[package_config] Implement relational operators for LanguageVersion

pkgs/package_config/CHANGELOG.md

@@ -1,4 +1,7 @@
-## 2.1.2-wip
+## 2.2.0-wip
+
+- Add relational operators to `LanguageVersion` with extension methods
+  exported under `LanguageVersionRelationalOperators`.
 
 - Include correct parameter names in errors when validating
   the `major` and `minor` versions in the `LanguageVersion.new` constructor.

pkgs/package_config/lib/package_config_types.dart

@@ -14,4 +14,9 @@ library;
 
 export 'src/errors.dart' show PackageConfigError;
 export 'src/package_config.dart'
-    show InvalidLanguageVersion, LanguageVersion, Package, PackageConfig;
+    show
+        InvalidLanguageVersion,
+        LanguageVersion,
+        LanguageVersionRelationalOperators,
+        Package,
+        PackageConfig;

pkgs/package_config/lib/src/package_config.dart

@@ -355,7 +355,7 @@ abstract class LanguageVersion implements Comparable<LanguageVersion> {
   /// Two language versions are considered equal if they have the
   /// same major and minor version numbers.
   ///
-  /// A language version is greater then another if the former's major version
+  /// A language version is greater than another if the former's major version
   /// is greater than the latter's major version, or if they have
   /// the same major version and the former's minor version is greater than
   /// the latter's.
@@ -406,3 +406,90 @@ abstract class InvalidLanguageVersion implements LanguageVersion {
   @override
   String toString();
 }
+
+/// Relational operators for [LanguageVersion] that
+/// compare valid versions with [LanguageVersion.compareTo].
+///
+/// If either operand is an [InvalidLanguageVersion], a [StateError] is thrown.
+/// Versions should be verified as valid after parsing and before using them.
+extension LanguageVersionRelationalOperators on LanguageVersion {
+  /// Whether this language version is less than [other].
+  ///
+  /// If either version being compared is an [InvalidLanguageVersion],
+  /// a [StateError] is thrown. Verify versions are valid before comparing them.
+  ///
+  /// For details on how valid language versions are compared,
+  /// check out [LanguageVersion.compareTo].
+  bool operator <(LanguageVersion other) {
+    // Throw an error if comparing as or with an invalid language version.
+    if (this is InvalidLanguageVersion) {
+      _throwThisInvalid();
+    } else if (other is InvalidLanguageVersion) {
+      _throwOtherInvalid();
+    }
+
+    return compareTo(other) < 0;
+  }
+
+  /// Whether this language version is less than or equal to [other].
+  ///
+  /// If either version being compared is an [InvalidLanguageVersion],
+  /// a [StateError] is thrown. Verify versions are valid before comparing them.
+  ///
+  /// For details on how valid language versions are compared,
+  /// check out [LanguageVersion.compareTo].
+  bool operator <=(LanguageVersion other) {
+    // Throw an error if comparing as or with an invalid language version.
+    if (this is InvalidLanguageVersion) {
+      _throwThisInvalid();
+    } else if (other is InvalidLanguageVersion) {
+      _throwOtherInvalid();
+    }
+
+    return compareTo(other) <= 0;
+  }
+
+  /// Whether this language version is greater than [other].
+  ///
+  /// If either version being compared is an [InvalidLanguageVersion],
+  /// a [StateError] is thrown. Verify versions are valid before comparing them.
+  ///
+  /// For details on how valid language versions are compared,
+  /// check out [LanguageVersion.compareTo].
+  bool operator >(LanguageVersion other) {
+    // Throw an error if comparing as or with an invalid language version.
+    if (this is InvalidLanguageVersion) {
+      _throwThisInvalid();
+    } else if (other is InvalidLanguageVersion) {
+      _throwOtherInvalid();
+    }
+
+    return compareTo(other) > 0;
+  }
+
+  /// Whether this language version is greater than or equal to [other].
+  ///
+  /// If either version being compared is an [InvalidLanguageVersion],
+  /// a [StateError] is thrown. Verify versions are valid before comparing them.
+  ///
+  /// For details on how valid language versions are compared,
+  /// check out [LanguageVersion.compareTo].
+  bool operator >=(LanguageVersion other) {
+    // Throw an error if comparing as or with an invalid language version.
+    if (this is InvalidLanguageVersion) {
+      _throwThisInvalid();
+    } else if (other is InvalidLanguageVersion) {
+      _throwOtherInvalid();
+    }
+
+    return compareTo(other) >= 0;
+  }
+
+  static Never _throwThisInvalid() => throw StateError(
+      'Can\'t compare an invalid language version to another language version. '
+      'Verify language versions are valid after parsing.');
+
+  static Never _throwOtherInvalid() => throw StateError(
+      'Can\'t compare a language version to an invalid language version. '
+      'Verify language versions are valid after parsing.');
+}

pkgs/package_config/pubspec.yaml

@@ -1,5 +1,5 @@
 name: package_config
-version: 2.1.2-wip
+version: 2.2.0-wip
 description: Support for reading and writing Dart Package Configuration files.
 repository: https://github.com/dart-lang/tools/tree/main/pkgs/package_config
 issue_tracker: https://github.com/dart-lang/tools/labels/package%3Apackage_config

pkgs/package_config/test/package_config_impl_test.dart

@@ -69,6 +69,86 @@ void main() {
     failParse('WhiteSpace 2', '1 .1');
     failParse('WhiteSpace 3', '1. 1');
     failParse('WhiteSpace 4', '1.1 ');
+
+    test('compareTo valid', () {
+      var version = LanguageVersion(3, 5);
+
+      for (var (otherVersion, matcher) in [
+        (version, isZero), // Identical.
+        (LanguageVersion(3, 5), isZero), // Same major, same minor.
+        (LanguageVersion(3, 4), isPositive), // Same major, lower minor.
+        (LanguageVersion(3, 6), isNegative), // Same major, greater minor.
+        (LanguageVersion(2, 5), isPositive), // Lower major, same minor.
+        (LanguageVersion(2, 4), isPositive), // Lower major, lower minor.
+        (LanguageVersion(2, 6), isPositive), // Lower major, greater minor.
+        (LanguageVersion(4, 5), isNegative), // Greater major, same minor.
+        (LanguageVersion(4, 4), isNegative), // Greater major, lower minor.
+        (LanguageVersion(4, 6), isNegative), // Greater major, greater minor.
+      ]) {
+        expect(version.compareTo(otherVersion), matcher);
+      }
+    });
+
+    test('compareTo invalid', () {
+      var validVersion = LanguageVersion(3, 5);
+      var invalidVersion = LanguageVersion.parse('', onError: (_) {});
+
+      expect(validVersion.compareTo(invalidVersion), isPositive);
+      expect(invalidVersion.compareTo(validVersion), isNegative);
+    });
+
+    test('relational valid', () {
+      /// Test that the relational comparisons between two valid versions
+      /// match the results of `compareTo`.
+      void testComparisons(
+          LanguageVersion version, LanguageVersion otherVersion) {
+        expect(version == otherVersion, version.compareTo(otherVersion) == 0);
+
+        expect(version < otherVersion, version.compareTo(otherVersion) < 0);
+        expect(version <= otherVersion, version.compareTo(otherVersion) <= 0);
+
+        expect(version > otherVersion, version.compareTo(otherVersion) > 0);
+        expect(version >= otherVersion, version.compareTo(otherVersion) >= 0);
+      }
+
+      var version = LanguageVersion(3, 5);
+
+      // Check relational comparisons of a version to itself.
+      testComparisons(version, version);
+
+      // Check relational comparisons of a version to versions with all
+      // possible combinations of minor and major versions that are
+      // the same, lower, and greater.
+      for (final major in [2, 3, 4]) {
+        for (final minor in [4, 5, 6]) {
+          testComparisons(version, LanguageVersion(major, minor));
+        }
+      }
+    });
+
+    test('relational invalid', () {
+      void testComparisonsWithInvalid(
+        LanguageVersion version,
+        LanguageVersion otherVersion,
+      ) {
+        expect(version == otherVersion, identical(version, otherVersion));
+
+        expect(() => version < otherVersion, throwsA(isA<StateError>()));
+        expect(() => version <= otherVersion, throwsA(isA<StateError>()));
+
+        expect(() => version > otherVersion, throwsA(isA<StateError>()));
+        expect(() => version >= otherVersion, throwsA(isA<StateError>()));
+      }
+
+      var validVersion = LanguageVersion(3, 5);
+      var invalidVersion = LanguageVersion.parse('', onError: (_) {});
+      var differentInvalidVersion = LanguageVersion.parse('-', onError: (_) {});
+
+      testComparisonsWithInvalid(validVersion, invalidVersion);
+      testComparisonsWithInvalid(invalidVersion, validVersion);
+      testComparisonsWithInvalid(invalidVersion, invalidVersion);
+      testComparisonsWithInvalid(invalidVersion, differentInvalidVersion);
+    });
   });
 
   group('Package', () {