From c7e259ecdee4ec4cf723bfd1eb073a9473d7ef88 Mon Sep 17 00:00:00 2001
From: Vincent Latombe <vincent@latombe.net>
Date: Sun, 10 Oct 2021 11:08:16 +0200
Subject: [PATCH] Fix support of implicit collections when using Xstream2
 (#5757)

---
 .../util/RobustReflectionConverter.java       |  3 ++-
 .../util/RobustReflectionConverterTest.java   | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/hudson/util/RobustReflectionConverter.java b/core/src/main/java/hudson/util/RobustReflectionConverter.java
index 4192ea7b53..96b10f6ef9 100644
--- a/core/src/main/java/hudson/util/RobustReflectionConverter.java
+++ b/core/src/main/java/hudson/util/RobustReflectionConverter.java
@@ -506,9 +506,9 @@ public class RobustReflectionConverter implements Converter {
 
     private Class determineType(HierarchicalStreamReader reader, boolean validField, Object result, String fieldName, Class definedInCls) {
         String classAttribute = reader.getAttribute(mapper.aliasForAttribute("class"));
-        Class fieldType = reflectionProvider.getFieldType(result, fieldName, definedInCls);
         if (classAttribute != null) {
             Class specifiedType = mapper.realClass(classAttribute);
+            Class fieldType = reflectionProvider.getFieldType(result, fieldName, definedInCls);
             if(fieldType.isAssignableFrom(specifiedType))
                 // make sure that the specified type in XML is compatible with the field type.
                 // this allows the code to evolve in more flexible way.
@@ -522,6 +522,7 @@ public class RobustReflectionConverter implements Converter {
                 return mapper.realClass(reader.getNodeName());
             }
         } else {
+            Class fieldType = reflectionProvider.getFieldType(result, fieldName, definedInCls);
             return mapper.defaultImplementationOf(fieldType);
         }
     }
diff --git a/core/src/test/java/hudson/util/RobustReflectionConverterTest.java b/core/src/test/java/hudson/util/RobustReflectionConverterTest.java
index 08c34df29d..2ef437512a 100644
--- a/core/src/test/java/hudson/util/RobustReflectionConverterTest.java
+++ b/core/src/test/java/hudson/util/RobustReflectionConverterTest.java
@@ -32,8 +32,10 @@ import com.thoughtworks.xstream.XStream;
 import com.thoughtworks.xstream.converters.ConversionException;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.List;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import org.hamcrest.Matchers;
 import org.junit.Test;
 
 /**
@@ -100,6 +102,23 @@ public class RobustReflectionConverterTest {
         assertEquals(Billy.class, s.lover.getClass());
     }
 
+    @Test
+    public void implicitCollection() {
+        XStream2 xs = new XStream2();
+        xs.alias("hold", Hold.class);
+        xs.addImplicitCollection(Hold.class,"items", "item", String.class);
+        Hold h = (Hold) xs.fromXML("<hold><item>a</item><item>b</item></hold>");
+        assertThat(h.items, Matchers.containsInAnyOrder("a", "b"));
+        assertEquals("<hold>\n" +
+                "  <item>a</item>\n" +
+                "  <item>b</item>\n" +
+                "</hold>", xs.toXML(h));
+    }
+
+    public static class Hold {
+        List<String> items;
+    }
+
     @Retention(RetentionPolicy.RUNTIME) @interface Owner {String value();}
     public static class Projekt {
         Bild[] bildz;