func dropEmpty()

in lib/collections.go [732:792]
56 lines of code
16 McCabe index (conditional complexity)

func dropEmpty(val ref.Val) ref.Val {
	obj, ok := val.(iterator)
	if !ok || !hasEmpty(obj) {
		return val
	}

	switch obj := val.(type) {
	case traits.Lister:
		new := make([]ref.Val, 0, obj.Size().Value().(int64))
		it := obj.Iterator()
		for it.HasNext() == types.True {
			elem := it.Next()
			switch val := elem.(type) {
			case iterator:
				if val.Size() != types.IntZero {
					res := dropEmpty(val)
					if v, ok := res.(traits.Sizer); ok {
						if v.Size() != types.IntZero {
							new = append(new, res)
						}
					} else {
						new = append(new, res)
					}
				}
			default:
				new = append(new, val)
			}
		}
		return types.NewRefValList(types.DefaultTypeAdapter, new)

	case traits.Mapper:
		new := make(map[ref.Val]ref.Val)
		m, err := obj.ConvertToNative(refValMap)
		if err != nil {
			return types.NewErr("unable to convert map to native: %v", err)
		}
		for k, v := range m.(map[ref.Val]ref.Val) {
			switch val := v.(type) {
			case iterator:
				if val.Size() != types.IntZero {
					res := dropEmpty(v)
					if v, ok := res.(traits.Sizer); ok {
						if v.Size() != types.IntZero {
							new[k] = res
						}
					} else {
						new[k] = res
					}
				}
			default:
				new[k] = v
			}
		}
		return types.NewRefValMap(types.DefaultTypeAdapter, new)

	default:
		// This should never happen since non-iterator
		// types will have been returned in the preamble.
		return val
	}
}