Work on #74: allow customizing whether the == and != operators are generated for classes

Generator.Equals.Runtime/Attributes.cs

@@ -18,6 +18,12 @@ public class EquatableAttribute : Attribute
         /// Equality and hash code do not consider members of base classes.
         /// </summary>
         public bool IgnoreInheritedMembers { get; set; }
+
+        /// <summary>
+        /// Indicates whether the equality operators (<c>==</c> and <c>!=</c>) will be overridden for the decorated member.
+        /// <br/>Default value is <see langword="true"/>.
+        /// </summary>
+        public bool OverrideEqualityOperators { get; set; } = true;
     }
 
     [GeneratedCode("Generator.Equals", "1.0.0.0")]

Generator.Equals.SnapshotTests/Classes/BaseEqualityWithoutOperators.Net60.Diagnostics.verified.txt

@@ -0,0 +1 @@
+[]

Generator.Equals.SnapshotTests/Classes/BaseEqualityWithoutOperators.NetFramework48.Diagnostics.verified.txt

@@ -0,0 +1 @@
+[]

Generator.Equals.Tests/Classes/BaseEqualityWithoutOperators.Sample.cs

@@ -0,0 +1,27 @@
+namespace Generator.Equals.Tests.Classes
+{
+    public partial class BaseEqualityWithoutOperators
+    {
+        [Equatable(OverrideEqualityOperators = false)]
+        public partial class Person
+        {
+            public Person(int age)
+            {
+                Age = age;
+            }
+
+            public int Age { get; }
+        }
+
+        [Equatable(OverrideEqualityOperators = false)]
+        public partial class Manager : Person
+        {
+            public Manager(int age, string department) : base(age)
+            {
+                Department = department;
+            }
+
+            public string Department { get; }
+        }
+    }
+}

Generator.Equals.Tests/Classes/BaseEqualityWithoutOperators.cs

@@ -0,0 +1,22 @@
+namespace Generator.Equals.Tests.Classes
+{
+    public partial class BaseEqualityWithoutOperators
+    {
+        public class EqualsTest : EqualityTestCase<Person>
+        {
+            public override object Factory1() => new Manager(25, "IT");
+            public override bool EqualsOperator(object value1, object value2) => (Manager) value1 == (Manager) value2;
+            public override bool NotEqualsOperator(object value1, object value2) => (Manager) value1 != (Manager) value2;
+            public override bool ExpectedOperatorEquals => false;
+        }
+
+        public class NotEqualsTest : EqualityTestCase<Person>
+        {
+            public override bool Expected => false;
+            public override object Factory1() => new Manager(25, "IT");
+            public override object Factory2() => new Manager(25, "Sales");
+            public override bool EqualsOperator(object value1, object value2) => (Manager) value1 == (Person) value2;
+            public override bool NotEqualsOperator(object value1, object value2) => (Manager) value1 != (Person) value2;
+        }
+    }
+}

Generator.Equals.Tests/EqualityTestCase.cs

@@ -9,6 +9,7 @@ public abstract class EqualityTestCase
         public abstract object Factory1();
         public virtual object Factory2() => Factory1();
         public virtual bool Expected => true;
+        public virtual bool ExpectedOperatorEquals => Expected;
         public abstract bool EqualsOperator(object value1, object value2);
         public abstract bool NotEqualsOperator(object value1, object value2);
 
@@ -27,7 +28,7 @@ public void TestEqualsOperator()
             var value1 = Factory1();
             var value2 = Factory2();
             var result = EqualsOperator(value1, value2);
-            result.Should().Be(Expected);
+            result.Should().Be(ExpectedOperatorEquals);
         }
 
         [Fact]
@@ -36,7 +37,7 @@ public void TestNotEqualsOperator()
             var value1 = Factory1();
             var value2 = Factory2();
             var result = NotEqualsOperator(value1, value2);
-            result.Should().NotBe(Expected);
+            result.Should().NotBe(ExpectedOperatorEquals);
         }
 
         [Fact]

Generator.Equals/EqualityTypeModelTransformer.cs

@@ -41,6 +41,7 @@ public EqualityTypeModelTransformer(GeneratorAttributeSyntaxContext context)
 
         var explicitMode = equatableAttributeData.GetNamedArgumentValue("Explicit") is true;
         var ignoreInheritedMembers = equatableAttributeData.GetNamedArgumentValue("IgnoreInheritedMembers") is true;
+        var overrideEqualityOperators = equatableAttributeData.GetNamedArgumentValue(nameof(EquatableAttribute.OverrideEqualityOperators)) is not false;
 
         if (_context.TargetSymbol is not ITypeSymbol symbol)
         {
@@ -83,7 +84,8 @@ public EqualityTypeModelTransformer(GeneratorAttributeSyntaxContext context)
             IsSealed = symbol.IsSealed,
             BaseTypeName = baseTypeName,
             Fullname = fullname,
-            SyntaxKind = _context.TargetNode.Kind()
+            SyntaxKind = _context.TargetNode.Kind(),
+            OverrideEqualityOperators = overrideEqualityOperators,
         };
 
         if (model.SyntaxKind is not (

Generator.Equals/Generators/ClassEqualityGenerator.cs

@@ -16,20 +16,23 @@ IndentedTextWriter writer
             var baseTypeName = model.BaseTypeName;
             var isRootClass = baseTypeName == "object";
 
-            writer.WriteLines(EqualsOperatorCodeComment);
-            writer.WriteLine(GeneratedCodeAttributeDeclaration);
-            writer.WriteLine("public static bool operator ==(");
-            writer.WriteLine(1, $"{symbolName}? left,");
-            writer.WriteLine(1, $"{symbolName}? right) =>");
-            writer.WriteLine(1, $"global::Generator.Equals.DefaultEqualityComparer<{symbolName}?>.Default");
-            writer.WriteLine(2, $".Equals(left, right);");
-            writer.WriteLine();
+            if (model.OverrideEqualityOperators)
+            {
+                writer.WriteLines(EqualsOperatorCodeComment);
+                writer.WriteLine(GeneratedCodeAttributeDeclaration);
+                writer.WriteLine("public static bool operator ==(");
+                writer.WriteLine(1, $"{symbolName}? left,");
+                writer.WriteLine(1, $"{symbolName}? right) =>");
+                writer.WriteLine(1, $"global::Generator.Equals.DefaultEqualityComparer<{symbolName}?>.Default");
+                writer.WriteLine(2, $".Equals(left, right);");
+                writer.WriteLine();
 
-            writer.WriteLines(NotEqualsOperatorCodeComment);
-            writer.WriteLine(GeneratedCodeAttributeDeclaration);
-            writer.WriteLine($"public static bool operator !=({symbolName}? left, {symbolName}? right) =>");
-            writer.WriteLine(1, "!(left == right);");
-            writer.WriteLine();
+                writer.WriteLines(NotEqualsOperatorCodeComment);
+                writer.WriteLine(GeneratedCodeAttributeDeclaration);
+                writer.WriteLine($"public static bool operator !=({symbolName}? left, {symbolName}? right) =>");
+                writer.WriteLine(1, "!(left == right);");
+                writer.WriteLine();
+            }
 
             writer.WriteLine(InheritDocComment);
             writer.WriteLine(GeneratedCodeAttributeDeclaration);

Generator.Equals/Models/EqualityTypeModel.cs

@@ -15,4 +15,5 @@ internal sealed record EqualityTypeModel
     public required bool IgnoreInheritedMembers { get; init; }
     public required EquatableImmutableArray<EqualityMemberModel> BuildEqualityModels { get; init; }
     public required string Fullname { get; init; }
+    public required bool OverrideEqualityOperators { get; init; }
 }