Stubs: Different behavior inside "if version_check" blocks

[srittau]

Operating system: Debian buster
Python version: 3.7.3
Black version: 19.3b0
Does also happen on master: yes

We are currently looking into reformatting typeshed with black. One snag I ran into is in the following example:

import sys

class Foo:
    def bar(self): ...

def abc(): ...

if sys.version_info >= (3,):
    class Foo:
        def bar(self): ...

    def abc(): ...

Reformatting this with black removes the empty line between the class and the function inside the "if" block, but not outside it:

import sys

class Foo:
    def bar(self): ...

def abc(): ...

if sys.version_info >= (3,):
    class Foo:
        def bar(self): ...
    def abc(): ...

This causes some sub-module that are basically one big "if" block (since they were added in later Python versions) to be very "dense". One example is: https://github.com/python/typeshed/blob/c90b41bb230121a20e18da3adf772da1d03f7ab4/stdlib/3/importlib/metadata.pyi

[hauntsaninja]

I think I fixed this in #2784 / #2820