[flutter_tools] Delete system temp entries on fatal signals (#55513)

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

@@ -3,13 +3,19 @@
 // found in the LICENSE file.
 
 import 'package:file/file.dart';
+import 'package:file/local.dart' as local_fs;
 import 'package:meta/meta.dart';
 
 import 'common.dart' show throwToolExit;
+import 'io.dart';
 import 'platform.dart';
+import 'process.dart';
+import 'signals.dart';
 
+// package:file/local.dart must not be exported. This exposes LocalFileSystem,
+// which we override to ensure that temporary directories are cleaned up when
+// the tool is killed by a signal.
 export 'package:file/file.dart';
-export 'package:file/local.dart';
 
 /// Exception indicating that a file that was expected to exist was not found.
 class FileNotFoundException implements IOException {
@@ -136,11 +142,94 @@ class FileSystemUtils {
   /// Return the absolute path of the user's home directory
   String get homeDirPath {
     String path = _platform.isWindows
-        ? _platform.environment['USERPROFILE']
-        : _platform.environment['HOME'];
+      ? _platform.environment['USERPROFILE']
+      : _platform.environment['HOME'];
     if (path != null) {
       path = _fileSystem.path.absolute(path);
     }
     return path;
   }
 }
+
+/// This class extends [local_fs.LocalFileSystem] in order to clean up
+/// directories and files that the tool creates under the system temporary
+/// directory when the tool exits either normally or when killed by a signal.
+class LocalFileSystem extends local_fs.LocalFileSystem {
+  LocalFileSystem._(Signals signals, List<ProcessSignal> fatalSignals) :
+    _signals = signals, _fatalSignals = fatalSignals;
+
+  @visibleForTesting
+  LocalFileSystem.test({
+    @required Signals signals,
+    List<ProcessSignal> fatalSignals = Signals.defaultExitSignals,
+  }) : this._(signals, fatalSignals);
+
+  // Unless we're in a test of this class's signal hanlding features, we must
+  // have only one instance created with the singleton LocalSignals instance
+  // and the catchable signals it considers to be fatal.
+  static LocalFileSystem _instance;
+  static LocalFileSystem get instance => _instance ??= LocalFileSystem._(
+    LocalSignals.instance,
+    Signals.defaultExitSignals,
+  );
+
+  Directory _systemTemp;
+  final Map<ProcessSignal, Object> _signalTokens = <ProcessSignal, Object>{};
+
+  @visibleForTesting
+  static Future<void> dispose() => LocalFileSystem.instance?._dispose();
+
+  Future<void> _dispose() async {
+    _tryToDeleteTemp();
+    for (final MapEntry<ProcessSignal, Object> signalToken in _signalTokens.entries) {
+      await _signals.removeHandler(signalToken.key, signalToken.value);
+    }
+    _signalTokens.clear();
+  }
+
+  final Signals _signals;
+  final List<ProcessSignal> _fatalSignals;
+
+  void _tryToDeleteTemp() {
+    try {
+      if (_systemTemp?.existsSync() ?? false) {
+        _systemTemp.deleteSync(recursive: true);
+      }
+    } on FileSystemException {
+      // ignore.
+    }
+    _systemTemp = null;
+  }
+
+  // This getter returns a fresh entry under /tmp, like
+  // /tmp/flutter_tools.abcxyz, then the rest of the tool creates /tmp entries
+  // under that, like /tmp/flutter_tools.abcxyz/flutter_build_stuff.123456.
+  // Right before exiting because of a signal or otherwise, we delete
+  // /tmp/flutter_tools.abcxyz, not the whole of /tmp.
+  @override
+  Directory get systemTempDirectory {
+    if (_systemTemp == null) {
+      _systemTemp = super.systemTempDirectory.createTempSync(
+        'flutter_tools.',
+      )..createSync(recursive: true);
+      // Make sure that the temporary directory is cleaned up if the tool is
+      // killed by a signal.
+      for (final ProcessSignal signal in _fatalSignals) {
+        final Object token = _signals.addHandler(
+          signal,
+          (ProcessSignal _) {
+            _tryToDeleteTemp();
+          },
+        );
+        _signalTokens[signal] = token;
+      }
+      // Make sure that the temporary directory is cleaned up when the tool
+      // exits normally.
+      shutdownHooks?.addShutdownHook(
+        _tryToDeleteTemp,
+        ShutdownStage.CLEANUP,
+      );
+    }
+    return _systemTemp;
+  }
+}

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

@@ -90,6 +90,7 @@ export 'dart:io'
         ProcessStartMode,
         // RandomAccessFile  NO! Use `file_system.dart`
         ServerSocket,
+        SignalException,
         // stderr,           NO! Use `io.dart`
         // stdin,            NO! Use `io.dart`
         Stdin,

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

@@ -4,30 +4,27 @@
 
 import 'dart:async';
 
+import 'package:meta/meta.dart';
+
 import 'async_guard.dart';
-import 'context.dart';
 import 'io.dart';
 
 typedef SignalHandler = FutureOr<void> Function(ProcessSignal signal);
 
-Signals get signals => Signals.instance;
-
-// The default list of signals that should cause the process to exit.
-const List<ProcessSignal> _defaultExitSignals = <ProcessSignal>[
-  ProcessSignal.SIGTERM,
-  ProcessSignal.SIGINT,
-  ProcessSignal.SIGKILL,
-];
-
 /// A class that manages signal handlers
 ///
 /// Signal handlers are run in the order that they were added.
 abstract class Signals {
-  factory Signals({
-    List<ProcessSignal> exitSignals = _defaultExitSignals,
-  }) => _DefaultSignals._(exitSignals);
+  @visibleForTesting
+  factory Signals.test({
+    List<ProcessSignal> exitSignals = defaultExitSignals,
+  }) => LocalSignals._(exitSignals);
 
-  static Signals get instance => context.get<Signals>();
+  // The default list of signals that should cause the process to exit.
+  static const List<ProcessSignal> defaultExitSignals = <ProcessSignal>[
+    ProcessSignal.SIGTERM,
+    ProcessSignal.SIGINT,
+  ];
 
   /// Adds a signal handler to run on receipt of signal.
   ///
@@ -48,8 +45,17 @@ abstract class Signals {
   Stream<Object> get errors;
 }
 
-class _DefaultSignals implements Signals {
-  _DefaultSignals._(this.exitSignals);
+/// A class that manages the real dart:io signal handlers.
+///
+/// We use a singleton instance of this class to ensure that all handlers for
+/// fatal signals run before this class calls exit().
+class LocalSignals implements Signals {
+  LocalSignals._(this.exitSignals);
+
+  static LocalSignals _instance;
+  static LocalSignals get instance => _instance ??= LocalSignals._(
+    Signals.defaultExitSignals,
+  );
 
   final List<ProcessSignal> exitSignals;
 
@@ -84,7 +90,13 @@ class _DefaultSignals implements Signals {
     // If we added the first one, then call signal.watch(), listen, and cache
     // the stream controller.
     if (_handlersList[signal].length == 1) {
-      _streamSubscriptions[signal] = signal.watch().listen(_handleSignal);
+      _streamSubscriptions[signal] = signal.watch().listen(
+        _handleSignal,
+        onError: (Object e) {
+          _handlersTable[signal].remove(token);
+          _handlersList[signal].remove(handler);
+        },
+      );
     }
     return token;
   }
@@ -99,7 +111,10 @@ class _DefaultSignals implements Signals {
     if (!_handlersTable[signal].containsKey(token)) {
       return false;
     }
-    final SignalHandler handler = _handlersTable[signal][token];
+    final SignalHandler handler = _handlersTable[signal].remove(token);
+    if (handler == null) {
+      return false;
+    }
     final bool removed = _handlersList[signal].remove(handler);
     if (!removed) {
       return false;

packages/flutter_tools/lib/src/commands/analyze_once.dart

@@ -103,41 +103,50 @@ class AnalyzeOnce extends AnalyzeBase {
       experiments: experiments,
     );
 
-    StreamSubscription<bool> subscription;
-    subscription = server.onAnalyzing.listen((bool isAnalyzing) {
-      if (!isAnalyzing) {
-        analysisCompleter.complete();
-        subscription?.cancel();
-        subscription = null;
-      }
-    });
-    server.onErrors.listen((FileAnalysisErrors fileErrors) {
-      // Record the issues found (but filter out to do comments).
-      errors.addAll(fileErrors.errors.where((AnalysisError error) => error.type != 'TODO'));
-    });
-
-    await server.start();
-    // Completing the future in the callback can't fail.
-    unawaited(server.onExit.then<void>((int exitCode) {
-      if (!analysisCompleter.isCompleted) {
-        analysisCompleter.completeError('analysis server exited: $exitCode');
-      }
-    }));
-
-    Cache.releaseLockEarly();
-
-    // collect results
-    final Stopwatch timer = Stopwatch()..start();
-    final String message = directories.length > 1
-        ? '${directories.length} ${directories.length == 1 ? 'directory' : 'directories'}'
-        : fileSystem.path.basename(directories.first);
-    final Status progress = argResults['preamble'] as bool
-        ? logger.startProgress('Analyzing $message...', timeout: timeoutConfiguration.slowOperation)
-        : null;
-
-    await analysisCompleter.future;
-    progress?.cancel();
-    timer.stop();
+    Stopwatch timer;
+    Status progress;
+    try {
+      StreamSubscription<bool> subscription;
+      subscription = server.onAnalyzing.listen((bool isAnalyzing) {
+        if (!isAnalyzing) {
+          analysisCompleter.complete();
+          subscription?.cancel();
+          subscription = null;
+        }
+      });
+      server.onErrors.listen((FileAnalysisErrors fileErrors) {
+        // Record the issues found (but filter out to do comments).
+        errors.addAll(fileErrors.errors.where((AnalysisError error) => error.type != 'TODO'));
+      });
+
+      await server.start();
+      // Completing the future in the callback can't fail.
+      unawaited(server.onExit.then<void>((int exitCode) {
+        if (!analysisCompleter.isCompleted) {
+          analysisCompleter.completeError('analysis server exited: $exitCode');
+        }
+      }));
+
+      Cache.releaseLockEarly();
+
+      // collect results
+      timer = Stopwatch()..start();
+      final String message = directories.length > 1
+          ? '${directories.length} ${directories.length == 1 ? 'directory' : 'directories'}'
+          : fileSystem.path.basename(directories.first);
+      progress = argResults['preamble'] as bool
+          ? logger.startProgress(
+            'Analyzing $message...',
+            timeout: timeoutConfiguration.slowOperation,
+          )
+          : null;
+
+      await analysisCompleter.future;
+    } finally {
+      await server.dispose();
+      progress?.cancel();
+      timer?.stop();
+    }
 
     // count missing dartdocs
     final int undocumentedMembers = errors.where((AnalysisError error) {

packages/flutter_tools/lib/src/context_runner.dart

@@ -17,7 +17,6 @@ import 'base/io.dart';
 import 'base/logger.dart';
 import 'base/os.dart';
 import 'base/process.dart';
-import 'base/signals.dart';
 import 'base/time.dart';
 import 'base/user_messages.dart';
 import 'build_system/build_system.dart';
@@ -182,7 +181,6 @@ Future<T> runInContext<T>(
         usage: globals.flutterUsage,
       ),
       ShutdownHooks: () => ShutdownHooks(logger: globals.logger),
-      Signals: () => Signals(),
       Stdio: () => Stdio(),
       SystemClock: () => const SystemClock(),
       TimeoutConfiguration: () => const TimeoutConfiguration(),

packages/flutter_tools/lib/src/globals.dart

@@ -17,6 +17,7 @@ import 'base/logger.dart';
 import 'base/net.dart';
 import 'base/os.dart';
 import 'base/platform.dart';
+import 'base/signals.dart';
 import 'base/template.dart';
 import 'base/terminal.dart';
 import 'base/user_messages.dart';
@@ -45,20 +46,22 @@ HttpClientFactory get httpClientFactory => context.get<HttpClientFactory>();
 Logger get logger => context.get<Logger>();
 OperatingSystemUtils get os => context.get<OperatingSystemUtils>();
 PersistentToolState get persistentToolState => PersistentToolState.instance;
+Signals get signals => context.get<Signals>() ?? LocalSignals.instance;
 Usage get flutterUsage => context.get<Usage>();
-FlutterProjectFactory get projectFactory => context.get<FlutterProjectFactory>() ?? FlutterProjectFactory(
-  logger: logger,
-  fileSystem: fs,
-);
 
-const FileSystem _kLocalFs = LocalFileSystem();
+FlutterProjectFactory get projectFactory {
+  return context.get<FlutterProjectFactory>() ?? FlutterProjectFactory(
+    logger: logger,
+    fileSystem: fs,
+  );
+}
 
 /// Currently active implementation of the file system.
 ///
 /// By default it uses local disk-based implementation. Override this in tests
 /// with [MemoryFileSystem].
 FileSystem get fs => ErrorHandlingFileSystem(
-  delegate: context.get<FileSystem>() ?? _kLocalFs,
+  delegate: context.get<FileSystem>() ?? LocalFileSystem.instance,
   platform: platform,
 );
 

packages/flutter_tools/lib/src/resident_runner.dart

@@ -1295,7 +1295,7 @@ class TerminalHandler {
   final Map<io.ProcessSignal, Object> _signalTokens = <io.ProcessSignal, Object>{};
 
   void _addSignalHandler(io.ProcessSignal signal, SignalHandler handler) {
-    _signalTokens[signal] = signals.addHandler(signal, handler);
+    _signalTokens[signal] = globals.signals.addHandler(signal, handler);
   }
 
   void registerSignalHandlers() {
@@ -1314,7 +1314,7 @@ class TerminalHandler {
   void stop() {
     assert(residentRunner.stayResident);
     for (final MapEntry<io.ProcessSignal, Object> entry in _signalTokens.entries) {
-      signals.removeHandler(entry.key, entry.value);
+      globals.signals.removeHandler(entry.key, entry.value);
     }
     _signalTokens.clear();
     subscription.cancel();

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -712,8 +712,8 @@ abstract class FlutterCommand extends Command<void> {
         systemClock.now(),
       );
     };
-    signals.addHandler(io.ProcessSignal.SIGTERM, handler);
-    signals.addHandler(io.ProcessSignal.SIGINT, handler);
+    globals.signals.addHandler(io.ProcessSignal.SIGTERM, handler);
+    globals.signals.addHandler(io.ProcessSignal.SIGINT, handler);
   }
 
   /// Logs data about this command.

packages/flutter_tools/test/commands.shard/hermetic/analyze_continuously_test.dart

@@ -31,7 +31,7 @@ void main() {
 
   setUp(() {
     platform = const LocalPlatform();
-    fileSystem = const LocalFileSystem();
+    fileSystem = LocalFileSystem.instance;
     platform = const LocalPlatform();
     processManager = const LocalProcessManager();
     terminal = AnsiTerminal(platform: platform, stdio: Stdio());

packages/flutter_tools/test/commands.shard/permeable/analyze_once_test.dart

@@ -76,37 +76,39 @@ sky_engine:$flutterRootUri/bin/cache/pkg/sky_engine/lib/
 flutter_project:lib/
 ''';
     fileSystem.file(fileSystem.path.join(projectPath, '.packages'))
-        ..createSync(recursive: true)
-        ..writeAsStringSync(dotPackagesSrc);
+      ..createSync(recursive: true)
+      ..writeAsStringSync(dotPackagesSrc);
   }
 
   setUpAll(() {
     Cache.disableLocking();
     Cache.flutterRoot = FlutterCommandRunner.defaultFlutterRoot;
     processManager = const LocalProcessManager();
-    terminal = AnsiTerminal(platform: platform, stdio: Stdio());
-    fileSystem = const LocalFileSystem();
     platform = const LocalPlatform();
+    terminal = AnsiTerminal(platform: platform, stdio: Stdio());
+    fileSystem = LocalFileSystem.instance;
     logger = BufferLogger(
       outputPreferences: OutputPreferences.test(),
       terminal: terminal,
     );
     analyzerSeparator = platform.isWindows ? '-' : '•';
-    tempDir = fileSystem.systemTempDirectory.createTempSync('flutter_analyze_once_test_1.').absolute;
+  });
+
+  setUp(() {
+    tempDir = fileSystem.systemTempDirectory.createTempSync(
+      'flutter_analyze_once_test_1.',
+    ).absolute;
     projectPath = fileSystem.path.join(tempDir.path, 'flutter_project');
     fileSystem.file(fileSystem.path.join(projectPath, 'pubspec.yaml'))
         ..createSync(recursive: true)
         ..writeAsStringSync(pubspecYamlSrc);
     _createDotPackages(projectPath);
-  });
-
-  setUp(() {
     libMain = fileSystem.file(fileSystem.path.join(projectPath, 'lib', 'main.dart'))
         ..createSync(recursive: true)
         ..writeAsStringSync(mainDartSrc);
   });
 
-  tearDownAll(() {
+  tearDown(() {
     tryToDelete(tempDir);
   });
 

packages/flutter_tools/test/general.shard/base/error_handling_file_system_test.dart

@@ -226,7 +226,7 @@ void main() {
 
   testWithoutContext('Throws type error if Directory type is set to curentDirectory with LocalFileSystem', () {
     final FileSystem fs = ErrorHandlingFileSystem(
-      delegate: const LocalFileSystem(),
+      delegate: LocalFileSystem.instance,
       platform: const LocalPlatform(),
     );
     final MockDirectory directory = MockDirectory();

packages/flutter_tools/test/general.shard/base/file_system_test.dart

@@ -2,12 +2,18 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+import 'dart:io' as io;
+
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/base/signals.dart';
 import 'package:mockito/mockito.dart';
 
 import '../../src/common.dart';
+import '../../src/context.dart';
 
 class MockPlatform extends Mock implements Platform {}
 
@@ -121,4 +127,40 @@ void main() {
       expect(fsUtils.escapePath(r'foo\cool.dart'), r'foo\cool.dart');
     });
   });
+
+  group('LocalFileSystem', () {
+    MockIoProcessSignal mockSignal;
+    ProcessSignal signalUnderTest;
+    StreamController<io.ProcessSignal> controller;
+
+    setUp(() {
+      mockSignal = MockIoProcessSignal();
+      signalUnderTest = ProcessSignal(mockSignal);
+      controller = StreamController<io.ProcessSignal>();
+      when(mockSignal.watch()).thenAnswer((Invocation invocation) => controller.stream);
+    });
+
+    testUsingContext('deletes system temp entry on a fatal signal', () async {
+      final Completer<void> completer = Completer<void>();
+      final Signals signals = Signals.test();
+      final LocalFileSystem localFileSystem = LocalFileSystem.test(
+        signals: signals,
+        fatalSignals: <ProcessSignal>[signalUnderTest],
+      );
+      final Directory temp = localFileSystem.systemTempDirectory;
+
+      signals.addHandler(signalUnderTest, (ProcessSignal s) {
+        completer.complete();
+      });
+
+      expect(temp.existsSync(), isTrue);
+
+      controller.add(mockSignal);
+      await completer.future;
+
+      expect(temp.existsSync(), isFalse);
+    });
+  });
 }
+
+class MockIoProcessSignal extends Mock implements io.ProcessSignal {}

packages/flutter_tools/test/general.shard/base/signals_test.dart

@@ -10,22 +10,23 @@ import 'package:flutter_tools/src/base/signals.dart';
 import 'package:mockito/mockito.dart';
 
 import '../../src/common.dart';
-import '../../src/context.dart';
 
 void main() {
   group('Signals', () {
+    Signals signals;
     MockIoProcessSignal mockSignal;
     ProcessSignal signalUnderTest;
     StreamController<io.ProcessSignal> controller;
 
     setUp(() {
+      signals = Signals.test();
       mockSignal = MockIoProcessSignal();
       signalUnderTest = ProcessSignal(mockSignal);
       controller = StreamController<io.ProcessSignal>();
       when(mockSignal.watch()).thenAnswer((Invocation invocation) => controller.stream);
     });
 
-    testUsingContext('signal handler runs', () async {
+    testWithoutContext('signal handler runs', () async {
       final Completer<void> completer = Completer<void>();
       signals.addHandler(signalUnderTest, (ProcessSignal s) {
         expect(s, signalUnderTest);
@@ -34,11 +35,9 @@ void main() {
 
       controller.add(mockSignal);
       await completer.future;
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('signal handlers run in order', () async {
+    testWithoutContext('signal handlers run in order', () async {
       final Completer<void> completer = Completer<void>();
 
       bool first = false;
@@ -56,11 +55,9 @@ void main() {
 
       controller.add(mockSignal);
       await completer.future;
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('signal handler error goes on error stream', () async {
+    testWithoutContext('signal handler error goes on error stream', () async {
       final Exception exn = Exception('Error');
       signals.addHandler(signalUnderTest, (ProcessSignal s) {
         throw exn;
@@ -68,65 +65,71 @@ void main() {
 
       final Completer<void> completer = Completer<void>();
       final List<Object> errList = <Object>[];
-      final StreamSubscription<Object> errSub = signals.errors.listen((Object err) {
-        errList.add(err);
-        completer.complete();
-      });
+      final StreamSubscription<Object> errSub = signals.errors.listen(
+        (Object err) {
+          errList.add(err);
+          completer.complete();
+        },
+      );
 
       controller.add(mockSignal);
       await completer.future;
       await errSub.cancel();
       expect(errList, contains(exn));
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('removed signal handler does not run', () async {
-      final Object token = signals.addHandler(signalUnderTest, (ProcessSignal s) {
-        fail('Signal handler should have been removed.');
-      });
+    testWithoutContext('removed signal handler does not run', () async {
+      final Object token = signals.addHandler(
+        signalUnderTest,
+        (ProcessSignal s) {
+          fail('Signal handler should have been removed.');
+        },
+      );
 
       await signals.removeHandler(signalUnderTest, token);
 
       final List<Object> errList = <Object>[];
-      final StreamSubscription<Object> errSub = signals.errors.listen((Object err) {
-        errList.add(err);
-      });
+      final StreamSubscription<Object> errSub = signals.errors.listen(
+        (Object err) {
+          errList.add(err);
+        },
+      );
 
       controller.add(mockSignal);
 
       await errSub.cancel();
       expect(errList, isEmpty);
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('non-removed signal handler still runs', () async {
+    testWithoutContext('non-removed signal handler still runs', () async {
       final Completer<void> completer = Completer<void>();
       signals.addHandler(signalUnderTest, (ProcessSignal s) {
         expect(s, signalUnderTest);
         completer.complete();
       });
 
-      final Object token = signals.addHandler(signalUnderTest, (ProcessSignal s) {
-        fail('Signal handler should have been removed.');
-      });
+      final Object token = signals.addHandler(
+        signalUnderTest,
+        (ProcessSignal s) {
+          fail('Signal handler should have been removed.');
+        },
+      );
       await signals.removeHandler(signalUnderTest, token);
 
       final List<Object> errList = <Object>[];
-      final StreamSubscription<Object> errSub = signals.errors.listen((Object err) {
-        errList.add(err);
-      });
+      final StreamSubscription<Object> errSub = signals.errors.listen(
+        (Object err) {
+          errList.add(err);
+        },
+      );
 
       controller.add(mockSignal);
       await completer.future;
       await errSub.cancel();
       expect(errList, isEmpty);
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('only handlers for the correct signal run', () async {
+    testWithoutContext('only handlers for the correct signal run', () async {
       final MockIoProcessSignal mockSignal2 = MockIoProcessSignal();
       final StreamController<io.ProcessSignal> controller2 = StreamController<io.ProcessSignal>();
       final ProcessSignal otherSignal = ProcessSignal(mockSignal2);
@@ -144,19 +147,22 @@ void main() {
       });
 
       final List<Object> errList = <Object>[];
-      final StreamSubscription<Object> errSub = signals.errors.listen((Object err) {
-        errList.add(err);
-      });
+      final StreamSubscription<Object> errSub = signals.errors.listen(
+        (Object err) {
+          errList.add(err);
+        },
+      );
 
       controller.add(mockSignal);
       await completer.future;
       await errSub.cancel();
       expect(errList, isEmpty);
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(),
     });
 
-    testUsingContext('all handlers for exiting signals are run before exit', () async {
+    testWithoutContext('all handlers for exiting signals are run before exit', () async {
+      final Signals signals = Signals.test(
+        exitSignals: <ProcessSignal>[signalUnderTest],
+      );
       final Completer<void> completer = Completer<void>();
       bool first = false;
       bool second = false;
@@ -186,8 +192,6 @@ void main() {
 
       controller.add(mockSignal);
       await completer.future;
-    }, overrides: <Type, Generator>{
-      Signals: () => Signals(exitSignals: <ProcessSignal>[signalUnderTest]),
     });
   });
 }

packages/flutter_tools/test/general.shard/flutter_platform_test.dart

@@ -53,6 +53,7 @@ void main() {
 
       setUp(() {
         mockPlatform = MockPlatform();
+        when(mockPlatform.isWindows).thenReturn(false);
         mockProcessManager = MockProcessManager();
         flutterPlatform = TestFlutterPlatform();
       });

packages/flutter_tools/test/general.shard/forbidden_imports_test.dart

@@ -134,6 +134,27 @@ void main() {
     }
   });
 
+  test('no unauthorized imports of package:file/local.dart', () {
+    final List<String> whitelistedPath = <String>[
+      globals.fs.path.join(flutterTools, 'lib', 'src', 'base', 'file_system.dart'),
+    ];
+    for (final String dirName in <String>['lib', 'bin', 'test']) {
+      final Iterable<File> files =  globals.fs.directory(globals.fs.path.join(flutterTools, dirName))
+        .listSync(recursive: true)
+        .where(_isDartFile)
+        .where((FileSystemEntity entity) => !whitelistedPath.contains(entity.path))
+        .map(_asFile);
+      for (final File file in files) {
+        for (final String line in file.readAsLinesSync()) {
+          if (line.startsWith(RegExp(r'import.*package:file/local.dart'))) {
+            final String relativePath = globals.fs.path.relative(file.path, from:flutterTools);
+            fail("$relativePath imports 'package:file/local.dart'; use 'lib/src/base/file_system.dart' instead");
+          }
+        }
+      }
+    }
+  });
+
   test('no unauthorized imports of dart:convert', () {
     final List<String> whitelistedPaths = <String>[
       globals.fs.path.join(flutterTools, 'lib', 'src', 'convert.dart'),

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

@@ -52,7 +52,7 @@ void main() {
         stdio: null,
       ),
     );
-    fileSystem = const LocalFileSystemBlockingSetCurrentDirectory();
+    fileSystem = LocalFileSystemBlockingSetCurrentDirectory();
     processManager = const LocalProcessManager();
     parser = PlistParser(
       fileSystem: fileSystem,

packages/flutter_tools/test/general.shard/runner/flutter_command_test.dart

@@ -450,7 +450,7 @@ class FakeSignals implements Signals {
   FakeSignals({
     this.subForSigTerm,
     List<ProcessSignal> exitSignals,
-  }) : delegate = Signals(exitSignals: exitSignals);
+  }) : delegate = Signals.test(exitSignals: exitSignals);
 
   final ProcessSignal subForSigTerm;
   final Signals delegate;

packages/flutter_tools/test/integration.shard/downgrade_upgrade_integration_test.dart

@@ -14,7 +14,7 @@ import '../src/common.dart';
 
 const String _kInitialVersion = 'v1.9.1';
 const String _kBranch = 'dev';
-const FileSystem fileSystem = LocalFileSystem();
+final FileSystem fileSystem = LocalFileSystem.instance;
 const ProcessManager processManager = LocalProcessManager();
 final Stdio stdio = Stdio();
 final ProcessUtils processUtils = ProcessUtils(processManager: processManager, logger: StdoutLogger(

packages/flutter_tools/test/integration.shard/vmservice_integration_test.dart

@@ -21,7 +21,7 @@ void main() {
     FlutterRunTestDriver flutter;
     VmService vmService;
 
-    setUpAll(() async {
+    setUp(() async {
       tempDir = createResolvedTempDirectorySync('vmservice_integration_test.');
 
       final BasicProject _project = BasicProject();
@@ -33,7 +33,7 @@ void main() {
       vmService = await vmServiceConnectUri('ws://localhost:$port/ws');
     });
 
-    tearDownAll(() async {
+    tearDown(() async {
       await flutter?.stop();
       tryToDelete(tempDir);
     });

packages/flutter_tools/test/src/common.dart

@@ -20,7 +20,7 @@ import 'package:meta/meta.dart';
 import 'package:test_api/test_api.dart' as test_package show TypeMatcher, test; // ignore: deprecated_member_use
 import 'package:test_api/test_api.dart' hide TypeMatcher, isInstanceOf; // ignore: deprecated_member_use
 // ignore: deprecated_member_use
-export 'package:test_core/test_core.dart' hide TypeMatcher, isInstanceOf; // Defines a 'package:test' shim.
+export 'package:test_core/test_core.dart' hide TypeMatcher, isInstanceOf, test; // Defines a 'package:test' shim.
 
 /// A matcher that compares the type of the actual value to the type argument T.
 // TODO(ianh): Remove this once https://github.com/dart-lang/matcher/issues/98 is fixed
@@ -31,7 +31,9 @@ void tryToDelete(Directory directory) {
   // on Windows it's common for deletions to fail due to
   // bogus (we think) "access denied" errors.
   try {
-    directory.deleteSync(recursive: true);
+    if (directory.existsSync()) {
+      directory.deleteSync(recursive: true);
+    }
   } on FileSystemException catch (error) {
     print('Failed to delete ${directory.path}: $error');
   }
@@ -156,6 +158,35 @@ Matcher containsIgnoringWhitespace(String toSearch) {
   );
 }
 
+/// The tool overrides `test` to ensure that files created under the
+/// system temporary directory are deleted after each test by calling
+/// `LocalFileSystem.dispose()`.
+@isTest
+void test(String description, FutureOr<void> body(), {
+  String testOn,
+  Timeout timeout,
+  dynamic skip,
+  List<String> tags,
+  Map<String, dynamic> onPlatform,
+  int retry,
+}) {
+  test_package.test(
+    description,
+    () async {
+      addTearDown(() async {
+        await LocalFileSystem.dispose();
+      });
+      return body();
+    },
+    timeout: timeout,
+    skip: skip,
+    tags: tags,
+    onPlatform: onPlatform,
+    retry: retry,
+    testOn: testOn,
+  );
+}
+
 /// Executes a test body in zone that does not allow context-based injection.
 ///
 /// For classes which have been refactored to excluded context-based injection
@@ -168,12 +199,12 @@ Matcher containsIgnoringWhitespace(String toSearch) {
 void testWithoutContext(String description, FutureOr<void> body(), {
   String testOn,
   Timeout timeout,
-  bool skip,
+  dynamic skip,
   List<String> tags,
   Map<String, dynamic> onPlatform,
   int retry,
   }) {
-  return test_package.test(
+  return test(
     description, () async {
       return runZoned(body, zoneValues: <Object, Object>{
         contextKey: const NoContext(),

packages/flutter_tools/test/src/context.dart

@@ -126,7 +126,7 @@ void testUsingContext(
           SimControl: () => MockSimControl(),
           Usage: () => FakeUsage(),
           XcodeProjectInterpreter: () => FakeXcodeProjectInterpreter(),
-          FileSystem: () => const LocalFileSystemBlockingSetCurrentDirectory(),
+          FileSystem: () => LocalFileSystemBlockingSetCurrentDirectory(),
           TimeoutConfiguration: () => const TimeoutConfiguration(),
           PlistParser: () => FakePlistParser(),
           Signals: () => FakeSignals(),
@@ -443,7 +443,9 @@ class FakePlistParser implements PlistParser {
 }
 
 class LocalFileSystemBlockingSetCurrentDirectory extends LocalFileSystem {
-  const LocalFileSystemBlockingSetCurrentDirectory();
+  LocalFileSystemBlockingSetCurrentDirectory() : super.test(
+    signals: LocalSignals.instance,
+  );
 
   @override
   set currentDirectory(dynamic value) {