Switch to more modern async idioms (#176)

I converted AiofilesContextManager to an awaitable from a coroutine, and the interface was simplified as a result. In addition to that, open is now a proper async function and types.coroutine is not used anymore.

README.md

@@ -170,6 +170,7 @@ async def test_stuff():
 - Import `os.link` conditionally to fix importing on android.
   [#175](https://github.com/Tinche/aiofiles/issues/175)
 - Remove spurious items from `aiofiles.os.__all__` when running on Windows.
+- Switch to more modern async idioms: Remove types.coroutine and make AiofilesContextManager an awaitable instead a coroutine.
 
 #### 23.2.1 (2023-08-09)
 

src/aiofiles/base.py

@@ -1,6 +1,6 @@
 """Various base classes."""
-from types import coroutine
-from collections.abc import Coroutine
+from collections.abc import Awaitable
+from contextlib import AbstractAsyncContextManager
 from asyncio import get_running_loop
 
 
@@ -45,66 +45,22 @@ def _file(self, v):
         pass  # discard writes
 
 
-class _ContextManager(Coroutine):
+class AiofilesContextManager(Awaitable, AbstractAsyncContextManager):
+    """An adjusted async context manager for aiofiles."""
+
     __slots__ = ("_coro", "_obj")
 
     def __init__(self, coro):
         self._coro = coro
         self._obj = None
 
-    def send(self, value):
-        return self._coro.send(value)
-
-    def throw(self, typ, val=None, tb=None):
-        if val is None:
-            return self._coro.throw(typ)
-        elif tb is None:
-            return self._coro.throw(typ, val)
-        else:
-            return self._coro.throw(typ, val, tb)
-
-    def close(self):
-        return self._coro.close()
-
-    @property
-    def gi_frame(self):
-        return self._coro.gi_frame
-
-    @property
-    def gi_running(self):
-        return self._coro.gi_running
-
-    @property
-    def gi_code(self):
-        return self._coro.gi_code
-
-    def __next__(self):
-        return self.send(None)
-
-    @coroutine
-    def __iter__(self):
-        resp = yield from self._coro
-        return resp
-
     def __await__(self):
-        resp = yield from self._coro
-        return resp
-
-    async def __anext__(self):
-        resp = await self._coro
-        return resp
-
-    async def __aenter__(self):
-        self._obj = await self._coro
+        if self._obj is None:
+            self._obj = yield from self._coro.__await__()
         return self._obj
 
-    async def __aexit__(self, exc_type, exc, tb):
-        self._obj.close()
-        self._obj = None
-
-
-class AiofilesContextManager(_ContextManager):
-    """An adjusted async context manager for aiofiles."""
+    async def __aenter__(self):
+        return await self
 
     async def __aexit__(self, exc_type, exc_val, exc_tb):
         await get_running_loop().run_in_executor(

src/aiofiles/threadpool/__init__.py

@@ -10,7 +10,6 @@
     FileIO,
     TextIOBase,
 )
-from types import coroutine
 
 from ..base import AiofilesContextManager
 from .binary import (
@@ -63,8 +62,7 @@ def open(
     )
 
 
-@coroutine
-def _open(
+async def _open(
     file,
     mode="r",
     buffering=-1,
@@ -91,7 +89,7 @@ def _open(
         closefd=closefd,
         opener=opener,
     )
-    f = yield from loop.run_in_executor(executor, cb)
+    f = await loop.run_in_executor(executor, cb)
 
     return wrap(f, loop=loop, executor=executor)