EnumFormatter.formatEnum throws a NoSuchElementException

[pbarron]

Noticed this while completing #181. When parsing an empty Json object the following exceptions is thrown

java.util.NoSuchElementException: None.get
	at scala.None$.get(Option.scala:349)
	at scala.None$.get(Option.scala:347)
	at skuber.json.format.package$EnumFormatter.$anonfun$formatEnum$3(package.scala:87)
	at scala.Option.getOrElse(Option.scala:121)
	at skuber.json.format.package$EnumFormatter.$anonfun$formatEnum$1(package.scala:87)
	at play.api.libs.json.JsSuccess.map(JsResult.scala:18)
	at play.api.libs.json.OFormat$$anon$5.$anonfun$inmap$1(Format.scala:29)
	at play.api.libs.json.OFormat$$anon$1.reads(Format.scala:37)
	at play.api.libs.json.Reads.$anonfun$map$1(Reads.scala:43)
	at play.api.libs.json.Reads$$anon$8.reads(Reads.scala:132)
	at play.api.libs.json.Reads$$anon$3$$anon$4.reads(Reads.scala:110)
	at play.api.libs.json.OFormat$$anon$2.reads(Format.scala:44)
...

instead of returning a JsError. The issue seems to be here where a get on the default optional value is made.

[doriordan]

Thanks @pbarronfor the bug report, so this looks like it will be thrown if no default is supplied by the applicable Json formatter but the field is missing, in this case no value can be returned.
At first glance I think the best solution might be to split formatEnum into two different functions - one (formatEnumWithDefault) has a mandatory default value parameter and the other (formatEnum) has no default parameter. formatNullable can be used with the first, knowing there is always a default to fall back on if it is missing, and the non-nullable variation offormat can be used with the second to automatically get a normal JsError if the value is missing.

[pbarron]

so this looks like it will be thrown if no default is supplied by the applicable Json formatter but the field is missing, in this case no value can be returned.

Yes that is correct.

The solution you are suggesting should work. Though, probably also need to review the usages of the function where default is None to determine if the field needs to changed to an "Option" or left as is and return a JSError.

If i get time I'll have a look at it in the coming week.