This is with CE 14 (freshly built against 85b24a86 but it's been doing this for a while). Also, my apologies: I have tried very hard to reproduce this with self-contained code, but it's unclear what exactly is setting off the NPE warning.
In the following snippet, the has() protects the get() from returning null, although as IJ correctly determined, it could NPE if the subclass that readTree() returns doesn't override the get() from the abstract class JsonNode which is defined as return null.
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class Main { public static void main(String[] args) throws Exception { JsonNode n = new ObjectMapper().readTree("{\"hello\": \"world\"}"); if (n.has("hello")) { String s = n.get("hello").asText();
//-----------------------------------^^^^^^^^^
// warns that the asText could produce NPE } }
}
So I understand that conclusion, and thus am willing to compromise with the inference engine and cast the result to the concrete subclass that I know it is:
String s = ((TextNode)n.get("hello")).asText();
//-----------^^^^^^^^
// redundant cast
However, now I get a different warning, in that the cast is redundant because I am not invoking a method that requires the downcast to access.
I would prefer not to litter the code with assert thing != null, nor the inspection suppression //noinspection ConstantConditions.
I almost filed a YouTrack for this, but I realized I can't quite articulate what the bug is; I can't expect IJ to know every API in the world, nor would I necessarily want to switch off the redundant cast inspection.
What is the correct behavior here, either on my part or on IJ's part?