In issue 11610* abstractclassmethod and abstractstaticmethod were deprecated,
apparently because they were redundant with the new technique of calling
`classmethod` or `staticmethod` followed by a call to `abstractmethod`. To put
it in code:
# deprecated
class Foo(ABC):
@abstractclassmethod
def foo_happens(cls):
# do some fooey stuff
# the new(er) way
class Foo(ABC):
@classmethod
@abstractmethod
def foo_happens(cls):
# do some fooey stuff
I would like to remove the deprecated status of `abstractclassmethod` and
`abstractstaticmethod` mainly because:
- using the combined decorator is easy to get right
(@abstractmethod followed by @classmethod doesn't work)
- getting the order wrong can be hard to spot and fix
Obviously, decorator order matters for many, if not most, decorators out there -- so why should
these two be any different? Because 'abstract', 'class', and 'static' are adjectives -- they're
describing the method, rather than changing it**; to use an example, what is the difference between
"hot, dry sand" and "dry, hot sand"? The sand is just as dry and just as hot
either way. In a debugging session looking at:
@abstractmethod
@classmethod
def some_func(self, this, that, the_other):
# many
# many
...
...
...
# many
# lines
# of
# code
Not noticing that the two decorators are in reverse order would be very easy to
do.
Because order matters here, but cognitively should not, a helper function to
make sure it is always done right is a prime candidate to be added to a module
-- and, luckily for us, those helper functions already exist! Unfortunately,
they are also deprecated, discouraging their use, when we should be encouraging
their use.
What are the reasons to /not/ remove the deprecation?
--
~Ethan~
* https://bugs.python.org/issue11610
** I realize that abstractmethod does actually change the function, but that's
an implementation detail.
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