Native assets support for Android Add2app (#140802)

Support for FFI calls with @Native external functions through Native assets on Android add to app. This enables bundling native code without any build-system boilerplate code.

For more info see:

*  https://github.com/flutter/flutter/issues/129757

## Implementation details for Android add2app

The `.so` files are bundled with the same mechanism that bundles `libapp.so`.

dev/devicelab/bin/tasks/module_test.dart

@@ -132,43 +132,6 @@ class ModuleTest {
       });
 
       // TODO(dacoharkes): Implement Add2app. https://github.com/flutter/flutter/issues/129757
-      section('Check native assets error');
-
-      await inDirectory(Directory(path.join(projectDir.path, '.android')),
-          () async {
-        final StringBuffer stderr = StringBuffer();
-        final int exitCode = await exec(
-          gradlewExecutable,
-          <String>['flutter:assembleDebug'],
-          environment: <String, String>{'JAVA_HOME': javaHome},
-          canFail: true,
-          stderr: stderr,
-        );
-        const String errorString =
-            'Native assets are not yet supported in Android add2app.';
-        if (!stderr.toString().contains(errorString) || exitCode == 0) {
-          throw TaskResult.failure(
-              '''
-Expected to find `$errorString` in stderr and nonZero exit code.
-$stderr
-exitCode: $exitCode
-''');
-        }
-      });
-
-      section('Remove FFI package');
-
-      content = content.replaceFirst(
-        '  $ffiPackageName:$platformLineSep    path: ..${Platform.pathSeparator}$ffiPackageName$platformLineSep',
-        '',
-      );
-      await pubspec.writeAsString(content, flush: true);
-      await inDirectory(projectDir, () async {
-        await flutter(
-          'packages',
-          options: <String>['get'],
-        );
-      });
 
       section('Build Flutter module library archive');
 
@@ -331,6 +294,8 @@ exitCode: $exitCode
         ...flutterAssets,
         ...debugAssets,
         ...baseApkFiles,
+        'lib/arm64-v8a/lib$ffiPackageName.so',
+        'lib/armeabi-v7a/lib$ffiPackageName.so',
       ], await getFilesInApk(debugHostApk));
 
       section('Check debug AndroidManifest.xml');
@@ -409,8 +374,10 @@ exitCode: $exitCode
       checkCollectionContains<String>(<String>[
         ...flutterAssets,
         ...baseApkFiles,
+        'lib/arm64-v8a/lib$ffiPackageName.so',
         'lib/arm64-v8a/libapp.so',
         'lib/arm64-v8a/libflutter.so',
+        'lib/armeabi-v7a/lib$ffiPackageName.so',
         'lib/armeabi-v7a/libapp.so',
         'lib/armeabi-v7a/libflutter.so',
       ], await getFilesInApk(releaseHostApk));

packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

@@ -1083,7 +1083,6 @@ class FlutterPlugin implements Plugin<Project> {
             Task packageAssets = project.tasks.findByPath(":flutter:package${variant.name.capitalize()}Assets")
             Task cleanPackageAssets = project.tasks.findByPath(":flutter:cleanPackage${variant.name.capitalize()}Assets")
             boolean isUsedAsSubproject = packageAssets && cleanPackageAssets && !isBuildingAar
-            boolean isAndroidLibraryValue = isBuildingAar || isUsedAsSubproject
 
             String variantBuildMode = buildModeFor(variant.buildType)
             String flavorValue = variant.getFlavorName()
@@ -1123,11 +1122,10 @@ class FlutterPlugin implements Plugin<Project> {
                 codeSizeDirectory(codeSizeDirectoryValue)
                 deferredComponents(deferredComponentsValue)
                 validateDeferredComponents(validateDeferredComponentsValue)
-                isAndroidLibrary(isAndroidLibraryValue)
                 flavor(flavorValue)
             }
             File libJar = project.file("${project.buildDir}/$INTERMEDIATES_DIR/flutter/${variant.name}/libs.jar")
-            Task packFlutterAppAotTask = project.tasks.create(name: "packLibs${FLUTTER_BUILD_PREFIX}${variant.name.capitalize()}", type: Jar) {
+            Task packJniLibsTask = project.tasks.create(name: "packJniLibs${FLUTTER_BUILD_PREFIX}${variant.name.capitalize()}", type: Jar) {
                 destinationDirectory = libJar.parentFile
                 archiveFileName = libJar.name
                 dependsOn compileTask
@@ -1140,10 +1138,20 @@ class FlutterPlugin implements Plugin<Project> {
                             return "lib/${abi}/lib${filename}"
                         }
                     }
+                    // Copy the native assets created by build.dart and placed in build/native_assets by flutter assemble.
+                    // The `$project.buildDir` is '.android/Flutter/build/' instead of 'build/'.
+                    def buildDir = "${getFlutterSourceDirectory()}/build"
+                    def nativeAssetsDir = "${buildDir}/native_assets/android/jniLibs/lib"
+                    from("${nativeAssetsDir}/${abi}") {
+                        include "*.so"
+                        rename { String filename ->
+                            return "lib/${abi}/${filename}"
+                        }
+                    }
                 }
             }
             addApiDependencies(project, variant.name, project.files {
-                packFlutterAppAotTask
+                packJniLibsTask
             })
             Task copyFlutterAssetsTask = project.tasks.create(
                 name: "copyFlutterAssets${variant.name.capitalize()}",
@@ -1413,8 +1421,6 @@ abstract class BaseFlutterTask extends DefaultTask {
     @Optional @Input
     Boolean validateDeferredComponents
     @Optional @Input
-    Boolean isAndroidLibrary
-    @Optional @Input
     String flavor
 
     @OutputFiles
@@ -1510,9 +1516,6 @@ abstract class BaseFlutterTask extends DefaultTask {
             }
             args("-dAndroidArchs=${targetPlatformValues.join(' ')}")
             args("-dMinSdkVersion=${minSdkVersion}")
-            if (isAndroidLibrary != null) {
-                args("-dIsAndroidLibrary=${isAndroidLibrary ? "true" : "false"}")
-            }
             args(ruleNames)
         }
     }

packages/flutter_tools/lib/src/android/native_assets.dart

@@ -78,7 +78,6 @@ Future<(Uri? nativeAssetsYaml, List<Uri> dependencies)>
   Uri? yamlParentDirectory,
   required FileSystem fileSystem,
   required int targetAndroidNdkApi,
-  bool isAndroidLibrary = false,
 }) async {
   const OS targetOS = OS.android;
   final Uri buildUri_ = nativeAssetsBuildUri(projectUri, targetOS);
@@ -115,9 +114,6 @@ Future<(Uri? nativeAssetsYaml, List<Uri> dependencies)>
   }
   ensureNoLinkModeStatic(nativeAssets);
   globals.logger.printTrace('Building native assets for $targets done.');
-  if (isAndroidLibrary && nativeAssets.isNotEmpty) {
-    throwToolExit('Native assets are not yet supported in Android add2app.');
-  }
   final Map<Asset, Asset> assetTargetLocations =
       _assetTargetLocations(nativeAssets);
   await _copyNativeAssetsAndroid(buildUri_, assetTargetLocations, fileSystem);

packages/flutter_tools/lib/src/build_info.dart

@@ -932,13 +932,6 @@ const String kDarwinArchs = 'DarwinArchs';
 /// This is expected to be a space-delimited list of architectures.
 const String kAndroidArchs = 'AndroidArchs';
 
-/// If the current build is `flutter build aar`.
-///
-/// This is expected to be a boolean.
-///
-/// If not provided, defaults to false.
-const String kIsAndroidLibrary = 'IsAndroidLibrary';
-
 /// The define to control what min Android SDK version is built for.
 ///
 /// This is expected to be int.

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

@@ -306,8 +306,6 @@ class NativeAssets extends Target {
       Uri projectUri,
       FileSystem fileSystem,
       NativeAssetsBuildRunner buildRunner) {
-    final bool isAndroidLibrary =
-        environment.defines[kIsAndroidLibrary] == 'true';
     final String? androidArchsEnvironment = environment.defines[kAndroidArchs];
     final List<AndroidArch> androidArchs = _androidArchs(
       targetPlatform,
@@ -323,7 +321,6 @@ class NativeAssets extends Target {
       buildRunner: buildRunner,
       androidArchs: androidArchs,
       targetAndroidNdkApi: targetAndroidNdkApi,
-      isAndroidLibrary: isAndroidLibrary,
     );
   }
 

packages/flutter_tools/test/general.shard/build_system/targets/native_assets_test.dart

@@ -171,15 +171,10 @@ void main() {
     },
   );
 
-
-  for (final bool isAndroidLibrary in <bool>[true, false]) {
   for (final bool hasAssets in <bool>[true, false]) {
-      final String buildType = isAndroidLibrary ? 'aar' : 'not-aar';
     final String withOrWithout = hasAssets ? 'with' : 'without';
-      final String throwsOrDoesntThrow =
-          (isAndroidLibrary && hasAssets) ? 'throws' : 'does not throw';
     testUsingContext(
-        'flutter build $buildType $withOrWithout native assets $throwsOrDoesntThrow',
+      'flutter build $withOrWithout native assets',
       overrides: <Type, Generator>{
         FileSystem: () => fileSystem,
         ProcessManager: () => processManager,
@@ -191,8 +186,7 @@ void main() {
         await createPackageConfig(androidEnvironment);
         await fileSystem.file('libfoo.so').create();
 
-          final NativeAssetsBuildRunner buildRunner =
-              FakeNativeAssetsBuildRunner(
+        final NativeAssetsBuildRunner buildRunner = FakeNativeAssetsBuildRunner(
           packagesWithNativeAssetsResult: <Package>[
             Package('foo', androidEnvironment.buildDir.uri)
           ],
@@ -211,22 +205,10 @@ void main() {
             Uri.file('src/foo.c'),
           ]),
         );
-          if (isAndroidLibrary) {
-            androidEnvironment.defines[kIsAndroidLibrary] = 'true';
-          }
-          if (hasAssets && isAndroidLibrary) {
-            expect(
-              NativeAssets(buildRunner: buildRunner).build(androidEnvironment),
-              throwsToolExit(),
-            );
-          } else {
-            await NativeAssets(buildRunner: buildRunner)
-                .build(androidEnvironment);
-          }
+        await NativeAssets(buildRunner: buildRunner).build(androidEnvironment);
       },
     );
   }
-  }
 }
 
 Future<void> createPackageConfig(Environment iosEnvironment) async {