Fix #2972

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -9,6 +9,8 @@ Project: jackson-databind
 #2962: Auto-detection of constructor-based creator method skipped if there is
    an annotated factory-based creator method (regression from 2.11)
  (reported by Halil I-S)
+#2972: `ObjectMapper.treeToValue()` no longer invokes `JsonDeserializer.getNullValue()`
+ (reported by andpal@github)
 #2973: DeserializationProblemHandler is not invoked when trying to deserializing String
  (reported by zigzago@github)
 

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

@@ -2796,7 +2796,7 @@ public <T> T readValue(JsonParser p, Class<T> valueType)
     {
         _assertNotNull("p", p);
         return (T) _readValue(getDeserializationConfig(), p, _typeFactory.constructType(valueType));
-    } 
+    }
 
     /**
      * Method to deserialize JSON content into a Java type, reference
@@ -3242,10 +3242,6 @@ public <T> T treeToValue(TreeNode n, Class<T> valueType)
                 return (T) n;
             }
             final JsonToken tt = n.asToken();
-            // 22-Aug-2019, tatu: [databind#2430] Consider "null node" (minor optimization)
-            if (tt == JsonToken.VALUE_NULL) {
-                return null;
-            }
             // 20-Apr-2016, tatu: Another thing: for VALUE_EMBEDDED_OBJECT, assume similar
             //    short-cut coercion
             if (tt == JsonToken.VALUE_EMBEDDED_OBJECT) {
@@ -3256,6 +3252,12 @@ public <T> T treeToValue(TreeNode n, Class<T> valueType)
                     }
                 }
             }
+            // 22-Aug-2019, tatu: [databind#2430] Consider "null node" (minor optimization)
+            // 08-Dec-2020, tatu: Alas, lead to [databind#2972], optimization gets complicated
+            //    so leave out for now...
+            /*if (tt == JsonToken.VALUE_NULL) {
+                 return null;
+            }*/
             return readValue(treeAsTokens(n), valueType);
         } catch (JsonProcessingException e) {
             // 12-Nov-2020, tatu: These can legit happen, during conversion, especially

src/test/java/com/fasterxml/jackson/databind/node/TestConversions.java

@@ -3,6 +3,7 @@
 import java.io.IOException;
 import java.math.BigDecimal;
 import java.util.*;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.junit.Assert.*;
 
@@ -326,5 +327,11 @@ public void testConversionsOfNull() throws Exception
         // and vice versa
         Object pojo = MAPPER.treeToValue(n, Root.class);
         assertNull(pojo);
+
+        // [databind#2972]
+        AtomicReference<?> result = MAPPER.treeToValue(NullNode.instance,
+                AtomicReference.class);
+        assertNotNull(result);
+        assertNull(result.get());
     }
 }