Fix #883 - Add class ctor using default value for param

src/Mapster.Tests/WhenMappingRecordRegression.cs

@@ -2,6 +2,7 @@
 using Shouldly;
 using System;
 using System.Collections.Generic;
+using static Mapster.Tests.WhenExplicitMappingRequired;
 using static Mapster.Tests.WhenMappingDerived;
 
 namespace Mapster.Tests
@@ -474,22 +475,6 @@ public void ClassCtorAutomapingWorking()
             result.X.ShouldBe(100);
         }
 
-        /// <summary>
-        /// https://github.com/MapsterMapper/Mapster/issues/842
-        /// </summary>
-        [TestMethod]
-        public void ClassCustomCtorWitoutMapNotWorking()
-        {
-            TypeAdapterConfig.GlobalSettings.Clear();
-
-            var source = new TestRecord() { X = 100 };
-
-            Should.Throw<InvalidOperationException>(() => 
-            {
-                source.Adapt<AutoCtorDestYx>();
-            });
-        }
-
         /// <summary>
         /// https://github.com/MapsterMapper/Mapster/issues/842
         /// </summary>
@@ -537,6 +522,24 @@ public void ClassUpdateAutoPropertyWitoutSetterWorking()
             result.X.ShouldBe(200);
         }
 
+        /// <summary>
+        /// https://github.com/MapsterMapper/Mapster/issues/883
+        /// </summary>
+        [TestMethod]
+        public void ClassCtorActivateDefaultValue()
+        {
+            var source = new Source833
+            {
+                Value1 = "123",
+            };
+
+            Should.NotThrow(() =>
+            {
+                var target = source.Adapt<Target833>();
+                target.Value1.ShouldBe("123");
+                target.Value2.ShouldBe(default);
+            });
+        }
 
         #region NowNotWorking
 
@@ -565,6 +568,24 @@ public void CollectionUpdate()
 
     #region TestClasses
 
+    public class Source833
+    {
+        public required string Value1 { get; init; }
+    }
+
+    public class Target833
+    {
+        public Target833(string value1, string value2)
+        {
+            Value1 = value1;
+            Value2 = value2;
+        }
+
+        public string Value1 { get; }
+
+        public string Value2 { get; }
+    }
+
     public sealed record Database746(
     string Server = "",
     string Name = "",

src/Mapster.Tests/WhenUsingNonDefaultConstructor.cs

@@ -72,6 +72,10 @@ public void Map_To_Existing_Destination_Instance_Should_Pass()
             dto.Unmapped.ShouldBe("unmapped");
         }
 
+        /// <summary>
+        ///  ignore after implement fix https://github.com/MapsterMapper/Mapster/issues/883
+        /// </summary>
+        [Ignore]
         [TestMethod]
         public void Map_To_Destination_Type_Without_Default_Constructor_Shoud_Throw_Exception()
         {

src/Mapster/Adapters/ClassAdapter.cs

@@ -66,11 +66,16 @@ protected override Expression CreateInstantiationExpression(Expression source, E
                     : arg.DestinationType;
                 if (destType == null)
                     return base.CreateInstantiationExpression(source, destination, arg);
-                classConverter = destType.GetConstructors()
+
+                var constructors = destType.GetConstructors();
+                classConverter = constructors
                     .OrderByDescending(it => it.GetParameters().Length)
                     .Select(it => GetConstructorModel(it, true))
-                    .Select(it => CreateClassConverter(source, it, arg, ctorMapping:true))
+                    .Select(it => CreateClassConverter(source, it, arg, ctorMapping: true))
                     .FirstOrDefault(it => it != null);
+
+                if (classConverter == null && constructors.Length > 0)
+                    classConverter = CreateClassConverter(source, GetConstructorModel(constructors[0], false), arg, ctorMapping: true);
             }
             else
             {