Entity creation type safety

[pcostell]

Right now, if you create an entity like:

e = datastore.entity.Entity(key, ('data'))

The unindexable properties will be 'd', 'a', or 't'. Obviously in this case the user meant to specify:

e = datastore.entity.Entity(key, ('data',))

Perhaps the Entity constructor should verify that exclude_from_indexes is a list or tuple.

Here is the discussion where the user ran into this: https://groups.google.com/forum/#!topic/gcd-discuss/rqwF8CRdTAY

[dhermes]

Thanks for the pointer to the discussion! I'm torn on this.

Getting bit by passing in a string as an iterable is somewhat of a rite of passage in Python (as we saw, the user misunderstood the ('data') syntax as being a way to create a tuple). By whitelisting list and tuple it rules out people that might want to pass in their own custom iterables. On the flipside, this is a really straightforward property so maybe we'd just suggest they pass in list(custom_iterable).

[pcostell]

I'm not partial either way, just wanted to pass it on.

[dhermes]

Got it. Thanks.

@tseaver WDYT?

[pcostell]

One extra thought --

Maybe it should be an error if you provide properties to exclude_from_indexes that you never actually store in the entity. It could indicate bad application logic.

[dhermes]

When do we decide the Entity is "final"?

[pcostell]

In this instance probably on put.