Fix #3711: type id for DEDUCTION case was not working for scalar valu…

…es (#3716)

release-notes/VERSION-2.x

@@ -10,6 +10,8 @@ Project: jackson-databind
  (reported by @marvin-we)
 #3699: Allow custom `JsonNode` implementations
  (contributed by Philippe M)
+#3711: Enum polymorphism not working correctly with DEDUCTION
+ (reported by @smilep)
 
 2.14.1 (21-Nov-2022)
 

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

@@ -0,0 +1,57 @@
+package com.fasterxml.jackson.databind.jsontype.impl;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.type.WritableTypeId;
+import com.fasterxml.jackson.databind.BeanProperty;
+
+/**
+ * @since 2.14.2
+ */
+public class AsDeductionTypeSerializer extends TypeSerializerBase
+{
+    private final static AsDeductionTypeSerializer INSTANCE = new AsDeductionTypeSerializer();
+
+    protected AsDeductionTypeSerializer() {
+        super(null, null);
+    }
+
+    public static AsDeductionTypeSerializer instance() {
+        return INSTANCE;
+    }
+
+    @Override
+    public AsDeductionTypeSerializer forProperty(BeanProperty prop) {
+        return this;
+    }
+
+    // This isn't really right but there's no "none" option
+    @Override
+    public As getTypeInclusion() { return As.EXISTING_PROPERTY; }
+
+    @Override
+    public WritableTypeId writeTypePrefix(JsonGenerator g,
+            WritableTypeId idMetadata) throws IOException
+    {
+        // NOTE: We can NOT simply skip writing since we may have to
+        // write surrounding Object or Array start/end markers. But
+        // we are not to generate type id to write (compared to base class)
+
+        if (idMetadata.valueShape.isStructStart()
+                // also: do not try to write native type id
+                && !g.canWriteTypeId()) {
+            return g.writeTypePrefix(idMetadata);
+        }
+        return null;
+    }
+
+    @Override
+    public WritableTypeId writeTypeSuffix(JsonGenerator g,
+            WritableTypeId idMetadata) throws IOException
+    {
+        return (idMetadata == null) ? null
+            : g.writeTypeSuffix(idMetadata);
+    }
+}

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

@@ -108,15 +108,14 @@ public TypeSerializer buildTypeSerializer(SerializationConfig config,
                 return null;
             }
         }
-
-        TypeIdResolver idRes = idResolver(config, baseType, subTypeValidator(config),
-                subtypes, true, false);
-
         if(_idType == JsonTypeInfo.Id.DEDUCTION) {
             // Deduction doesn't require a type property. We use EXISTING_PROPERTY with a name of <null> to drive this.
-            return new AsExistingPropertyTypeSerializer(idRes, null, _typeProperty);
+            // 04-Jan-2023, tatu: Actually as per [databind#3711] that won't quite work so:
+            return AsDeductionTypeSerializer.instance();
         }
 
+        TypeIdResolver idRes = idResolver(config, baseType, subTypeValidator(config),
+                subtypes, true, false);
         switch (_includeAs) {
         case WRAPPER_ARRAY:
             return new AsArrayTypeSerializer(idRes, null);

src/test/java/com/fasterxml/jackson/databind/jsontype/TestPolymorphicDeduction.java

@@ -5,7 +5,7 @@
 
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
-
+import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.databind.BaseMapTest;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.JavaType;
@@ -54,6 +54,15 @@ static class Box {
     public Feline feline;
   }
 
+  @JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION)
+  static class Bean3711 {
+      @JsonValue
+      public String ser = "value";
+  }
+
+  @JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION)
+  static enum Enum3711 { A, B }
+
   /*
   /**********************************************************
   /* Mock data
@@ -269,4 +278,16 @@ public void testListSerialization() throws Exception {
     // Then:
     assertEquals(arrayOfCatsJson, json);
   }
+
+  // [databind#3711]
+  public void testWithPojoAsJsonValue() throws Exception
+  {
+      assertEquals(q("value"), MAPPER.writeValueAsString(new Bean3711()));
+  }
+
+  // [databind#3711]
+  public void testWithEnum() throws Exception
+  {
+      assertEquals(q("B"), MAPPER.writeValueAsString(Enum3711.B));
+  }
 }