API: remove deep keyword from EA.copy
Not clear on what type of deprecation cycle we want here

- [x] closes #26995, closes #27024
cc @TomAugspurger 

Looks good to me. As usual (sorry ...), I would only add `view()` if we actually need it (meaning: use it internally) > Slight preference for deprecation, but don't have strong thoughts here.

So a user only runs into this when they directly interface with an ExtensionArray themselves (as the uses within pandas get fixed). Further, for EA authors only implementing the EA itself, it's not a backwards incompatible change, as we don't have a problem that the EA still has the keyword, it will just never be called from inside pandas.

It seems that users doing `Series.array.copy(deep=True)` is something very specific, and also only introduced very recently (eg Categorical is longest out there, but has actually no copy keyword). IntegerArray and IntervalArray eg does have one. Sounds good.

On Thu, Jun 27, 2019 at 3:04 PM Joris Van den Bossche <
notifications@github.com> wrote:

> Slight preference for deprecation, but don't have strong thoughts here.
>
> So a user only runs into this when they directly interface with an
> ExtensionArray themselves (as the uses within pandas get fixed). Further,
> for EA authors only implementing the EA itself, it's not a backwards
> incompatible change, as we don't have a problem that the EA still has the
> keyword, it will just never be called from inside pandas.
>
> It seems that users doing Series.array.copy(deep=True) is something very
> specific, and also only introduced very recently (eg Categorical is longest
> out there, but has actually no copy keyword). IntegerArray and
> IntervalArray eg does have one.
>
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 lgtm. ping on green. Thanks!