Fix #4934 (#4943)

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -1904,3 +1904,8 @@ Konstantin Maliuga (@badoken)
 Lars Benedetto (@lbenedetto)
  * Contributed #4676: Support other enum naming strategies than camelCase
   (2.19.0)
+
+Floris Westerman (@FWest98)
+ * Reported #4934: `DeserializationContext.readTreeAsValue()` handles null nodes
+   differently from `ObjectMapper.treeToValue()`
+  (2.19.0)

release-notes/VERSION-2.x

@@ -43,6 +43,9 @@ Project: jackson-databind
 #4869: Add `JsonNode.values()` to replace `elements()`
 #4896: Coercion shouldn't be necessary for Enums specifying an empty string
  (reported by @joaocanaverde-blue)
+#4934: `DeserializationContext.readTreeAsValue()` handles null nodes
+  differently from `ObjectMapper.treeToValue()`
+ (reported by Floris W)
 
 2.18.3 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/DeserializationContext.java

@@ -989,9 +989,9 @@ public <T> T readValue(JsonParser p, JavaType type) throws IOException {
             return reportBadDefinition(type,
                     "Could not find JsonDeserializer for type "+ClassUtil.getTypeDescription(type));
         }
-        return (T) deser.deserialize(p, this);
+        return (T) _readValue(p, deser);
     }
-
+    
     /**
      * Convenience method that may be used by composite or container deserializers,
      * for reading one-off values for the composite type, taking into account
@@ -1023,7 +1023,7 @@ public <T> T readPropertyValue(JsonParser p, BeanProperty prop, JavaType type) t
                     "Could not find JsonDeserializer for type %s (via property %s)",
                     ClassUtil.getTypeDescription(type), ClassUtil.nameOf(prop)));
         }
-        return (T) deser.deserialize(p, this);
+        return (T) _readValue(p, deser);
     }
 
     /**
@@ -1116,6 +1116,20 @@ private TreeTraversingParser _treeAsTokens(JsonNode n) throws IOException
         return p;
     }
 
+    /**
+     * Helper method that should handle special cases for deserialization; most
+     * notably handling {@code null} (and possibly absent values).
+     *
+     * @since 2.19
+     */
+    private Object _readValue(JsonParser p, JsonDeserializer<Object> deser) throws IOException
+    {
+        if (p.hasToken(JsonToken.VALUE_NULL)) {
+             return deser.getNullValue(this);
+        }
+        return deser.deserialize(p, this);
+    }
+    
     /*
     /**********************************************************
     /* Methods for problem handling

src/test/java/com/fasterxml/jackson/databind/DeserializationContextTest.java

@@ -11,7 +11,10 @@
 
 public class DeserializationContextTest extends DatabindTestUtil
 {
-    private final ObjectMapper MAPPER = newJsonMapper();
+    // Not testing "no nulls for primitives", so
+    private final ObjectMapper MAPPER = jsonMapperBuilder()
+            .disable(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES)
+            .build();
 
     static class Bean4934 {
         public String value;
@@ -27,10 +30,9 @@ public void testTreeAsValueFromNulls() throws Exception
 
             assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), Boolean.class));
             assertEquals(Boolean.FALSE, ctxt.readTreeAsValue(nodeF.nullNode(), Boolean.TYPE));
+            assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), String.class));
 
-            // Only fixed in 2.19:
-            //assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), Bean4934.class));
-
+            assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), Bean4934.class));
         }
     }
 
@@ -42,12 +44,12 @@ public void testTreeAsValueFromMissing() throws Exception
         try (JsonParser p = MAPPER.createParser("abc")) {
             DeserializationContext ctxt = MAPPER.readerFor(String.class).createDeserializationContext(p);
 
-            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Boolean.class));
             // Absent becomes `null` for now as well
+            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Boolean.class));
             assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Boolean.TYPE));
+            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), String.class));
 
-            // Only fixed in 2.19:
-            //assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Bean4934.class));
+            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Bean4934.class));
         }
     }
 }