How to include nested EF entities in include

Description

I’m using AutoMapper as I expose through a Resource information that I take from several classes that require EF navigation. See src.EntityTypeNameType.NameType.Code in the mapping that I use…

 CreateMap<Model.EntityName, DTO.EntityName>()
    .ForMember(dest => dest.NameType,
        opts => opts.MapFrom(src => src.EntityTypeNameType.NameType.Code));

What happens is that with the DefaultEntityRepository I see only the base include is included unless I force it.

My idea is to override the IQueryable<Entity> Include(...) and create a Dictionary of the nested includes required that need to be loaded to query all the tables in the relationship.

This is more a design question or feature-request rather than a bug. Does it make sense the solution I’m planning?

btw, congrats for this project looks very nice! 😉

Environment

• JsonApiDotNetCore Version: v3.1.0
• Other Relevant Package Versions: AutoMapper

[bart-degreed]

The problem here is that these dependencies cross resource-specific services and repositories, so it cannot be solved in a good way at those levels.

Let me illustrate using an example. Consider the next models:

public class User : Identifiable
{
    [Attr(isImmutable: true)] 
    [NotMapped] 
    public string DisplayName => Name.First + " " + Name.Last;

    public Name Name { get; set; }
}

public class Name // not exposed as resource, only database table
{
    public string First { get; set; }
    public string Last { get; set; }
}

public class Blog : Identifiable
{
    [HasOne]
    public User Author { get; set; }
}

When getting users, it fails with a NullReferenceException in DisplayName because the Name navigation property was not loaded. In this case, it must be loaded unconditionally. One solution, at first sight, would be to override DefaultResourceRepository.Get():

public class UserRepository : DefaultResourceRepository<User>
{
    public override IQueryable<User> Get() => base.Get().Include(user => user.Name);
}

That works for the /users endpoint. But getting /blogs?include=author will cause the NullReferenceException again. So now we need a conditional include in the blogs repository:

public class BlogRepository : DefaultResourceRepository<Blog>
{
    public override IQueryable<Blog> Get()
    {
        if (QueryStringHasAuthorIncluded())
        {
            return base.Get().Include(blog => blog.Author.Name);
        }
        else
        {
            return base.Get();
        }
    }
}

I know there are other places we can do the inclusion, like the DefaultResourceRepository.Include() method or DefaultResourceService.ApplyInclude(), but that does not change my point. The problem is we need to duplicate the inclusion logic whenever a resource contains a User resource, or when a resource contains another resource that contains a User resource, etc.

The best way I think to deal with this is to indicate on the resource itself which EF navigation properties must be unconditionally loaded. And then have the framework dynamically add EF includes for them.

Something like this (but with a better name):

public class User : Identifiable
{
    [Attr(isImmutable: true)] 
    [NotMapped] 
    public string DisplayName => Name.First + " " + Name.Last;

    [JsonApiAlwaysAutoLoad] // <-------
    public Name Name { get; set; }
}

[maurei]

I will get back at this tomorrow.