Throwable getMessage can return null

[daddykotex]

We've had instances where a throwable with no error message would break the logger.

For instance, if you call asJson on a null it does:

//> using scala "2.13.10"
//> using lib "io.circe::circe-core:0.14.5"

import io.circe._
import io.circe.syntax._

case class CrappyError(msg: String) extends RuntimeException(msg)
object MyTest extends App {
  val err = CrappyError(null)
  println(err.getMessage.asJson)
}

results in:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.length()" because "value" is null
        at io.circe.Printer$PrintingFolder.onString(Printer.scala:319)
        at io.circe.Printer$PrintingFolder.onString(Printer.scala:302)
        at io.circe.Json$JString.foldWith(Json.scala:369)
        at io.circe.Printer.unsafePrintToAppendable(Printer.scala:229)
        at io.circe.Printer.print(Printer.scala:197)
        at io.circe.Json.spaces2(Json.scala:127)
        at io.circe.Json.toString(Json.scala:220)
        at java.base/java.lang.String.valueOf(String.java:4215)
        at java.base/java.io.PrintStream.println(PrintStream.java:1047)
        at scala.Console$.println(Console.scala:268)
        at scala.Predef$.println(Predef.scala:427)

[daddykotex]

During a discussion, it was brought up to me that toString is not necessarily implemented in terms of getMessage so an alternative implementation might be to use getMessage and fallback to toString

wdyt?

[mpilquist]

How about Option(t.getMessage).map(_.asJson).getOrElse(Json.nullValue)

[daddykotex]

How about Option(t.getMessage).map(_.asJson).getOrElse(Json.nullValue)

yeah, that's a good idea. we have the class already so, I'll do that.

[daddykotex]

Thanks for your review <3