Use LLDB as the default debugging method for iOS 17+ and Xcode 26+ (flutter#173443)

This PR introduces a new feature flag called `lldb-debugging`, which is
turned on by default. When this feature is turned on, if deploying to a
physical iOS 17+ device with Xcode 26+, it will use a mixture of
`devicectl` and `lldb` to install, launch, and debug the app.

If LLDB fails, it will fallback to use Xcode automation. If LLDB times
out, it will warn the user they may want to disable it. If LLDB is
disabled, it will use Xcode automation.

This PR also adds analytics to track what deployment method is used and
if it's successful.

Part 2 and 3 of flutter#173416.

Fixes flutter#144218. Fixes
flutter#133465.

## Pre-launch Checklist

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there for submitting PRs.
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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.

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Author: vashworth

.ci.yaml

@@ -5481,6 +5481,16 @@ targets:
         ["devicelab", "hostonly", "mac"]
       task_name: hot_mode_dev_cycle_ios_simulator
 
+  - name: Mac_ios hot_mode_dev_cycle_ios_xcode_debug
+    recipe: devicelab/devicelab_drone
+    bringup: true
+    presubmit: false
+    timeout: 60
+    properties:
+      tags: >
+        ["devicelab", "ios", "mac"]
+      task_name: hot_mode_dev_cycle_ios_xcode_debug
+
   - name: Mac_ios fullscreen_textfield_perf_ios__e2e_summary
     recipe: devicelab/devicelab_drone
     presubmit: false

TESTOWNERS

@@ -267,6 +267,7 @@
 /dev/devicelab/bin/tasks/hello_world_macos__compile.dart @cbracken @flutter/desktop
 /dev/devicelab/bin/tasks/hello_world_win_desktop__compile.dart @yaakovschectman @flutter/desktop
 /dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios_simulator.dart @louisehsu @flutter/tool
+/dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios_xcode_debug.dart @vashworth @flutter/tool
 /dev/devicelab/bin/tasks/hot_mode_dev_cycle_macos_target__benchmark.dart @cbracken @flutter/tool
 /dev/devicelab/bin/tasks/hot_mode_dev_cycle_win_target__benchmark.dart @cbracken @flutter/desktop
 /dev/devicelab/bin/tasks/integration_ui_test_test_macos.dart @cbracken @flutter/desktop

dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios_xcode_debug.dart

@@ -0,0 +1,45 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_devicelab/framework/devices.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/framework/task_result.dart';
+import 'package:flutter_devicelab/framework/utils.dart';
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:path/path.dart' as path;
+
+/// This is a test to validate that Xcode debugging still works now that LLDB is the default.
+Future<void> main() async {
+  await task(() async {
+    deviceOperatingSystem = DeviceOperatingSystem.ios;
+    try {
+      await disableLLDBDebugging();
+      // This isn't actually a benchmark test, so do not use the returned `benchmarkScoreKeys` result.
+      await createHotModeTest()();
+      return TaskResult.success(null);
+    } finally {
+      await enableLLDBDebugging();
+    }
+  });
+}
+
+Future<void> disableLLDBDebugging() async {
+  final int configResult = await exec(path.join(flutterDirectory.path, 'bin', 'flutter'), <String>[
+    'config',
+    '--no-enable-lldb-debugging',
+  ]);
+  if (configResult != 0) {
+    print('Failed to disable configuration, tasks may not run.');
+  }
+}
+
+Future<void> enableLLDBDebugging() async {
+  final int configResult = await exec(path.join(flutterDirectory.path, 'bin', 'flutter'), <String>[
+    'config',
+    '--enable-lldb-debugging',
+  ], canFail: true);
+  if (configResult != 0) {
+    print('Failed to enable configuration.');
+  }
+}

packages/flutter_tools/lib/src/device.dart

@@ -1181,7 +1181,6 @@ class DebuggingOptions {
     String? route,
     Map<String, Object?> platformArgs, {
     DeviceConnectionInterface interfaceType = DeviceConnectionInterface.attached,
-    bool isCoreDevice = false,
   }) {
     return <String>[
       if (enableDartProfiling) '--enable-dart-profiling',
@@ -1195,13 +1194,7 @@ class DebuggingOptions {
       if (environmentType == EnvironmentType.simulator && dartFlags.isNotEmpty)
         '--dart-flags=$dartFlags',
       if (useTestFonts) '--use-test-fonts',
-      // Core Devices (iOS 17 devices) are debugged through Xcode so don't
-      // include these flags, which are used to check if the app was launched
-      // via Flutter CLI and `ios-deploy`.
-      if (debuggingEnabled && !isCoreDevice) ...<String>[
-        '--enable-checked-mode',
-        '--verify-entry-points',
-      ],
+      if (debuggingEnabled) ...<String>['--enable-checked-mode', '--verify-entry-points'],
       if (enableSoftwareRendering) '--enable-software-rendering',
       if (traceSystrace) '--trace-systrace',
       if (traceToFile != null) '--trace-to-file="$traceToFile"',

packages/flutter_tools/lib/src/features.dart

@@ -67,6 +67,9 @@ abstract class FeatureFlags {
   /// Whether desktop windowing is enabled.
   bool get isWindowingEnabled;
 
+  /// Whether physical iOS devices are debugging with LLDB.
+  bool get isLLDBDebuggingEnabled;
+
   /// Whether a particular feature is enabled for the current channel.
   ///
   /// Prefer using one of the specific getters above instead of this API.
@@ -87,6 +90,7 @@ abstract class FeatureFlags {
     swiftPackageManager,
     omitLegacyVersionFile,
     windowingFeature,
+    lldbDebugging,
   ];
 
   /// All current Flutter feature flags that can be configured.
@@ -218,6 +222,23 @@ const windowingFeature = Feature(
   master: FeatureChannelSetting(available: true),
 );
 
+/// Enable LLDB debugging for physical iOS devices. When LLDB debugging is off,
+/// Xcode debugging is used instead.
+///
+/// Requires iOS 17+ and Xcode 26+. If those requirements are not met, the previous
+/// default debugging method is used instead.
+const lldbDebugging = Feature(
+  name: 'support for debugging with LLDB for physical iOS devices',
+  extraHelpText:
+      'If LLDB debugging is off, Xcode debugging is used instead. '
+      'Only available for iOS 17 or newer devices. Requires Xcode 26 or greater.',
+  configSetting: 'enable-lldb-debugging',
+  environmentOverride: 'FLUTTER_LLDB_DEBUGGING',
+  master: FeatureChannelSetting(available: true, enabledByDefault: true),
+  beta: FeatureChannelSetting(available: true, enabledByDefault: true),
+  stable: FeatureChannelSetting(available: true, enabledByDefault: true),
+);
+
 /// A [Feature] is a process for conditionally enabling tool features.
 ///
 /// All settings are optional, and if not provided will generally default to

packages/flutter_tools/lib/src/flutter_features.dart

@@ -57,6 +57,9 @@ mixin FlutterFeatureFlagsIsEnabled implements FeatureFlags {
 
   @override
   bool get isWindowingEnabled => isEnabled(windowingFeature);
+
+  @override
+  bool get isLLDBDebuggingEnabled => isEnabled(lldbDebugging);
 }
 
 interface class FlutterFeatureFlags extends FeatureFlags with FlutterFeatureFlagsIsEnabled {

packages/flutter_tools/lib/src/ios/core_devices.dart

@@ -66,7 +66,7 @@ class IOSCoreDeviceLauncher {
     }
 
     // Launch app to device
-    final IOSCoreDeviceLaunchResult? launchResult = await _coreDeviceControl.launchAppInternal(
+    final IOSCoreDeviceLaunchResult? launchResult = await _coreDeviceControl.launchApp(
       deviceId: deviceId,
       bundleId: bundleId,
       launchArguments: launchArguments,
@@ -99,7 +99,7 @@ class IOSCoreDeviceLauncher {
     }
 
     // Launch app on device, but start it stopped so it will wait until the debugger is attached before starting.
-    final IOSCoreDeviceLaunchResult? launchResult = await _coreDeviceControl.launchAppInternal(
+    final IOSCoreDeviceLaunchResult? launchResult = await _coreDeviceControl.launchApp(
       deviceId: deviceId,
       bundleId: bundleId,
       launchArguments: launchArguments,
@@ -532,66 +532,11 @@ class IOSCoreDeviceControl {
     }
   }
 
-  Future<bool> launchApp({
-    required String deviceId,
-    required String bundleId,
-    List<String> launchArguments = const <String>[],
-  }) async {
-    if (!_xcode.isDevicectlInstalled) {
-      _logger.printError('devicectl is not installed.');
-      return false;
-    }
-
-    final Directory tempDirectory = _fileSystem.systemTempDirectory.createTempSync('core_devices.');
-    final File output = tempDirectory.childFile('launch_results.json');
-    output.createSync();
-
-    final command = <String>[
-      ..._xcode.xcrunCommand(),
-      'devicectl',
-      'device',
-      'process',
-      'launch',
-      '--device',
-      deviceId,
-      bundleId,
-      if (launchArguments.isNotEmpty) ...launchArguments,
-      '--json-output',
-      output.path,
-    ];
-
-    try {
-      await _processUtils.run(command, throwOnError: true);
-      final String stringOutput = output.readAsStringSync();
-
-      try {
-        final Object? decodeResult = (json.decode(stringOutput) as Map<String, Object?>)['info'];
-        if (decodeResult is Map<String, Object?> && decodeResult['outcome'] == 'success') {
-          return true;
-        }
-        _logger.printError('devicectl returned unexpected JSON response: $stringOutput');
-        return false;
-      } on FormatException {
-        // We failed to parse the devicectl output, or it returned junk.
-        _logger.printError('devicectl returned non-JSON response: $stringOutput');
-        return false;
-      }
-    } on ProcessException catch (err) {
-      _logger.printError('Error executing devicectl: $err');
-      return false;
-    } finally {
-      tempDirectory.deleteSync(recursive: true);
-    }
-  }
-
   /// Launches the app on the device.
   ///
   /// If [startStopped] is true, the app will be launched and paused, waiting
   /// for a debugger to attach.
-  // TODO(vashworth): Rename this method to launchApp and replace old version.
-  // See https://github.com/flutter/flutter/issues/173416.
-  @visibleForTesting
-  Future<IOSCoreDeviceLaunchResult?> launchAppInternal({
+  Future<IOSCoreDeviceLaunchResult?> launchApp({
     required String deviceId,
     required String bundleId,
     List<String> launchArguments = const <String>[],