Fix #3741: Delegate getNullValue() and related to delegatee deserializer (#3750)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -14,6 +14,7 @@ Project: jackson-databind
  (contributed by Philippe M)
 #3711: Enum polymorphism not working correctly with DEDUCTION
  (reported by @smilep)
+#3741: `StdDelegatingDeserializer` ignores `nullValue` of `_delegateDeserializer`.
 
 2.14.1 (21-Nov-2022)
 

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

@@ -1,6 +1,7 @@
 package com.fasterxml.jackson.databind.deser.std;
 
 import java.io.IOException;
+import java.util.Collection;
 
 import com.fasterxml.jackson.core.JsonParser;
 
@@ -9,6 +10,7 @@
 import com.fasterxml.jackson.databind.deser.ResolvableDeserializer;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
 import com.fasterxml.jackson.databind.type.LogicalType;
+import com.fasterxml.jackson.databind.util.AccessPattern;
 import com.fasterxml.jackson.databind.util.ClassUtil;
 import com.fasterxml.jackson.databind.util.Converter;
 
@@ -210,11 +212,6 @@ protected Object _handleIncompatibleUpdateValue(JsonParser p, DeserializationCon
     /**********************************************************
      */
 
-    @Override
-    public JsonDeserializer<?> getDelegatee() {
-        return _delegateDeserializer;
-    }
-
     @Override
     public Class<?> handledType() {
         return _delegateDeserializer.handledType();
@@ -224,7 +221,60 @@ public Class<?> handledType() {
     public LogicalType logicalType() {
         return _delegateDeserializer.logicalType();
     }
-    
+
+    // Let's assume we should be cachable if delegate is
+    @Override
+    public boolean isCachable() {
+        return (_delegateDeserializer != null) && _delegateDeserializer.isCachable();
+    }
+
+    @Override
+    public JsonDeserializer<?> getDelegatee() {
+        return _delegateDeserializer;
+    }
+
+    @Override
+    public Collection<Object> getKnownPropertyNames() {
+        return _delegateDeserializer.getKnownPropertyNames();
+    }
+
+    /*
+    /**********************************************************
+    /* Null/empty/absent accessors
+    /**********************************************************
+     */
+
+    @Override
+    public T getNullValue(DeserializationContext ctxt) throws JsonMappingException {
+        return _convertIfNonNull(_delegateDeserializer.getNullValue(ctxt));
+    }
+
+    @Override
+    public AccessPattern getNullAccessPattern() {
+        return _delegateDeserializer.getNullAccessPattern();
+    }
+
+    @Override
+    public Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
+        return _convertIfNonNull(_delegateDeserializer.getAbsentValue(ctxt));
+    }
+
+    @Override
+    public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException {
+        return _convertIfNonNull(_delegateDeserializer.getEmptyValue(ctxt));
+    }
+
+    @Override
+    public AccessPattern getEmptyAccessPattern() {
+        return _delegateDeserializer.getEmptyAccessPattern();
+    }
+
+    /*
+    /**********************************************************
+    /* Other accessors
+    /**********************************************************
+     */
+        
     @Override // since 2.9
     public Boolean supportsUpdate(DeserializationConfig config) {
         return _delegateDeserializer.supportsUpdate(config);
@@ -251,4 +301,16 @@ public Boolean supportsUpdate(DeserializationConfig config) {
     protected T convertValue(Object delegateValue) {
         return _converter.convert(delegateValue);
     }
+
+    /*
+    /**********************************************************
+    /* Helper methods
+    /**********************************************************
+     */
+
+    // @since 2.14.2
+    protected T _convertIfNonNull(Object delegateValue) {
+        return (delegateValue == null) ? null
+                : _converter.convert(delegateValue);
+    }
 }