bpo-43216: Remove @asyncio.coroutine (GH-26369)

Remove the @asyncio.coroutine decorator
enabling legacy generator-based coroutines to be compatible with async/await
code; remove asyncio.coroutines.CoroWrapper used for wrapping
legacy coroutine objects in the debug mode.

The decorator has been deprecated
since Python 3.8 and the removal was initially scheduled for Python 3.10.

Author: illia-v

Doc/library/asyncio-task.rst

@@ -148,9 +148,6 @@ other coroutines::
    * a *coroutine object*: an object returned by calling a
      *coroutine function*.
 
-asyncio also supports legacy :ref:`generator-based
-<asyncio_generator_based_coro>` coroutines.
-
 
 .. rubric:: Tasks
 
@@ -1042,60 +1039,3 @@ Task Object
       in the :func:`repr` output of a task object.
 
       .. versionadded:: 3.8
-
-
-.. _asyncio_generator_based_coro:
-
-Generator-based Coroutines
-==========================
-
-.. note::
-
-   Support for generator-based coroutines is **deprecated** and
-   is scheduled for removal in Python 3.10.
-
-Generator-based coroutines predate async/await syntax.  They are
-Python generators that use ``yield from`` expressions to await
-on Futures and other coroutines.
-
-Generator-based coroutines should be decorated with
-:func:`@asyncio.coroutine <asyncio.coroutine>`, although this is not
-enforced.
-
-
-.. decorator:: coroutine
-
-    Decorator to mark generator-based coroutines.
-
-    This decorator enables legacy generator-based coroutines to be
-    compatible with async/await code::
-
-        @asyncio.coroutine
-        def old_style_coroutine():
-            yield from asyncio.sleep(1)
-
-        async def main():
-            await old_style_coroutine()
-
-    This decorator should not be used for :keyword:`async def`
-    coroutines.
-
-    .. deprecated-removed:: 3.8 3.10
-
-       Use :keyword:`async def` instead.
-
-.. function:: iscoroutine(obj)
-
-   Return ``True`` if *obj* is a :ref:`coroutine object <coroutine>`.
-
-   This method is different from :func:`inspect.iscoroutine` because
-   it returns ``True`` for generator-based coroutines.
-
-.. function:: iscoroutinefunction(func)
-
-   Return ``True`` if *func* is a :ref:`coroutine function
-   <coroutine>`.
-
-   This method is different from :func:`inspect.iscoroutinefunction`
-   because it returns ``True`` for generator-based coroutine functions
-   decorated with :func:`@coroutine <coroutine>`.

Doc/library/collections.abc.rst

@@ -198,7 +198,7 @@ ABC                        Inherits from          Abstract Methods        Mixin
 
    .. note::
       In CPython, generator-based coroutines (generators decorated with
-      :func:`types.coroutine` or :func:`asyncio.coroutine`) are
+      :func:`types.coroutine`) are
       *awaitables*, even though they do not have an :meth:`__await__` method.
       Using ``isinstance(gencoro, Awaitable)`` for them will return ``False``.
       Use :func:`inspect.isawaitable` to detect them.
@@ -216,7 +216,7 @@ ABC                        Inherits from          Abstract Methods        Mixin
 
    .. note::
       In CPython, generator-based coroutines (generators decorated with
-      :func:`types.coroutine` or :func:`asyncio.coroutine`) are
+      :func:`types.coroutine`) are
       *awaitables*, even though they do not have an :meth:`__await__` method.
       Using ``isinstance(gencoro, Coroutine)`` for them will return ``False``.
       Use :func:`inspect.isawaitable` to detect them.

Doc/reference/datamodel.rst

@@ -2714,7 +2714,7 @@ are awaitable.
 .. note::
 
    The :term:`generator iterator` objects returned from generators
-   decorated with :func:`types.coroutine` or :func:`asyncio.coroutine`
+   decorated with :func:`types.coroutine`
    are also awaitable, but they do not implement :meth:`__await__`.
 
 .. method:: object.__await__(self)

Doc/whatsnew/3.11.rst

@@ -171,7 +171,15 @@ Deprecated
 Removed
 =======
 
-
+* The :func:`@asyncio.coroutine <asyncio.coroutine>` :term:`decorator` enabling
+  legacy generator-based coroutines to be compatible with async/await code.
+  The function has been deprecated since Python 3.8 and the removal was
+  initially scheduled for Python 3.10. Use :keyword:`async def` instead.
+  (Contributed by Illia Volochii in :issue:`43216`.)
+
+* :class:`asyncio.coroutines.CoroWrapper` used for wrapping legacy
+  generator-based coroutine objects in the debug mode.
+  (Contributed by Illia Volochii in :issue:`43216`.)
 
 Porting to Python 3.11
 ======================

Lib/asyncio/coroutines.py

@@ -1,162 +1,19 @@
-__all__ = 'coroutine', 'iscoroutinefunction', 'iscoroutine'
+__all__ = 'iscoroutinefunction', 'iscoroutine'
 
 import collections.abc
-import functools
 import inspect
 import os
 import sys
 import traceback
 import types
-import warnings
-
-from . import base_futures
-from . import constants
-from . import format_helpers
-from .log import logger
 
 
 def _is_debug_mode():
-    # If you set _DEBUG to true, @coroutine will wrap the resulting
-    # generator objects in a CoroWrapper instance (defined below).  That
-    # instance will log a message when the generator is never iterated
-    # over, which may happen when you forget to use "await" or "yield from"
-    # with a coroutine call.
-    # Note that the value of the _DEBUG flag is taken
-    # when the decorator is used, so to be of any use it must be set
-    # before you define your coroutines.  A downside of using this feature
-    # is that tracebacks show entries for the CoroWrapper.__next__ method
-    # when _DEBUG is true.
+    # See: https://docs.python.org/3/library/asyncio-dev.html#asyncio-debug-mode.
     return sys.flags.dev_mode or (not sys.flags.ignore_environment and
                                   bool(os.environ.get('PYTHONASYNCIODEBUG')))
 
 
-_DEBUG = _is_debug_mode()
-
-
-class CoroWrapper:
-    # Wrapper for coroutine object in _DEBUG mode.
-
-    def __init__(self, gen, func=None):
-        assert inspect.isgenerator(gen) or inspect.iscoroutine(gen), gen
-        self.gen = gen
-        self.func = func  # Used to unwrap @coroutine decorator
-        self._source_traceback = format_helpers.extract_stack(sys._getframe(1))
-        self.__name__ = getattr(gen, '__name__', None)
-        self.__qualname__ = getattr(gen, '__qualname__', None)
-
-    def __repr__(self):
-        coro_repr = _format_coroutine(self)
-        if self._source_traceback:
-            frame = self._source_traceback[-1]
-            coro_repr += f', created at {frame[0]}:{frame[1]}'
-
-        return f'<{self.__class__.__name__} {coro_repr}>'
-
-    def __iter__(self):
-        return self
-
-    def __next__(self):
-        return self.gen.send(None)
-
-    def send(self, value):
-        return self.gen.send(value)
-
-    def throw(self, type, value=None, traceback=None):
-        return self.gen.throw(type, value, traceback)
-
-    def close(self):
-        return self.gen.close()
-
-    @property
-    def gi_frame(self):
-        return self.gen.gi_frame
-
-    @property
-    def gi_running(self):
-        return self.gen.gi_running
-
-    @property
-    def gi_code(self):
-        return self.gen.gi_code
-
-    def __await__(self):
-        return self
-
-    @property
-    def gi_yieldfrom(self):
-        return self.gen.gi_yieldfrom
-
-    def __del__(self):
-        # Be careful accessing self.gen.frame -- self.gen might not exist.
-        gen = getattr(self, 'gen', None)
-        frame = getattr(gen, 'gi_frame', None)
-        if frame is not None and frame.f_lasti == -1:
-            msg = f'{self!r} was never yielded from'
-            tb = getattr(self, '_source_traceback', ())
-            if tb:
-                tb = ''.join(traceback.format_list(tb))
-                msg += (f'\nCoroutine object created at '
-                        f'(most recent call last, truncated to '
-                        f'{constants.DEBUG_STACK_DEPTH} last lines):\n')
-                msg += tb.rstrip()
-            logger.error(msg)
-
-
-def coroutine(func):
-    """Decorator to mark coroutines.
-
-    If the coroutine is not yielded from before it is destroyed,
-    an error message is logged.
-    """
-    warnings.warn('"@coroutine" decorator is deprecated since Python 3.8, use "async def" instead',
-                  DeprecationWarning,
-                  stacklevel=2)
-    if inspect.iscoroutinefunction(func):
-        # In Python 3.5 that's all we need to do for coroutines
-        # defined with "async def".
-        return func
-
-    if inspect.isgeneratorfunction(func):
-        coro = func
-    else:
-        @functools.wraps(func)
-        def coro(*args, **kw):
-            res = func(*args, **kw)
-            if (base_futures.isfuture(res) or inspect.isgenerator(res) or
-                    isinstance(res, CoroWrapper)):
-                res = yield from res
-            else:
-                # If 'res' is an awaitable, run it.
-                try:
-                    await_meth = res.__await__
-                except AttributeError:
-                    pass
-                else:
-                    if isinstance(res, collections.abc.Awaitable):
-                        res = yield from await_meth()
-            return res
-
-    coro = types.coroutine(coro)
-    if not _DEBUG:
-        wrapper = coro
-    else:
-        @functools.wraps(func)
-        def wrapper(*args, **kwds):
-            w = CoroWrapper(coro(*args, **kwds), func=func)
-            if w._source_traceback:
-                del w._source_traceback[-1]
-            # Python < 3.5 does not implement __qualname__
-            # on generator objects, so we set it manually.
-            # We use getattr as some callables (such as
-            # functools.partial may lack __qualname__).
-            w.__name__ = getattr(func, '__name__', None)
-            w.__qualname__ = getattr(func, '__qualname__', None)
-            return w
-
-    wrapper._is_coroutine = _is_coroutine  # For iscoroutinefunction().
-    return wrapper
-
-
 # A marker for iscoroutinefunction.
 _is_coroutine = object()
 
@@ -170,7 +27,7 @@ def iscoroutinefunction(func):
 # Prioritize native coroutine check to speed-up
 # asyncio.iscoroutine.
 _COROUTINE_TYPES = (types.CoroutineType, types.GeneratorType,
-                    collections.abc.Coroutine, CoroWrapper)
+                    collections.abc.Coroutine)
 _iscoroutine_typecache = set()
 
 
@@ -193,16 +50,11 @@ def iscoroutine(obj):
 def _format_coroutine(coro):
     assert iscoroutine(coro)
 
-    is_corowrapper = isinstance(coro, CoroWrapper)
-
     def get_name(coro):
         # Coroutines compiled with Cython sometimes don't have
         # proper __qualname__ or __name__.  While that is a bug
         # in Cython, asyncio shouldn't crash with an AttributeError
         # in its __repr__ functions.
-        if is_corowrapper:
-            return format_helpers._format_callback(coro.func, (), {})
-
         if hasattr(coro, '__qualname__') and coro.__qualname__:
             coro_name = coro.__qualname__
         elif hasattr(coro, '__name__') and coro.__name__:
@@ -247,18 +99,8 @@ def is_running(coro):
     filename = coro_code.co_filename or '<empty co_filename>'
 
     lineno = 0
-    if (is_corowrapper and
-            coro.func is not None and
-            not inspect.isgeneratorfunction(coro.func)):
-        source = format_helpers._get_function_source(coro.func)
-        if source is not None:
-            filename, lineno = source
-        if coro_frame is None:
-            coro_repr = f'{coro_name} done, defined at {filename}:{lineno}'
-        else:
-            coro_repr = f'{coro_name} running, defined at {filename}:{lineno}'
 
-    elif coro_frame is not None:
+    if coro_frame is not None:
         lineno = coro_frame.f_lineno
         coro_repr = f'{coro_name} running at {filename}:{lineno}'
 

Lib/test/test_asyncio/test_base_events.py

@@ -1884,10 +1884,8 @@ def test_accept_connection_exception(self, m_log):
             MyProto, sock, None, None, mock.ANY, mock.ANY)
 
     def test_call_coroutine(self):
-        with self.assertWarns(DeprecationWarning):
-            @asyncio.coroutine
-            def simple_coroutine():
-                pass
+        async def simple_coroutine():
+            pass
 
         self.loop.set_debug(True)
         coro_func = simple_coroutine

Lib/test/test_asyncio/test_events.py

@@ -17,6 +17,7 @@
 import sys
 import threading
 import time
+import types
 import errno
 import unittest
 from unittest import mock
@@ -2163,8 +2164,7 @@ def test_handle_repr(self):
                         '<Handle cancelled>')
 
         # decorated function
-        with self.assertWarns(DeprecationWarning):
-            cb = asyncio.coroutine(noop)
+        cb = types.coroutine(noop)
         h = asyncio.Handle(cb, (), self.loop)
         self.assertEqual(repr(h),
                         '<Handle noop() at %s:%s>'