Fix #4602: handling of Array-delegating Creator (#4609)

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -1812,3 +1812,8 @@ Alexandre Jacob (ajacob@github)
  * Reported #4545: Unexpected deserialization behavior with `@JsonCreator`,
    `@JsonProperty` and javac `-parameters`
   (2.18.0)
+
+Eduard Gomoliako (Gems@github)
+ * Reported #4602: Possible wrong use of _arrayDelegateDeserializer in
+   BeanDeserializerBase::deserializeFromObjectUsingNonDefault()
+  (2.18.0)

release-notes/VERSION-2.x

@@ -50,6 +50,9 @@ Project: jackson-databind
 #4570: Deprecate `ObjectMapper.canDeserialize()`/`ObjectMapper.canSerialize()`
 #4580: Add `MapperFeature.SORT_CREATOR_PROPERTIES_BY_DECLARATION_ORDER` to use
   Creator properties' declaration order for sorting
+#4602: Possible wrong use of _arrayDelegateDeserializer in
+  BeanDeserializerBase::deserializeFromObjectUsingNonDefault()
+ (reported by Eduard G)
 
 2.17.2 (not yet released)
 

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

@@ -1482,7 +1482,9 @@ protected Object deserializeFromObjectId(JsonParser p, DeserializationContext ct
     protected Object deserializeFromObjectUsingNonDefault(JsonParser p,
             DeserializationContext ctxt) throws IOException
     {
-        final JsonDeserializer<Object> delegateDeser = _delegateDeserializer();
+        // 02-Jul-2024, tatu: [databind#4602] Need to tweak regular and "array" delegating
+        //   Creator handling
+        final JsonDeserializer<Object> delegateDeser = _delegateDeserializer(p);
         if (delegateDeser != null) {
             final Object bean = _valueInstantiator.createUsingDelegate(ctxt,
                     delegateDeser.deserialize(p, ctxt));
@@ -1505,7 +1507,7 @@ protected Object deserializeFromObjectUsingNonDefault(JsonParser p,
         // 01-May-2022, tatu: [databind#3417] special handling for (Graal) native images
         if (NativeImageUtil.needsReflectionConfiguration(raw)) {
             return ctxt.handleMissingInstantiator(raw, null, p,
-                    "cannot deserialize from Object value (no delegate- or property-based Creator): this appears to be a native image, in which case you may need to configure reflection for the class that is to be deserialized");
+"cannot deserialize from Object value (no delegate- or property-based Creator): this appears to be a native image, in which case you may need to configure reflection for the class that is to be deserialized");
         }
         return ctxt.handleMissingInstantiator(raw, getValueInstantiator(), p,
 "cannot deserialize from Object value (no delegate- or property-based Creator)");
@@ -1710,6 +1712,30 @@ protected final JsonDeserializer<Object> _delegateDeserializer() {
         return deser;
     }
 
+    /**
+     * Alternate to {@link #_delegateDeserializer()} which will only consider
+     * {@code _arrayDelegateDeserializer} if given {@link JsonParser} points to
+     * {@link JsonToken#START_ARRAY} token.
+     *
+     * @since 2.18
+     */
+    protected final JsonDeserializer<Object> _delegateDeserializer(JsonParser p) {
+        if (_delegateDeserializer == null) {
+            // Note! Will not call `JsonParser.isExpectedArrayToken()` as that could
+            // "transform" `JsonToken.START_OBJECT` into `JsonToken.START_ARRAY` and
+            // here there is no strong expectation of Array value
+            if (_arrayDelegateDeserializer != null) {
+                // Alas, need bit elaborate logic: either JSON Array, OR no
+                // Properties-based Creator
+                if (p.hasToken(JsonToken.START_ARRAY)
+                        || (_propertyBasedCreator == null)) {
+                    return _arrayDelegateDeserializer;
+                }
+            }
+        }
+        return _delegateDeserializer;
+    }
+
     /*
     /**********************************************************
     /* Overridable helper methods

src/test/java/com/fasterxml/jackson/failing/TwoCreators4602Test.java renamed to src/test/java/com/fasterxml/jackson/databind/deser/creators/TwoCreators4602Test.java

@@ -1,4 +1,4 @@
-package com.fasterxml.jackson.failing;
+package com.fasterxml.jackson.databind.deser.creators;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;

src/test/java/com/fasterxml/jackson/databind/struct/SingleValueAsArrayTest.java

@@ -19,8 +19,6 @@
 
 public class SingleValueAsArrayTest extends DatabindTestUtil
 {
-    private static final String JSON = "[{\"message\":\"messageHere\"}]";
-
     static class Bean1421A
     {
         List<Messages> bs = Collections.emptyList();
@@ -77,8 +75,10 @@ public Bean1421B(T value) {
     @Test
     public void testSuccessfulDeserializationOfObjectWithChainedArrayCreators() throws IOException
     {
-        Bean1421A result = MAPPER.readValue(JSON, Bean1421A.class);
+        Bean1421A result = MAPPER.readValue("[{\"message\":\"messageHere\"}]", Bean1421A.class);
         assertNotNull(result);
+        assertNotNull(result.bs);
+        assertEquals(1, result.bs.size());
     }
 
     @Test