Check for devicectl launch logs from std and file (flutter#178167)

vashworth · IvoneDjaja · commit c2606830f8df · 2025-11-22T08:44:55.000+08:00
For some reason in different editors, `devicectl` does not appear to stream its logs to `stdout`. Usually after calling `xcrun devicectl device process launch --console ...`, the `stdout` stream will receive a log of `'Waiting for the application to terminate'`. To workaround this, we use the `--log-ouput` flag with the `devicectl` command, which tells `devicectl` to write its logs to a file. We then periodically read the file looking for the `'Waiting for the application to terminate'` log. Fixes b/454953393. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
diff --git a/packages/flutter_tools/lib/src/ios/core_devices.dart b/packages/flutter_tools/lib/src/ios/core_devices.dart
@@ -335,6 +335,8 @@ class IOSCoreDeviceControl {
     'Failed to execute code (error: EXC_BAD_ACCESS, debugger assist: not detected)',
   ];
 
+  static const kCoreDeviceLaunchCompleteLog = 'Waiting for the application to terminate';
+
   /// Executes `devicectl` command to get list of devices. The command will
   /// likely complete before [timeout] is reached. If [timeout] is reached,
   /// the command will be stopped as a failure.
@@ -650,13 +652,21 @@ class IOSCoreDeviceControl {
   ///
   /// If [attachToConsole] is true, attaches the application to the console and waits for the app
   /// to terminate.
+  ///
+  /// When [jsonOutputFile] is provided, devicectl will write a JSON file with the command results
+  /// after the command has completed. This will not have the results when using [attachToConsole]
+  /// until the process has exited.
+  ///
+  /// When [logOutputFile] is provided, devicectl will write all logging otherwise passed to
+  /// stdout/stderr to the file. It will also continue to stream the logs to stdout/stderr.
   List<String> _launchAppCommand({
     required String deviceId,
     required String bundleId,
     List<String> launchArguments = const <String>[],
     bool startStopped = false,
     bool attachToConsole = false,
-    File? outputFile,
+    File? jsonOutputFile,
+    File? logOutputFile,
   }) {
     return <String>[
       ..._xcode.xcrunCommand(),
@@ -674,7 +684,8 @@ class IOSCoreDeviceControl {
         // See https://github.com/llvm/llvm-project/blob/19b43e1757b4fd3d0f188cf8a08e9febb0dbec2f/lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp#L1227-L1233
         '{"OS_ACTIVITY_DT_MODE": "enable"}',
       ],
-      if (outputFile != null) ...<String>['--json-output', outputFile.path],
+      if (jsonOutputFile != null) ...<String>['--json-output', jsonOutputFile.path],
+      if (logOutputFile != null) ...<String>['--log-output', logOutputFile.path],
       bundleId,
       if (launchArguments.isNotEmpty) ...launchArguments,
     ];
@@ -703,7 +714,7 @@ class IOSCoreDeviceControl {
       deviceId: deviceId,
       launchArguments: launchArguments,
       startStopped: startStopped,
-      outputFile: output,
+      jsonOutputFile: output,
     );
 
     try {
@@ -754,15 +765,19 @@ class IOSCoreDeviceControl {
       return false;
     }
 
+    final Directory tempDirectory = _fileSystem.systemTempDirectory.createTempSync('core_devices.');
+    final File output = tempDirectory.childFile('launch_log.txt')..createSync();
+
     final launchCompleter = Completer<bool>();
     final List<String> command = _launchAppCommand(
       bundleId: bundleId,
       deviceId: deviceId,
       launchArguments: launchArguments,
       startStopped: startStopped,
       attachToConsole: true,
+      logOutputFile: output,
     );
-
+    Timer? timer;
     try {
       final Process launchProcess = await _processUtils.start(command);
       coreDeviceLogForwarder.launchProcess = launchProcess;
@@ -776,7 +791,7 @@ class IOSCoreDeviceControl {
               _logger.printTrace(line);
             }
 
-            if (line.contains('Waiting for the application to terminate')) {
+            if (!launchCompleter.isCompleted && line.contains(kCoreDeviceLaunchCompleteLog)) {
               launchCompleter.complete(true);
             }
           });
@@ -805,10 +820,27 @@ class IOSCoreDeviceControl {
               }
             }),
       );
-      return launchCompleter.future;
+
+      // Sometimes devicectl launch logs don't stream to stdout.
+      // As a workaround, we also use the log output file to check if it has finished launching.
+      timer = Timer.periodic(const Duration(seconds: 1), (timer) async {
+        if (await output.exists()) {
+          final String contents = await output.readAsString();
+          if (!launchCompleter.isCompleted && contents.contains(kCoreDeviceLaunchCompleteLog)) {
+            launchCompleter.complete(true);
+          }
+        }
+      });
+
+      // Do not return the launchCompleter.future directly, otherwise, the timer will be canceled
+      // prematurely.
+      final bool status = await launchCompleter.future;
+      return status;
     } on ProcessException catch (err) {
       _logger.printTrace('Error executing devicectl: $err');
       return false;
+    } finally {
+      timer?.cancel();
     }
   }
 
diff --git a/packages/flutter_tools/test/general.shard/ios/core_devices_test.dart b/packages/flutter_tools/test/general.shard/ios/core_devices_test.dart
@@ -1791,6 +1791,8 @@ invalid JSON
               '--console',
               '--environment-variables',
               '{"OS_ACTIVITY_DT_MODE": "enable"}',
+              '--log-output',
+              '/.tmp_rand0/core_devices.rand0/launch_log.txt',
               bundleId,
             ],
             stdout: '''
@@ -1830,6 +1832,8 @@ Waiting for the application to terminate...
               '--console',
               '--environment-variables',
               '{"OS_ACTIVITY_DT_MODE": "enable"}',
+              '--log-output',
+              '/.tmp_rand0/core_devices.rand0/launch_log.txt',
               bundleId,
               '--arg1',
               '--arg2',
@@ -1872,6 +1876,8 @@ Waiting for the application to terminate...
               '--console',
               '--environment-variables',
               '{"OS_ACTIVITY_DT_MODE": "enable"}',
+              '--log-output',
+              '/.tmp_rand0/core_devices.rand0/launch_log.txt',
               bundleId,
             ],
             stdout: '''
@@ -1939,6 +1945,8 @@ Waiting for the application to terminate...
               '--console',
               '--environment-variables',
               '{"OS_ACTIVITY_DT_MODE": "enable"}',
+              '--log-output',
+              '/.tmp_rand0/core_devices.rand0/launch_log.txt',
               bundleId,
             ],
             exitCode: 1,
@@ -1961,6 +1969,54 @@ ERROR: The operation couldn?t be completed. (OSStatus error -10814.) (NSOSStatus
         expect(logger.errorText, isEmpty);
         expect(result, isFalse);
       });
+
+      testWithoutContext('Successful launch with output in log file', () async {
+        final Completer<void> launchCompleter = Completer();
+        fakeProcessManager.addCommand(
+          FakeCommand(
+            command: const <String>[
+              'xcrun',
+              'devicectl',
+              'device',
+              'process',
+              'launch',
+              '--device',
+              deviceId,
+              '--start-stopped',
+              '--console',
+              '--environment-variables',
+              '{"OS_ACTIVITY_DT_MODE": "enable"}',
+              '--log-output',
+              '/.tmp_rand0/core_devices.rand0/launch_log.txt',
+              bundleId,
+            ],
+            onRun: (command) {
+              fileSystem.file('/.tmp_rand0/core_devices.rand0/launch_log.txt')
+                ..createSync(recursive: true)
+                ..writeAsStringSync('''
+10:04:12  Acquired tunnel connection to device.
+10:04:12  Enabling developer disk image services.
+10:04:12  Acquired usage assertion.
+Launched application with com.example.my_app bundle identifier.
+Waiting for the application to terminate...
+''');
+            },
+            completer: launchCompleter,
+          ),
+        );
+
+        final bool result = await deviceControl.launchAppAndStreamLogs(
+          deviceId: deviceId,
+          bundleId: bundleId,
+          coreDeviceLogForwarder: FakeIOSCoreDeviceLogForwarder(),
+          startStopped: true,
+        );
+        launchCompleter.complete();
+
+        expect(fakeProcessManager, hasNoRemainingExpectations);
+        expect(logger.errorText, isEmpty);
+        expect(result, isTrue);
+      });
     });
 
     group('terminate app', () {
