#14823: Unexpected behavior with core.serializers.register_serializer and
unregister_serializer
-----------------------------+----------------------------------------------
Reporter: miker...@uw.edu | Owner: nobody
Status: new | Milestone:
Component: Serialization | Version: SVN
Keywords: | Stage: Unreviewed
Has_patch: 1 |
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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
1. Include it in settings.SERIALIZATION_MODULES (probably the "right way"
to do things, but then why make register_serializer public?)
1. call _load_serializers (non-public API)
1. manually register both the built-ins and those listed in
settings.SERIALIZATION_MODULES (duplicating _load_serializers)
1. call any public function in {{{__init__.py}}} except
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.
--
Ticket URL: <http://code.djangoproject.com/ticket/14823>
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