FhirJsonParser from Hl7.Fhir.R4 does not work with STU3 Data

[MLuebbers]

We generally work with R4 data and have installed the hl7.fhir.r4 nuget package accordingly. However one of our services needs to return STU3 resource bundle and we noticed that FhirJsonParser isn't parsing the string to the Resource object correctly; we just get an exception for an invalid format (presumably because of the difference between the STU3 resource and the R4 resource.)

To me this is a reasonable error, but the FhirJsonParser in Hl7.Fhir.R4 seems to suggest it's backwards compatible judging from the source code here. Is this not the case? This looks to be the only FhirJsonParser defined in the whole repo.

I was able to fix the issue by installing both R4 and STU3 packages and creating an alias for FhirJsonParser from each package, then conditionally picking which parser to use. That was extra logic that we'd prefer to not have to handle on our end so is there a proper way to handle deserializing both R4 and STU3 bundles?

[MLuebbers]

Thank you, that is helpful for information for us.