Merge pull request #1169 from mikependon/generic-attributes

Generic Attribute for ClassHandler

Author: mikependon

RepoDb.Core/RepoDb.Tests/RepoDb.UnitTests/ClassHandlers/ClassHandlerPrecedenceTest.cs

@@ -24,6 +24,13 @@ public void Initialize()
             DbSettingMapper.Add<ClassHandlerForEntityWithAttributeConnection>(new CustomDbSetting(), true);
             DbHelperMapper.Add<ClassHandlerForEntityWithAttributeConnection>(new CustomDbHelper(), true);
             StatementBuilderMapper.Add<ClassHandlerForEntityWithAttributeConnection>(new CustomStatementBuilder(), true);
+            
+#if NET7_0_OR_GREATER
+            // For Generic Attributed Entity
+            DbSettingMapper.Add<ClassHandlerForEntityWithGenericAttributeConnection>(new CustomDbSetting(), true);
+            DbHelperMapper.Add<ClassHandlerForEntityWithGenericAttributeConnection>(new CustomDbHelper(), true);
+            StatementBuilderMapper.Add<ClassHandlerForEntityWithGenericAttributeConnection>(new CustomStatementBuilder(), true);
+#endif
         }
 
         [TestCleanup]
@@ -73,7 +80,28 @@ protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior)
                 return reader;
             }
         }
+        
+#if NET7_0_OR_GREATER
+        private class ClassHandlerForEntityWithGenericAttributeConnection : CustomDbConnection
+        {
+            protected override DbCommand CreateDbCommand()
+            {
+                return new ClassHandlerForEntityWithGenericAttributeDbCommand();
+            }
+        }
 
+        private class ClassHandlerForEntityWithGenericAttributeDbCommand : CustomDbCommand
+        {
+            protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior)
+            {
+                var reader = new DataEntityDataReader<ClassHandlerTestClassWithGenericAttribute>(new[]
+                {
+                    new ClassHandlerTestClassWithGenericAttribute { Id = 1, Name = "James Doe" }
+                });
+                return reader;
+            }
+        }
+#endif
         #endregion
 
         #region ClassHandlers
@@ -103,6 +131,21 @@ public ClassHandlerTestClassWithAttribute Set(ClassHandlerTestClassWithAttribute
                 return entity;
             }
         }
+        
+#if NET7_0_OR_GREATER
+        public class TestClassHandlerForEntityWithGenericAttribute : IClassHandler<ClassHandlerTestClassWithGenericAttribute>
+        {
+            public ClassHandlerTestClassWithGenericAttribute Get(ClassHandlerTestClassWithGenericAttribute entity, ClassHandlerGetOptions options)
+            {
+                return entity;
+            }
+
+            public ClassHandlerTestClassWithGenericAttribute Set(ClassHandlerTestClassWithGenericAttribute entity, ClassHandlerSetOptions options)
+            {
+                return entity;
+            }
+        }
+#endif
 
         #endregion
 
@@ -120,7 +163,15 @@ public class ClassHandlerTestClassWithAttribute
             public int Id { get; set; }
             public string Name { get; set; }
         }
-
+        
+#if NET7_0_OR_GREATER
+        [ClassHandler<TestClassHandlerForEntityWithGenericAttribute>]
+        public class ClassHandlerTestClassWithGenericAttribute
+        {
+            public int Id { get; set; }
+            public string Name { get; set; }
+        }
+#endif
         #endregion
 
         #region Methods
@@ -162,7 +213,27 @@ public void TestClassHandlerPrecedenceWithAttribute()
             // Assert
             classHandler.Verify(c => c.Get(It.IsAny<ClassHandlerTestClassWithAttribute>(), It.IsAny<ClassHandlerGetOptions>()), Times.Never);
         }
+        
+#if NET7_0_OR_GREATER
+        [TestMethod]
+        public void TestClassHandlerPrecedenceWithGenericAttribute()
+        {
+            // Prepare
+            var classHandler = new Mock<IClassHandler<ClassHandlerTestClassWithGenericAttribute>>();
+            FluentMapper
+                .Entity<ClassHandlerTestClassWithGenericAttribute>()
+                .ClassHandler(classHandler.Object);
 
+            // Act
+            using (var connection = new ClassHandlerForEntityWithGenericAttributeConnection())
+            {
+                var result = connection.QueryAll<ClassHandlerTestClassWithGenericAttribute>();
+            }
+
+            // Assert
+            classHandler.Verify(c => c.Get(It.IsAny<ClassHandlerTestClassWithGenericAttribute>(), It.IsAny<ClassHandlerGetOptions>()), Times.Never);
+        }
+#endif
         #endregion
     }
 }

RepoDb.Core/RepoDb/Attributes/ClassHandlerAttribute.cs

@@ -34,7 +34,7 @@ public ClassHandlerAttribute(Type handlerType)
         /// 
         /// </summary>
         /// <param name="handlerType"></param>
-        private void Validate(Type handlerType)
+        private static void Validate(Type handlerType)
         {
             if (handlerType?.IsInterfacedTo(StaticType.IClassHandler) != true)
             {
@@ -44,4 +44,33 @@ private void Validate(Type handlerType)
 
         #endregion
     }
+    
+#if NET7_0_OR_GREATER
+    /// <summary>
+    /// An attribute that is used to define a handler for the property transformation.
+    /// </summary>
+    public class ClassHandlerAttribute<T> : Attribute
+    {
+        /// <summary>
+        /// Creates a new instance of <see cref="ClassHandlerAttribute{T}"/> class.
+        /// </summary>
+        public ClassHandlerAttribute() => Validate(typeof(T));
+
+        #region Methods
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="handlerType"></param>
+        private static void Validate(Type handlerType)
+        {
+            if (handlerType?.IsInterfacedTo(StaticType.IClassHandler) != true)
+            {
+                throw new InvalidTypeException($"Type '{handlerType.FullName}' must implement the '{StaticType.IClassHandler}' interface.");
+            }
+        }
+
+        #endregion
+    }
+#endif
 }

RepoDb.Core/RepoDb/Resolvers/ClassHandlerResolver.cs

@@ -1,6 +1,7 @@
 using RepoDb.Attributes;
 using RepoDb.Interfaces;
 using System;
+using System.Linq;
 using System.Reflection;
 
 namespace RepoDb.Resolvers
@@ -17,23 +18,29 @@ public class ClassHandlerResolver : IResolver<Type, object>
         /// <returns>The equivalent <see cref="IClassHandler{TEntity}"/> object of the .NET CLR type.</returns>
         public object Resolve(Type type)
         {
-            var classHandler = (object)null;
-
-            // Attribute
+            object classHandler = null;
+            
             var attribute = type.GetCustomAttribute<ClassHandlerAttribute>();
-            if (attribute != null)
+            if (attribute is not null)
             {
-                classHandler = Converter.ToType<object>(Activator.CreateInstance(attribute.HandlerType));
+                classHandler = Activator.CreateInstance(attribute.HandlerType);
             }
 
-            // Type Level
-            if (classHandler == null)
+            if (classHandler is not null) return classHandler;
+            
+#if NET7_0_OR_GREATER
+            var genericAttribute = type.GetCustomAttribute(typeof(ClassHandlerAttribute<>));
+            if (genericAttribute is not null)
             {
-                classHandler = ClassHandlerMapper.Get<object>(type);
+                var handlerType = genericAttribute.GetType()
+                    .GetGenericArguments()
+                    .First();
+
+                classHandler = Activator.CreateInstance(handlerType);
             }
+#endif
 
-            // Return the value
-            return classHandler;
+            return classHandler ?? ClassHandlerMapper.Get<object>(type);
         }
     }
 }