XmlItemExporter: added built-in support for exporting multi-valued fields (for convenience)

docs/topics/exporters.rst

@@ -240,6 +240,26 @@ XmlItemExporter
         </item>
        </items>
 
+   Unless overriden in :meth:`serialize_field` method, multi-valued fields are
+   exported by serializing each value inside a ``<value>`` element. This is for
+   convenience, as multi-valued fields are very common.
+
+   For example, the item::
+
+        Item(name=['John', 'Doe'], age='23')
+
+   Would be serialized as::
+
+       <?xml version="1.0" encoding="utf-8"?>
+       <items>
+         <item>
+           <name>
+             <value>John</value>
+             <value>Doe</value>
+           </name>
+           <age>23</age>
+         </item>
+       </items>
 
 CsvItemExporter
 ---------------

scrapy/contrib/exporter/__init__.py

@@ -95,7 +95,11 @@ class XmlItemExporter(BaseItemExporter):
 
     def _export_xml_field(self, name, serialized_value):
         self.xg.startElement(name, {})
-        self.xg.characters(serialized_value)
+        if hasattr(serialized_value, '__iter__'):
+            for value in serialized_value:
+                self._export_xml_field('value', value)
+        else:
+            self.xg.characters(serialized_value)
         self.xg.endElement(name)
 
 

scrapy/tests/test_contrib_exporter.py

@@ -137,6 +137,15 @@ class XmlItemExporterTest(BaseItemExporterTest):
         expected_value = '<?xml version="1.0" encoding="utf-8"?>\n<items><item><age>22</age><name>John\xc2\xa3</name></item></items>'
         self.assertEqual(self.output.getvalue(), expected_value)
 
+    def test_multivalued_fields(self):
+        output = StringIO()
+        item = TestItem(name=[u'John\xa3', u'Doe'])
+        ie = XmlItemExporter(output)
+        ie.start_exporting()
+        ie.export_item(item)
+        ie.finish_exporting()
+        expected_value = '<?xml version="1.0" encoding="utf-8"?>\n<items><item><name><value>John\xc2\xa3</value><value>Doe</value></name></item></items>'
+        self.assertEqual(output.getvalue(), expected_value)
 
 class JsonLinesItemExporterTest(BaseItemExporterTest):