Scalacheck json and case classes - scala

Question

I'm writing a service that takes a case class and serializes it to json, that I will then send to an instance running Elastic Search.
I'd like scalacheck to generate several case classes, with random missing data, like this:
val searchDescAndBrand = SearchEntry("", "Ac Adapters", "Sony", "", "", "", "", "", "", "", "", "", "", "", "","", "", "", "", "", "", 0L)
val searchBrand = SearchEntry("", ", "Sony", "", "", "", "", "", "", "", "", "", "", "", "","", "", "", "", "", "", 0L)
val searchPartNumberAndBrand = SearchEntry("02DUYT", "", "Sony", "", "", "", "", "", "", "", "", "", "", "", "","", "", "", "", "", "", 0L)
you get the idea, either fill in the values or leave them empty (the last one is a Long type.
This is the easy part, the problem is that the generated json doesn't just omit the "filed", but omits a whole section, for example:
"""
|{
| "from" : 0,
| "size" : 10,
| "query" : {
| "bool" : {
| "must" : [
| {"match" : {
| "description" : {
| "query" : "Ac Adapters",
| "type" : "phrase"
| }
| }},
| {"match" : {
| "brand" : {
| "query" : "Sony",
| "type" : "phrase"
| }
| }}
| ]
| }
| }
|}
|
""".stripMargin)
if I had a case class with the first 3 fields with data, the json would be:
"""
|{
| "from" : 0,
| "size" : 10,
| "query" : {
| "bool" : {
| "must" : [
| {"match" : {
| "part_number" : {
| "query" : "02D875",
| "type" : "phrase"
| }
| }},
| {"match" : {
| "description" : {
| "query" : "Ac Adapters",
| "type" : "phrase"
| }
| }},
| {"match" : {
| "brand" : {
| "query" : "Sony",
| "type" : "phrase"
| }
| }}
| ]
| }
| }
|}
|
""".stripMargin)
So, in short, having a value means adding
{"match" : {
| "<specific name here, based on which value we have>" : {
| "query" : "<value from scalacheck>",
| "type" : "phrase"
| }
| }}
to the result.
How would you handle such a use case?