Fix a problem with empty value for non-primitive array type deserialization

3 files changed, 37 insertions, 7 deletions

diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/ObjectArrayDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/ObjectArrayDeserializer.java
index f050604da..6225f53ff 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/ObjectArrayDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/ObjectArrayDeserializer.java
@@ -12,6 +12,7 @@ import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
 import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
 import com.fasterxml.jackson.databind.deser.NullValueProvider;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
+import com.fasterxml.jackson.databind.type.ArrayType;
 import com.fasterxml.jackson.databind.type.LogicalType;
 import com.fasterxml.jackson.databind.util.AccessPattern;
 import com.fasterxml.jackson.databind.util.ObjectBuffer;
@@ -26,8 +27,6 @@ public class ObjectArrayDeserializer
 {
     private static final long serialVersionUID = 1L;
 
-    protected final static Object[] NO_OBJECTS = new Object[0];
-
     // // Configuration
 
     /**
@@ -53,20 +52,27 @@ public class ObjectArrayDeserializer
      */
     protected final TypeDeserializer _elementTypeDeserializer;
 
+    /**
+     * @since 2.12
+     */
+    protected final Object[] _emptyValue;
+
     /*
     /**********************************************************
     /* Life-cycle
     /**********************************************************
      */
 
-    public ObjectArrayDeserializer(JavaType arrayType,
+    public ObjectArrayDeserializer(JavaType arrayType0,
             JsonDeserializer<Object> elemDeser, TypeDeserializer elemTypeDeser)
     {
-        super(arrayType, null, null);
+        super(arrayType0, null, null);
+        ArrayType arrayType = (ArrayType) arrayType0;
         _elementClass = arrayType.getContentType().getRawClass();
         _untyped = (_elementClass == Object.class);
         _elementDeserializer = elemDeser;
         _elementTypeDeserializer = elemTypeDeser;
+        _emptyValue = arrayType.getEmptyArray();
     }
 
     protected ObjectArrayDeserializer(ObjectArrayDeserializer base,
@@ -76,6 +82,7 @@ public class ObjectArrayDeserializer
         super(base, nuller, unwrapSingle);
         _elementClass = base._elementClass;
         _untyped = base._untyped;
+        _emptyValue = base._emptyValue;
 
         _elementDeserializer = elemDeser;
         _elementTypeDeserializer = elemTypeDeser;
@@ -166,7 +173,9 @@ public class ObjectArrayDeserializer
     // need to override as we can't expose ValueInstantiator
     @Override // since 2.9
     public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException {
-        return NO_OBJECTS;
+        // 03-Jul-2020, tatu: Must be assignment-compatible; can not just return `new Object[0]`
+        //   if element type is different
+        return _emptyValue;
     }
 
     /*
@@ -337,7 +346,7 @@ public class ObjectArrayDeserializer
         if (p.hasToken(JsonToken.VALUE_NULL)) {
             // 03-Feb-2017, tatu: Should this be skipped or not?
             if (_skipNullValues) {
-                return NO_OBJECTS;
+                return _emptyValue;
             }
             value = _nullProvider.getNullValue(ctxt);
         } else if (_elementTypeDeserializer == null) {
diff --git a/src/main/java/com/fasterxml/jackson/databind/type/ArrayType.java b/src/main/java/com/fasterxml/jackson/databind/type/ArrayType.java
index ef3e6aafb..901b342fe 100644
--- a/src/main/java/com/fasterxml/jackson/databind/type/ArrayType.java
+++ b/src/main/java/com/fasterxml/jackson/databind/type/ArrayType.java
@@ -197,7 +197,20 @@ public final class ArrayType
         sb.append('[');
         return _componentType.getErasedSignature(sb);
     }
-    
+
+    /*
+    /**********************************************************
+    /* Extended API
+    /**********************************************************
+     */
+
+    /**
+     * @since 2.12
+     */
+    public Object[] getEmptyArray() {
+        return  (Object[]) _emptyArray;
+    }
+
     /*
     /**********************************************************
     /* Standard methods
diff --git a/src/test/java/com/fasterxml/jackson/databind/convert/CoerceContainersTest.java b/src/test/java/com/fasterxml/jackson/databind/convert/CoerceContainersTest.java
index a22326445..163588155 100644
--- a/src/test/java/com/fasterxml/jackson/databind/convert/CoerceContainersTest.java
+++ b/src/test/java/com/fasterxml/jackson/databind/convert/CoerceContainersTest.java
@@ -137,6 +137,14 @@ public class CoerceContainersTest extends BaseMapTest
         assertEquals(0, result.length);
     }
 
+    public void testPOJOArray() throws Exception
+    {
+        _verifyNoCoercion(StringWrapper[].class);
+        StringWrapper[] result = _readWithCoercion(StringWrapper[].class);
+        assertNotNull(result);
+        assertEquals(0, result.length);
+    }
+    
     /*
     /********************************************************
     /* Helper methods