Fixed #3214 (I hope ;) )

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -58,6 +58,9 @@ Project: jackson-databind
  (contributed by Klaas D)
 #3193: Add `MapperFeature.APPLY_DEFAULT_VALUES`, initially for Scala module
  (suggested by Nick B)
+#3214: For an absent property Jackson injects `NullNode` instead of `null` to a
+  JsonNode-typed constructor argument of a `@ConstructorProperties`-annotated constructor
+ (repored by robvarga@github)
 #3217: `XMLGregorianCalendar` doesn't work with default typing
  (reported by Xinzhe Y)
 #3227: Content `null` handling not working for root values

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

@@ -315,8 +315,9 @@ public T getNullValue(DeserializationContext ctxt) throws JsonMappingException {
      * to be called just once (static values), or each time empty value is
      * needed.
      *<p>
-     * Default implementation indicates that "null value" to use for input null
-     * is simply Java `null` for all deserializers, unless overridden by sub-classes.
+     * Default implementation indicates that the "null value" to use for input null
+     * does not vary across uses so that {@link #getNullValue(DeserializationContext)}
+     * need not be called more than once per deserializer instance.
      * This information may be used as optimization.
      */
     @Override
@@ -327,6 +328,28 @@ public AccessPattern getNullAccessPattern() {
         return AccessPattern.CONSTANT;
     }
 
+    /**
+     * Method called to determine placeholder value to be used for cases
+     * where no value was obtained from input but we must pass a value
+     * nonetheless: the common case is that of Creator methods requiring
+     * passing a value for every parameter.
+     * Usually this is same as {@link #getNullValue} (which in turn
+     * is usually simply Java {@code null}), but it can be overridden
+     * for specific types: most notable scalar types must use "default"
+     * values.
+     *<p>
+     * This method needs to be called every time a determination is made.
+     *<p>
+     * Default implementation simply calls {@link #getNullValue} and
+     * returns value.
+     *
+     * @since 2.13
+     */
+    @Override
+    public Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
+        return getNullValue(ctxt);
+    }
+
     /*
     /**********************************************************
     /* Accessors for other replacement/placeholder values

src/main/java/com/fasterxml/jackson/databind/deser/NullValueProvider.java

@@ -31,4 +31,24 @@ public interface NullValueProvider
      * access null replacement value.
      */
     public AccessPattern getNullAccessPattern(); 
+
+    /**
+     * Method called to determine placeholder value to be used for cases
+     * where no value was obtained from input but we must pass a value
+     * nonetheless: the common case is that of Creator methods requiring
+     * passing a value for every parameter.
+     * Usually this is same as {@link #getNullValue} (which in turn
+     * is usually simply Java {@code null}), but it can be overridden
+     * for specific types: most notable scalar types must use "default"
+     * values.
+     *<p>
+     * This method needs to be called every time a determination is made.
+     *<p>
+     * Default implementation simply calls and returns {@link #getNullValue}.
+     *
+     * @since 2.13
+     */
+    default Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
+        return getNullValue(ctxt);
+    }
 }

src/main/java/com/fasterxml/jackson/databind/deser/impl/PropertyValueBuffer.java

@@ -4,11 +4,8 @@
 import java.util.BitSet;
 
 import com.fasterxml.jackson.core.JsonParser;
-import com.fasterxml.jackson.databind.DatabindException;
-import com.fasterxml.jackson.databind.DeserializationContext;
-import com.fasterxml.jackson.databind.DeserializationFeature;
-import com.fasterxml.jackson.databind.JsonDeserializer;
-import com.fasterxml.jackson.databind.JsonMappingException;
+
+import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.deser.SettableAnyProperty;
 import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
 import com.fasterxml.jackson.databind.introspect.AnnotatedMember;
@@ -202,14 +199,15 @@ protected Object _findMissing(SettableBeanProperty prop) throws JsonMappingExcep
         }
         try {
             // Third: NullValueProvider? (22-Sep-2019, [databind#2458])
-            Object nullValue = prop.getNullValueProvider().getNullValue(_context);
-            if (nullValue != null) {
-                return nullValue;
+            // 08-Aug-2021, tatu: consider [databind#3214]; not null but "absent" value...
+            Object absentValue = prop.getNullValueProvider().getAbsentValue(_context);
+            if (absentValue != null) {
+                return absentValue;
             }
 
             // Fourth: default value
             JsonDeserializer<Object> deser = prop.getValueDeserializer();
-            return deser.getNullValue(_context);
+            return deser.getAbsentValue(_context);
         } catch (DatabindException e) {
             // [databind#2101]: Include property name, if we have it
             AnnotatedMember member = prop.getMember();

src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java

@@ -60,6 +60,15 @@ public JsonNode getNullValue(DeserializationContext ctxt) {
         return ctxt.getNodeFactory().nullNode();
     }
 
+    /**
+     * Overridden variant to ensure that absent values are NOT coerced into
+     * {@code NullNode}s, unlike incoming {@code null} values.
+     */
+    @Override // since 2.13
+    public Object getAbsentValue(DeserializationContext ctxt) {
+        return null;
+    }
+
     /**
      * Implementation that will produce types of any JSON nodes; not just one
      * deserializer is registered to handle (in case of more specialized handler).

src/test/java/com/fasterxml/jackson/failing/NullJsonNodeViaCreator3214Test.java renamed to src/test/java/com/fasterxml/jackson/databind/node/AbsentNodeViaCreator3214Test.java

@@ -1,11 +1,11 @@
-package com.fasterxml.jackson.failing;
+package com.fasterxml.jackson.databind.node;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
+
 import com.fasterxml.jackson.databind.*;
-import com.fasterxml.jackson.databind.node.TextNode;
 
-public class NullJsonNodeViaCreator3214Test extends BaseMapTest
+public class AbsentNodeViaCreator3214Test extends BaseMapTest
 {
     static class Pojo3214
     {