Issues related to use of TransportException

Lagom Version (2.5.x / etc)

Lagom 1.3.0-RC1

API (Scala / Java / Neither / Both)

Scala

There are several minor annoyances related to using TransportException, e.g. to return NotFound results. I’m happy to submit a PR with the appropriate changes if I can get some feedback about the most desirable approaches:

• (#1247) The use of getClass in the TransportException constructor results in the ExceptionMessage name being set to "Predef$". This doesn’t affect the built-in exceptions since they explicitly pass classOf[X].getSimpleName as the name, but it affects subclasses of TransportException which use the default constructors, e.g. this test fails:

import com.lightbend.lagom.scaladsl.api.transport.{TransportErrorCode, TransportException}
import org.scalatest.WordSpec
class ResponseExceptionsSpec extends WordSpec {
  "TransportException" should {
      "not use Predef$ as the exception name" in {
        val e = new TransportException(TransportErrorCode.NotFound, "Not found")
        assert(e.exceptionMessage.name != "Predef$")
      }
   }
}

• It is often not desirable to log a TransportException, e.g. ScaladslServiceRouter overrides maybeLogException to not log NotFound when a service call throws it. However, there is no way to extend this to an app’s own TransportException subclasses since LagomServerBuilder is final, and it always constructs a ScaladslServiceRouter. Possible solutions could be:

  • Provide an option to ignore all TransportExceptions (other than the ones being reported as warnings)
  • Introduce a marker trait which could indicate that the exception is not to be logged
  • Allow the router to be specified by the application so that maybeLogException can be overridden with custom logic.

• (almost done in #1247) The built-in TransportExceptions don’t provide any tests for equality, so returning them from a PersistentEntity causes the PersistentEntityTestDriver to report that they are not the same before/after serialization/deserialization. E.g.

org.scalatest.exceptions.TestFailedException: Vector(Object [com.lightbend.lagom.scaladsl.api.transport.NotFound: not found (TransportErrorCodeImpl(404,1008,Policy Violation))] does not equal [com.lightbend.lagom.scaladsl.api.transport.NotFound: not found (TransportErrorCodeImpl(404,1008,Policy Violation))] after serialization/deserialization) had length 1 instead of expected length 0

[steinybot]

#1247 doesn’t fix the third item. I think a TODO was left for this https://github.com/lagom/lagom/pull/1247/files#r173299260

[ignasi35]

@notNotDaniel I edited the original description so your list is now a todo list. Also added a ref to the PR fixing the first item as @TimMoore pointed out.