opaque-keys: Adds support for opaque keys

Inspired from https://github.com/edx/edx-ora2/pull/330

mentoring/answer.py

@@ -31,7 +31,7 @@ from xblock.fragment import Fragment
 
 from .light_children import LightChild, Boolean, Scope, String, Integer
 from .models import Answer
-from .utils import render_template
+from .utils import render_template, serialize_opaque_key
 
 
 # Globals ###########################################################
@@ -141,7 +141,7 @@ class AnswerBlock(LightChild):
 
         # TODO: Why do we need to use `xmodule_runtime` and not `runtime`?
         student_id = self.xmodule_runtime.anonymous_student_id
-        course_id = self.xmodule_runtime.course_id
+        course_id = serialize_opaque_key(self.xmodule_runtime.course_id)
 
         answer_data, created = Answer.objects.get_or_create(
             student_id=student_id,

mentoring/dataexport.py

@@ -31,7 +31,7 @@ from xblock.core import XBlock
 from xblock.fragment import Fragment
 
 from .models import Answer
-from .utils import list2csv, render_template
+from .utils import list2csv, render_template, serialize_opaque_key
 
 
 # Globals ###########################################################
@@ -70,7 +70,7 @@ class MentoringDataExportBlock(XBlock):
         return response
 
     def get_csv(self):
-        course_id = self.xmodule_runtime.course_id
+        course_id = serialize_opaque_key(self.xmodule_runtime.course_id)
 
         answers = Answer.objects.filter(course_id=course_id).order_by('student_id', 'name')
         answers_names = answers.values_list('name', flat=True).distinct().order_by('name')

mentoring/light_children.py

@@ -46,7 +46,7 @@ except:
     # TODO-WORKBENCH-WORKAROUND: To allow to load from the workbench
     replace_jump_to_id_urls = lambda a,b,c,d,frag,f: frag
 
-from .utils import XBlockWithChildrenFragmentsMixin
+from .utils import serialize_opaque_key, XBlockWithChildrenFragmentsMixin
 
 
 # Globals ###########################################################
@@ -188,7 +188,7 @@ class XBlockWithLightChildren(LightChildrenMixin, XBlock):
         """
         # TODO: Why do we need to use `xmodule_runtime` and not `runtime`?
         try:
-            course_id = self.xmodule_runtime.course_id
+            course_id = serialize_opaque_key(self.xmodule_runtime.course_id)
         except AttributeError:
             # TODO-WORKBENCH-WORKAROUND: To allow to load from the workbench
             course_id = 'sample-course'

mentoring/utils.py

@@ -94,6 +94,28 @@ def load_scenarios_from_path(scenarios_path):
     """
     return get_scenarios_from_path(scenarios_path, include_identifier=True)
 
+def serialize_opaque_key(key):
+    """
+    Gracefully handle opaque keys, both before and after the transition.
+    https://github.com/edx/edx-platform/wiki/Opaque-Keys
+
+    From https://github.com/edx/edx-ora2/pull/330
+
+    Currently uses `to_deprecated_string()` to ensure that new keys
+    are backwards-compatible with keys we store in ORA2 database models.
+
+    Args:
+    key (unicode or OpaqueKey subclass): The key to serialize.
+
+    Returns:
+    unicode
+
+    """
+    if hasattr(key, 'to_deprecated_string'):
+        return key.to_deprecated_string()
+    else:
+        return unicode(key)
+
 
 # Classes ###########################################################