Only write the pid-file while listening to SIGUSR signals. (#74533)

dev/integration_tests/ui/lib/commands.dart

@@ -2,19 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:flutter_driver/driver_extension.dart';
-
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 
-String log = '';
-
 void main() {
-  enableFlutterDriverExtension(handler: (String message) async {
+  print('called main');
-    log = 'log:';
-    await WidgetsBinding.instance.reassembleApplication();
-    return log;
-  });
   runApp(const MaterialApp(home: Test()));
 }
 
@@ -22,9 +14,7 @@ class Test extends SingleChildRenderObjectWidget {
   const Test({ Key key }) : super(key: key);
 
   @override
-  RenderTest createRenderObject(BuildContext context) {
+  RenderTest createRenderObject(BuildContext context) => RenderTest();
-    return RenderTest();
-  }
 }
 
 class RenderTest extends RenderProxyBox {
@@ -33,11 +23,17 @@ class RenderTest extends RenderProxyBox {
   @override
   void debugPaintSize(PaintingContext context, Offset offset) {
     super.debugPaintSize(context, offset);
-    log += ' debugPaintSize';
+    print('called debugPaintSize');
   }
 
   @override
   void paint(PaintingContext context, Offset offset) {
-    log += ' paint';
+    print('called paint');
+  }
+
+  @override
+  void reassemble() {
+    print('called reassemble');
+    super.reassemble();
   }
 }

dev/integration_tests/ui/lib/overflow.dart

@@ -0,0 +1,41 @@
+// 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/material.dart';
+
+void main() {
+  runApp(const MaterialApp(home: Test()));
+}
+
+class Test extends StatefulWidget {
+  const Test({ Key key }) : super(key: key);
+
+  @override
+  State<Test> createState() => _TestState();
+}
+
+class _TestState extends State<Test> {
+  bool _triggered = false;
+
+  @override
+  void reassemble() {
+    _triggered = true;
+    super.reassemble();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (!_triggered)
+      return const SizedBox.shrink();
+    return Row(children: const <Widget>[
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+      SizedBox(width: 10000.0),
+    ]);
+  }
+}

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

@@ -52,6 +52,7 @@ import 'package:meta/meta.dart';
 import '../globals.dart' as globals;
 import 'async_guard.dart';
 import 'context.dart';
+import 'file_system.dart';
 import 'process.dart';
 
 export 'dart:io'
@@ -364,34 +365,60 @@ class Stdio {
   Future<void> addStderrStream(Stream<List<int>> stream) => stderr.addStream(stream);
 }
 
-// TODO(zra): Move pid and writePidFile into `ProcessInfo`.
-void writePidFile(String pidFile) {
-  if (pidFile != null) {
-    // Write our pid to the file.
-    globals.fs.file(pidFile).writeAsStringSync(io.pid.toString());
-  }
-}
-
 /// An overridable version of io.ProcessInfo.
 abstract class ProcessInfo {
-  factory ProcessInfo() => _DefaultProcessInfo();
+  factory ProcessInfo() => _DefaultProcessInfo(globals.fs);
+  factory ProcessInfo.test(FileSystem fs) => _TestProcessInfo(fs);
 
   static ProcessInfo get instance => context.get<ProcessInfo>();
 
   int get currentRss;
 
   int get maxRss;
+
+  File writePidFile(String pidFile);
 }
 
 ProcessInfo get processInfo => ProcessInfo.instance;
 
 /// The default implementation of [ProcessInfo], which uses [io.ProcessInfo].
 class _DefaultProcessInfo implements ProcessInfo {
+  _DefaultProcessInfo(this._fileSystem);
+
+  final FileSystem _fileSystem;
+
   @override
   int get currentRss => io.ProcessInfo.currentRss;
 
   @override
   int get maxRss => io.ProcessInfo.maxRss;
+
+  @override
+  File writePidFile(String pidFile) {
+    assert(pidFile != null);
+    return _fileSystem.file(pidFile)
+      ..writeAsStringSync(io.pid.toString());
+  }
+}
+
+/// The test version of [ProcessInfo].
+class _TestProcessInfo implements ProcessInfo {
+  _TestProcessInfo(this._fileSystem);
+
+  final FileSystem _fileSystem;
+
+  @override
+  int currentRss = 1000;
+
+  @override
+  int maxRss = 2000;
+
+  @override
+  File writePidFile(String pidFile) {
+    assert(pidFile != null);
+    return _fileSystem.file(pidFile)
+      ..writeAsStringSync('12345');
+  }
 }
 
 /// The return type for [listNetworkInterfaces].

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

@@ -90,18 +90,26 @@ class AttachCommand extends FlutterCommand {
               'This parameter is case-insensitive.',
       )..addOption(
         'pid-file',
-        help: 'Specify a file to write the process id to. '
+        help: 'Specify a file to write the process ID to. '
               'You can send SIGUSR1 to trigger a hot reload '
-              'and SIGUSR2 to trigger a hot restart.',
+              'and SIGUSR2 to trigger a hot restart. '
+              'The file is created when the signal handlers '
+              'are hooked and deleted when they are removed.',
+      )..addFlag(
+        'report-ready',
+        help: 'Print "ready" to the console after handling a keyboard command.\n'
+              'This is primarily useful for tests and other automation, but consider '
+              'using --machine instead.',
+        hide: !verboseHelp,
       )..addOption(
         'project-root',
         hide: !verboseHelp,
-        help: 'Normally used only in run target',
+        help: 'Normally used only in run target.',
       )..addFlag('machine',
         hide: !verboseHelp,
         negatable: false,
         help: 'Handle machine structured JSON command input and provide output '
-              'and progress in machine friendly format.',
+              'and progress in machine-friendly format.',
       );
     usesTrackWidgetCreation(verboseHelp: verboseHelp);
     addDdsOptions(verboseHelp: verboseHelp);
@@ -200,8 +208,6 @@ known, it can be explicitly provided to attach via the command-line, e.g.
   Future<FlutterCommandResult> runCommand() async {
     await _validateArguments();
 
-    writePidFile(stringArg('pid-file'));
-
     final Device device = await findTargetDevice();
 
     final Artifacts overrideArtifacts = device.artifactOverrides ?? globals.artifacts;
@@ -362,9 +368,12 @@ known, it can be explicitly provided to attach via the command-line, e.g.
             logger: globals.logger,
             terminal: globals.terminal,
             signals: globals.signals,
+            processInfo: processInfo,
+            reportReady: boolArg('report-ready'),
+            pidFile: stringArg('pid-file'),
           )
-            ..setupTerminal()
+            ..registerSignalHandlers()
-            ..registerSignalHandlers();
+            ..setupTerminal();
         }));
         result = await runner.attach(
           appStartedCompleter: onAppStart,

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

@@ -289,11 +289,18 @@ class RunCommand extends RunCommandBase {
         help: 'Stay resident after launching the application. Not available with "--trace-startup".',
       )
       ..addOption('pid-file',
-        help: 'Specify a file to write the process id to. '
+        help: 'Specify a file to write the process ID to. '
               'You can send SIGUSR1 to trigger a hot reload '
-              'and SIGUSR2 to trigger a hot restart.',
+              'and SIGUSR2 to trigger a hot restart. '
-      )
+              'The file is created when the signal handlers '
-      ..addFlag('benchmark',
+              'are hooked and deleted when they are removed.',
+      )..addFlag(
+        'report-ready',
+        help: 'Print "ready" to the console after handling a keyboard command.\n'
+              'This is primarily useful for tests and other automation, but consider '
+              'using --machine instead.',
+        hide: !verboseHelp,
+      )..addFlag('benchmark',
         negatable: false,
         hide: !verboseHelp,
         help: 'Enable a benchmarking mode. This will run the given application, '
@@ -514,8 +521,6 @@ class RunCommand extends RunCommandBase {
     final bool hotMode = shouldUseHotMode(buildInfo);
     final String applicationBinaryPath = stringArg('use-application-binary');
 
-    writePidFile(stringArg('pid-file'));
-
     if (boolArg('machine')) {
       if (devices.length > 1) {
         throwToolExit('--machine does not support -d all.');
@@ -620,34 +625,39 @@ class RunCommand extends RunCommandBase {
     //
     // Do not add more operations to the future.
     final Completer<void> appStartedTimeRecorder = Completer<void>.sync();
+
+    TerminalHandler handler;
     // This callback can't throw.
     unawaited(appStartedTimeRecorder.future.then<void>(
       (_) {
         appStartedTime = globals.systemClock.now();
         if (stayResident) {
-          TerminalHandler(
+          handler = TerminalHandler(
             runner,
             logger: globals.logger,
             terminal: globals.terminal,
             signals: globals.signals,
+            processInfo: processInfo,
+            reportReady: boolArg('report-ready'),
+            pidFile: stringArg('pid-file'),
           )
-            ..setupTerminal()
+            ..registerSignalHandlers()
-            ..registerSignalHandlers();
+            ..setupTerminal();
         }
       }
     ));
-
     try {
       final int result = await runner.run(
         appStartedCompleter: appStartedTimeRecorder,
         enableDevTools: stayResident && boolArg(FlutterCommand.kEnableDevTools),
         route: route,
       );
+      handler?.stop();
       if (result != 0) {
         throwToolExit(null, exitCode: result);
       }
-    } on RPCError catch (err) {
+    } on RPCError catch (error) {
-      if (err.code == RPCErrorCodes.kServiceDisappeared) {
+      if (error.code == RPCErrorCodes.kServiceDisappeared) {
         throwToolExit('Lost connection to device.');
       }
       rethrow;

packages/flutter_tools/lib/src/devtools_launcher.dart

@@ -177,7 +177,9 @@ class DevtoolsServerLauncher extends DevtoolsLauncher {
 
   @override
   Future<void> close() async {
-    devToolsUrl = null;
+    if (devToolsUrl != null) {
+      devToolsUrl = null;
+    }
     if (_devToolsProcess != null) {
       _devToolsProcess.kill();
       await _devToolsProcess.exitCode;

packages/flutter_tools/lib/src/resident_runner.dart

@@ -969,7 +969,7 @@ abstract class ResidentRunner {
     await residentDevtoolsHandler.shutdown();
     await stopEchoingDeviceLog();
     await preExit();
-    await exitApp();
+    await exitApp(); // calls appFinished
     await shutdownDartDevelopmentService();
   }
 
@@ -1452,17 +1452,27 @@ class TerminalHandler {
     @required Logger logger,
     @required Terminal terminal,
     @required Signals signals,
+    @required io.ProcessInfo processInfo,
+    @required bool reportReady,
+    String pidFile,
   }) : _logger = logger,
        _terminal = terminal,
-       _signals = signals;
+       _signals = signals,
+       _processInfo = processInfo,
+       _reportReady = reportReady,
+       _pidFile = pidFile;
 
   final Logger _logger;
   final Terminal _terminal;
   final Signals _signals;
+  final io.ProcessInfo _processInfo;
+  final bool _reportReady;
+  final String _pidFile;
 
   final ResidentRunner residentRunner;
   bool _processingUserRequest = false;
   StreamSubscription<void> subscription;
+  File _actualPidFile;
 
   @visibleForTesting
   String lastReceivedCommand;
@@ -1476,7 +1486,6 @@ class TerminalHandler {
     subscription = _terminal.keystrokes.listen(processTerminalInput);
   }
 
-
   final Map<io.ProcessSignal, Object> _signalTokens = <io.ProcessSignal, Object>{};
 
   void _addSignalHandler(io.ProcessSignal signal, SignalHandler handler) {
@@ -1485,19 +1494,30 @@ class TerminalHandler {
 
   void registerSignalHandlers() {
     assert(residentRunner.stayResident);
-
     _addSignalHandler(io.ProcessSignal.SIGINT, _cleanUp);
     _addSignalHandler(io.ProcessSignal.SIGTERM, _cleanUp);
-    if (!residentRunner.supportsServiceProtocol || !residentRunner.supportsRestart) {
+    if (residentRunner.supportsServiceProtocol && residentRunner.supportsRestart) {
-      return;
+      _addSignalHandler(io.ProcessSignal.SIGUSR1, _handleSignal);
+      _addSignalHandler(io.ProcessSignal.SIGUSR2, _handleSignal);
+      if (_pidFile != null) {
+        _logger.printTrace('Writing pid to: $_pidFile');
+        _actualPidFile = _processInfo.writePidFile(_pidFile);
+      }
     }
-    _addSignalHandler(io.ProcessSignal.SIGUSR1, _handleSignal);
-    _addSignalHandler(io.ProcessSignal.SIGUSR2, _handleSignal);
   }
 
   /// Unregisters terminal signal and keystroke handlers.
   void stop() {
     assert(residentRunner.stayResident);
+    if (_actualPidFile != null) {
+      try {
+        _logger.printTrace('Deleting pid file (${_actualPidFile.path}).');
+        _actualPidFile.deleteSync();
+      } on FileSystemException catch (error) {
+        _logger.printError('Failed to delete pid file (${_actualPidFile.path}): ${error.message}');
+      }
+      _actualPidFile = null;
+    }
     for (final MapEntry<io.ProcessSignal, Object> entry in _signalTokens.entries) {
       _signals.removeHandler(entry.key, entry.value);
     }
@@ -1623,6 +1643,9 @@ class TerminalHandler {
       rethrow;
     } finally {
       _processingUserRequest = false;
+      if (_reportReady) {
+        _logger.printStatus('ready');
+      }
     }
   }
 

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

@@ -6,6 +6,8 @@
 
 import 'dart:async';
 
+import 'package:file/memory.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/terminal.dart';
@@ -22,11 +24,15 @@ void main() {
     final Logger logger = BufferLogger.test();
     final Signals signals = Signals.test();
     final Terminal terminal = Terminal.test();
+    final MemoryFileSystem fs = MemoryFileSystem.test();
+    final ProcessInfo processInfo = ProcessInfo.test(fs);
     final TerminalHandler terminalHandler = TerminalHandler(
       testRunner,
       logger: logger,
       signals: signals,
       terminal: terminal,
+      processInfo: processInfo,
+      reportReady: false,
     );
 
     expect(testRunner.hasHelpBeenPrinted, false);
@@ -39,11 +45,15 @@ void main() {
     final Logger logger = BufferLogger.test();
     final Signals signals = Signals.test();
     final Terminal terminal = Terminal.test();
+    final MemoryFileSystem fs = MemoryFileSystem.test();
+    final ProcessInfo processInfo = ProcessInfo.test(fs);
     final TerminalHandler terminalHandler = TerminalHandler(
       testRunner,
       logger: logger,
       signals: signals,
       terminal: terminal,
+      processInfo: processInfo,
+      reportReady: false,
     );
 
     expect(testRunner.hasHelpBeenPrinted, false);
@@ -60,12 +70,16 @@ void main() {
       testLogger = BufferLogger.test();
       final Signals signals = Signals.test();
       final Terminal terminal = Terminal.test();
+      final MemoryFileSystem fs = MemoryFileSystem.test();
+      final ProcessInfo processInfo = ProcessInfo.test(fs);
       mockResidentRunner = MockResidentRunner();
       terminalHandler = TerminalHandler(
         mockResidentRunner,
         logger: testLogger,
         signals: signals,
         terminal: terminal,
+        processInfo: processInfo,
+      reportReady: false,
       );
       when(mockResidentRunner.supportsServiceProtocol).thenReturn(true);
     });
@@ -310,6 +324,34 @@ void main() {
       verify(mockResidentRunner.debugToggleDebugCheckElevationsEnabled()).called(2);
     });
   });
+
+  testWithoutContext('pidfile creation', () {
+    final BufferLogger testLogger = BufferLogger.test();
+    final Signals signals = _TestSignals(Signals.defaultExitSignals);
+    final Terminal terminal = Terminal.test();
+    final MemoryFileSystem fs = MemoryFileSystem.test();
+    final ProcessInfo processInfo = ProcessInfo.test(fs);
+    final ResidentRunner mockResidentRunner = MockResidentRunner();
+    when(mockResidentRunner.stayResident).thenReturn(true);
+    when(mockResidentRunner.supportsServiceProtocol).thenReturn(true);
+    when(mockResidentRunner.supportsRestart).thenReturn(true);
+    const String filename = 'test.pid';
+    final TerminalHandler terminalHandler = TerminalHandler(
+      mockResidentRunner,
+      logger: testLogger,
+      signals: signals,
+      terminal: terminal,
+      processInfo: processInfo,
+      reportReady: false,
+      pidFile: filename,
+    );
+    expect(fs.file(filename).existsSync(), isFalse);
+    terminalHandler.setupTerminal();
+    terminalHandler.registerSignalHandlers();
+    expect(fs.file(filename).existsSync(), isTrue);
+    terminalHandler.stop();
+    expect(fs.file(filename).existsSync(), isFalse);
+  });
 }
 
 class MockDevice extends Mock implements Device {
@@ -353,3 +395,35 @@ class TestRunner extends Mock implements ResidentRunner {
     bool enableDevTools = false,
   }) async => null;
 }
+
+class _TestSignals implements Signals {
+  _TestSignals(this.exitSignals);
+
+  final List<ProcessSignal> exitSignals;
+
+  final Map<ProcessSignal, Map<Object, SignalHandler>> _handlersTable =
+      <ProcessSignal, Map<Object, SignalHandler>>{};
+
+  @override
+  Object addHandler(ProcessSignal signal, SignalHandler handler) {
+    final Object token = Object();
+    _handlersTable.putIfAbsent(signal, () => <Object, SignalHandler>{})[token] = handler;
+    return token;
+  }
+
+  @override
+  Future<bool> removeHandler(ProcessSignal signal, Object token) async {
+    if (!_handlersTable.containsKey(signal)) {
+      return false;
+    }
+    if (!_handlersTable[signal].containsKey(token)) {
+      return false;
+    }
+    _handlersTable[signal].remove(token);
+    return true;
+  }
+
+  @override
+  Stream<Object> get errors => _errors.stream;
+  final StreamController<Object> _errors = StreamController<Object>();
+}

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

@@ -39,16 +39,6 @@ void main() {
     tryToDelete(tempDir);
   });
 
-  testWithoutContext('writes pid-file', () async {
-    final File pidFile = tempDir.childFile('test.pid');
-    await _flutterRun.run(withDebugger: true);
-    await _flutterAttach.attach(
-      _flutterRun.vmServicePort,
-      pidFile: pidFile,
-    );
-    expect(pidFile.existsSync(), isTrue);
-  });
-
   testWithoutContext('can hot reload', () async {
     await _flutterRun.run(withDebugger: true);
     await _flutterAttach.attach(_flutterRun.vmServicePort);

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

@@ -51,12 +51,6 @@ void main() {
     }
   });
 
-  testWithoutContext('flutter run writes pid-file', () async {
-    final File pidFile = tempDir.childFile('test.pid');
-    await _flutter.run(pidFile: pidFile);
-    expect(pidFile.existsSync(), isTrue);
-  });
-
   testWithoutContext('sets activeDevToolsServerAddress extension', () async {
     await _flutter.run(
       startPaused: true,

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

@@ -103,36 +103,4 @@ void main() {
 
     expect(stdout.toString(), isNot(contains(_exceptionStart)));
   });
-
-  testWithoutContext('flutter run for web reports an early error in an application', () async {
-    final StringBuffer stdout = StringBuffer();
-
-    await _flutter.run(
-      startPaused: true,
-      withDebugger: true,
-      structuredErrors: true,
-      chrome: true,
-      machine: false,
-    );
-    await _flutter.resume();
-    final Completer<void> completer = Completer<void>();
-    bool lineFound = false;
-
-    await Future<void>(() async {
-      _flutter.stdout.listen((String line) {
-        stdout.writeln(line);
-        if (line.startsWith('Another exception was thrown') && !lineFound) {
-          lineFound = true;
-          completer.complete();
-        }
-      });
-      await completer.future;
-    }).timeout(const Duration(seconds: 15), onTimeout: () {
-      // Complete anyway in case we don't see the 'Another exception' line.
-      completer.complete();
-    });
-
-    expect(stdout.toString(), contains(_exceptionStart));
-    await _flutter.stop();
-  }, skip: 'Running in cirrus environment causes premature exit');
 }

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

@@ -0,0 +1,587 @@
+// 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.
+
+// The purpose of this test is to verify the end-to-end behavior of
+// "flutter run" and other such commands, as closely as possible to
+// the default behavior. To that end, it avoids the use of any test
+// features that are not critical (-dflutter-test being the primary
+// example of a test feature that it does use). For example, no use
+// is made of "--machine" in these tests.
+
+// There are a number of risks when it comes to writing a test such
+// as this one. Typically these tests are hard to debug if they are
+// in a failing condition, because they just hang as they await the
+// next expected line that never comes. To avoid this, here we have
+// the policy of looking for multiple lines, printing what expected
+// lines were not seen when a short timeout expires (but timing out
+// does not cause the test to fail, to reduce flakes), and wherever
+// possible recording all output and comparing the actual output to
+// the expected output only once the test is completed.
+
+// To aid in debugging, consider passing the `debug: true` argument
+// to the runFlutter function.
+
+// @dart = 2.8
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:meta/meta.dart';
+import 'package:pedantic/pedantic.dart';
+import 'package:process/process.dart';
+
+import '../src/common.dart';
+import 'test_utils.dart' show fileSystem;
+
+const ProcessManager processManager = LocalProcessManager();
+final String flutterRoot = getFlutterRoot();
+final String flutterBin = fileSystem.path.join(flutterRoot, 'bin', 'flutter');
+
+typedef LineHandler = String/*?*/ Function(String line);
+
+abstract class Transition {
+  const Transition({this.handler, this.logging});
+
+  /// Callback that is invoked when the transition matches.
+  ///
+  /// This should not throw, even if the test is failing. (For example, don't use "expect"
+  /// in these callbacks.) Throwing here would prevent the [runFlutter] function from running
+  /// to completion, which would leave zombie `flutter` processes around.
+  final LineHandler/*?*/ handler;
+
+  /// Whether to enable or disable logging when this transition is matched.
+  ///
+  /// The default value, null, leaves the logging state unaffected.
+  final bool/*?*/ logging;
+
+  bool matches(String line);
+
+  @protected
+  bool lineMatchesPattern(String line, Pattern pattern) {
+    if (pattern is String) {
+      return line == pattern;
+    }
+    return line.contains(pattern);
+  }
+
+  @protected
+  String describe(Pattern pattern) {
+    if (pattern is String) {
+      return '"$pattern"';
+    }
+    if (pattern is RegExp) {
+      return '/${pattern.pattern}/';
+    }
+    return '$pattern';
+  }
+}
+
+class Barrier extends Transition {
+  const Barrier(this.pattern, {LineHandler/*?*/ handler, bool/*?*/ logging}) : super(handler: handler, logging: logging);
+  final Pattern pattern;
+
+  @override
+  bool matches(String line) => lineMatchesPattern(line, pattern);
+
+  @override
+  String toString() => describe(pattern);
+}
+
+class Multiple extends Transition {
+  Multiple(List<Pattern> patterns, {
+    LineHandler/*?*/ handler,
+    bool/*?*/ logging,
+  }) : _originalPatterns = patterns,
+       patterns = patterns.toList(),
+       super(handler: handler, logging: logging);
+
+  final List<Pattern> _originalPatterns;
+  final List<Pattern> patterns;
+
+  @override
+  bool matches(String line) {
+    for (int index = 0; index < patterns.length; index += 1) {
+      if (lineMatchesPattern(line, patterns[index])) {
+        patterns.removeAt(index);
+        break;
+      }
+    }
+    return patterns.isEmpty;
+  }
+
+  @override
+  String toString() {
+    return _originalPatterns.map(describe).join(', ') + ' (matched ${_originalPatterns.length - patterns.length} so far)';
+  }
+}
+
+class ProcessTestResult {
+  const ProcessTestResult(this.exitCode, this.stdout, this.stderr);
+  final int exitCode;
+  final List<String> stdout;
+  final List<String> stderr;
+
+  @override
+  String toString() => 'exit code $exitCode\nstdout:\n  ${stdout.join('\n  ')}\nstderr:\n  ${stderr.join('\n  ')}\n';
+}
+
+String clarify(String line) {
+  return line.runes.map<String>((int rune) {
+    if (rune >= 0x20 && rune <= 0x7F) {
+      return String.fromCharCode(rune);
+    }
+    switch (rune) {
+      case 0x00: return '<NUL>';
+      case 0x07: return '<BEL>';
+      case 0x08: return '<TAB>';
+      case 0x09: return '<BS>';
+      case 0x0A: return '<LF>';
+      case 0x0D: return '<CR>';
+    }
+    return '<${rune.toRadixString(16).padLeft(rune <= 0xFF ? 2 : rune <= 0xFFFF ? 4 : 5, '0')}>';
+  }).join('');
+}
+
+void printClearly(String line) {
+  print(clarify(line));
+}
+
+Future<ProcessTestResult> runFlutter(
+  List<String> arguments,
+  String workingDirectory,
+  List<Transition> transitions, {
+  bool debug = false,
+  bool logging = true,
+  Duration expectedMaxDuration = const Duration(seconds: 25), // must be less than test timeout of 30 seconds!
+}) async {
+  final Process process = await processManager.start(
+    <String>[flutterBin, ...arguments],
+    workingDirectory: workingDirectory,
+  );
+  final List<String> stdoutLog = <String>[];
+  final List<String> stderrLog = <String>[];
+  final List<String> stdinLog = <String>[];
+  int nextTransition = 0;
+  void describeStatus() {
+    if (transitions.isNotEmpty) {
+      print('Expected state transitions:');
+      for (int index = 0; index < transitions.length; index += 1) {
+        print(
+          '${index.toString().padLeft(5)} '
+          '${index <  nextTransition ? 'ALREADY MATCHED ' :
+             index == nextTransition ? 'NOW WAITING FOR>' :
+                                       '                '} ${transitions[index]}');
+      }
+    }
+    if (stdoutLog.isEmpty && stderrLog.isEmpty && stdinLog.isEmpty) {
+      print('So far nothing has been logged${ debug ? "" : "; use debug:true to print all output" }.');
+    } else {
+      print('Log${ debug ? "" : " (only contains logged lines; use debug:true to print all output)" }:');
+      stdoutLog.map<String>((String line) => 'stdout: $line').forEach(printClearly);
+      stderrLog.map<String>((String line) => 'stderr: $line').forEach(printClearly);
+      stdinLog.map<String>((String line) => 'stdin: $line').forEach(printClearly);
+    }
+  }
+  bool streamingLogs = false;
+  Timer/*?*/ timeout;
+  void processTimeout() {
+    if (!streamingLogs) {
+      streamingLogs = true;
+      if (!debug) {
+        print('Test is taking a long time.');
+      }
+      describeStatus();
+      print('(streaming all logs from this point on...)');
+    } else {
+      print('(taking a long time...)');
+    }
+  }
+  void processStdout(String line) {
+    if (logging) {
+      stdoutLog.add(line);
+    }
+    if (streamingLogs) {
+      print('stdout: $line');
+    }
+    if (nextTransition < transitions.length && transitions[nextTransition].matches(line)) {
+      if (streamingLogs) {
+        print('(matched ${transitions[nextTransition]})');
+      }
+      if (transitions[nextTransition].logging != null) {
+        if (!logging && transitions[nextTransition].logging/*!*/) {
+          stdoutLog.add(line);
+        }
+        logging = transitions[nextTransition].logging/*!*/;
+        if (streamingLogs) {
+          if (logging) {
+            print('(enabled logging)');
+          } else {
+            print('(disabled logging)');
+          }
+        }
+      }
+      if (transitions[nextTransition].handler != null) {
+        final String/*?*/ command = transitions[nextTransition].handler/*!*/(line);
+        if (command != null) {
+          stdinLog.add(command);
+          if (streamingLogs) {
+            print('stdin: $command');
+          }
+          process.stdin.write(command);
+        }
+      }
+      nextTransition += 1;
+      timeout?.cancel();
+      timeout = Timer(expectedMaxDuration ~/ 5, processTimeout);
+    }
+  }
+  void processStderr(String line) {
+    stderrLog.add(line);
+    if (streamingLogs) {
+      print('stderr: $line');
+    }
+  }
+  if (debug) {
+    processTimeout();
+  } else {
+    timeout = Timer(expectedMaxDuration ~/ 2, processTimeout);
+  }
+  process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(processStdout);
+  process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(processStderr);
+  unawaited(process.exitCode.timeout(expectedMaxDuration, onTimeout: () {
+    print('(process is not quitting, trying to send a "q" just in case that helps)');
+    print('(a functional test should never reach this point)');
+    process.stdin.write('q');
+    return null;
+  }).catchError((Object error) { /* ignore the error here, it'll be reported on the next line */ }));
+  final int exitCode = await process.exitCode;
+  if (streamingLogs) {
+    print('(process terminated with exit code $exitCode)');
+  }
+  timeout?.cancel();
+  if (nextTransition < transitions.length) {
+    print('The subprocess terminated before all the expected transitions had been matched.');
+    if (stderrLog.any((String line) => line.contains('Oops; flutter has exited unexpectedly:'))) {
+      print('The subprocess may in fact have crashed. Check the stderr logs below.');
+    }
+    print('The transition that we were hoping to see next but that we never saw was:');
+    print('${nextTransition.toString().padLeft(5)} NOW WAITING FOR> ${transitions[nextTransition]}');
+    if (!streamingLogs) {
+      describeStatus();
+      print('(process terminated with exit code $exitCode)');
+    }
+    throw TestFailure('Missed some expected transitions.');
+  }
+  if (streamingLogs) {
+    print('(completed execution successfully!)');
+  }
+  return ProcessTestResult(exitCode, stdoutLog, stderrLog);
+}
+
+void main() {
+  testWithoutContext('flutter run writes and clears pidfile appropriately', () async {
+    final String tempDirectory = fileSystem.systemTempDirectory.createTempSync('flutter_overall_experience_test.').resolveSymbolicLinksSync();
+    final String pidFile = fileSystem.path.join(tempDirectory, 'flutter.pid');
+    final String testDirectory = fileSystem.path.join(flutterRoot, 'examples', 'hello_world');
+    bool/*?*/ existsDuringTest;
+    try {
+      expect(fileSystem.file(pidFile).existsSync(), isFalse);
+      final ProcessTestResult result = await runFlutter(
+        <String>['run', '-dflutter-tester', '--pid-file', pidFile],
+        testDirectory,
+        <Transition>[
+          Barrier('q Quit (terminate the application on the device).', handler: (String line) {
+            existsDuringTest = fileSystem.file(pidFile).existsSync();
+            return 'q';
+          }),
+          const Barrier('Application finished.'),
+        ],
+      );
+      expect(existsDuringTest, isNot(isNull));
+      expect(existsDuringTest, isTrue);
+      expect(result.exitCode, 0, reason: 'subprocess failed; $result');
+      expect(fileSystem.file(pidFile).existsSync(), isFalse);
+      // This first test ignores the stdout and stderr, so that if the
+      // first run outputs "building flutter", or the "there's a new
+      // flutter" banner, or other such first-run messages, they won't
+      // fail the tests. This does mean that running this test first is
+      // actually important in the case where you're running the tests
+      // manually. (On CI, all those messages are expected to be seen
+      // long before we get here, e.g. because we run "flutter doctor".)
+    } finally {
+      tryToDelete(fileSystem.directory(tempDirectory));
+    }
+  });
+
+  testWithoutContext('flutter run handle SIGUSR1/2', () async {
+    final String tempDirectory = fileSystem.systemTempDirectory.createTempSync('flutter_overall_experience_test.').resolveSymbolicLinksSync();
+    final String pidFile = fileSystem.path.join(tempDirectory, 'flutter.pid');
+    final String testDirectory = fileSystem.path.join(flutterRoot, 'dev', 'integration_tests', 'ui');
+    final String testScript = fileSystem.path.join('lib', 'commands.dart');
+    /*late*/ int pid;
+    try {
+      final ProcessTestResult result = await runFlutter(
+        <String>['run', '-dflutter-tester', '--report-ready', '--pid-file', pidFile, '--no-devtools', testScript],
+        testDirectory,
+        <Transition>[
+          Barrier('Flutter run key commands.', handler: (String line) {
+            pid = int.parse(fileSystem.file(pidFile).readAsStringSync());
+            processManager.killPid(pid, ProcessSignal.sigusr1);
+            return null;
+          }),
+          Barrier(RegExp(r'^Performing hot reload\.\.\.'), logging: true),
+          Multiple(<Pattern>[RegExp(r'^Reloaded 0 libraries in [0-9]+ms\.$'), /*'called reassemble', (see TODO below)*/ 'called paint'], handler: (String line) {
+            processManager.killPid(pid, ProcessSignal.sigusr2);
+            return null;
+          }),
+          Barrier(RegExp(r'^Performing hot restart\.\.\.')),
+          Multiple(<Pattern>[RegExp(r'^Restarted application in [0-9]+ms.$'), 'called main', 'called paint'], handler: (String line) {
+            return 'q';
+          }),
+          const Barrier('Application finished.'),
+        ],
+        logging: false, // we ignore leading log lines to avoid making this test sensitive to e.g. the help message text
+      );
+      // We check the output from the app (all starts with "called ...") and the output from the tool
+      // (everything else) separately, because their relative timing isn't guaranteed. Their rough timing
+      // is verified by the expected transitions above.
+      // TODO(ianh): Fix the tool so that the output isn't garbled (right now we're putting debug output from
+      // the app on the line where we're spinning the busy signal, rather than adding a newline).
+      expect(result.stdout.where((String line) => line.startsWith('called ') && line != 'called reassemble' /* see todo above*/), <Object>[
+        // logs start after we receive the response to sending SIGUSR1
+        // SIGUSR1:
+        // 'called reassemble', // see todo above, this only sometimes gets included, other times it's on the "performing..." line
+        'called paint',
+        // SIGUSR2:
+        'called main',
+        'called paint',
+      ]);
+      expect(result.stdout.where((String line) => !line.startsWith('called ')), <Object>[
+        // logs start after we receive the response to sending SIGUSR1
+        startsWith('Performing hot reload...'), // see todo above, this sometimes ends with "called reassemble"
+        '', // this newline is probably the misplaced one for the reassemble; see todo above
+        startsWith('Reloaded 0 libraries in '),
+        'Performing hot restart...                                       ',
+        startsWith('Restarted application in '),
+        '', // this newline is the one for after we hit "q"
+        'Application finished.',
+        'ready',
+      ]);
+      expect(result.exitCode, 0);
+    } finally {
+      tryToDelete(fileSystem.directory(tempDirectory));
+    }
+  }, skip: Platform.isWindows); // Windows doesn't support sending signals.
+
+  testWithoutContext('flutter run can hot reload and hot restart, handle "p" key', () async {
+    final String tempDirectory = fileSystem.systemTempDirectory.createTempSync('flutter_overall_experience_test.').resolveSymbolicLinksSync();
+    final String testDirectory = fileSystem.path.join(flutterRoot, 'dev', 'integration_tests', 'ui');
+    final String testScript = fileSystem.path.join('lib', 'commands.dart');
+    try {
+      final ProcessTestResult result = await runFlutter(
+        <String>['run', '-dflutter-tester', '--report-ready', '--no-devtools', testScript],
+        testDirectory,
+        <Transition>[
+          Multiple(<Pattern>['Flutter run key commands.', 'called main'], handler: (String line) {
+            return 'r';
+          }),
+          Barrier(RegExp(r'^Performing hot reload\.\.\.'), logging: true),
+          Multiple(<Pattern>['ready', /*'reassemble', (see todo below)*/ 'called paint'], handler: (String line) {
+            return 'R';
+          }),
+          Barrier(RegExp(r'^Performing hot restart\.\.\.')),
+          Multiple(<Pattern>['ready', 'called main', 'called paint'], handler: (String line) {
+            return 'p';
+          }),
+          Multiple(<Pattern>['ready', 'called paint', 'called debugPaintSize'], handler: (String line) {
+            return 'p';
+          }),
+          Multiple(<Pattern>['ready', 'called paint'], handler: (String line) {
+            return 'q';
+          }),
+          const Barrier('Application finished.'),
+        ],
+        logging: false, // we ignore leading log lines to avoid making this test sensitive to e.g. the help message text
+      );
+      // We check the output from the app (all starts with "called ...") and the output from the tool
+      // (everything else) separately, because their relative timing isn't guaranteed. Their rough timing
+      // is verified by the expected transitions above.
+      // TODO(ianh): Fix the tool so that the output isn't garbled (right now we're putting debug output from
+      // the app on the line where we're spinning the busy signal, rather than adding a newline).
+      expect(result.stdout.where((String line) => line.startsWith('called ') && line != 'called reassemble' /* see todo above*/), <Object>[
+        // hot reload:
+        // 'called reassemble', // see todo above, this sometimes gets placed on the "Performing hot reload..." line
+        'called paint',
+        // hot restart:
+        'called main',
+        'called paint',
+        // debugPaintSizeEnabled = true:
+        'called paint',
+        'called debugPaintSize',
+        // debugPaintSizeEnabled = false:
+        'called paint',
+      ]);
+      expect(result.stdout.where((String line) => !line.startsWith('called ')), <Object>[
+        // logs start after we receive the response to hitting "r"
+        startsWith('Performing hot reload...'), // see todo above, this sometimes ends with "called reassemble"
+        '', // this newline is probably the misplaced one for the reassemble; see todo above
+        startsWith('Reloaded 0 libraries in '),
+        'ready',
+        '', // this newline is the one for after we hit "R"
+        'Performing hot restart...                                       ',
+        startsWith('Restarted application in '),
+        'ready',
+        '', // newline for after we hit "p" the first time
+        'ready',
+        '', // newline for after we hit "p" the second time
+        'ready',
+        '', // this newline is the one for after we hit "q"
+        'Application finished.',
+        'ready',
+      ]);
+      expect(result.exitCode, 0);
+    } finally {
+      tryToDelete(fileSystem.directory(tempDirectory));
+    }
+  });
+
+  testWithoutContext('flutter error messages include a DevTools link', () async {
+    final String tempDirectory = fileSystem.systemTempDirectory.createTempSync('flutter_overall_experience_test.').resolveSymbolicLinksSync();
+    final String testDirectory = fileSystem.path.join(flutterRoot, 'dev', 'integration_tests', 'ui');
+    final String testScript = fileSystem.path.join('lib', 'overflow.dart');
+    try {
+      final ProcessTestResult result = await runFlutter(
+        <String>['run', '-dflutter-tester', testScript],
+        testDirectory,
+        <Transition>[
+          Barrier(RegExp(r'^An Observatory debugger and profiler on Flutter test device is available at: ')),
+          Barrier(RegExp(r'^The Flutter DevTools debugger and profiler on Flutter test device is available at: '), handler: (String line) {
+            return 'r';
+          }),
+          Barrier(RegExp(r'^Performing hot reload\.\.\.'), logging: true),
+          Barrier(RegExp(r'^Reloaded 0 libraries in [0-9]+ms.'), handler: (String line) {
+            return 'q';
+          }),
+        ],
+        logging: false,
+      );
+      expect(result.exitCode, 0);
+      expect(result.stdout, <Object>[
+        startsWith('Performing hot reload...'),
+        '══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════',
+        'The following assertion was thrown during layout:',
+        'A RenderFlex overflowed by 69200 pixels on the right.',
+        '',
+        'The relevant error-causing widget was:',
+        matches(RegExp(r'^  Row .+flutter/dev/integration_tests/ui/lib/overflow\.dart:31:12$')),
+        '',
+        'To inspect this widget in Flutter DevTools, visit:',
+        startsWith('http'),
+        '',
+        'The overflowing RenderFlex has an orientation of Axis.horizontal.',
+        'The edge of the RenderFlex that is overflowing has been marked in the rendering with a yellow and',
+        'black striped pattern. This is usually caused by the contents being too big for the RenderFlex.',
+        'Consider applying a flex factor (e.g. using an Expanded widget) to force the children of the',
+        'RenderFlex to fit within the available space instead of being sized to their natural size.',
+        'This is considered an error condition because it indicates that there is content that cannot be',
+        'seen. If the content is legitimately bigger than the available space, consider clipping it with a',
+        'ClipRect widget before putting it in the flex, or using a scrollable container rather than a Flex,',
+        'like a ListView.',
+        matches(RegExp(r'^The specific RenderFlex in question is: RenderFlex#..... OVERFLOWING:$')),
+        startsWith('  creator: Row ← Test ← '),
+        contains(' ← '),
+        endsWith(' ← ⋯'),
+        '  parentData: <none> (can use size)',
+        '  constraints: BoxConstraints(w=800.0, h=600.0)',
+        '  size: Size(800.0, 600.0)',
+        '  direction: horizontal',
+        '  mainAxisAlignment: start',
+        '  mainAxisSize: max',
+        '  crossAxisAlignment: center',
+        '  textDirection: ltr',
+        '  verticalDirection: down',
+        '◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤',
+        '════════════════════════════════════════════════════════════════════════════════════════════════════',
+        '',
+        startsWith('Reloaded 0 libraries in '),
+        '',
+        'Application finished.',
+      ]);
+    } finally {
+      tryToDelete(fileSystem.directory(tempDirectory));
+    }
+  }, skip: 'DevTools does not reliably launch on bots currently.'); // TODO(ianh): fix and re-enable test.
+
+  testWithoutContext('flutter run help output', () async {
+    // This test enables all logging so that it checks the exact text of starting up an application.
+    // The idea is to verify that we're not outputting spurious messages.
+    // WHEN EDITING THIS TEST PLEASE CAREFULLY CONSIDER WHETHER THE NEW OUTPUT IS AN IMPROVEMENT.
+    final String testDirectory = fileSystem.path.join(flutterRoot, 'examples', 'hello_world');
+    final RegExp finalLine = RegExp(r'^An Observatory'); /* RegExp(r'^The Flutter DevTools'); */ // TODO(ianh): use this when enabling devtools
+    final ProcessTestResult result = await runFlutter(
+      <String>['run', '-dflutter-tester', '--no-devtools'], // TODO(ianh): enable devtools
+      testDirectory,
+      <Transition>[
+        Barrier(finalLine, handler: (String line) {
+          return 'h';
+        }),
+        Barrier(finalLine, handler: (String line) {
+          return 'q';
+        }),
+        const Barrier('Application finished.'),
+      ],
+    );
+    expect(result.exitCode, 0);
+    expect(result.stderr, isEmpty);
+    expect(result.stdout, <Object>[
+      startsWith('Launching '),
+      startsWith('Syncing files to device Flutter test device...'),
+      '',
+      'Flutter run key commands.',
+      startsWith('r Hot reload.'),
+      'R Hot restart.',
+      'h Repeat this help message.',
+      'd Detach (terminate "flutter run" but leave application running).',
+      'c Clear the screen',
+      'q Quit (terminate the application on the device).',
+      '',
+      contains('Running with sound null safety'),
+      '',
+      startsWith('An Observatory debugger and profiler on Flutter test device is available at: http://'),
+      /* startsWith('The Flutter DevTools debugger and profiler on Flutter test device is available at: http://'), */ // TODO(ianh): enable devtools
+      '',
+      'Flutter run key commands.',
+      startsWith('r Hot reload.'),
+      'R Hot restart.',
+      'h Repeat this help message.',
+      'd Detach (terminate "flutter run" but leave application running).',
+      'c Clear the screen',
+      'q Quit (terminate the application on the device).',
+      'b Toggle the platform brightness setting (dark and light mode).            (debugBrightnessOverride)',
+      'w Dump widget hierarchy to the console.                                               (debugDumpApp)',
+      't Dump rendering tree to the console.                                          (debugDumpRenderTree)',
+      'L Dump layer tree to the console.                                               (debugDumpLayerTree)',
+      'S Dump accessibility tree in traversal order.                                   (debugDumpSemantics)',
+      'U Dump accessibility tree in inverse hit test order.                            (debugDumpSemantics)',
+      'i Toggle widget inspector.                                  (WidgetsApp.showWidgetInspectorOverride)',
+      startsWith('I Toggle oversized image inversion'),
+      'p Toggle the display of construction lines.                                  (debugPaintSizeEnabled)',
+      'o Simulate different operating systems.                                      (defaultTargetPlatform)',
+      'z Toggle elevation checker.',
+      'g Run source code generators.',
+      'M Write SkSL shaders to a unique file in the project directory.',
+      'v Launch DevTools.', // TODO(ianh): hide this when devtools isn't available
+      'P Toggle performance overlay.                                    (WidgetsApp.showPerformanceOverlay)',
+      'a Toggle timeline events for all widget build methods.                    (debugProfileWidgetBuilds)',
+      '',
+      contains('Running with sound null safety'),
+      '',
+      startsWith('An Observatory debugger and profiler on Flutter test device is available at: http://'),
+      /* startsWith('The Flutter DevTools debugger and profiler on Flutter test device is available at: http://'), */ // TODO(ianh): enable devtools
+      '',
+      'Application finished.',
+    ]);
+  });
+}

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

@@ -86,7 +86,6 @@ abstract class FlutterTestDriver {
     List<String> arguments, {
     String script,
     bool withDebugger = false,
-    File pidFile,
     bool singleWidgetReloads = false,
   }) async {
     final String flutterBin = fileSystem.path.join(getFlutterRoot(), 'bin', 'flutter');
@@ -96,9 +95,6 @@ abstract class FlutterTestDriver {
     if (_printDebugOutputToStdOut) {
       arguments.add('--verbose');
     }
-    if (pidFile != null) {
-      arguments.addAll(<String>['--pid-file', pidFile.path]);
-    }
     if (script != null) {
       arguments.add(script);
     }
@@ -467,9 +463,7 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool chrome = false,
     bool expressionEvaluation = true,
     bool structuredErrors = false,
-    bool machine = true,
     bool singleWidgetReloads = false,
-    File pidFile,
     String script,
     List<String> additionalCommandArgs,
   }) async {
@@ -478,7 +472,7 @@ class FlutterRunTestDriver extends FlutterTestDriver {
         'run',
         if (!chrome)
           '--disable-service-auth-codes',
-        if (machine) '--machine',
+        '--machine',
         if (!spawnDdsInstance) '--disable-dds',
         ...getLocalEngineArguments(),
         '-d',
@@ -497,7 +491,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       withDebugger: withDebugger,
       startPaused: startPaused,
       pauseOnExceptions: pauseOnExceptions,
-      pidFile: pidFile,
       script: script,
       singleWidgetReloads: singleWidgetReloads,
     );
@@ -508,7 +501,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool withDebugger = false,
     bool startPaused = false,
     bool pauseOnExceptions = false,
-    File pidFile,
     bool singleWidgetReloads = false,
     List<String> additionalCommandArgs,
   }) async {
@@ -529,7 +521,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       withDebugger: withDebugger,
       startPaused: startPaused,
       pauseOnExceptions: pauseOnExceptions,
-      pidFile: pidFile,
       singleWidgetReloads: singleWidgetReloads,
       attachPort: port,
     );
@@ -543,7 +534,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool startPaused = false,
     bool pauseOnExceptions = false,
     bool singleWidgetReloads = false,
-    File pidFile,
     int attachPort,
   }) async {
     assert(!startPaused || withDebugger);
@@ -551,7 +541,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       args,
       script: script,
       withDebugger: withDebugger,
-      pidFile: pidFile,
       singleWidgetReloads: singleWidgetReloads,
     );
 
@@ -738,7 +727,6 @@ class FlutterTestTestDriver extends FlutterTestDriver {
     bool withDebugger = false,
     bool pauseOnExceptions = false,
     bool coverage = false,
-    File pidFile,
     Future<void> Function() beforeStart,
   }) async {
     await _setupProcess(<String>[
@@ -748,7 +736,7 @@ class FlutterTestTestDriver extends FlutterTestDriver {
       '--machine',
       if (coverage)
         '--coverage',
-    ], script: testFile, withDebugger: withDebugger, pauseOnExceptions: pauseOnExceptions, pidFile: pidFile, beforeStart: beforeStart);
+    ], script: testFile, withDebugger: withDebugger, pauseOnExceptions: pauseOnExceptions, beforeStart: beforeStart);
   }
 
   @override
@@ -757,7 +745,6 @@ class FlutterTestTestDriver extends FlutterTestDriver {
     String script,
     bool withDebugger = false,
     bool pauseOnExceptions = false,
-    File pidFile,
     Future<void> Function() beforeStart,
     bool singleWidgetReloads = false,
   }) async {
@@ -765,7 +752,6 @@ class FlutterTestTestDriver extends FlutterTestDriver {
       args,
       script: script,
       withDebugger: withDebugger,
-      pidFile: pidFile,
       singleWidgetReloads: singleWidgetReloads,
     );