Unexpected behavior with core.serializers.register_serializer and unregister_serializer
|Reported by:||Owned by:||nobody|
|Cc:||Triage Stage:||Ready for checkin|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Almost all the functions in
serializers/__init__.py begin with the lines
if not _serializers: _load_serializers()
but register_serializer and unregister_serializer do not.
When only using the built-in serializers you didn't have to manually register them but if you used an additional serializer you either have to
- Include it in settings.SERIALIZATION_MODULES (probably the "right way" to do things, but then why make register_serializer public?)
- call _load_serializers (non-public API)
- manually register both the built-ins and those listed in settings.SERIALIZATION_MODULES (duplicating _load_serializers)
- call any public function in
__init__.pyexcept register_serializer or unregister_serializer before registering (strange order of operations)
To reproduce (from a fresh
python manage.py shell)
from django.core import serializers serializers.register_serializer('json2', 'django.core.serializers.json') serializers.get_public_serializer_formats() # ['json2'] serializers.get_serializer('xml') # KeyError: 'xml'
I've attached a patch that adds the same
if not _serializers: check for register_serializer and unregister_serializer. It keeps with the general mentality of the existing code (e.g., not using a separate boolean value to check for registration) but introduces an edge case where code that attempts to unregister all built-in serializers before registering it's own will effectively do nothing. e.g.
from django.core import serializers serializers.unregister_serializer('json') # loads json/python/xml (assume no yaml), then unregisters json serializers.unregister_serializer('xml') serializers.unregister_serializer('python') # _serializers is now an empty dict serializers.register_serializer('foo', 'foo.bar.baz') # re-registers json/python/xml, then registers foo.
Under the existing code you'd get a
KeyError when attempting to unregister json (since it hasn't been loaded yet).
Alternatively, it could be determined that register_serializer and unregister_serializer aren't stable API (they're not documented on the Serialization topic page). If that's the case it may make more sense to just prefix them with an _ and/or leave a note similar to the thread-safe notes.