Fix Issues #536 -> Set properties with reflection if destination has init only properties.

src/Mapster.Tool.Tests/.config/dotnet-tools.json

@@ -0,0 +1,12 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "mapster.tool": {
+      "version": "8.3.0",
+      "commands": [
+        "dotnet-mapster"
+      ]
+    }
+  }
+}

src/Mapster.Tool.Tests/Mappers/IUserMapper.cs

@@ -0,0 +1,11 @@
+using System.Linq.Expressions;
+
+namespace Mapster.Tool.Tests.Mappers;
+
+[Mapper]
+public interface IUserMapper
+{
+    Expression<Func<_User, _UserDto>> UserProjection { get; }
+    _UserDto MapTo(_User user);
+    _UserDto MapTo(_User user, _UserDto userDto);
+}

src/Mapster.Tool.Tests/Mappers/UserMapper.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Linq.Expressions;
+using Mapster.Tool.Tests;
+using Mapster.Tool.Tests.Mappers;
+
+namespace Mapster.Tool.Tests.Mappers
+{
+    public partial class UserMapper : IUserMapper
+    {
+        public Expression<Func<_User, _UserDto>> UserProjection => p1 => new _UserDto()
+        {
+            Id = p1.Id,
+            Name = p1.Name
+        };
+        public _UserDto MapTo(_User p2)
+        {
+            return p2 == null ? null : new _UserDto()
+            {
+                Id = p2.Id,
+                Name = p2.Name
+            };
+        }
+        public _UserDto MapTo(_User p3, _UserDto p4)
+        {
+            if (p3 == null)
+            {
+                return null;
+            }
+            _UserDto result = p4 ?? new _UserDto();
+
+            typeof(_UserDto).GetProperty("Id").SetValue(result, (object)p3.Id);
+            typeof(_UserDto).GetProperty("Name").SetValue(result, p3.Name);
+            return result;
+
+        }
+    }
+}

src/Mapster.Tool.Tests/Mapster.Tool.Tests.csproj

@@ -0,0 +1,52 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+
+        <IsPackable>false</IsPackable>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="FluentAssertions" Version="6.9.0" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
+        <PackageReference Include="Scrutor" Version="4.2.1" />
+        <PackageReference Include="xunit" Version="2.4.2" />
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+            <PrivateAssets>all</PrivateAssets>
+        </PackageReference>
+        <PackageReference Include="coverlet.collector" Version="3.1.2">
+            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+            <PrivateAssets>all</PrivateAssets>
+        </PackageReference>
+    </ItemGroup>
+    <ItemGroup>
+        <Generated Include="**\*.g.cs" />
+        <Generated Remove="obj\**" />
+    </ItemGroup>
+    <Target Name="CleanGenerated">
+        <Delete Files="@(Generated)" />
+    </Target>
+    <Target Name="Mapster">
+        <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet build" />
+        <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet tool restore" />
+        <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet mapster model -a $(TargetDir)$(ProjectName).dll -n Sample.CodeGen.Models -o Models -r" />
+        <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet mapster extension -a $(TargetDir)$(ProjectName).dll -n Sample.CodeGen.Models -o Models" />
+        <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet mapster mapper -a $(TargetDir)$(ProjectName).dll -n Sample.CodeGen.Mappers -o Mappers" />
+    </Target>
+    <ItemGroup>
+      <Compile Remove="obj\**" />
+    </ItemGroup>
+    <ItemGroup>
+      <EmbeddedResource Remove="obj\**" />
+    </ItemGroup>
+    <ItemGroup>
+      <None Remove="obj\**" />
+    </ItemGroup>
+    <ItemGroup>
+      <ProjectReference Include="..\Mapster.Tool\Mapster.Tool.csproj" />
+    </ItemGroup>
+
+</Project>

src/Mapster.Tool.Tests/TestBase.cs

@@ -0,0 +1,38 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Mapster.Tool.Tests;
+
+public class TestBase
+{
+    private readonly IServiceScopeFactory _scopeFactory;
+
+    public TestBase()
+    {
+        var services = ConfigureServiceCollection();
+        using var scope = services.BuildServiceProvider().CreateScope();
+        _scopeFactory = scope.ServiceProvider.GetRequiredService<IServiceScopeFactory>();
+    }
+
+    private ServiceCollection ConfigureServiceCollection()
+    {
+        ServiceCollection services = new();
+        services.Scan(selector => selector
+            .FromCallingAssembly()
+            .AddClasses()
+            .AsMatchingInterface()
+            .WithSingletonLifetime());
+        return services;
+    }
+
+    protected TInterface GetMappingInterface<TInterface>()
+    {
+        using var scope = _scopeFactory.CreateScope();
+        var service = scope.ServiceProvider.GetService(typeof(TInterface));
+        if (service == null)
+        {
+            throw new Exception($"Service of type {typeof(TInterface).Name} not found!");
+        }
+
+        return (TInterface)service;
+    }
+}

src/Mapster.Tool.Tests/Usings.cs

@@ -0,0 +1 @@
+global using Xunit;

src/Mapster.Tool.Tests/WhenMappingWithExistingObjectAndInitProperties.cs

@@ -0,0 +1,47 @@
+using System.Reflection;
+using FluentAssertions;
+using Mapster.Tool.Tests.Mappers;
+
+namespace Mapster.Tool.Tests;
+
+/// <summary>
+/// Tests for https://github.com/MapsterMapper/Mapster/issues/536
+/// </summary>
+public class WhenMappingWithExistingObjectAndInitProperties : TestBase
+{
+    [Fact]
+    public void MapWithReflection()
+    {
+        TypeAdapterConfig.GlobalSettings
+            .Scan(Assembly.GetExecutingAssembly());
+
+        var userMapper = GetMappingInterface<IUserMapper>();
+        var expected = "Aref";
+        var user = new _User { Name = expected, Id = 1 };
+        var dto = new _UserDto();
+        userMapper.MapTo(user, dto);
+        dto.Name.Should().Be(expected);
+    }
+}
+
+public class UserMappingRegister : IRegister
+{
+    public void Register(TypeAdapterConfig config)
+    {
+        config.NewConfig<_User, _UserDto>()
+            .MapToConstructor(true)
+            .ConstructUsing(s => new _UserDto());
+    }
+}
+
+public class _User
+{
+    public int Id { get; init; }
+    public string Name { get; init; }
+}
+
+public class _UserDto
+{
+    public int Id { get; init; }
+    public string Name { get; init; }
+}

src/Mapster.sln

@@ -61,6 +61,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ExpressionTranslator", "Exp
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TemplateTest", "TemplateTest\TemplateTest.csproj", "{ED390145-FA22-46BA-86A6-9FA6AC869BA4}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Mapster.Tool.Tests", "Mapster.Tool.Tests\Mapster.Tool.Tests.csproj", "{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -155,6 +157,10 @@ Global
 		{ED390145-FA22-46BA-86A6-9FA6AC869BA4}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{ED390145-FA22-46BA-86A6-9FA6AC869BA4}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{ED390145-FA22-46BA-86A6-9FA6AC869BA4}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -175,6 +181,7 @@ Global
 		{D5DF0FB7-44A5-4326-9EC4-5B8F7FCCE00F} = {D33E5A90-ABCA-4B2D-8758-2873CC5AB847}
 		{3CB56440-5449-4DE5-A8D3-549C87C1B36A} = {EF7E343F-592E-4EAC-A0A4-92EB4B95CB89}
 		{ED390145-FA22-46BA-86A6-9FA6AC869BA4} = {D33E5A90-ABCA-4B2D-8758-2873CC5AB847}
+		{E64E9CEB-8FB2-4012-BBA8-4C2B99FD54C1} = {D33E5A90-ABCA-4B2D-8758-2873CC5AB847}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {83B87DBA-277C-49F1-B597-E3B78C2C8275}

src/Mapster/Adapters/ClassAdapter.cs

@@ -129,7 +129,18 @@ protected override Expression CreateBlockExpression(Expression source, Expressio
                     }
                     else
                     {
-                        adapt = member.DestinationMember.SetExpression(destination, adapt);
+                        //Todo Try catch block should be removed after pull request approved
+                        try
+                        {
+                            var destinationPropertyInfo = (PropertyInfo)member.DestinationMember.Info!;
+                            adapt = destinationPropertyInfo.IsInitOnly()
+                                ? SetValueByReflection(destination, (MemberExpression)adapt, arg.DestinationType)
+                                : member.DestinationMember.SetExpression(destination, adapt);
+                        }
+                        catch (Exception e)
+                        {
+                            adapt = member.DestinationMember.SetExpression(destination, adapt);
+                        }
                     }
                 }
                 else if (!adapt.IsComplex())
@@ -146,6 +157,7 @@ protected override Expression CreateBlockExpression(Expression source, Expressio
                         tuple = Tuple.Create(new List<Expression>(), body);
                         conditions[member.Ignore.Condition] = tuple;
                     }
+
                     tuple.Item1.Add(adapt);
                 }
                 else
@@ -166,6 +178,21 @@ protected override Expression CreateBlockExpression(Expression source, Expressio
             return lines.Count > 0 ? (Expression)Expression.Block(lines) : Expression.Empty();
         }
 
+        private static Expression SetValueByReflection(Expression destination, MemberExpression adapt,
+            Type destinationType)
+        {
+            var memberName = adapt.Member.Name;
+            var typeofExpression = Expression.Constant(destinationType);
+            var getPropertyMethod = typeof(Type).GetMethod("GetProperty", new[] { typeof(string) })!;
+            var getPropertyExpression = Expression.Call(typeofExpression, getPropertyMethod,
+                Expression.Constant(memberName));
+            var setValueMethod =
+                typeof(PropertyInfo).GetMethod("SetValue", new[] { typeof(object), typeof(object) })!;
+            var memberAsObject = adapt.To(typeof(object));
+            return Expression.Call(getPropertyExpression, setValueMethod,
+                new[] { destination, memberAsObject });
+        }
+
         protected override Expression? CreateInlineExpression(Expression source, CompileArgument arg)
         {
             //new TDestination {

src/Mapster/Utils/ReflectionUtils.cs

@@ -374,5 +374,15 @@ public static IEnumerable<Type> GetAllTypes(this Type type)
                 type = type.GetTypeInfo().BaseType;
             } while (type != null && type != typeof(object));
         }
+
+        public static bool IsInitOnly(this PropertyInfo propertyInfo)
+        {
+            var setMethod = propertyInfo.SetMethod;
+            if (setMethod == null)
+                return false;
+
+            var isExternalInitType = typeof(System.Runtime.CompilerServices.IsExternalInit);
+            return setMethod.ReturnParameter.GetRequiredCustomModifiers().Contains(isExternalInitType);
+        }
     }
 }