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.

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 _format_coroutine(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}'