Coalesce object or null

[Jonathan Eckman]

Is your feature request related to a problem? Please describe.
Yes. I would like to Coalesce to return either an object or null.

The gremlin query snipper will return an object with "id" if a vertex is found on the "serves" relationship. If a vertex is not found, an empty string is returned.

.by(coalesce(out('serves')
            .project('id')
            .by('id'), constant('')))

Describe the solution you'd like
I would like to recreate this in Gremlinq.

The following is close to the original Gremlin query, but throws a compile error: The type arguments for method Coalesce cannot be inferred from the usage. Try specifying the type arguments explicitly.

 .Coalesce(
         __ => __
            .Out<Serves>()
            .OfType<Meal>()
            .Project(e => e
               .ToDynamic()
               .By("id", __ => __.Id)
             ),
            __ => __.Constant("")
)

This compiles and is what I'd ultimately like to have, but throws a runtime error: Value of variable _w is not a constant type. Cannot assign complex values to groovy variable.

.Coalesce(
    __ => __
      .Out<Serves>()
      .OfType<Meal>()
      .Project(e => e
          .ToDynamic()
          .By(nameof(EventMealDto.Id), __ => __.Id)
       )
       .Cast<EventMealDto>(),
    __ => __.Constant(new EventMealDto {})
)

Describe alternatives you've considered
Still exploring Gremlin alternatives for this use case.

.By("meal", __ => if out returns a result, the result; otherwise null, an empty object, or skip this By all together)

[Jonathan Eckman]

Ignore this. Still learning Gremlin. This is much easier and more effective way to do what I wanted:

.by(out('serves')
            .project('id')
            .by('id').fold())