Fix #2775

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -7,6 +7,8 @@ Project: jackson-databind
 
 2.12.0-rc2 (not yet released)
 
+#2775: Disabling `FAIL_ON_INVALID_SUBTYPE` breaks polymorphic deserialization of Enums
+ (reported by holgerknoche@github)
 #2878: Revert change initially made to fix #2805: change in signature
   of `ObjectMapper.treeToValue()` regarding exceptions
 #2880: Revert removal of 2.7-deprecated `PropertyNamingStrategy` constants

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

@@ -467,7 +467,7 @@ public boolean hasTypePropertyName(String n) {
         }
 
         public boolean hasDefaultType() {
-            return _typeDeserializer.getDefaultImpl() != null;
+            return _typeDeserializer.hasDefaultImpl();
         }
 
         /**

src/main/java/com/fasterxml/jackson/databind/jsontype/TypeDeserializer.java

@@ -71,6 +71,11 @@ public abstract class TypeDeserializer
      */
     public abstract Class<?> getDefaultImpl();
 
+    /**
+     * @since 2.12
+     */
+    public boolean hasDefaultImpl() { return getDefaultImpl() != null; }
+
     /*
     /**********************************************************
     /* Type deserialization methods

src/main/java/com/fasterxml/jackson/databind/jsontype/impl/AsPropertyTypeDeserializer.java

@@ -78,7 +78,7 @@ public Object deserializeTypedFromObject(JsonParser p, DeserializationContext ct
                 return _deserializeWithNativeTypeId(p, ctxt, typeId);
             }
         }
-        
+
         // but first, sanity check to ensure we have START_OBJECT or FIELD_NAME
         JsonToken t = p.currentToken();
         if (t == JsonToken.START_OBJECT) {
@@ -115,7 +115,7 @@ public Object deserializeTypedFromObject(JsonParser p, DeserializationContext ct
 
     @SuppressWarnings("resource")
     protected Object _deserializeTypedForId(JsonParser p, DeserializationContext ctxt,
-                                            TokenBuffer tb, String typeId) throws IOException {
+            TokenBuffer tb, String typeId) throws IOException {
         JsonDeserializer<Object> deser = _findDeserializer(ctxt, typeId);
         if (_typeIdVisible) { // need to merge id back in JSON input?
             if (tb == null) {
@@ -142,8 +142,9 @@ protected Object _deserializeTypedUsingDefaultImpl(JsonParser p,
             DeserializationContext ctxt, TokenBuffer tb) throws IOException
     {
         // May have default implementation to use
-        JsonDeserializer<Object> deser = _findDefaultImplDeserializer(ctxt);
-        if (deser == null) {
+        // 13-Oct-2020, tatu: As per [databind#2775], need to be careful to
+        //    avoid ending up using "nullifying" deserializer
+        if (!hasDefaultImpl()) {
             // or, perhaps we just bumped into a "natural" value (boolean/int/double/String)?
             Object result = TypeDeserializer.deserializeIfNatural(p, ctxt, _baseType);
             if (result != null) {
@@ -161,6 +162,11 @@ protected Object _deserializeTypedUsingDefaultImpl(JsonParser p,
                     }
                 }
             }
+        }
+        // ... and here we will check for default implementation handling (either
+        // genuine, or faked for "dont fail on bad type id")
+        JsonDeserializer<Object> deser = _findDefaultImplDeserializer(ctxt);
+        if (deser == null) {
             String msg = String.format("missing type id property '%s'",
                     _typePropertyName);
             // even better, may know POJO property polymorphic value would be assigned to
@@ -190,9 +196,8 @@ protected Object _deserializeTypedUsingDefaultImpl(JsonParser p,
      */
     @Override
     public Object deserializeTypedFromAny(JsonParser p, DeserializationContext ctxt) throws IOException {
-        /* Sometimes, however, we get an array wrapper; specifically
-         * when an array or list has been serialized with type information.
-         */
+        // Sometimes, however, we get an array wrapper; specifically
+        // when an array or list has been serialized with type information.
         if (p.hasToken(JsonToken.START_ARRAY)) {
             return super.deserializeTypedFromArray(p, ctxt);
         }

src/main/java/com/fasterxml/jackson/databind/jsontype/impl/TypeDeserializerBase.java

@@ -112,11 +112,16 @@ protected TypeDeserializerBase(TypeDeserializerBase src, BeanProperty property)
     @Override    
     public TypeIdResolver getTypeIdResolver() { return _idResolver; }
 
-    @Override    
+    @Override
     public Class<?> getDefaultImpl() {
         return ClassUtil.rawClass(_defaultImpl);
     }
 
+    @Override
+    public boolean hasDefaultImpl() {
+        return (_defaultImpl != null);
+    }
+
     /**
      * @since 2.9
      */

src/test/java/com/fasterxml/jackson/databind/introspect/CustomAnnotationIntrospector1756Test.java

@@ -7,6 +7,7 @@
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.cfg.MapperConfig;
 import com.fasterxml.jackson.databind.json.JsonMapper;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 
@@ -89,10 +90,14 @@ public String findImplicitPropertyName(final AnnotatedMember member) {
       }
 
       @Override
-      public boolean hasCreatorAnnotation(Annotated a) {
-        final AnnotatedConstructor ctor = (AnnotatedConstructor) a;
-        return (ctor.getParameterCount() > 0)
-                && (ctor.getParameter(0).getAnnotation(Field1756.class) != null);
+      public JsonCreator.Mode findCreatorAnnotation(MapperConfig<?> config, Annotated ann) {
+          final AnnotatedConstructor ctor = (AnnotatedConstructor) ann;
+          if (ctor.getParameterCount() > 0) {
+              if (ctor.getParameter(0).getAnnotation(Field1756.class) != null) {
+                  return JsonCreator.Mode.PROPERTIES;
+              }
+          }
+          return null;
       }
     }