[flutter_tools] Remove `Version.unknown` (#124771)

Fixes #124756 by removing the concept of `Version.unknown`.

`Version` fields that needed the ability to represent an unknown version have been made nullable. Assigning `null` to them represents an unknown version.

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

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/process.dart';
@@ -39,15 +40,16 @@ final RegExp _dotHomeStudioVersionMatcher =
 // See https://github.com/flutter/flutter/issues/124252.
 String? get javaPath => globals.androidStudio?.javaPath;
 
-class AndroidStudio implements Comparable<AndroidStudio> {
+class AndroidStudio {
+  /// A [version] value of null represents an unknown version.
   AndroidStudio(
     this.directory, {
-    Version? version,
-    this.configured,
+    this.version,
+    this.configuredPath,
     this.studioAppName = 'AndroidStudio',
     this.presetPluginsPath,
-  }) : version = version ?? Version.unknown {
-    _init(version: version);
+  }) {
+    _initAndValidate();
   }
 
   static AndroidStudio? fromMacOSBundle(String bundlePath) {
@@ -147,8 +149,13 @@ class AndroidStudio implements Comparable<AndroidStudio> {
 
   final String directory;
   final String studioAppName;
-  final Version version;
-  final String? configured;
+
+  /// The version of Android Studio.
+  ///
+  /// A null value represents an unknown version.
+  final Version? version;
+
+  final String? configuredPath;
   final String? presetPluginsPath;
 
   String? _javaPath;
@@ -163,8 +170,12 @@ class AndroidStudio implements Comparable<AndroidStudio> {
     if (presetPluginsPath != null) {
       return presetPluginsPath!;
     }
-    final int major = version.major;
-    final int minor = version.minor;
+
+    // TODO(andrewkolos): This is a bug. We shouldn't treat an unknown
+    // version as equivalent to 0.0.
+    // See https://github.com/flutter/flutter/issues/121468.
+    final int major = version?.major ?? 0;
+    final int minor = version?.minor ?? 0;
     final String? homeDirPath = globals.fsUtils.homeDirPath;
     if (homeDirPath == null) {
       return null;
@@ -217,25 +228,31 @@ class AndroidStudio implements Comparable<AndroidStudio> {
 
   List<String> get validationMessages => _validationMessages;
 
-  @override
-  int compareTo(AndroidStudio other) {
-    final int result = version.compareTo(other.version);
-    if (result == 0) {
-      return directory.compareTo(other.directory);
-    }
-    return result;
-  }
-
   /// Locates the newest, valid version of Android Studio.
+  ///
+  /// In the case that `--android-studio-dir` is configured, the version of
+  /// Android Studio found at that location is always returned, even if it is
+  /// invalid.
   static AndroidStudio? latestValid() {
-    final String? configuredStudio = globals.config.getValue('android-studio-dir') as String?;
-    if (configuredStudio != null) {
-      String configuredStudioPath = configuredStudio;
-      if (globals.platform.isMacOS && !configuredStudioPath.endsWith('Contents')) {
-        configuredStudioPath = globals.fs.path.join(configuredStudioPath, 'Contents');
+    final String? configuredStudioPath = globals.config.getValue('android-studio-dir') as String?;
+    if (configuredStudioPath != null) {
+      String correctedConfiguredStudioPath = configuredStudioPath;
+      if (globals.platform.isMacOS && !correctedConfiguredStudioPath.endsWith('Contents')) {
+        correctedConfiguredStudioPath = globals.fs.path.join(correctedConfiguredStudioPath, 'Contents');
       }
-      return AndroidStudio(configuredStudioPath,
-          configured: configuredStudio);
+
+      if (!globals.fs.directory(correctedConfiguredStudioPath).existsSync()) {
+        throwToolExit('''
+Could not find the Android Studio installation at the manually configured path "$configuredStudioPath".
+Please verify that the path is correct and update it by running this command: flutter config --android-studio-dir '<path>'
+
+To have flutter search for Android Studio installations automatically, remove
+the configured path by running this command: flutter config --android-studio-dir ''
+''');
+      }
+
+      return AndroidStudio(correctedConfiguredStudioPath,
+          configuredPath: configuredStudioPath);
     }
 
     // Find all available Studio installations.
@@ -245,7 +262,19 @@ class AndroidStudio implements Comparable<AndroidStudio> {
     }
     AndroidStudio? newest;
     for (final AndroidStudio studio in studios.where((AndroidStudio s) => s.isValid)) {
-      if (newest == null || studio.compareTo(newest) > 0) {
+      if (newest == null) {
+        newest = studio;
+        continue;
+      }
+
+      // We prefer installs with known versions.
+      if (studio.version != null && newest.version == null) {
+        newest = studio;
+      } else if (studio.version != null && newest.version != null &&
+          studio.version! > newest.version!) {
+        newest = studio;
+      } else if (studio.version == null && newest.version == null &&
+            studio.directory.compareTo(newest.directory) > 0) {
         newest = studio;
       }
     }
@@ -331,13 +360,16 @@ class AndroidStudio implements Comparable<AndroidStudio> {
   static List<AndroidStudio> _allLinuxOrWindows() {
     final List<AndroidStudio> studios = <AndroidStudio>[];
 
-    bool hasStudioAt(String path, { Version? newerThan }) {
+    bool alreadyFoundStudioAt(String path, { Version? newerThan }) {
       return studios.any((AndroidStudio studio) {
         if (studio.directory != path) {
           return false;
         }
         if (newerThan != null) {
-          return studio.version.compareTo(newerThan) >= 0;
+          if (studio.version == null) {
+            return false;
+          }
+          return studio.version!.compareTo(newerThan) >= 0;
         }
         return true;
       });
@@ -373,7 +405,7 @@ class AndroidStudio implements Comparable<AndroidStudio> {
 
       for (final Directory entity in entities) {
         final AndroidStudio? studio = AndroidStudio.fromHomeDot(entity);
-        if (studio != null && !hasStudioAt(studio.directory, newerThan: studio.version)) {
+        if (studio != null && !alreadyFoundStudioAt(studio.directory, newerThan: studio.version)) {
           studios.removeWhere((AndroidStudio other) => other.directory == studio.directory);
           studios.add(studio);
         }
@@ -404,7 +436,7 @@ class AndroidStudio implements Comparable<AndroidStudio> {
                 version: Version.parse(version),
                 studioAppName: title,
               );
-              if (!hasStudioAt(studio.directory, newerThan: studio.version)) {
+              if (!alreadyFoundStudioAt(studio.directory, newerThan: studio.version)) {
                 studios.removeWhere((AndroidStudio other) => other.directory == studio.directory);
                 studios.add(studio);
               }
@@ -415,14 +447,14 @@ class AndroidStudio implements Comparable<AndroidStudio> {
     }
 
     final String? configuredStudioDir = globals.config.getValue('android-studio-dir') as String?;
-    if (configuredStudioDir != null && !hasStudioAt(configuredStudioDir)) {
+    if (configuredStudioDir != null && !alreadyFoundStudioAt(configuredStudioDir)) {
       studios.add(AndroidStudio(configuredStudioDir,
-          configured: configuredStudioDir));
+          configuredPath: configuredStudioDir));
     }
 
     if (globals.platform.isLinux) {
       void checkWellKnownPath(String path) {
-        if (globals.fs.isDirectorySync(path) && !hasStudioAt(path)) {
+        if (globals.fs.isDirectorySync(path) && !alreadyFoundStudioAt(path)) {
           studios.add(AndroidStudio(path));
         }
       }
@@ -438,12 +470,12 @@ class AndroidStudio implements Comparable<AndroidStudio> {
     return keyMatcher.stringMatch(plistValue)?.split('=').last.trim().replaceAll('"', '');
   }
 
-  void _init({Version? version}) {
+  void _initAndValidate() {
     _isValid = false;
     _validationMessages.clear();
 
-    if (configured != null) {
-      _validationMessages.add('android-studio-dir = $configured');
+    if (configuredPath != null) {
+      _validationMessages.add('android-studio-dir = $configuredPath');
     }
 
     if (!globals.fs.isDirectorySync(directory)) {
@@ -453,15 +485,15 @@ class AndroidStudio implements Comparable<AndroidStudio> {
 
     final String javaPath;
     if (globals.platform.isMacOS) {
-      if (version != null && version.major < 2020) {
+      if (version != null && version!.major < 2020) {
         javaPath = globals.fs.path.join(directory, 'jre', 'jdk', 'Contents', 'Home');
-      } else if (version != null && version.major == 2022) {
+      } else if (version != null && version!.major == 2022) {
         javaPath = globals.fs.path.join(directory, 'jbr', 'Contents', 'Home');
       } else {
         javaPath = globals.fs.path.join(directory, 'jre', 'Contents', 'Home');
       }
     } else {
-      if (version != null && version.major == 2022) {
+      if (version != null && version!.major == 2022) {
         javaPath = globals.fs.path.join(directory, 'jbr');
       } else {
         javaPath = globals.fs.path.join(directory, 'jre');

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

@@ -6,7 +6,6 @@ import '../base/config.dart';
 import '../base/file_system.dart';
 import '../base/platform.dart';
 import '../base/user_messages.dart';
-import '../base/version.dart';
 import '../doctor_validator.dart';
 import '../intellij/intellij.dart';
 import 'android_studio.dart';
@@ -46,7 +45,7 @@ class AndroidStudioValidator extends DoctorValidator {
     final List<ValidationMessage> messages = <ValidationMessage>[];
     ValidationType type = ValidationType.missing;
 
-    final String? studioVersionText = _studio.version == Version.unknown
+    final String? studioVersionText = _studio.version == null
       ? null
       : userMessages.androidStudioVersion(_studio.version.toString());
     messages.add(ValidationMessage(
@@ -83,7 +82,7 @@ class AndroidStudioValidator extends DoctorValidator {
         (String m) => ValidationMessage.error(m),
       ));
       messages.add(ValidationMessage(userMessages.androidStudioNeedsUpdate));
-      if (_studio.configured != null) {
+      if (_studio.configuredPath != null) {
         messages.add(ValidationMessage(userMessages.androidStudioResetDir));
       }
     }

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

@@ -4,13 +4,20 @@
 
 import 'package:meta/meta.dart';
 
-// TODO(reidbaker): Investigate using pub_semver instead of this class.
+/// Represents the version of some piece of software.
+///
+/// While a [Version] object has fields resembling semver, it does not
+/// necessarily represent a semver version.
 @immutable
 class Version implements Comparable<Version> {
   /// Creates a new [Version] object.
-  factory Version(int? major, int? minor, int? patch, {String? text}) {
+  ///
+  /// A null [minor] or [patch] version is logically equivalent to 0. Using null
+  /// for these parameters only affects the generation of [text], if no value
+  /// for it is provided.
+  factory Version(int major, int? minor, int? patch, {String? text}) {
     if (text == null) {
-      text = major == null ? '0' : '$major';
+      text = '$major';
       if (minor != null) {
         text = '$text.$minor';
       }
@@ -19,7 +26,7 @@ class Version implements Comparable<Version> {
       }
     }
 
-    return Version._(major ?? 0, minor ?? 0, patch ?? 0, text);
+    return Version._(major, minor ?? 0, patch ?? 0, text);
   }
 
   /// Public constant constructor when all fields are non-null, without default value fallbacks.
@@ -67,9 +74,6 @@ class Version implements Comparable<Version> {
     return primary;
   }
 
-
-  static Version get unknown => Version(0, 0, 0, text: 'unknown');
-
   /// The major version number: "1" in "1.2.3".
   final int major;
 

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

@@ -19,7 +19,7 @@ class ConfigCommand extends FlutterCommand {
       negatable: false,
       help: 'Clear the saved development certificate choice used to sign apps for iOS device deployment.');
     argParser.addOption('android-sdk', help: 'The Android SDK directory.');
-    argParser.addOption('android-studio-dir', help: 'The Android Studio install directory.');
+    argParser.addOption('android-studio-dir', help: 'The Android Studio install directory. If unset, flutter will search for valid installs at well-known locations.');
     argParser.addOption('build-dir', help: 'The relative path to override a projects build directory.',
         valueHelp: 'out/');
     argParser.addFlag('machine',

packages/flutter_tools/lib/src/intellij/intellij_validator.dart

@@ -125,11 +125,6 @@ abstract class IntelliJValidator extends DoctorValidator {
   }
 
   void _validateIntelliJVersion(List<ValidationMessage> messages, Version minVersion) {
-    // Ignore unknown versions.
-    if (minVersion == Version.unknown) {
-      return;
-    }
-
     final Version? installedVersion = Version.parse(version);
     if (installedVersion == null) {
       return;

packages/flutter_tools/lib/src/vscode/vscode.dart

@@ -18,8 +18,7 @@ const String extensionMarketplaceUrl =
   'https://marketplace.visualstudio.com/items?itemName=$extensionIdentifier';
 
 class VsCode {
-  VsCode._(this.directory, this.extensionDirectory, { Version? version, this.edition, required FileSystem fileSystem})
-      : version = version ?? Version.unknown {
+  VsCode._(this.directory, this.extensionDirectory, { this.version, this.edition, required FileSystem fileSystem}) {
 
     if (!fileSystem.isDirectorySync(directory)) {
       _validationMessages.add(ValidationMessage.error('VS Code not found at $directory'));
@@ -76,7 +75,7 @@ class VsCode {
 
   final String directory;
   final String extensionDirectory;
-  final Version version;
+  final Version? version;
   final String? edition;
 
   Version? _extensionVersion;
@@ -284,7 +283,7 @@ class VsCode {
 
   @override
   String toString() =>
-      'VS Code ($version)${_extensionVersion != Version.unknown ? ', Flutter ($_extensionVersion)' : ''}';
+      'VS Code ($version)${_extensionVersion != null ? ', Flutter ($_extensionVersion)' : ''}';
 
   static String? _getVersionFromPackageJson(String packageJsonPath, FileSystem fileSystem) {
     if (!fileSystem.isFileSync(packageJsonPath)) {

packages/flutter_tools/lib/src/vscode/vscode_validator.dart

@@ -7,7 +7,6 @@ import 'package:process/process.dart';
 import '../base/file_system.dart';
 import '../base/platform.dart';
 import '../base/user_messages.dart';
-import '../base/version.dart';
 import '../doctor_validator.dart';
 import 'vscode.dart';
 
@@ -24,7 +23,7 @@ class VsCodeValidator extends DoctorValidator {
 
   @override
   Future<ValidationResult> validate() async {
-    final String? vsCodeVersionText = _vsCode.version == Version.unknown
+    final String? vsCodeVersionText = _vsCode.version == null
         ? null
         : userMessages.vsCodeVersion(_vsCode.version.toString());
 

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

@@ -4,6 +4,8 @@
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/android_studio.dart';
+import 'package:flutter_tools/src/base/common.dart';
+import 'package:flutter_tools/src/base/config.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/base/version.dart';
@@ -849,6 +851,177 @@ void main() {
       ),
     });
   });
+
+  group('latestValid', () {
+    late Platform platform;
+    late FileSystem fileSystem;
+
+    setUp(() {
+      platform = FakePlatform(
+        operatingSystem: 'windows',
+        environment: <String, String>{
+          'LOCALAPPDATA': r'C:\Users\Dash\AppData\Local',
+        }
+      );
+      fileSystem = MemoryFileSystem.test(style: FileSystemStyle.windows);
+    });
+
+    testUsingContext('choses the install with the latest version', () {
+      const List<String> versions = <String> [
+        '4.0',
+        '2022.0',
+        '3.1',
+      ];
+
+      for (final String version in versions) {
+        fileSystem.file('C:\\Users\\Dash\\AppData\\Local\\Google\\AndroidStudio$version\\.home')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('C:\\Program Files\\AndroidStudio$version');
+        fileSystem.directory('C:\\Program Files\\AndroidStudio$version')
+          .createSync(recursive: true);
+      }
+
+      expect(AndroidStudio.allInstalled().length, 3);
+      expect(AndroidStudio.latestValid()!.version, Version(2022, 0, 0));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+
+    testUsingContext('prefers installs with known versions over installs with unknown versions', () {
+      const List<String> versions = <String> [
+        '3.0',
+        'unknown',
+      ];
+
+      for (final String version in versions) {
+        fileSystem.file('C:\\Users\\Dash\\AppData\\Local\\Google\\AndroidStudio$version\\.home')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('C:\\Program Files\\AndroidStudio$version');
+        fileSystem.directory('C:\\Program Files\\AndroidStudio$version')
+          .createSync(recursive: true);
+      }
+
+      expect(AndroidStudio.allInstalled().length, 2);
+      expect(AndroidStudio.latestValid()!.version, Version(3, 0, 0));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+
+    testUsingContext('choses install with lexicographically greatest directory if no installs have known versions', () {
+      const List<String> versions = <String> [
+        'Apple',
+        'Zucchini',
+        'Banana',
+      ];
+
+      for (final String version in versions) {
+        fileSystem.file('C:\\Users\\Dash\\AppData\\Local\\Google\\AndroidStudio$version\\.home')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('C:\\Program Files\\AndroidStudio$version');
+        fileSystem.directory('C:\\Program Files\\AndroidStudio$version')
+          .createSync(recursive: true);
+      }
+
+      expect(AndroidStudio.allInstalled().length, 3);
+      expect(AndroidStudio.latestValid()!.directory, r'C:\Program Files\AndroidStudioZucchini');
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+
+    testUsingContext('choses install with lexicographically greatest directory if all installs have the same version', () {
+      fileSystem.file(r'C:\Users\Dash\AppData\Local\Google\AndroidStudioPreview4.0\.home')
+        ..createSync(recursive: true)
+        ..writeAsStringSync(r'C:\Program Files\AndroidStudioPreview4.0');
+      fileSystem.directory(r'C:\Program Files\AndroidStudioPreview4.0')
+        .createSync(recursive: true);
+
+      fileSystem.file(r'C:\Users\Dash\AppData\Local\Google\AndroidStudio4.0\.home')
+        ..createSync(recursive: true)
+        ..writeAsStringSync(r'C:\Program Files\AndroidStudio4.0');
+      fileSystem.directory(r'C:\Program Files\AndroidStudio4.0')
+        .createSync(recursive: true);
+
+      expect(AndroidStudio.allInstalled().length, 2);
+      expect(AndroidStudio.latestValid()!.directory, contains('Preview'));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+
+    testUsingContext('always chooses the install configured by --android-studio-dir, even if the install is invalid', () {
+      const String configuredAndroidStudioDir = r'C:\Users\Dash\Desktop\android-studio';
+      globals.config.setValue('android-studio-dir', configuredAndroidStudioDir);
+
+      // The directory exists, but nothing is inside.
+      fileSystem.directory(configuredAndroidStudioDir).createSync(recursive: true);
+      (globals.processManager as FakeProcessManager).excludedExecutables.add(
+        fileSystem.path.join(configuredAndroidStudioDir, 'jre', 'bin', 'java'),
+      );
+
+      const List<String> validVersions = <String> [
+        '4.0',
+        '2.0',
+        '3.1',
+      ];
+
+      for (final String version in validVersions) {
+        fileSystem.file('C:\\Users\\Dash\\AppData\\Local\\Google\\AndroidStudio$version\\.home')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('C:\\Program Files\\AndroidStudio$version');
+        fileSystem.directory('C:\\Program Files\\AndroidStudio$version')
+          .createSync(recursive: true);
+      }
+
+      const List<String> validJavaPaths = <String>[
+        r'C:\Program Files\AndroidStudio4.0\jre\bin\java',
+        r'C:\Program Files\AndroidStudio2.0\jre\bin\java',
+        r'C:\Program Files\AndroidStudio3.1\jre\bin\java',
+      ];
+
+      for (final String javaPath in validJavaPaths) {
+        (globals.processManager as FakeProcessManager).addCommand(FakeCommand(
+          command: <String>[
+            globals.fs.path.join(javaPath),
+            '-version',
+          ],
+        ));
+      }
+
+      expect(AndroidStudio.allInstalled().length, 4);
+      final AndroidStudio chosenInstall = AndroidStudio.latestValid()!;
+      expect(chosenInstall.directory, configuredAndroidStudioDir);
+      expect(chosenInstall.isValid, false);
+    }, overrides: <Type, Generator>{
+      Config: () => Config.test(),
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.empty(),
+    });
+
+    testUsingContext('throws a ToolExit if --android-studio-dir is configured but the directory does not exist', () async {
+      const String configuredAndroidStudioDir = r'C:\Users\Dash\Desktop\android-studio';
+      globals.config.setValue('android-studio-dir', configuredAndroidStudioDir);
+
+      expect(fileSystem.directory(configuredAndroidStudioDir).existsSync(), false);
+      expect(() => AndroidStudio.latestValid(), throwsA(
+        (dynamic e) => e is ToolExit &&
+          e.message!.startsWith('Could not find the Android Studio installation at the manually configured path')
+        )
+      );
+    }, overrides: <Type, Generator>{
+      Config: () => Config.test(),
+      FileSystem: () => fileSystem,
+      Platform: () => platform,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+  });
 }
 
 class FakePlistUtils extends Fake implements PlistParser {

packages/flutter_tools/test/general.shard/macos/xcode_test.dart

@@ -1064,7 +1064,7 @@ void main() {
 
 class FakeXcodeProjectInterpreter extends Fake implements XcodeProjectInterpreter {
   @override
-  Version version = Version.unknown;
+  Version version = Version(0, 0, 0);
 
   @override
   bool isInstalled = false;

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

@@ -24,8 +24,7 @@ baz=qux
 
   group('Version', () {
     testWithoutContext('can parse and compare', () {
-      expect(Version.unknown.toString(), equals('unknown'));
-      expect(Version(null, null, null).toString(), equals('0'));
+      expect(Version(0, null, null).toString(), equals('0'));
       expect(const Version.withText(1, 2, 3, 'versionText').toString(), 'versionText');
 
       final Version v1 = Version.parse('1')!;
@@ -33,7 +32,7 @@ baz=qux
       expect(v1.minor, equals(0));
       expect(v1.patch, equals(0));
 
-      expect(v1, greaterThan(Version.unknown));
+      expect(v1, greaterThan(Version(0, 0, 0)));
 
       final Version v2 = Version.parse('1.2')!;
       expect(v2.major, equals(1));

packages/flutter_tools/test/general.shard/vscode/vscode_test.dart

@@ -5,7 +5,6 @@
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
-import 'package:flutter_tools/src/base/version.dart';
 import 'package:flutter_tools/src/vscode/vscode.dart';
 
 import '../../src/common.dart';
@@ -38,7 +37,7 @@ void main() {
 
     final VsCode vsCode = VsCode.fromDirectory('', '', fileSystem: fileSystem);
 
-    expect(vsCode.version, Version.unknown);
+    expect(vsCode.version, null);
   });
 
   testWithoutContext('can locate VS Code installed via Snap', () {