Check for simulator runtime in flutter doctor (flutter#131795)

Redo of flutter#130728 - code is the same as before. That PR was stuck in Google testing and then I messed up the rebase so started over.

----

Starting in Xcode 15, the simulator is no longer included in Xcode and must be downloaded and installed separately. This adds a validation to `flutter doctor` to warn when the needed simulator runtime is missing.

Validation message looks like:
```
[!] Xcode - develop for iOS and macOS (Xcode 15.0)
    ! iOS 17.0 Simulator not installed; this may be necessary for iOS and macOS development.
      To download and install the platform, open Xcode, select Xcode > Settings > Platforms,
      and click the GET button for the required platform.

      For more information, please visit:
        https://developer.apple.com/documentation/xcode/installing-additional-simulator-runtimes
```

It may also show an error like this when something goes wrong when checking for the simulator:
```
[!] Xcode - develop for iOS and macOS (Xcode 15.0)
    � Unable to find the iPhone Simulator SDK.
```

Note: I'm unsure of in the future if the SDK and the simulator runtime will need to match the exact version or just the major. For now, it only checks against the major version.

Part 3 of flutter#129558.

Author: vashworth

packages/flutter_tools/lib/src/doctor.dart

@@ -138,7 +138,14 @@ class _DefaultDoctorValidatorsProvider implements DoctorValidatorsProvider {
       if (androidWorkflow!.appliesToHostPlatform)
         GroupedValidator(<DoctorValidator>[androidValidator!, androidLicenseValidator!]),
       if (globals.iosWorkflow!.appliesToHostPlatform || macOSWorkflow.appliesToHostPlatform)
-        GroupedValidator(<DoctorValidator>[XcodeValidator(xcode: globals.xcode!, userMessages: userMessages), globals.cocoapodsValidator!]),
+        GroupedValidator(<DoctorValidator>[
+          XcodeValidator(
+            xcode: globals.xcode!,
+            userMessages: userMessages,
+            iosSimulatorUtils: globals.iosSimulatorUtils!,
+          ),
+          globals.cocoapodsValidator!,
+        ]),
       if (webWorkflow.appliesToHostPlatform)
         ChromeValidator(
           chromiumLauncher: ChromiumLauncher(

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

@@ -15,6 +15,7 @@ import '../base/io.dart';
 import '../base/logger.dart';
 import '../base/process.dart';
 import '../base/utils.dart';
+import '../base/version.dart';
 import '../build_info.dart';
 import '../convert.dart';
 import '../devfs.dart';
@@ -91,6 +92,14 @@ class IOSSimulatorUtils {
       );
     }).whereType<IOSSimulator>().toList();
   }
+
+  Future<List<IOSSimulatorRuntime>> getAvailableIOSRuntimes() async {
+    if (!_xcode.isInstalledAndMeetsVersionCheck) {
+      return <IOSSimulatorRuntime>[];
+    }
+
+    return _simControl.listAvailableIOSRuntimes();
+  }
 }
 
 /// A wrapper around the `simctl` command line tool.
@@ -293,6 +302,46 @@ class SimControl {
       _logger.printError('Unable to take screenshot of $deviceId:\n$exception');
     }
   }
+
+  /// Runs `simctl list runtimes available iOS --json` and returns all available iOS simulator runtimes.
+  Future<List<IOSSimulatorRuntime>> listAvailableIOSRuntimes() async {
+    final List<IOSSimulatorRuntime> runtimes = <IOSSimulatorRuntime>[];
+    final RunResult results = await _processUtils.run(
+      <String>[
+        ..._xcode.xcrunCommand(),
+        'simctl',
+        'list',
+        'runtimes',
+        'available',
+        'iOS',
+        '--json',
+      ],
+    );
+
+    if (results.exitCode != 0) {
+      _logger.printError('Error executing simctl: ${results.exitCode}\n${results.stderr}');
+      return runtimes;
+    }
+
+    try {
+      final Object? decodeResult = (json.decode(results.stdout) as Map<String, Object?>)['runtimes'];
+      if (decodeResult is List<Object?>) {
+        for (final Object? runtimeData in decodeResult) {
+          if (runtimeData is Map<String, Object?>) {
+            runtimes.add(IOSSimulatorRuntime.fromJson(runtimeData));
+          }
+        }
+      }
+
+      return runtimes;
+    } on FormatException {
+      // We failed to parse the simctl output, or it returned junk.
+      // One known message is "Install Started" isn't valid JSON but is
+      // returned sometimes.
+      _logger.printError('simctl returned non-JSON response: ${results.stdout}');
+      return runtimes;
+    }
+  }
 }
 
 
@@ -624,6 +673,64 @@ class IOSSimulator extends Device {
   }
 }
 
+class IOSSimulatorRuntime {
+  IOSSimulatorRuntime._({
+    this.bundlePath,
+    this.buildVersion,
+    this.platform,
+    this.runtimeRoot,
+    this.identifier,
+    this.version,
+    this.isInternal,
+    this.isAvailable,
+    this.name,
+  });
+
+  // Example:
+  // {
+  //   "bundlePath" : "\/Library\/Developer\/CoreSimulator\/Volumes\/iOS_21A5277g\/Library\/Developer\/CoreSimulator\/Profiles\/Runtimes\/iOS 17.0.simruntime",
+  //   "buildversion" : "21A5277g",
+  //   "platform" : "iOS",
+  //   "runtimeRoot" : "\/Library\/Developer\/CoreSimulator\/Volumes\/iOS_21A5277g\/Library\/Developer\/CoreSimulator\/Profiles\/Runtimes\/iOS 17.0.simruntime\/Contents\/Resources\/RuntimeRoot",
+  //   "identifier" : "com.apple.CoreSimulator.SimRuntime.iOS-17-0",
+  //   "version" : "17.0",
+  //   "isInternal" : false,
+  //   "isAvailable" : true,
+  //   "name" : "iOS 17.0",
+  //   "supportedDeviceTypes" : [
+  //     {
+  //       "bundlePath" : "\/Applications\/Xcode.app\/Contents\/Developer\/Platforms\/iPhoneOS.platform\/Library\/Developer\/CoreSimulator\/Profiles\/DeviceTypes\/iPhone 8.simdevicetype",
+  //       "name" : "iPhone 8",
+  //       "identifier" : "com.apple.CoreSimulator.SimDeviceType.iPhone-8",
+  //       "productFamily" : "iPhone"
+  //     }
+  //   ]
+  // },
+  factory IOSSimulatorRuntime.fromJson(Map<String, Object?> data) {
+    return IOSSimulatorRuntime._(
+      bundlePath: data['bundlePath']?.toString(),
+      buildVersion: data['buildversion']?.toString(),
+      platform: data['platform']?.toString(),
+      runtimeRoot: data['runtimeRoot']?.toString(),
+      identifier: data['identifier']?.toString(),
+      version: Version.parse(data['version']?.toString()),
+      isInternal: data['isInternal'] is bool? ? data['isInternal'] as bool? : null,
+      isAvailable: data['isAvailable'] is bool? ? data['isAvailable'] as bool? : null,
+      name: data['name']?.toString(),
+    );
+  }
+
+  final String? bundlePath;
+  final String? buildVersion;
+  final String? platform;
+  final String? runtimeRoot;
+  final String? identifier;
+  final Version? version;
+  final bool? isInternal;
+  final bool? isAvailable;
+  final String? name;
+}
+
 /// Launches the device log reader process on the host and parses the syslog.
 @visibleForTesting
 Future<Process> launchDeviceSystemLogTool(IOSSimulator device) async {

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

@@ -48,7 +48,8 @@ class Xcode {
         _fileSystem = fileSystem,
         _xcodeProjectInterpreter = xcodeProjectInterpreter,
         _processUtils =
-            ProcessUtils(logger: logger, processManager: processManager);
+            ProcessUtils(logger: logger, processManager: processManager),
+        _logger = logger;
 
   /// Create an [Xcode] for testing.
   ///
@@ -60,16 +61,18 @@ class Xcode {
     XcodeProjectInterpreter? xcodeProjectInterpreter,
     Platform? platform,
     FileSystem? fileSystem,
+    Logger? logger,
   }) {
     platform ??= FakePlatform(
       operatingSystem: 'macos',
       environment: <String, String>{},
     );
+    logger ??= BufferLogger.test();
     return Xcode(
       platform: platform,
       processManager: processManager,
       fileSystem: fileSystem ?? MemoryFileSystem.test(),
-      logger: BufferLogger.test(),
+      logger: logger,
       xcodeProjectInterpreter: xcodeProjectInterpreter ?? XcodeProjectInterpreter.test(processManager: processManager),
     );
   }
@@ -78,6 +81,7 @@ class Xcode {
   final ProcessUtils _processUtils;
   final FileSystem _fileSystem;
   final XcodeProjectInterpreter _xcodeProjectInterpreter;
+  final Logger _logger;
 
   bool get isInstalledAndMeetsVersionCheck => _platform.isMacOS && isInstalled && isRequiredVersionSatisfactory;
 
@@ -198,6 +202,19 @@ class Xcode {
     final String appPath = _fileSystem.path.join(selectPath, 'Applications', 'Simulator.app');
     return _fileSystem.directory(appPath).existsSync() ? appPath : null;
   }
+
+  /// Gets the version number of the platform for the selected SDK.
+  Future<Version?> sdkPlatformVersion(EnvironmentType environmentType) async {
+    final RunResult runResult = await _processUtils.run(
+      <String>[...xcrunCommand(), '--sdk', getSDKNameForIOSEnvironmentType(environmentType), '--show-sdk-platform-version'],
+    );
+    if (runResult.exitCode != 0) {
+      _logger.printError('Could not find SDK Platform Version: ${runResult.stderr}');
+      return null;
+    }
+    final String versionString = runResult.stdout.trim();
+    return Version.parse(versionString);
+  }
 }
 
 EnvironmentType? environmentTypeFromSdkroot(String sdkroot, FileSystem fileSystem) {

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

@@ -3,18 +3,32 @@
 // found in the LICENSE file.
 
 import '../base/user_messages.dart';
+import '../base/version.dart';
+import '../build_info.dart';
 import '../doctor_validator.dart';
+import '../ios/simulators.dart';
 import 'xcode.dart';
 
+String _iOSSimulatorMissing(String version) => '''
+iOS $version Simulator not installed; this may be necessary for iOS and macOS development.
+To download and install the platform, open Xcode, select Xcode > Settings > Platforms,
+and click the GET button for the required platform.
+
+For more information, please visit:
+  https://developer.apple.com/documentation/xcode/installing-additional-simulator-runtimes''';
+
 class XcodeValidator extends DoctorValidator {
   XcodeValidator({
     required Xcode xcode,
+    required IOSSimulatorUtils iosSimulatorUtils,
     required UserMessages userMessages,
-  }) : _xcode = xcode,
-      _userMessages = userMessages,
-      super('Xcode - develop for iOS and macOS');
+  })  : _xcode = xcode,
+        _iosSimulatorUtils = iosSimulatorUtils,
+        _userMessages = userMessages,
+        super('Xcode - develop for iOS and macOS');
 
   final Xcode _xcode;
+  final IOSSimulatorUtils _iosSimulatorUtils;
   final UserMessages _userMessages;
 
   @override
@@ -57,6 +71,11 @@ class XcodeValidator extends DoctorValidator {
         messages.add(ValidationMessage.error(_userMessages.xcodeMissingSimct));
       }
 
+      final ValidationMessage? missingSimulatorMessage = await _validateSimulatorRuntimeInstalled();
+      if (missingSimulatorMessage != null) {
+        xcodeStatus = ValidationType.partial;
+        messages.add(missingSimulatorMessage);
+      }
     } else {
       xcodeStatus = ValidationType.missing;
       if (xcodeSelectPath == null || xcodeSelectPath.isEmpty) {
@@ -68,4 +87,45 @@ class XcodeValidator extends DoctorValidator {
 
     return ValidationResult(xcodeStatus, messages, statusInfo: xcodeVersionInfo);
   }
+
+  /// Validate the Xcode-installed iOS simulator SDK has a corresponding iOS
+  /// simulator runtime installed.
+  ///
+  /// Starting with Xcode 15, the iOS simulator runtime is no longer downloaded
+  /// with Xcode and must be downloaded and installed separately.
+  /// iOS applications cannot be run without it.
+  Future<ValidationMessage?> _validateSimulatorRuntimeInstalled() async {
+    // Skip this validation if Xcode is not installed, Xcode is a version less
+    // than 15, simctl is not installed, or if the EULA is not signed.
+    if (!_xcode.isInstalled ||
+        _xcode.currentVersion == null ||
+        _xcode.currentVersion!.major < 15 ||
+        !_xcode.isSimctlInstalled ||
+        !_xcode.eulaSigned) {
+      return null;
+    }
+
+    final Version? platformSDKVersion = await _xcode.sdkPlatformVersion(EnvironmentType.simulator);
+    if (platformSDKVersion == null) {
+      return const ValidationMessage.error('Unable to find the iPhone Simulator SDK.');
+    }
+
+    final List<IOSSimulatorRuntime> runtimes = await _iosSimulatorUtils.getAvailableIOSRuntimes();
+    if (runtimes.isEmpty) {
+      return const ValidationMessage.error('Unable to get list of installed Simulator runtimes.');
+    }
+
+    // Verify there is a simulator runtime installed matching the
+    // iphonesimulator SDK major version.
+    try {
+      runtimes.firstWhere(
+        (IOSSimulatorRuntime runtime) =>
+            runtime.version?.major == platformSDKVersion.major,
+      );
+    } on StateError {
+      return ValidationMessage.hint(_iOSSimulatorMissing(platformSDKVersion.toString()));
+    }
+
+    return null;
+  }
 }