bug fix for seeAlso, for issue #3357

Author: wenshao

core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderSeeAlso.java

@@ -215,7 +215,7 @@ public T readObject(JSONReader jsonReader, Type fieldType, Object fieldName, lon
                     }
                 }
 
-                if (i != 0) {
+                if (i != 0 || fieldReader != null) {
                     jsonReader.reset(savePoint);
                 }
 

core/src/test/java/com/alibaba/fastjson2/issues_3300/Issue3357.java

@@ -0,0 +1,43 @@
+package com.alibaba.fastjson2.issues_3300;
+
+import com.alibaba.fastjson2.JSON;
+import com.alibaba.fastjson2.annotation.JSONType;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue3357 {
+    @Test
+    public void cat() {
+        String s1 = "{\"age\": 20, \"type\": \"cat\"}";  // type comes second
+        Cat c1 = (Cat) JSON.parseObject(s1, Animal.class);
+        assertEquals("cat", c1.type);  // succeeds
+
+        String s2 = "{\"type\": \"cat\", \"age\": 20}";  // type comes first
+        Cat c2 = (Cat) JSON.parseObject(s2, Animal.class);
+        assertEquals("cat", c2.type);  // fails
+    }
+
+    @JSONType(typeKey = "type", seeAlso = Cat.class)
+    interface Animal {
+    }
+
+    @JSONType(typeName = "cat")
+    static class Cat {
+        private final String type;
+        private final int age;
+
+        public Cat(String type, int age) {
+            this.type = type;
+            this.age = age;
+        }
+
+        public String getType() {
+            return type;
+        }
+
+        public int getAge() {
+            return age;
+        }
+    }
+}