Dictionary projection by key not working

[YeskaNova]

Hi,
I need to select only some values to be copied from a dictionary but it doesn't work. You can reproduce it with this code:

Version: 6.1.1

Exception:
Mapster.CompileException
ArgumentException: 'Name' is not a member of type 'System.Collections.Generic.IDictionary`2[System.String,System.Object]' (Parameter 'propertyOrFieldName')
System.Linq.Expressions.Expression.PropertyOrField(System.Linq.Expressions.Expression, string)
Mapster.Utils.ExpressionEx.PropertyOrField(System.Linq.Expressions.Expression, string)
System.Linq.Enumerable.Aggregate<TSource, TAccumulate>(System.Collections.Generic.IEnumerable, TAccumulate, System.Func<TAccumulate, TSource, TAccumulate>)
Mapster.Utils.ExpressionEx.PropertyOrFieldPath(System.Linq.Expressions.Expression, string)
Mapster.Models.InvokerModel.GetInvokingExpression(System.Linq.Expressions.Expression, Mapster.MapType)
Mapster.Models.InvokerModel.Next(System.Linq.Expressions.ParameterExpression, string)
Mapster.ReflectionUtils.Next.AnonymousMethod__1(Mapster.Models.InvokerModel)
System.Linq.Enumerable.WhereSelectListIterator<TSource, TResult>.MoveNext()
System.Linq.Enumerable.WhereEnumerableIterator.ToList()
System.Linq.Enumerable.ToList(System.Collections.Generic.IEnumerable)

using Mapster;
using MapsterMapper;
using System.Collections.Generic;
using System.Diagnostics;

namespace ConsoleApp22
{
    public class Post
    {
        public IDictionary<string, object> Dic { get; set; }
    }
    class Program
    {

        static void Main(string[] args)
        {
            var config = TypeAdapterConfig<Post, Post>
                .NewConfig()
                .Map(nameof(Post.Dic) + ".Name", nameof(Post.Dic) + ".Name");
            config.Compile();
            var mapper = new Mapper(config.Config);

            var p1 = new Post{ Dic = new Dictionary<string, object>() { { "Name", "test"}, {"Secret" , "password" }} };
            var p2 = new Post();
            mapper.From(p1).AdaptTo(p2);
            Debug.Assert(p1.Dic["Name"] == p2.Dic["Name"]);
            Debug.Assert(! p2.Dic.ContainsKey("Secret"));

        }
    }
}

[YeskaNova]

@chaowlert , this specific exception is not there anymore, but still the projection is not working as expected, the whole dictionary is copied, and if the dictionary is null, there is an exception ( I think that we can consider a null dictionary like an empty one ):

using Mapster;
using MapsterMapper;
using System.Collections.Generic;
using System.Diagnostics;

namespace ConsoleApp22
{
    public class Post
    {
        public IDictionary<string, object> Dic { get; set; }
    }
    class Program
    {

        static void Main(string[] args)
        {
            var config = TypeAdapterConfig<Post, Post>
                .NewConfig()
                .Map(nameof(Post.Dic) + ".Name", nameof(Post.Dic) + ".Name");
            config.Compile();
            var mapper = new Mapper(config.Config);

            var p1 = new Post { Dic = new Dictionary<string, object>() { { "Name", "test" }, { "Secret", "password" } } };
            var p2 = new Post();

            mapper.From(p1).AdaptTo(p2);

            Debug.Assert(p1.Dic["Name"] == p2.Dic["Name"]);
            Debug.Assert(!p2.Dic.ContainsKey("Secret"));

            var p3 = new Post();
            mapper.From(p3).AdaptTo(p2);
            Debug.Assert(!p2.Dic.ContainsKey("Name"));
        }
    }
}

[YeskaNova]

@chaowlert As a workaround, can we have AfterMapping and BeforeMapping in TypeAdapterSetter too, and not only in TypeAdapterSetter<T,T> ? My types are not known at compile-time and I need to add code to AfterMapping to handle dictionaries projection. Is that possible ?

[chaowlert]

Can, however what type for the input parameter for AfterMapping? object? Could you also describe your use case, what AfterMapping will do and why you cannot know at compile time?

[YeskaNova]

Hmm, my current workaround is to have a generic configurator that will use TypeAdapterSetter<T,T> that a construct at runtime :

private static TypeAdapterSetter<T,T> ConfigureMapper<T>(TypeAdapterConfig config, IList<EntityPropertyDescriptorDbo> permittedfields, IList<EntityPropertyDescriptorDbo> allFields, EntityDescriptorDbo ed)
...
private static readonly MethodInfo ConfigureMapperMethod =typeof(Extensions).GetMethod(nameof(ConfigureMapper), BindingFlags.Static | BindingFlags.NonPublic);
...
ConfigureMapperMethod.MakeGenericMethod(t).Invoke(null,new object[]{config, permittedfields, allFields, ed});

I look for the dictionary properties by name ( independently of the type of the object ) so having a simple AfterMapping for object can be helpful too. But anyway, it's just a workaround because the mapping by key for dictionaries is not yet working, so maybe I will have just to wait for that to be fixed, no need to add something if it wasn't needed by someone before me.

[chaowlert]

I just have chance to debug, in fact it works as expected. Mapping null dictionary will also produce null dictionary. If you would like to create dictionary if source is null, you can use AddDestinationTransform.

example:

config.NewConfig<Post, Post>()
    .Map(nameof(Post.Dic) + ".Name", nameof(Post.Dic) + ".Name")
    .AddDestinationTransform(DestinationTransform.EmptyCollectionIfNull
        .WithCondition(type => type == typeof(IDictionary<string, string>)));

Then your dictionary will be empty instead of null.