Copy artifacts to `applicationBinaryPath` when specified for build+test separation (#109879)

dev/devicelab/lib/tasks/build_test_task.dart

@@ -59,6 +59,7 @@ abstract class BuildTestTask {
       }
       section('BUILDING APPLICATION');
       await flutter('build', options: getBuildArgs(deviceOperatingSystem));
+      copyArtifacts();
     });
 
   }
@@ -83,6 +84,11 @@ abstract class BuildTestTask {
   /// Args passed to flutter drive to test the built application.
   List<String> getTestArgs(DeviceOperatingSystem deviceOperatingSystem, String deviceId) => throw UnimplementedError('getTestArgs is not implemented');
 
+  /// Copy artifacts to [applicationBinaryPath] if specified.
+  ///
+  /// This is needed when running from CI, so that LUCI recipes know where to locate and upload artifacts to GCS.
+  void copyArtifacts() => throw UnimplementedError('copyArtifacts is not implemented');
+
   /// Logic to construct [TaskResult] from this test's results.
   Future<TaskResult> parseTaskResult() => throw UnimplementedError('parseTaskResult is not implemented');
 
@@ -100,10 +106,6 @@ abstract class BuildTestTask {
       throw Exception('Both build and test should not be passed. Pass only one.');
     }
 
-    if (buildOnly && applicationBinaryPath != null) {
-      throw Exception('Application binary path is only used for tests');
-    }
-
     if (!testOnly) {
       await build();
     }

dev/devicelab/lib/tasks/gallery.dart

@@ -212,6 +212,16 @@ class GalleryTransitionBuildTest extends BuildTestTask {
 
   final String testOutputDirectory = Platform.environment['FLUTTER_TEST_OUTPUTS_DIR'] ?? '${galleryDirectory.path}/build';
 
+  @override
+  void copyArtifacts() {
+    if(applicationBinaryPath != null) {
+      copy(
+        file('${galleryDirectory.path}/build/app/outputs/flutter-apk/app-profile.apk'),
+        Directory(applicationBinaryPath!),
+      );
+    }
+  }
+
   @override
   List<String> getBuildArgs(DeviceOperatingSystem deviceOperatingSystem) {
     return <String>[
@@ -310,7 +320,7 @@ class GalleryTransitionBuildTest extends BuildTestTask {
   @override
   String getApplicationBinaryPath() {
     if (applicationBinaryPath != null) {
-      return applicationBinaryPath!;
+      return '${applicationBinaryPath!}/app-profile.apk';
     }
 
     return 'build/app/outputs/flutter-apk/app-profile.apk';

dev/devicelab/test/tasks/build_test_task_test.dart

@@ -78,13 +78,13 @@ void main() {
     expect(result.message, 'Task failed: Exception: Both build and test should not be passed. Pass only one.');
   });
 
-  test('throws exception when build and application binary arg are given', () async {
+  test('copies artifacts when build and application binary arg are given', () async {
     final TaskResult result = await runTask(
       'smoke_test_build_test',
-      taskArgs: <String>['--build', '--application-binary-path=test.apk'],
+      taskArgs: <String>['--build', '--application-binary-path=test'],
       deviceId: 'FAKE_SUCCESS',
       isolateParams: isolateParams,
     );
-    expect(result.message, 'Task failed: Exception: Application binary path is only used for tests');
+    expect(result.message, 'No tests run');
   });
 }