Fix #1977

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -23,6 +23,8 @@ Project: jackson-databind
  (reported by ayushgp@github)
 #1947: `MapperFeature.AUTO_DETECT_XXX` do not work if all disabled
  (reported by Timur S)
+#1977: Serializing an Iterator with multiple sub-types fails after upgrading to 2.9.x
+ (reported by ssivanand@github)
 
 2.9.4 (24-Jan-2018)
 

src/main/java/com/fasterxml/jackson/databind/ser/impl/IteratorSerializer.java

@@ -96,7 +96,6 @@ public void serializeContents(Iterator<?> value, JsonGenerator g,
     protected void _serializeDynamicContents(Iterator<?> value, JsonGenerator g,
             SerializerProvider provider) throws IOException
     {
-        JsonSerializer<Object> serializer = _elementSerializer;
         final TypeSerializer typeSer = _valueTypeSerializer;
         PropertySerializerMap serializers = _dynamicSerializers;
         do {
@@ -106,7 +105,7 @@ protected void _serializeDynamicContents(Iterator<?> value, JsonGenerator g,
                 continue;
             }
             Class<?> cc = elem.getClass();
-            serializers.serializerFor(cc);
+            JsonSerializer<Object> serializer = serializers.serializerFor(cc);
             if (serializer == null) {
                 if (_elementType.hasGenericTypes()) {
                     serializer = _findAndAddDynamic(serializers,

src/test/java/com/fasterxml/jackson/databind/ser/TestIterable.java

@@ -143,6 +143,13 @@ public void testWithIterator() throws IOException
     {
         assertEquals("{\"values\":[\"itValue\"]}",
                 STATIC_MAPPER.writeValueAsString(new BeanWithIterator()));
+
+        // [databind#1977]
+        ArrayList<Number> numbersList = new ArrayList<>();
+        numbersList.add(1);
+        numbersList.add(0.25);
+        String json = MAPPER.writeValueAsString(numbersList.iterator());
+        assertEquals("[1,0.25]", json);
     }
 
     // [databind#358]