[MapperIgnore] on properties of classes

[mutzl]

A common usecase is, that entities have properties that never need to be mapped to any DTO.
Some of these metadata properties might even be defined in a base class.
For example:

public abstract class BaseEntity
{
    public DateTime CreatedDate { get; set; }
    public string CreatedBy { get; set; } = default!;
    public DateTime? UpdatedDate { get; set; }
    public string? UpdatedBy { get; set; }
}

public class MyEntity : BaseEntity 
{
    public string Foo { get; set; }
}

public class MyDto 
{
    public string Foo { get; set; }
}

So the mapper configuration is always pretty verbose:

    [MapperIgnoreTarget(nameof(BaseEntity.CreatedDate))]
    [MapperIgnoreTarget(nameof(BaseEntity.CreatedBy))]
    [MapperIgnoreTarget(nameof(BaseEntity.UpdatedDate))]
    [MapperIgnoreTarget(nameof(BaseEntity.UpdatedBy))]
    public static partial MyEntity ToEntity(this MyDto dto);

    [MapperIgnoreSource(nameof(BaseEntity.CreatedDate))]
    [MapperIgnoreSource(nameof(BaseEntity.CreatedBy))]
    [MapperIgnoreSource(nameof(BaseEntity.UpdatedDate))]
    [MapperIgnoreSource(nameof(BaseEntity.UpdatedBy))]
    public static partial MyDto ToDto(this MyEntity entity);

A MapperIgnoreAttribute - similar to the well known [JsonIgnore] - directly on the property would make code way cleaner.

public abstract class BaseEntity
{
    [MapperIgnore] public DateTime CreatedDate { get; set; }
    [MapperIgnore] public string CreatedBy { get; set; } = default!;
    [MapperIgnore] public DateTime? UpdatedDate { get; set; }
    [MapperIgnore] public string? UpdatedBy { get; set; }
}

[TimothyMakkison]

Would #513 and #201 help?

[mutzl]

Would #513 and #201 help?

#201 would help, I suppose.

The [MapperIgnore] looks way more intuitive to me, though.
(at least for the use case I described above - for this kind of metadata, I know upfront, that it's never gonna be mapped).

BTW: Und vielen Dank für diese großartige Idee und Umsetzung von mapperly!

[TimothyMakkison]

Good point with 513. If #201 supports adding ignores then it will be perfect for you.

Failing that it would be pretty easy to modify the IgnoreObsolete code to support [MapperIgnore] 👍

[latonz]

MapperIgnoreAttribute is currently used to ignore target properties for backward compatibility (is marked as obsolete). I like the idea of using MapperIgnoreAttribute on properties to ignore them. However, this needs a breaking change in Mapperly or would need to allow it on properties without a constructor parameter...

The idea of #201 is to allow MapperAttribute configurations on an assembly level which wouldn't work for the use case mentioned here.

[latonz]

#611 removes the MapperIgnoreAttribute from the API, it may in a later release be reused to ignore properties/fields.