Conditional Mapping

[samusaran]

I'm currently migrating from AutoMapper to Mapperly.

On AutoMapper I have a mapping setup like this

CreateMap<MyUser, MyUser>()
   .ForMember(x => x.UserPrincipalName, opts => opts
      .Condition((_, dest) => string.IsNullOrWhiteSpace(dest.UserPrincipalName))); // only map to empty values

Since MyUser is a EF Core entity and UserPrincipalName is the primary key, I want to avoid replacing it (even casing matters in this case).

Is anything similar to this possible? Basically I want to map UserPrincipalName only when the destination is null, and not when a value already exists.

[latonz]

Thanks for the suggestion!

We currently don't have plans to support conditional mapping. We aim to keep Mapperly focused strictly on object mapping and avoid mixing in business logic or complex runtime state checks.

For this specific scenario, the best approach is to ignore the target property in the generated method and handle the condition manually in a wrapper:

public void Map(MyUser source, MyUser target)
{
    // Map standard properties
    MapInternal(source, target);

    // Apply specific business logic/conditions
    if (string.IsNullOrWhiteSpace(target.UserPrincipalName))
    {
        target.UserPrincipalName = source.UserPrincipalName;
    }
}

// Generate mapping but skip the sensitive property
[MapperIgnoreTarget(nameof(MyUser.UserPrincipalName))]
private partial void MapInternal(MyUser source, MyUser target);