Load modules from the mongo modulestore as errordescriptors if creating a regular descriptor fails, but leave the location the same

common/lib/xmodule/xmodule/error_module.py

@@ -7,6 +7,7 @@ from lxml import etree
 from xmodule.x_module import XModule
 from xmodule.editing_module import JSONEditingDescriptor
 from xmodule.errortracker import exc_info_to_str
+from xmodule.modulestore import Location
 
 
 log = logging.getLogger(__name__)
@@ -52,14 +53,18 @@ class ErrorDescriptor(JSONEditingDescriptor):
     module_class = ErrorModule
 
     @classmethod
-    def _construct(self, system, contents, error_msg, org=None, course=None):
+    def _construct(self, system, contents, error_msg, location):
 
-        # Pick a unique url_name -- the sha1 hash of the contents.
-        # 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.
-        url_name = hashlib.sha1(contents).hexdigest()
+        if location.name is None:
+            location = location._replace(
+                category='error',
+                # Pick a unique url_name -- the sha1 hash of the contents.
+                # 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.
+                name=hashlib.sha1(contents).hexdigest()
+            )
 
         definition = {
             'data': {
@@ -68,12 +73,8 @@ class ErrorDescriptor(JSONEditingDescriptor):
             }
         }
 
-        # TODO (vshnayder): Do we need a unique slug here?  Just pick a random
-        # 64-bit num?
-        location = ['i4x', org, course, 'error', url_name]
-
         # real metadata stays in the content, but add a display name
-        metadata = {'display_name': 'Error ' + url_name}
+        metadata = {'display_name': 'Error: ' + location.name}
         super(ErrorDescriptor, self).__init__(
             system,
             definition,
@@ -81,6 +82,21 @@ class ErrorDescriptor(JSONEditingDescriptor):
             metadata=metadata
         )
 
+    def get_context(self):
+        return {
+            'module': self,
+            'data': self.definition['data']['contents'],
+        }
+
+    @classmethod
+    def from_json(cls, json_data, system, error_msg='Error not available'):
+        return cls(
+            system,
+            json.dumps(json_data, indent=4),
+            error_msg,
+            location=Location(json_data['location']),
+        )
+
     @classmethod
     def from_descriptor(cls, descriptor, error_msg='Error not available'):
         return cls._construct(
@@ -89,7 +105,8 @@ class ErrorDescriptor(JSONEditingDescriptor):
                 'definition': descriptor.definition,
                 'metadata': descriptor.metadata,
             }, indent=4),
-            error_msg
+            error_msg,
+            location=descriptor.location,
         )
 
     @classmethod
@@ -119,7 +136,7 @@ class ErrorDescriptor(JSONEditingDescriptor):
             # Save the error to display later--overrides other problems
             error_msg = exc_info_to_str(sys.exc_info())
 
-        return cls._construct(system, xml_data, error_msg, org=org, course=course)
+        return cls._construct(system, xml_data, error_msg, location=Location('i4x', org, course, None, None))
 
     def export_to_xml(self, resource_fs):
         '''

common/lib/xmodule/xmodule/modulestore/mongo.py

@@ -1,4 +1,5 @@
 import pymongo
+import sys
 
 from bson.son import SON
 from fs.osfs import OSFS
@@ -6,13 +7,14 @@ from itertools import repeat
 from path import path
 
 from importlib import import_module
-from xmodule.errortracker import null_error_tracker
+from xmodule.errortracker import null_error_tracker, exc_info_to_str
 from xmodule.x_module import XModuleDescriptor
 from xmodule.mako_module import MakoDescriptorSystem
+from xmodule.error_module import ErrorDescriptor
 
 from . import ModuleStoreBase, Location
 from .exceptions import (ItemNotFoundError,
-                         NoPathToItem, DuplicateItemError)
+                         DuplicateItemError)
 
 # TODO (cpennington): This code currently operates under the assumption that
 # there is only one revision for each item. Once we start versioning inside the CMS,
@@ -57,7 +59,14 @@ class CachingDescriptorSystem(MakoDescriptorSystem):
             # TODO (vshnayder): metadata inheritance is somewhat broken because mongo, doesn't
             # always load an entire course.  We're punting on this until after launch, and then
             # will build a proper course policy framework.
-            return XModuleDescriptor.load_from_json(json_data, self, self.default_class)
+            try:
+                return XModuleDescriptor.load_from_json(json_data, self, self.default_class)
+            except:
+                return ErrorDescriptor.from_json(
+                    json_data,
+                    self,
+                    error_msg=exc_info_to_str(sys.exc_info())
+                )
 
 
 def location_to_query(location):
@@ -154,7 +163,7 @@ class MongoModuleStore(ModuleStoreBase):
         """
         data_dir = item.get('metadata', {}).get('data_dir', item['location']['course'])
         root = self.fs_root / data_dir
-        
+
         if not root.isdir():
             root.mkdir()
 
@@ -267,7 +276,6 @@ class MongoModuleStore(ModuleStoreBase):
         if result['n'] == 0:
             raise ItemNotFoundError(location)
 
-
     def update_item(self, location, data):
         """
         Set the data in the item specified by the location to
@@ -313,7 +321,7 @@ class MongoModuleStore(ModuleStoreBase):
         '''
         location = Location.ensure_fully_specified(location)
         # Check that it's actually in this modulestore.
-        item = self._find_one(location)
+        self._find_one(location)
         # now get the parents
         items = self.collection.find({'definition.children': location.url()},
                                     {'_id': True})