Simple PyYAML constructor for handling Ruby Flash Hash

sessions.py

# Simple PyYAML constructor for handling Ruby Flash Hash
# Not perfect or graceful - just takes the Ruby Flash object
# and the Set object inside of it, and nullifies them.
# This could be expanded to handled different tags.

# If you wanted to maintain the Ruby objects across requests,
# or use convert a Ruby object to a Python object, you'll
# need something a little more complex, but this should get
# you started.

import yaml

def nullify_ruby_objects(loader, node):
    # Below is an example of how you could map the keys/values
    # However, with the FlashHash specifically, it won't work
    # because it creases an alias when FlashNow exists.
    # value = loader.construct_mapping(node)
    
    # All that really matters is that we just return None (nil)
    return None

yaml.add_constructor(u'!ruby/object:ActionDispatch::Flash::FlashHash', nullify_ruby_objects)
yaml.add_constructor(u'!ruby/object:ActionDispatch::Flash::FlashNow', nullify_ruby_objects)
yaml.add_constructor(u'!ruby/object:Set', nullify_ruby_objects)

yaml.load(session)