FHIR Chat · Publisher: Null-pointer exception during snapshot generation

Stream: IG creation

Topic: Publisher: Null-pointer exception during snapshot generation

Pétur Valdimarsson (Apr 03 2020 at 09:30):

Hi! Not sure if this is by design or a newly introduced bug, but running later IG-publishers, I'm getting a null-pointer exception if mapping for an element is a blank string. From what I have seen this happens both with an empty string and a whitespace.

Example snippet from differential:

{
        "id": "Observation.valueQuantity.value",
        "path": "Observation.valueQuantity.value",
        "mapping": [
          {
            "identity": "v2",
            "map": "SN.2  / CQ - N/A"
          },
          {
            "identity": "other-mapping",
            "map": ""
          }
        ]
      }

The stacktrace:

java.lang.Exception: Error generating snapshot for ExampleProfile(example-profile): Unable to generate snapshot for http://example.com/StructureDefinition/example-profile in ..
        at org.hl7.fhir.igtools.publisher.Publisher.generateSnapshots(Publisher.java:4019)
        at org.hl7.fhir.igtools.publisher.Publisher.loadConformance(Publisher.java:3448)
        at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:796)
        at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:657)
        at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:7062)
Caused by: org.hl7.fhir.exceptions.FHIRException: Unable to generate snapshot for http://example.com/StructureDefinition/example-profile in ..
        at org.hl7.fhir.igtools.publisher.Publisher.generateSnapshot(Publisher.java:4072)
        at org.hl7.fhir.igtools.publisher.Publisher.generateSnapshots(Publisher.java:4017)
        ... 4 more
Caused by: java.lang.NullPointerException
        at org.hl7.fhir.r5.conformance.ProfileUtilities.generateSnapshot(ProfileUtilities.java:591)
        at org.hl7.fhir.igtools.publisher.Publisher.generateSnapshot(Publisher.java:4070)
        ... 5 more
Exception in thread "main" java.lang.NullPointerException
        at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:7085)

I haven't done too much debugging, but can see that the ElementDefinitionMappingComponent.map is null which causes a null-pointer due to the trim call in mm.setMap(mm.getMap().trim()). I don't know if the fix, if one is to be done, should be to ensure that the ElementDefinitionMappingComponent.map is not null, to compensate for the possibility of it being null before mm.setMap(mm.getMap().trim()) or to throw a more verbose exception. Until then, I've ensured that the map always has some none-whitespace content in my profiles.