Kill interactive script job xcdevice observe processes on tool/daemon shutdown (#157646)

To convince `xcdevice observe` to redirect to stdout it's being launched in an interactive shell `/usr/bin/script -t 0 /dev/null /usr/bin/arch -arm64e xcrun xcdevice observe --usb`
https://github.com/flutter/flutter/blob/1cc8a07ace699de12fcd31ac9e8fcfa14f1017e2/packages/flutter_tools/lib/src/macos/xcdevice.dart#L261-L263

When the `flutter` command exits, the interactive script process is terminated, but not its jobs `xcdevice observe --usb`.

Instead of `-9` sigterm killing the interactive script, send it a [`SIGHUP`](https://linux.die.net/Bash-Beginners-Guide/sect_12_01.html#sect_12_01_01_02) (signal hangup) during `XCDevice.dispose()`, which will exit its processes.  Add a shutdown hook to ensure `dispose` is run when the process exits.

Fixes flutter/flutter#73859

Author: jmagman

packages/flutter_tools/lib/src/base/io.dart

@@ -174,6 +174,7 @@ class ProcessSignal {
   const ProcessSignal(this._delegate, {@visibleForTesting Platform platform = const LocalPlatform()})
     : _platform = platform;
 
+  static const ProcessSignal sighup = PosixProcessSignal(io.ProcessSignal.sighup);
   static const ProcessSignal sigwinch = PosixProcessSignal(io.ProcessSignal.sigwinch);
   static const ProcessSignal sigterm = PosixProcessSignal(io.ProcessSignal.sigterm);
   static const ProcessSignal sigusr1 = PosixProcessSignal(io.ProcessSignal.sigusr1);

packages/flutter_tools/lib/src/context_runner.dart

@@ -376,6 +376,7 @@ Future<T> runInContext<T>(
         ),
         fileSystem: globals.fs,
         analytics: globals.analytics,
+        shutdownHooks: globals.shutdownHooks,
       ),
       XcodeProjectInterpreter: () => XcodeProjectInterpreter(
         logger: globals.logger,

packages/flutter_tools/lib/src/macos/xcdevice.dart

@@ -71,6 +71,7 @@ class XCDevice {
     required IProxy iproxy,
     required FileSystem fileSystem,
     required Analytics analytics,
+    required ShutdownHooks shutdownHooks,
     @visibleForTesting
     IOSCoreDeviceControl? coreDeviceControl,
     XcodeDebug? xcodeDebug,
@@ -105,12 +106,13 @@ class XCDevice {
       _xcode = xcode,
       _analytics = analytics {
 
+    shutdownHooks.addShutdownHook(dispose);
+
     _setupDeviceIdentifierByEventStream();
   }
 
   void dispose() {
-    _usbDeviceObserveProcess?.kill();
-    _wifiDeviceObserveProcess?.kill();
+    _stopObservingTetheredIOSDevices();
     _usbDeviceWaitProcess?.kill();
     _wifiDeviceWaitProcess?.kill();
   }
@@ -227,13 +229,13 @@ class XCDevice {
       final Future<void> usbProcessExited = _usbDeviceObserveProcess!.exitCode.then((int status) {
         _logger.printTrace('xcdevice observe --usb exited with code $exitCode');
         // Kill other process in case only one was killed.
-        _wifiDeviceObserveProcess?.kill();
+        _stopObservingTetheredIOSDevices();
       });
 
       final Future<void> wifiProcessExited = _wifiDeviceObserveProcess!.exitCode.then((int status) {
         _logger.printTrace('xcdevice observe --wifi exited with code $exitCode');
         // Kill other process in case only one was killed.
-        _usbDeviceObserveProcess?.kill();
+        _stopObservingTetheredIOSDevices();
       });
 
       unawaited(Future.wait(<Future<void>>[
@@ -332,8 +334,15 @@ class XCDevice {
   }
 
   void _stopObservingTetheredIOSDevices() {
-    _usbDeviceObserveProcess?.kill();
-    _wifiDeviceObserveProcess?.kill();
+    // xcdevice observe is running in an interactive shell.
+    // Signal script child jobs to exit and exit the shell.
+    // See https://linux.die.net/Bash-Beginners-Guide/sect_12_01.html#sect_12_01_01_02.
+    if (_usbDeviceObserveProcess != null) {
+      ProcessSignal.sighup.kill(_usbDeviceObserveProcess!);
+    }
+    if (_wifiDeviceObserveProcess != null) {
+      ProcessSignal.sighup.kill(_wifiDeviceObserveProcess!);
+    }
   }
 
   XCDeviceEventNotification? _processXCDeviceStdOut(

packages/flutter_tools/test/general.shard/macos/xcode_test.dart

@@ -9,6 +9,7 @@ import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/io.dart' show ProcessException;
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/base/process.dart';
 import 'package:flutter_tools/src/base/user_messages.dart';
 import 'package:flutter_tools/src/base/version.dart';
 import 'package:flutter_tools/src/build_info.dart';
@@ -539,6 +540,7 @@ void main() {
           coreDeviceControl: FakeIOSCoreDeviceControl(),
           xcodeDebug: FakeXcodeDebug(),
           analytics: const NoOpAnalytics(),
+          shutdownHooks: FakeShutdownHooks(),
         );
       });
 
@@ -553,6 +555,35 @@ void main() {
       });
     });
 
+    testWithoutContext('shutdown hooks disposes xcdevice observers', () async {
+      final ShutdownHooks shutdownHooks = ShutdownHooks();
+
+      final XCDevice xcdevice = XCDevice(
+        processManager: FakeProcessManager.any(),
+        logger: logger,
+        xcode: Xcode.test(processManager: FakeProcessManager.any()),
+        platform: FakePlatform(operatingSystem: 'macos'),
+        artifacts: Artifacts.test(),
+        cache: Cache.test(processManager: FakeProcessManager.any()),
+        iproxy: IProxy.test(logger: logger, processManager: FakeProcessManager.any()),
+        fileSystem: MemoryFileSystem.test(),
+        coreDeviceControl: FakeIOSCoreDeviceControl(),
+        xcodeDebug: FakeXcodeDebug(),
+        analytics: const NoOpAnalytics(),
+        shutdownHooks: shutdownHooks,
+      );
+
+      expect(shutdownHooks.registeredHooks, hasLength(1));
+      final Completer<void> doneCompleter = Completer<void>();
+      xcdevice.observedDeviceEvents()!.listen(null, onDone: () {
+        doneCompleter.complete();
+      });
+      await doneCompleter.future;
+      xcdevice.dispose();
+      expect(logger.traceText, contains('xcdevice observe --usb exited with code 0'));
+      expect(logger.traceText, contains('xcdevice observe --wifi exited with code 0'));
+    });
+
     group('xcdevice', () {
       late XCDevice xcdevice;
       late Xcode xcode;
@@ -580,6 +611,7 @@ void main() {
           coreDeviceControl: coreDeviceControl,
           xcodeDebug: FakeXcodeDebug(),
           analytics: fakeAnalytics,
+          shutdownHooks: FakeShutdownHooks(),
         );
       });
 
@@ -1688,6 +1720,11 @@ class FakeXcodeProjectInterpreter extends Fake implements XcodeProjectInterprete
 
 class FakeXcodeDebug extends Fake implements XcodeDebug {}
 
+class FakeShutdownHooks extends Fake implements ShutdownHooks {
+  @override
+  void addShutdownHook(ShutdownHook shutdownHook) {}
+}
+
 class FakeIOSCoreDeviceControl extends Fake implements IOSCoreDeviceControl {
 
   List<FakeIOSCoreDevice> devices = <FakeIOSCoreDevice>[];