Fix flaky failure related to core_device_list.json not being found (#158946)

It's possible that the tool can be in the process of shutting down,
which could result in the temp directory being deleted after the
shutdown hooks run before we check if `output` exists. If this happens,
we shouldn't crash but just carry on as if no devices were found as the
tool will exit on its own.

Fixes https://github.com/flutter/flutter/issues/141892

---------

Co-authored-by: Andrew Kolos <andrewrkolos@gmail.com>

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

@@ -198,6 +198,11 @@ class LocalFileSystem extends local_fs.LocalFileSystem {
 
   final ShutdownHooks shutdownHooks;
 
+  // Indicates that `dispose()` has been invoked or some shutdown hook has executed,
+  // resulting in the underlying temporary directory being cleaned up.
+  bool get disposed => _disposed;
+  bool _disposed = false;
+
   Future<void> dispose() async {
     _tryToDeleteTemp();
     for (final MapEntry<ProcessSignal, Object> signalToken in _signalTokens.entries) {
@@ -210,6 +215,7 @@ class LocalFileSystem extends local_fs.LocalFileSystem {
   final List<ProcessSignal> _fatalSignals;
 
   void _tryToDeleteTemp() {
+    _disposed = true;
     try {
       if (_systemTemp?.existsSync() ?? false) {
         _systemTemp?.deleteSync(recursive: true);

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

@@ -79,14 +79,24 @@ class IOSCoreDeviceControl {
 
     try {
       final RunResult result = await _processUtils.run(command, throwOnError: true);
+      final bool isToolPossiblyShutdown = _fileSystem is LocalFileSystem && _fileSystem.disposed;
 
-      if (!output.existsSync()) {
+      // It's possible that the tool is in the process of shutting down, which
+      // could result in the temp directory being deleted after the shutdown hooks run
+      // before we check if `output` exists. If this happens, we shouldn't crash
+      // but just carry on as if no devices were found as the tool will exit on
+      // its own.
+      //
+      // See https://github.com/flutter/flutter/issues/141892 for details.
+      if (!isToolPossiblyShutdown && !output.existsSync()) {
         _logger.printError('After running the command ${command.join(' ')} the file');
         _logger.printError('${output.path} was expected to exist, but it did not.');
         _logger.printError('The process exited with code ${result.exitCode} and');
         _logger.printError('Stdout:\n\n${result.stdout.trim()}\n');
         _logger.printError('Stderr:\n\n${result.stderr.trim()}');
         throw StateError('Expected the file ${output.path} to exist but it did not');
+      } else if (isToolPossiblyShutdown) {
+        return <Object?>[];
       }
       final String stringOutput = output.readAsStringSync();
       _logger.printTrace(stringOutput);

packages/flutter_tools/test/general.shard/ios/core_devices_test.dart

@@ -7,6 +7,7 @@ import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/base/signals.dart';
 import 'package:flutter_tools/src/base/version.dart';
 import 'package:flutter_tools/src/ios/core_devices.dart';
 import 'package:flutter_tools/src/ios/xcodeproj.dart';
@@ -15,6 +16,15 @@ import 'package:flutter_tools/src/macos/xcode.dart';
 import '../../src/common.dart';
 import '../../src/fake_process_manager.dart';
 
+class LocalFileSystemFake extends LocalFileSystem {
+  LocalFileSystemFake.test({required super.signals}) : super.test();
+
+  MemoryFileSystem memoryFileSystem = MemoryFileSystem.test();
+
+  @override
+  Directory get systemTempDirectory => memoryFileSystem.systemTempDirectory;
+}
+
 void main() {
   late MemoryFileSystem fileSystem;
 
@@ -1400,6 +1410,53 @@ invalid JSON
         expect(fakeProcessManager, hasNoRemainingExpectations);
       });
 
+      testWithoutContext('Handles file system disposal', () async {
+        final LocalFileSystem localFs = LocalFileSystemFake.test(signals: Signals.test());
+        deviceControl = IOSCoreDeviceControl(
+          logger: logger,
+          processManager: fakeProcessManager,
+          xcode: xcode,
+          fileSystem: localFs,
+        );
+        final Directory tempDir = localFs.systemTempDirectory
+            .childDirectory('core_devices.rand0');
+        final File tempFile = tempDir.childFile('core_device_list.json');
+        final List<String> args = <String>[
+          'xcrun',
+          'devicectl',
+          'list',
+          'devices',
+          '--timeout',
+          '5',
+          '--json-output',
+          tempFile.path,
+        ];
+        fakeProcessManager.addCommand(FakeCommand(
+          command: args,
+          onRun: (_) {
+            // Simulate that the tool started shutting down and disposed the
+            // file system, causing the temp directory to be deleted before
+            // this program invocation returns a result.
+            localFs.dispose();
+            expect(localFs.disposed, true);
+          },
+        ));
+
+        final List<IOSCoreDevice> coreDevices = await deviceControl.getCoreDevices();
+        expect(coreDevices, isEmpty);
+        expect(
+          logger.errorText,
+          isNot(
+            contains('After running the command xcrun devicectl list devices '
+              '--timeout 5 --json-output ${tempFile.path} the file\n'
+              '${tempFile.path} was expected to exist, but it did not',
+            ),
+          ),
+        );
+        expect(fakeProcessManager, hasNoRemainingExpectations);
+      });
+
+
       testWithoutContext('No devices', () async {
         const String deviceControlOutput = '''
 {