fix: Allow LTI fallback on ExternalIdTypes for older edx-platform ver…

…sions (#299)

* fix: Allow LTI fallback on ExternalIdTypes for older edx-platform versions

Older versions don't have the XAPI and Caliper types.

CHANGELOG.rst

@@ -14,6 +14,11 @@ Change Log
 Unreleased
 ~~~~~~~~~~
 
+[5.3.1]
+~~~~~~~
+
+* Allow External ID type to fall back to LTI on older versions of edx-platform
+  to preserve backward compatibility
 
 [5.3.0]
 ~~~~~~~

event_routing_backends/__init__.py

@@ -2,6 +2,6 @@
 Various backends for receiving edX LMS events..
 """
 
-__version__ = '5.3.0'
+__version__ = '5.3.1'
 
 default_app_config = 'event_routing_backends.apps.EventRoutingBackendsConfig'  # pylint: disable=invalid-name

event_routing_backends/helpers.py

@@ -63,7 +63,17 @@ def get_anonymous_user_id(username_or_id, external_type):
 
         anonymous_id = str(uuid.uuid4())
     else:
-        type_name = getattr(ExternalIdType, external_type)
+        # Older versions of edx-platform do not have the XAPI or
+        # Caliper ExternalIdTypes, so we fall back to LTI here.
+        # Eventually this will be a problem when those instances
+        # upgrade and their actor id's all change, unless we
+        # eventually add a setting to force LTI here instead of the
+        # usual type.
+        try:
+            type_name = getattr(ExternalIdType, external_type)
+        except AttributeError:  # pragma: no cover
+            type_name = ExternalIdType.LTI
+
         external_id, _ = ExternalId.add_new_user_id(user, type_name)
         if not external_id:
             raise ValueError("External ID type: %s does not exist" % type_name)