri)
           .childDirectory('.dart_tool')
@@ -72,7 +78,7 @@ class NativeAssets extends Target {
             environment.logger,
           );
 
-    final List<Uri> dependencies;
+
       switch (targetPlatform) {
         case TargetPlatform.ios:
           final String? iosArchsEnvironment = environment.defines[kIosArchs];
@@ -197,8 +203,8 @@ class NativeAssets extends Target {
           await writeNativeAssetsYaml(<Asset>[], environment.buildDir.uri, fileSystem);
           dependencies = <Uri>[];
       }
+    }
 
-    final File nativeAssetsFile = environment.buildDir.childFile('native_assets.yaml');
     final Depfile depfile = Depfile(
       <File>[
         for (final Uri dependency in dependencies) fileSystem.file(dependency),

packages/flutter_tools/lib/src/bundle_builder.dart

@@ -26,7 +26,11 @@ class BundleBuilder {
   /// Builds the bundle for the given target platform.
   ///
   /// The default `mainPath` is `lib/main.dart`.
-  /// The default  `manifestPath` is `pubspec.yaml`
+  /// The default `manifestPath` is `pubspec.yaml`.
+  ///
+  /// If [buildNativeAssets], native assets are built and the mapping for native
+  /// assets lookup at runtime is embedded in the kernel file, otherwise an
+  /// empty native assets mapping is embedded in the kernel file.
   Future<void> build({
     required TargetPlatform platform,
     required BuildInfo buildInfo,
@@ -36,6 +40,7 @@ class BundleBuilder {
     String? applicationKernelFilePath,
     String? depfilePath,
     String? assetDirPath,
+    bool buildNativeAssets = true,
     @visibleForTesting BuildSystem? buildSystem,
   }) async {
     project ??= FlutterProject.current();
@@ -60,6 +65,7 @@ class BundleBuilder {
         kTargetFile: mainPath,
         kDeferredComponents: 'false',
         ...buildInfo.toBuildSystemEnvironment(),
+        if (!buildNativeAssets) kNativeAssets: 'false'
       },
       artifacts: globals.artifacts!,
       fileSystem: globals.fs,

packages/flutter_tools/lib/src/commands/build_bundle.dart

@@ -132,6 +132,7 @@ class BuildBundleCommand extends BuildSubCommand {
       mainPath: targetFile,
       depfilePath: stringArg('depfile'),
       assetDirPath: stringArg('asset-dir'),
+      buildNativeAssets: false,
     );
     return FlutterCommandResult.success();
   }

packages/flutter_tools/test/commands.shard/permeable/build_bundle_test.dart

@@ -252,6 +252,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -285,6 +286,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -317,6 +319,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -350,6 +353,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -383,6 +387,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -416,6 +421,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -457,6 +463,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -498,6 +505,7 @@ void main() {
         kIconTreeShakerFlag: 'false',
         kDeferredComponents: 'false',
         kDartObfuscation: 'false',
+        kNativeAssets: 'false',
       });
     }),
     FileSystem: fsFactory,
@@ -516,7 +524,7 @@ class FakeBundleBuilder extends Fake implements BundleBuilder {
     String? applicationKernelFilePath,
     String? depfilePath,
     String? assetDirPath,
-    Uri? nativeAssets,
+    bool buildNativeAssets = true,
     @visibleForTesting BuildSystem? buildSystem,
   }) async {}
 }

packages/flutter_tools/test/general.shard/custom_devices/custom_device_test.dart

@@ -645,6 +645,7 @@ class FakeBundleBuilder extends Fake implements BundleBuilder {
     String? depfilePath,
     String? assetDirPath,
     Uri? nativeAssets,
+    bool buildNativeAssets = true,
     @visibleForTesting BuildSystem? buildSystem
   }) async {}
 }

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

@@ -196,7 +196,7 @@ class FakeBundleBuilder extends Fake implements BundleBuilder {
     String? applicationKernelFilePath,
     String? depfilePath,
     String? assetDirPath,
-    Uri? nativeAssets,
+    bool buildNativeAssets = true,
     @visibleForTesting BuildSystem? buildSystem
   }) async {
     final Directory assetDirectory = fileSystem