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On 2013-10-10 07:40, Flavio Percoco wrote:
> Greetings,
> 
> I'd like to propose to change both ListOpt and DictOpt default values
> to [] and {} respectively. These values are, IMHO, saner defaults than
> None for this 2 options and behavior won't be altered - unles `is not
> None` is being used.
> 
> Since I may be missing some history, I'd like to ask if there's a
> reason why None was kept as the default `default` value for this 2 
> options?
> 
> As mentioned above, this change may be backward incompatible in cases
> like:
> 
>    if conf.my_list_opt is None:
>        ....
> 
> Does anyone if there are cases like this?
> 
> Also, I know it is possible to do:
> 
>    cfg.ListOpt('option', default=[])
> 
> This is not terrible, TBH, but it doesn't feel right. I've made the
> mistake to ignore the `default` keyword myself, although I know `[]`
> is not the default option for `ListOpt`. As already said, I'd expect
> `[]` to be the default, non-set value for `ListOpt`.
> 
> Thoughts?
> 
> Cheers,
> FF
> 
> P.S: I'm not sure I'll make it to tomorrows meeting so, I starting the
> discussion here made more sense.

Since this is technically an incompatible API change, would a major 
version bump be needed for oslo.config if we did this?  Maybe nobody's 
relying on the existing behavior, but since oslo.config is a released 
library its API is supposed to be stable.

-Ben