[Python-Dev] Dataclasses and correct hashability

[Elvis Pranskevichus]

> Because it's not the default, it will be documented as being an
> advanced use case, and it's useful in rare instances.
> 
> And as I've said a number of times, both here and in other
> discussions, I'm not arguing strenuously for this. I just think that,
> given that it's not the default and it's not recommended and is
> useful in advanced cases, I would prefer to leave it in. I understand
> that you disagree with me.

Is there a real world example of such an "advanced case"?  

Eric, have you read https://github.com/python-attrs/attrs/issues/136 ?  
Specifically this comment from Hynek [1]: 

"I never really thought about it, but yeah mutable objects shouldn’t 
have a __hash__ at all." 

It is clear from that thread that "hash=True" was an early design 
mistake, which was left in for compatibility reasons.  Why are we 
copying bad design to the standard library?

                              Elvis


[1] https://github.com/python-attrs/attrs/issues/
136#issuecomment-277425421