Fix #3654

release-notes/VERSION-2.x

@@ -6,6 +6,7 @@ Project: jackson-databind
 
 2.15.0 (not yet released)
 
+#3654: Infer `@JsonCreator(mode = Mode.DELEGATING)` from use of `@JsonValue`)
 #3676: Allow use of `@JsonCreator(mode = Mode.PROPERTIES)` creator for POJOs
  with"empty String" coercion
 #3680: Timestamp in classes inside jar showing 02/01/1980

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

@@ -498,7 +498,8 @@ protected void _addImplicitConstructorCreators(DeserializationContext ctxt,
             // some single-arg factory methods (String, number) are auto-detected
             if (argCount == 1) {
                 final BeanPropertyDefinition propDef = candidate.propertyDef(0);
-                final boolean useProps = preferPropsBased || _checkIfCreatorPropertyBased(intr, ctor, propDef);
+                final boolean useProps = preferPropsBased
+                        || _checkIfCreatorPropertyBased(beanDesc, intr, ctor, propDef);
 
                 if (useProps) {
                     SettableBeanProperty[] properties = new SettableBeanProperty[1];
@@ -705,7 +706,7 @@ protected void _addImplicitFactoryCreators(DeserializationContext ctxt,
                 continue; // 2 and more args? Must be explicit, handled earlier
             }
             BeanPropertyDefinition argDef = candidate.propertyDef(0);
-            boolean useProps = _checkIfCreatorPropertyBased(intr, factory, argDef);
+            boolean useProps = _checkIfCreatorPropertyBased(beanDesc, intr, factory, argDef);
             if (!useProps) { // not property based but delegating
                 /*boolean added=*/ _handleSingleArgumentCreator(creators,
                         factory, false, vchecker.isCreatorVisible(factory));
@@ -972,12 +973,16 @@ protected void _addExplicitAnyCreator(DeserializationContext ctxt,
                 if (!useProps && (paramDef != null)) {
                     // One more thing: if implicit name matches property with a getter
                     // or field, we'll consider it property-based as well
-
-                    // 25-May-2018, tatu: as per [databind#2051], looks like we have to get
-                    //    not implicit name, but name with possible strategy-based-rename
+
+                    // 01-Dec-2022, tatu: [databind#3654] Consider `@JsonValue` to strongly
+                    //    hint at delegation-based
+                    if (beanDesc.findJsonValueAccessor() == null) {
+                        // 25-May-2018, tatu: as per [databind#2051], looks like we have to get
+                        //    not implicit name, but name with possible strategy-based-rename
         //            paramName = candidate.findImplicitParamName(0);
-                    paramName = candidate.paramName(0);
-                    useProps = (paramName != null) && paramDef.couldSerialize();
+                        paramName = candidate.paramName(0);
+                        useProps = (paramName != null) && paramDef.couldSerialize();
+                    }
                 }
             }
         }
@@ -1000,14 +1005,21 @@ protected void _addExplicitAnyCreator(DeserializationContext ctxt,
         }
     }
 
-    private boolean _checkIfCreatorPropertyBased(AnnotationIntrospector intr,
+    private boolean _checkIfCreatorPropertyBased(BeanDescription beanDesc,
+            AnnotationIntrospector intr,
             AnnotatedWithParams creator, BeanPropertyDefinition propDef)
     {
         // If explicit name, or inject id, property-based
         if (((propDef != null) && propDef.isExplicitlyNamed())
                 || (intr.findInjectableValue(creator.getParameter(0)) != null)) {
             return true;
         }
+        // 01-Dec-2022, tatu: [databind#3654] Consider `@JsonValue` to strongly
+        //    hint at delegation-based
+        if (beanDesc.findJsonValueAccessor() != null) {
+            return false;
+        }
+
         if (propDef != null) {
             // One more thing: if implicit name matches property with a getter
             // or field, we'll consider it property-based as well

src/test/java/com/fasterxml/jackson/databind/deser/creators/ImplicitParamsForCreatorTest.java

@@ -1,5 +1,7 @@
 package com.fasterxml.jackson.databind.deser.creators;
 
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.fasterxml.jackson.databind.introspect.AnnotatedMember;
@@ -45,6 +47,21 @@ public Bean2932(/*@com.fasterxml.jackson.annotation.JsonProperty("paramName0")*/
         }
     }
 
+    // [databind#3654]: infer "DELEGATING" style from `@JsonValue`
+    static class XY3654 {
+        public int paramName0; // has to be public to misdirect
+
+        @JsonCreator
+        public XY3654(int paramName0) {
+            this.paramName0 = paramName0;
+        }
+
+        @JsonValue
+        public int serializedAs() {
+            return paramName0;
+        }
+    }
+
     /*
     /**********************************************************
     /* Test methods
@@ -72,4 +89,15 @@ public void testJsonCreatorWithOtherAnnotations() throws Exception
         assertEquals(1, bean._a);
         assertEquals(2, bean._b);
     }
+
+    // [databind#3654]
+    public void testDelegatingInferFromJsonValue() throws Exception
+    {
+        // First verify serialization via `@JsonValue`
+        assertEquals("123", MAPPER.writeValueAsString(new XY3654(123)));
+
+        // And then deser, should infer despite existence of "matching" property
+        XY3654 result = MAPPER.readValue("345", XY3654.class);
+        assertEquals(345, result.paramName0);
+    }
 }