Handling Errors

Error handling is critical for building robust workflows that can handle non-happy paths. It allows for short-circuiting operations and following an alternative path in the presence of expected but unusual situations. It can be seen as a more convenient alternative to Forks.

Errors defined and handled should be domain errors and not technical ones. Domain errors represent business-level exceptions that are meaningful in your workflow context, rather than implementation-specific exceptions like network failures or timeouts.

val doThings: WIO[MyState, MyError, Nothing]                        =
  WIO.pure.error(MyError()).autoNamed
val handleThatNastyError: WIO[(MyState, MyError), Nothing, MyState] =
  WIO.pure(MyState(1)).autoNamed

val errorHandled: WIO[MyState, Nothing, MyState] =
  doThings.handleErrorWith(handleThatNastyError)

Rendering Outputs

Flowchart

BPMN

Model

{
  "base" : {
    "meta" : {
      "name" : "Do Things",
      "error" : {
        "name" : "My Error"
      }
    },
    "_type" : "Pure"
  },
  "handler" : {
    "meta" : {
      "name" : "Handle That Nasty Error",
      "error" : null
    },
    "_type" : "Pure"
  },
  "meta" : {
    "newErrorMeta" : null,
    "handledErrorMeta" : {
      "name" : "My Error"
    }
  },
  "_type" : "HandleError"
}