Migrate emulators to null safety (#92738)

packages/flutter_tools/lib/src/android/android_emulator.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:meta/meta.dart';
@@ -23,11 +21,11 @@ import 'android_sdk.dart';
 
 class AndroidEmulators extends EmulatorDiscovery {
   AndroidEmulators({
-    @required AndroidSdk androidSdk,
-    @required AndroidWorkflow androidWorkflow,
-    @required FileSystem fileSystem,
-    @required Logger logger,
-    @required ProcessManager processManager,
+    AndroidSdk? androidSdk,
+    required AndroidWorkflow androidWorkflow,
+    required FileSystem fileSystem,
+    required Logger logger,
+    required ProcessManager processManager,
   }) : _androidSdk = androidSdk,
        _androidWorkflow = androidWorkflow,
        _fileSystem = fileSystem,
@@ -36,7 +34,7 @@ class AndroidEmulators extends EmulatorDiscovery {
        _processUtils = ProcessUtils(logger: logger, processManager: processManager);
 
   final AndroidWorkflow _androidWorkflow;
-  final AndroidSdk _androidSdk;
+  final AndroidSdk? _androidSdk;
   final FileSystem _fileSystem;
   final Logger _logger;
   final ProcessManager _processManager;
@@ -50,14 +48,14 @@ class AndroidEmulators extends EmulatorDiscovery {
 
   @override
   bool get canLaunchAnything => _androidWorkflow.canListEmulators
-    && _androidSdk.getAvdManagerPath() != null;
+    && _androidSdk?.getAvdManagerPath() != null;
 
   @override
   Future<List<Emulator>> get emulators => _getEmulatorAvds();
 
   /// Return the list of available emulator AVDs.
   Future<List<AndroidEmulator>> _getEmulatorAvds() async {
-    final String emulatorPath = _androidSdk?.emulatorPath;
+    final String? emulatorPath = _androidSdk?.emulatorPath;
     if (emulatorPath == null) {
       return <AndroidEmulator>[];
     }
@@ -82,7 +80,7 @@ class AndroidEmulators extends EmulatorDiscovery {
 
   AndroidEmulator _loadEmulatorInfo(String id) {
     id = id.trim();
-    final String avdPath = _androidSdk.getAvdPath();
+    final String? avdPath = _androidSdk?.getAvdPath();
     final AndroidEmulator androidEmulatorWithoutProperties = AndroidEmulator(
       id,
       processManager: _processManager,
@@ -97,10 +95,11 @@ class AndroidEmulators extends EmulatorDiscovery {
       return androidEmulatorWithoutProperties;
     }
     final Map<String, String> ini = parseIniLines(iniFile.readAsLinesSync());
-    if (ini['path'] == null) {
+    final String? path = ini['path'];
+    if (path == null) {
       return androidEmulatorWithoutProperties;
     }
-    final File configFile = _fileSystem.file(_fileSystem.path.join(ini['path'], 'config.ini'));
+    final File configFile = _fileSystem.file(_fileSystem.path.join(path, 'config.ini'));
     if (!configFile.existsSync()) {
       return androidEmulatorWithoutProperties;
     }
@@ -117,20 +116,20 @@ class AndroidEmulators extends EmulatorDiscovery {
 
 class AndroidEmulator extends Emulator {
   AndroidEmulator(String id, {
-    Map<String, String> properties,
-    @required Logger logger,
-    @required AndroidSdk androidSdk,
-    @required ProcessManager processManager,
+    Map<String, String>? properties,
+    required Logger logger,
+    AndroidSdk? androidSdk,
+    required ProcessManager processManager,
   }) : _properties = properties,
        _logger = logger,
        _androidSdk = androidSdk,
        _processUtils = ProcessUtils(logger: logger, processManager: processManager),
        super(id, properties != null && properties.isNotEmpty);
 
-  final Map<String, String> _properties;
+  final Map<String, String>? _properties;
   final Logger _logger;
   final ProcessUtils _processUtils;
-  final AndroidSdk _androidSdk;
+  final AndroidSdk? _androidSdk;
 
   // Android Studio uses the ID with underscores replaced with spaces
   // for the name if displayname is not set so we do the same.
@@ -138,7 +137,7 @@ class AndroidEmulator extends Emulator {
   String get name => _prop('avd.ini.displayname') ?? id.replaceAll('_', ' ').trim();
 
   @override
-  String get manufacturer => _prop('hw.device.manufacturer');
+  String? get manufacturer => _prop('hw.device.manufacturer');
 
   @override
   Category get category => Category.mobile;
@@ -146,12 +145,16 @@ class AndroidEmulator extends Emulator {
   @override
   PlatformType get platformType => PlatformType.android;
 
-  String _prop(String name) => _properties != null ? _properties[name] : null;
+  String? _prop(String name) => _properties != null ? _properties![name] : null;
 
   @override
-  Future<void> launch({@visibleForTesting Duration startupDuration, bool coldBoot = false}) async {
+  Future<void> launch({@visibleForTesting Duration? startupDuration, bool coldBoot = false}) async {
+    final String? emulatorPath = _androidSdk?.emulatorPath;
+    if (emulatorPath == null) {
+      throw Exception('Emulator is missing from the Android SDK');
+    }
     final List<String> command = <String>[
-      _androidSdk.emulatorPath,
+      emulatorPath,
       '-avd',
       id,
       if (coldBoot)

packages/flutter_tools/lib/src/emulator.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:math' as math;
 
 import 'package:meta/meta.dart';
@@ -19,16 +17,16 @@ import 'base/process.dart';
 import 'device.dart';
 import 'ios/ios_emulators.dart';
 
-EmulatorManager get emulatorManager => context.get<EmulatorManager>();
+EmulatorManager? get emulatorManager => context.get<EmulatorManager>();
 
 /// A class to get all available emulators.
 class EmulatorManager {
   EmulatorManager({
-    @required AndroidSdk androidSdk,
-    @required Logger logger,
-    @required ProcessManager processManager,
-    @required AndroidWorkflow androidWorkflow,
-    @required FileSystem fileSystem,
+    AndroidSdk? androidSdk,
+    required Logger logger,
+    required ProcessManager processManager,
+    required AndroidWorkflow androidWorkflow,
+    required FileSystem fileSystem,
   }) : _androidSdk = androidSdk,
        _processUtils = ProcessUtils(logger: logger, processManager: processManager),
        _androidEmulators = AndroidEmulators(
@@ -41,7 +39,7 @@ class EmulatorManager {
     _emulatorDiscoverers.add(_androidEmulators);
   }
 
-  final AndroidSdk _androidSdk;
+  final AndroidSdk? _androidSdk;
   final AndroidEmulators _androidEmulators;
   final ProcessUtils _processUtils;
 
@@ -55,14 +53,19 @@ class EmulatorManager {
     final List<Emulator> emulators = await getAllAvailableEmulators();
     searchText = searchText.toLowerCase();
     bool exactlyMatchesEmulatorId(Emulator emulator) =>
-        emulator.id?.toLowerCase() == searchText ||
-        emulator.name?.toLowerCase() == searchText;
+        emulator.id.toLowerCase() == searchText ||
+        emulator.name.toLowerCase() == searchText;
     bool startsWithEmulatorId(Emulator emulator) =>
-        emulator.id?.toLowerCase()?.startsWith(searchText) == true ||
-        emulator.name?.toLowerCase()?.startsWith(searchText) == true;
-
-    final Emulator exactMatch =
-        emulators.firstWhere(exactlyMatchesEmulatorId, orElse: () => null);
+        emulator.id.toLowerCase().startsWith(searchText) == true ||
+        emulator.name.toLowerCase().startsWith(searchText) == true;
+
+    Emulator? exactMatch;
+    for (final Emulator emulator in emulators) {
+      if (exactlyMatchesEmulatorId(emulator)) {
+        exactMatch = emulator;
+        break;
+      }
+    }
     if (exactMatch != null) {
       return <Emulator>[exactMatch];
     }
@@ -85,7 +88,7 @@ class EmulatorManager {
   }
 
   /// Return the list of all available emulators.
-  Future<CreateEmulatorResult> createEmulator({ String name }) async {
+  Future<CreateEmulatorResult> createEmulator({ String? name }) async {
     if (name == null || name.isEmpty) {
       const String autoName = 'flutter_emulator';
       // Don't use getEmulatorsMatching here, as it will only return one
@@ -102,21 +105,23 @@ class EmulatorManager {
         name = '${autoName}_${++suffix}';
       }
     }
-    if (!_androidEmulators.canLaunchAnything) {
-      return CreateEmulatorResult(name,
+    final String emulatorName = name!;
+    final String? avdManagerPath = _androidSdk?.avdManagerPath;
+    if (avdManagerPath == null || !_androidEmulators.canLaunchAnything) {
+      return CreateEmulatorResult(emulatorName,
         success: false, error: 'avdmanager is missing from the Android SDK'
       );
     }
 
-    final String device = await _getPreferredAvailableDevice();
+    final String? device = await _getPreferredAvailableDevice(avdManagerPath);
     if (device == null) {
-      return CreateEmulatorResult(name,
+      return CreateEmulatorResult(emulatorName,
           success: false, error: 'No device definitions are available');
     }
 
-    final String sdkId = await _getPreferredSdkId();
+    final String? sdkId = await _getPreferredSdkId(avdManagerPath);
     if (sdkId == null) {
-      return CreateEmulatorResult(name,
+      return CreateEmulatorResult(emulatorName,
           success: false,
           error:
               'No suitable Android AVD system images are available. You may need to install these'
@@ -128,7 +133,7 @@ class EmulatorManager {
     // to flutter users. Specifically:
     // - Removes lines that say "null" (!)
     // - Removes lines that tell the user to use '--force' to overwrite emulators
-    String cleanError(String error) {
+    String? cleanError(String? error) {
       if (error == null || error.trim() == '') {
         return null;
       }
@@ -141,16 +146,16 @@ class EmulatorManager {
           .trim();
     }
     final RunResult runResult = await _processUtils.run(<String>[
-      _androidSdk?.avdManagerPath,
+        avdManagerPath,
         'create',
         'avd',
-        '-n', name,
+        '-n', emulatorName,
         '-k', sdkId,
         '-d', device,
       ], environment: _androidSdk?.sdkManagerEnv,
     );
     return CreateEmulatorResult(
-      name,
+      emulatorName,
       success: runResult.exitCode == 0,
       output: runResult.stdout,
       error: cleanError(runResult.stderr),
@@ -162,9 +167,9 @@ class EmulatorManager {
     'pixel_xl',
   ];
 
-  Future<String> _getPreferredAvailableDevice() async {
+  Future<String?> _getPreferredAvailableDevice(String avdManagerPath) async {
     final List<String> args = <String>[
-      _androidSdk?.avdManagerPath,
+      avdManagerPath,
       'list',
       'device',
       '-c',
@@ -180,19 +185,21 @@ class EmulatorManager {
         .where((String l) => preferredDevices.contains(l.trim()))
         .toList();
 
-    return preferredDevices.firstWhere(
-      (String d) => availableDevices.contains(d),
-      orElse: () => null,
-    );
+    for (final String device in preferredDevices) {
+      if (availableDevices.contains(device)) {
+        return device;
+      }
+    }
+    return null;
   }
 
   static final RegExp _androidApiVersion = RegExp(r';android-(\d+);');
 
-  Future<String> _getPreferredSdkId() async {
+  Future<String?> _getPreferredSdkId(String avdManagerPath) async {
     // It seems that to get the available list of images, we need to send a
     // request to create without the image and it'll provide us a list :-(
     final List<String> args = <String>[
-      _androidSdk?.avdManagerPath,
+      avdManagerPath,
       'create',
       'avd',
       '-n', 'temp',
@@ -209,7 +216,7 @@ class EmulatorManager {
         .toList();
 
     final List<int> availableApiVersions = availableIDs
-        .map<String>((String id) => _androidApiVersion.firstMatch(id).group(1))
+        .map<String>((String id) => _androidApiVersion.firstMatch(id)!.group(1)!)
         .map<int>((String apiVersion) => int.parse(apiVersion))
         .toList();
 
@@ -220,10 +227,12 @@ class EmulatorManager {
 
     // We're out of preferences, we just have to return the first one with the high
     // API version.
-    return availableIDs.firstWhere(
-      (String id) => id.contains(';android-$apiVersion;'),
-      orElse: () => null,
-    );
+    for (final String id in availableIDs) {
+      if (id.contains(';android-$apiVersion;')) {
+        return id;
+      }
+    }
+    return null;
   }
 
   /// Whether we're capable of listing any emulators given the current environment configuration.
@@ -252,7 +261,7 @@ abstract class Emulator {
   final String id;
   final bool hasConfig;
   String get name;
-  String get manufacturer;
+  String? get manufacturer;
   Category get category;
   PlatformType get platformType;
 
@@ -282,10 +291,10 @@ abstract class Emulator {
     final List<List<String>> table = <List<String>>[
       for (final Emulator emulator in emulators)
         <String>[
-          emulator.id ?? '',
-          emulator.name ?? '',
+          emulator.id,
+          emulator.name,
           emulator.manufacturer ?? '',
-          emulator.platformType?.toString() ?? '',
+          emulator.platformType.toString(),
         ],
     ];
 
@@ -315,10 +324,10 @@ abstract class Emulator {
 }
 
 class CreateEmulatorResult {
-  CreateEmulatorResult(this.emulatorName, {this.success, this.output, this.error});
+  CreateEmulatorResult(this.emulatorName, {required this.success, this.output, this.error});
 
   final bool success;
   final String emulatorName;
-  final String output;
-  final String error;
+  final String? output;
+  final String? error;
 }

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

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
+import '../base/common.dart';
 import '../base/process.dart';
 import '../device.dart';
 import '../emulator.dart';
@@ -15,7 +14,7 @@ class IOSEmulators extends EmulatorDiscovery {
   bool get supportsPlatform => globals.platform.isMacOS;
 
   @override
-  bool get canListAnything => globals.iosWorkflow.canListEmulators;
+  bool get canListAnything => globals.iosWorkflow?.canListEmulators == true;
 
   @override
   Future<List<Emulator>> get emulators async => getEmulators();
@@ -41,12 +40,16 @@ class IOSEmulator extends Emulator {
 
   @override
   Future<void> launch({bool coldBoot = false}) async {
+    final String? simulatorPath = globals.xcode?.getSimulatorPath();
+    if (simulatorPath == null) {
+      throwToolExit('Could not find Simulator app');
+    }
     Future<bool> launchSimulator(List<String> additionalArgs) async {
       final List<String> args = <String>[
         'open',
         ...additionalArgs,
         '-a',
-        globals.xcode.getSimulatorPath(),
+        simulatorPath,
       ];
 
       final RunResult launchResult = await globals.processUtils.run(args);
@@ -70,7 +73,7 @@ class IOSEmulator extends Emulator {
 
 /// Return the list of iOS Simulators (there can only be zero or one).
 List<IOSEmulator> getEmulators() {
-  final String simulatorPath = globals.xcode.getSimulatorPath();
+  final String? simulatorPath = globals.xcode?.getSimulatorPath();
   if (simulatorPath == null) {
     return <IOSEmulator>[];
   }

packages/flutter_tools/test/general.shard/android/android_emulator_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:flutter_tools/src/android/android_emulator.dart';
@@ -125,7 +123,7 @@ void main() {
   });
 
   group('Android emulator launch ', () {
-    FakeAndroidSdk mockSdk;
+    late FakeAndroidSdk mockSdk;
 
     setUp(() {
       mockSdk = FakeAndroidSdk();
@@ -198,10 +196,30 @@ void main() {
 
       expect(logger.errorText, isEmpty);
     });
+
+    testWithoutContext('throws if emulator not found', () async {
+      mockSdk.emulatorPath = null;
+
+      final AndroidEmulator emulator = AndroidEmulator(
+        emulatorID,
+        processManager: FakeProcessManager.empty(),
+        androidSdk: mockSdk,
+        logger: BufferLogger.test(),
+      );
+
+      await expectLater(
+        () => emulator.launch(startupDuration: Duration.zero),
+        throwsA(isException.having(
+          (Exception exception) => exception.toString(),
+          'description',
+          contains('Emulator is missing from the Android SDK'),
+        )),
+      );
+    });
   });
 }
 
 class FakeAndroidSdk extends Fake implements AndroidSdk {
   @override
-  String emulatorPath;
+  String? emulatorPath;
 }

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

@@ -97,7 +97,6 @@ void main() {
             stdout: 'existing-avd-1',
           ),
         ]),
-        androidSdk: null,
         androidWorkflow: AndroidWorkflow(
           androidSdk: sdk,
           featureFlags: TestFeatureFlags(),