Make url_names on error descriptors unique

common/lib/xmodule/xmodule/error_module.py

-import sys
 import logging
+import random
+import string
+import sys
 
 from pkg_resources import resource_string
 from lxml import etree
@@ -35,7 +37,8 @@ class ErrorDescriptor(EditingDescriptor):
                  error_msg='Error not available'):
         '''Create an instance of this descriptor from the supplied data.
 
-        Does not try to parse the data--just stores it.
+        Does not require that xml_data be parseable--just stores it and exports
+        as-is if not.
 
         Takes an extra, optional, parameter--the error that caused an
         issue.  (should be a string, or convert usefully into one).
@@ -45,6 +48,14 @@ class ErrorDescriptor(EditingDescriptor):
         definition = {'data': inner}
         inner['error_msg'] = str(error_msg)
 
+        # Pick a unique (random) url_name.
+        # NOTE: We could try to pull out the url_name of the errored descriptor,
+        # but url_names aren't guaranteed to be unique between descriptor types,
+        # and ErrorDescriptor can wrap any type.  When the wrapped module is fixed,
+        # it will be written out with the original url_name.
+        chars = string.ascii_uppercase + string.ascii_lowercase + string.digits
+        url_name = ''.join(random.choice(chars) for i in range(16))
+
         try:
             # If this is already an error tag, don't want to re-wrap it.
             xml_obj = etree.fromstring(xml_data)
@@ -63,7 +74,7 @@ class ErrorDescriptor(EditingDescriptor):
         inner['contents'] = xml_data
         # TODO (vshnayder): Do we need a unique slug here?  Just pick a random
         # 64-bit num?
-        location = ['i4x', org, course, 'error', 'slug']
+        location = ['i4x', org, course, 'error', url_name]
         metadata = {}  # stays in the xml_data
 
         return cls(system, definition, location=location, metadata=metadata)

common/lib/xmodule/xmodule/tests/test_import.py

@@ -47,8 +47,6 @@ class DummySystem(XMLParsingSystem):
             raise Exception("Shouldn't be called")
 
 
-
-
 class ImportTestCase(unittest.TestCase):
     '''Make sure module imports work properly, including for malformed inputs'''
     @staticmethod
@@ -57,10 +55,9 @@ class ImportTestCase(unittest.TestCase):
         return DummySystem()
 
     def test_fallback(self):
-        '''Make sure that malformed xml loads as an ErrorDescriptor.'''
+        '''Check that malformed xml loads as an ErrorDescriptor.'''
 
         bad_xml = '''<sequential display_name="oops"><video url="hi"></sequential>'''
-
         system = self.get_system()
 
         descriptor = XModuleDescriptor.load_from_xml(bad_xml, system, 'org', 'course',
@@ -69,6 +66,22 @@ class ImportTestCase(unittest.TestCase):
         self.assertEqual(descriptor.__class__.__name__,
                          'ErrorDescriptor')
 
+
+    def test_unique_url_names(self):
+        '''Check that each error gets its very own url_name'''
+        bad_xml = '''<sequential display_name="oops"><video url="hi"></sequential>'''
+        bad_xml2 = '''<sequential url_name="oops"><video url="hi"></sequential>'''
+        system = self.get_system()
+
+        descriptor1 = XModuleDescriptor.load_from_xml(bad_xml, system, 'org',
+                                                      'course', None)
+
+        descriptor2 = XModuleDescriptor.load_from_xml(bad_xml2, system, 'org',
+                                                      'course', None)
+
+        self.assertNotEqual(descriptor1.location, descriptor2.location)
+
+
     def test_reimport(self):
         '''Make sure an already-exported error xml tag loads properly'''