Fixed #1451

Author: cowtowncoder

release-notes/CREDITS

@@ -485,3 +485,6 @@ Josh Caplan (jecaplan@github)
   * Reported, suggested fix for #1368: Problem serializing `JsonMappingException` due to addition
     of non-ignored `processor` property (added in 2.7)
    (2.7.8)
+
+Frédéric Camblor (fcamblor@github)
+  * Reported #1451: Type parameter not passed by `ObjectWriter` if serializer pre-fetch disabled

release-notes/VERSION

@@ -13,6 +13,8 @@ Project: jackson-databind
 #1432: Off by 1 bug in PropertyValueBuffer
  (reported by Kevin D)
 #1439: NPE when using with filter id, serializing `java.util.Map` types
+#1451: Type parameter not passed by `ObjectWriter` if serializer pre-fetch disabled
+ (reported by Frédéric C)
 #1456: `TypeFactory` type resolution broken in 2.7 for generic types
    when using `constructType` with context
  (reported by Dmitry S)

src/main/java/com/fasterxml/jackson/databind/ObjectWriter.java

@@ -1399,7 +1399,7 @@ public Prefetch forRootType(ObjectWriter parent, JavaType newType) {
                     ;
                 }
             }
-            return new Prefetch(null, null, typeSerializer);
+            return new Prefetch(newType, null, typeSerializer);
         }
 
         public final JsonSerializer<Object> getValueSerializer() {
@@ -1419,13 +1419,13 @@ public void serialize(JsonGenerator gen, Object value, DefaultSerializerProvider
         {
             if (typeSerializer != null) {
                 prov.serializePolymorphic(gen, value, rootType, valueSerializer, typeSerializer);
-                return;
-            }
-            if (valueSerializer != null) {
+            } else  if (valueSerializer != null) {
                 prov.serializeValue(gen, value, rootType, valueSerializer);
-                return;
+            } else if (rootType != null) {
+                prov.serializeValue(gen, value, rootType);
+            } else {
+                prov.serializeValue(gen, value);
             }
-            prov.serializeValue(gen, value);
         }
     }
 }

src/test/java/com/fasterxml/jackson/databind/jsontype/PolymorphicList1451SerTest.java

@@ -0,0 +1,53 @@
+package com.fasterxml.jackson.databind.jsontype;
+
+import java.util.*;
+
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.*;
+
+public class PolymorphicList1451SerTest extends BaseMapTest
+{
+    @JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@class")
+    public static class A {
+        public String a;
+    }
+    public static class B extends A {
+        public String b;
+    }
+
+    private final String CLASS_NAME = getClass().getSimpleName();
+
+    public void testCollectionWithTypeInfo() throws Exception {
+        ObjectMapper mapper = new ObjectMapper()
+                .disable(SerializationFeature.EAGER_SERIALIZER_FETCH)
+//                .disable(DeserializationFeature.EAGER_DESERIALIZER_FETCH)
+                ;
+
+        List<A> input = new ArrayList<A>();
+        A a = new A();
+        a.a = "a1";
+        input.add(a);
+
+        B b = new B();
+        b.b = "b";
+        b.a = "a2";
+        input.add(b);
+
+        final TypeReference<?> typeRef = 
+                new TypeReference<Collection<A>>(){};
+        ObjectWriter writer = mapper.writerFor(typeRef);
+
+        String result = writer.writeValueAsString(input);
+
+        assertEquals(aposToQuotes(
+"[{'@class':'."+CLASS_NAME+"$A','a':'a1'},{'@class':'."+CLASS_NAME+"$B','a':'a2','b':'b'}]"
+), result);
+
+        List<A> output = mapper.readerFor(typeRef)
+                .readValue(result);
+        assertEquals(2, output.size());
+        assertEquals(A.class, output.get(0).getClass());
+        assertEquals(B.class, output.get(1).getClass());
+    }
+}