Extruder has the ability to combine two of more data sources which fall back when decoding and write to multiple places on encoding. This can be achieved by chaining .combine when calling encode or decode.
There are multiple ways to call combine: by passing another data source, another decode or encode call, or by specifying type parameters. Below is an example of using another data source to encode and decode.
import extruder.map._
import extruder.circe.instances._
import io.circe.Json
import io.circe.generic.auto._
import io.circe.syntax._
case class Example(configuredString: String, optionalString: Option[String])
val example = Example("test", None)
val encoder = encode.combine(extruder.circe.datasource)
encode.combine(extruder.circe.datasource)(example) // Ior.Both(Map(example.configuredstring -> test),{ "configuredString" : "test", "optionalString" : null })
val map = Map("example.configuredstring" -> "test")
val json = Map("configuredString" -> "test").asJson
val decoder = decode[Example].combine(extruder.circe.datasource)
decoder((Map.empty[String, String], json)) == decoder((map, Json.Null)) // true
For usage information of the various combine methods see the API documentation for the various partially applied encoders and decoders: