On 3/1/2018 1:02 AM, Nick Coghlan wrote:
I'm assuming you meant "3.7.0b2" here (and similarly alpha->beta for the
other version numbers below)
Oops, yes. Thanks.
So going back to original questions above, my suggestions are:
1. What happens when a frozen dataclass inherits from a non-frozen
dataclass? The result is a frozen dataclass, and all fields are
non-writable. No non-fields can be added. This is a reversion to the
3.7.0a1 behavior.
2. What happens when a non-frozen dataclass inherits from a frozen
dataclass? The result is a frozen dataclass, and all fields are
non-writable. No non-fields can be added. This is a reversion to the
3.7.0a1 behavior. I'd also be okay with this case being an error,
and you'd have to explicitly mark the derived class as frozen. This
is the 3.7.0a2 behavior.
3. What happens when a non-dataclass inherits from a frozen
dataclass? The fields that are in the dataclass are non-writable,
but new non-field attributes can be added. This is new behavior.
4. Can new non-field attributes be created for frozen dataclasses?
No. This is existing behavior.
+1 from me for the variant of this where dataclasses inheriting from
frozen data classes must explicitly mark themselves as frozen (at least
for now). That way we leave the door open to allowing a variant where a
non-frozen dataclass that inherits from a frozen dataclass can set
"hash=False" on all of the new fields it adds to avoid becoming frozen
itself.
I tend to agree. It's not like this is a huge burden, and at least the
author is acknowledging that the class will end up frozen.
I'm hoping this change isn't so large that we can't get it in to
3.7.0a3 next month.
I think this qualifies as the beta period serving its intended purpose
(i.e. reviewing and refining the behaviour of already added features,
without allowing completely new features).
Thanks.
Eric
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