Agreed with nick's idea, the implicitly recreation of the context managers would confuse users.

How about removing the "generator must yield exactly one value" restriction of @contextlib.contextmanage? Then if I want a generator to be used as a common context manager, I can make it yield exactly one value, else further if I want the resulting context manager can be used as a decorator, (reusable), I can put the generator code in a "while True" loop and add a "yield" at the end of loop body, like this:

@contextmanager
def func():
    while True:
        print('begin func')
        yield
        print('end func')
        yield

:)