Add xml export infrastructure for all existing modules

common/lib/xmodule/abtest_module.py

@@ -103,3 +103,21 @@ class ABTestDescriptor(RawDescriptor, XmlDescriptor):
         definition['data']['group_portions'][DEFAULT] = default_portion
 
         return definition
+
+    def definition_to_xml(self, resource_fs):
+        xml_object = etree.Element('abtest')
+        xml_object.set('experiment', self.definition['data']['experiment'])
+        for name, group in self.definition['data']['group_content'].items():
+            if name == DEFAULT:
+                group_elem = etree.SubElement(xml_object, 'default')
+            else:
+                group_elem = etree.SubElement(xml_object, 'group', attrib={
+                    'portion': str(self.definition['data']['group_portions'][name]),
+                    'name': name,
+                })
+
+            for child_loc in group:
+                child = self.system.load_item(child_loc)
+                group_elem.append(etree.fromstring(child.export_to_xml(resource_fs)))
+
+        return xml_object

common/lib/xmodule/raw_module.py

@@ -21,3 +21,6 @@ class RawDescriptor(MakoModuleDescriptor, XmlDescriptor):
     @classmethod
     def definition_from_xml(cls, xml_object, system):
         return {'data': etree.tostring(xml_object)}
+
+    def definition_to_xml(self, resource_fs):
+        return etree.fromstring(self.definition['data'])

common/lib/xmodule/seq_module.py

@@ -108,3 +108,9 @@ class SequenceDescriptor(MakoModuleDescriptor, XmlDescriptor):
             system.process_xml(etree.tostring(child_module)).location.url()
             for child_module in xml_object
         ]}
+
+    def definition_to_xml(self, resource_fs):
+        xml_object = etree.Element('sequential')
+        for child in self.get_children():
+            xml_object.append(etree.fromstring(child.export_to_xml(resource_fs)))
+        return xml_object

common/lib/xmodule/xml_module.py

@@ -51,3 +51,36 @@ class XmlDescriptor(XModuleDescriptor):
                       xml_object.get('slug')],
             metadata=metadata,
         )
+
+    def export_to_xml(self, resource_fs):
+        """
+        Returns an xml string representing this module, and all modules underneath it.
+        May also write required resources out to resource_fs
+
+        Assumes that modules have single parantage (that no module appears twice in the same course),
+        and that it is thus safe to nest modules as xml children as appropriate.
+
+        The returned XML should be able to be parsed back into an identical XModuleDescriptor
+        using the from_xml method with the same system, org, and course
+        """
+        xml_object = self.definition_to_xml(resource_fs)
+        xml_object.set('slug', self.name)
+        xml_object.tag = self.type
+
+        for attr in ('format', 'graceperiod', 'showanswer', 'rerandomize', 'due'):
+            if attr in self.metadata:
+                xml_object.set(attr, self.metadata[attr])
+
+        if 'graded' in self.metadata:
+            xml_object.set('graded', str(self.metadata['graded']).lower())
+
+        if 'display_name' in self.metadata:
+            xml_object.set('name', self.metadata['display_name'])
+
+        return etree.tostring(xml_object, pretty_print=True)
+
+    def definition_to_xml(self, resource_fs):
+        """
+        Return a new etree Element object created from this modules definition.
+        """
+        raise NotImplementedError("%s does not implement definition_to_xml" % self.__class__.__name__)