allow custom json dumping for meta

[samuelcolvin]

currently if you want to customise the behaviour of the json dump method you would have to either:

• overwrite the whole of _update_obj_index_iter
• or do something ugly like return json.loads(json.dumps(meta, cls=CustomerEncoder)) at the end of get_meta.

This is particularly useful for things like lazy translations or Decimals where customer encoders can be very helpful in JSONifying data.

If you think this makes sense, I can also add:

• tests. There are currently no tests for customer adapers, and this should have full coverage but proper tests would be good.
• a simple default encoder which works for common django objects?

[etianen]

This is an excellent idea, but I'd suggest generalising it a little:

1. Call the method serialize_meta, which opens the doors to people using a non-JSON encoding, and puts it into the public namespace of the class.
2. Add another method deserialize_meta, which is a hook for turning it back into a dict again. Use this method instead of json.loads in the SearchEntry body.
3. As you suggested, use the Django JSON encoder for the serialize_meta implementation. This takes care of datetimes, I believe, which is nice.

I'm not sure that tests are needed, as the current test suite already checks that meta can be saved and loaded.

[samuelcolvin]

will do.

On a related note, I don't think meta is documented anywhere. Maybe worth adding to the wiki.

[samuelcolvin]

Ok, sorry for delay, I think this is done. Django's DjangoJSONEncoder isn't as powerful as one might hope, so I've extended it to cope with a few more types, code partially borrowed from raven-python.

[etianen]

This looks pretty sweet.

One last question: do you think that the serialize/deserialize meta methods belong on SearchAdapter or SearchEngine? Overriding them on SearchAdapter would seem to be easier for the majority of users, since overriding SearchEngine is a bit more arcane.

[samuelcolvin]

yes, i thought that when i was making the change but didn't want to change any more than I had to.

I'll move both methods to the adapter.

[etianen]

Wonderful! Thanks for your patience in getting this just right. :)