What to do with "Describe a way of annotating decorated declarations"
There's a PR for PEP 484 in the peps repo that has quite a bit of discussion in it: https://github.com/python/peps/pull/242 The basic idea is to have a way to declare the type of a decorated function *after it's been decorated*, to serve as either documentation or a type hint in the case the decorator is untyped. This is the full text of the paragraph that's being proposed as an addition to PEP 484: Decorators ---------- Decorators can modify the types of the functions or classes they decorate. Use the ``decorated_type`` decorator to declare the type of the resulting item after all other decorators have been applied:: from typing import ContextManager, Iterator, decorated_type from contextlib import contextmanager class DatabaseSession: ... @decorated_type(Callable[[str], ContextManager[DatabaseSession]]) @contextmanager def session(url: str) -> Iterator[DatabaseSession]: s = DatabaseSession(url) try: yield s finally: s.close() The argument of ``decorated_type`` is a type annotation on the name being declared (``session``, in the example above). If you have multiple decorators, ``decorated_type`` must be topmost. The ``decorated_type`` decorator is invalid on a function declaration that is also decorated with ``overload``, but you can annotate the implementation of the overload series with ``decorated_type``. This has been a "Work in Progress" PR since 2017. There are 40 comments but the last one is over two years old. I'm not sure that anybody really cares that much about this problem any more. Maybe we should just close it? Thoughts? -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
I agree with Sebastian, the issue was probably relevant when mypy didn't have support for context managers, but now it is much less relevant. Instead we should focus on adding support for variadic generics and argspecs. -- Ivan On Thu, 7 Nov 2019 at 08:23, Sebastian Rittau <srittau@rittau.biz> wrote:
Annotated functions whose signatures are modified by the decorator are still a problem with typing, but I feel we should work on improving the decorators themselves, instead.
- Sebastian
Am 07.11.2019 05:08 schrieb Guido van Rossum <guido@python.org>:
There's a PR for PEP 484 in the peps repo that has quite a bit of discussion in it: https://github.com/python/peps/pull/242
The basic idea is to have a way to declare the type of a decorated function *after it's been decorated*, to serve as either documentation or a type hint in the case the decorator is untyped.
This is the full text of the paragraph that's being proposed as an addition to PEP 484:
Decorators ----------
Decorators can modify the types of the functions or classes they decorate. Use the ``decorated_type`` decorator to declare the type of the resulting item after all other decorators have been applied::
from typing import ContextManager, Iterator, decorated_type from contextlib import contextmanager
class DatabaseSession: ...
@decorated_type(Callable[[str], ContextManager[DatabaseSession]]) @contextmanager def session(url: str) -> Iterator[DatabaseSession]: s = DatabaseSession(url) try: yield s finally: s.close()
The argument of ``decorated_type`` is a type annotation on the name being declared (``session``, in the example above). If you have multiple decorators, ``decorated_type`` must be topmost. The ``decorated_type`` decorator is invalid on a function declaration that is also decorated with ``overload``, but you can annotate the implementation of the overload series with ``decorated_type``.
This has been a "Work in Progress" PR since 2017. There are 40 comments but the last one is over two years old. I'm not sure that anybody really cares that much about this problem any more. Maybe we should just close it? Thoughts?
-- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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OK, I've closed the issue. Thanks for speaking up! On Thu, Nov 7, 2019 at 3:40 AM Ivan Levkivskyi <levkivskyi@gmail.com> wrote:
I agree with Sebastian, the issue was probably relevant when mypy didn't have support for context managers, but now it is much less relevant. Instead we should focus on adding support for variadic generics and argspecs.
-- Ivan
On Thu, 7 Nov 2019 at 08:23, Sebastian Rittau <srittau@rittau.biz> wrote:
Annotated functions whose signatures are modified by the decorator are still a problem with typing, but I feel we should work on improving the decorators themselves, instead.
- Sebastian
Am 07.11.2019 05:08 schrieb Guido van Rossum <guido@python.org>:
There's a PR for PEP 484 in the peps repo that has quite a bit of discussion in it: https://github.com/python/peps/pull/242
The basic idea is to have a way to declare the type of a decorated function *after it's been decorated*, to serve as either documentation or a type hint in the case the decorator is untyped.
This is the full text of the paragraph that's being proposed as an addition to PEP 484:
Decorators ----------
Decorators can modify the types of the functions or classes they decorate. Use the ``decorated_type`` decorator to declare the type of the resulting item after all other decorators have been applied::
from typing import ContextManager, Iterator, decorated_type from contextlib import contextmanager
class DatabaseSession: ...
@decorated_type(Callable[[str], ContextManager[DatabaseSession]]) @contextmanager def session(url: str) -> Iterator[DatabaseSession]: s = DatabaseSession(url) try: yield s finally: s.close()
The argument of ``decorated_type`` is a type annotation on the name being declared (``session``, in the example above). If you have multiple decorators, ``decorated_type`` must be topmost. The ``decorated_type`` decorator is invalid on a function declaration that is also decorated with ``overload``, but you can annotate the implementation of the overload series with ``decorated_type``.
This has been a "Work in Progress" PR since 2017. There are 40 comments but the last one is over two years old. I'm not sure that anybody really cares that much about this problem any more. Maybe we should just close it? Thoughts?
-- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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-- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
participants (3)
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Guido van Rossum -
Ivan Levkivskyi -
Sebastian Rittau