[PATCH v3 05/19] python: backport 'drop Python3.6 workarounds'

[John Snow <jsnow@redhat.com>]

Now that the minimum version is 3.7, drop some of the 3.6-specific hacks
we've been carrying. A single remaining compatibility hack concerning
3.6's lack of @asynccontextmanager is addressed in the following commit.

Signed-off-by: John Snow <jsnow@redhat.com>
cherry picked from commit python-qemu-qmp@3e8e34e594cfc6b707e6f67959166acde4b421b8
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 python/qemu/qmp/protocol.py |  13 ++---
 python/qemu/qmp/qmp_tui.py  |   8 +--
 python/qemu/qmp/util.py     | 107 ++----------------------------------
 python/tests/protocol.py    |   8 +--
 4 files changed, 17 insertions(+), 119 deletions(-)

diff --git a/python/qemu/qmp/protocol.py b/python/qemu/qmp/protocol.py
index ec4762c567b..208bdec5c89 100644
--- a/python/qemu/qmp/protocol.py
+++ b/python/qemu/qmp/protocol.py
@@ -36,13 +36,10 @@
 from .error import QMPError
 from .util import (
     bottom_half,
-    create_task,
     exception_summary,
     flush,
-    is_closing,
     pretty_traceback,
     upper_half,
-    wait_closed,
 )
 
 
@@ -682,8 +679,8 @@ async def _establish_session(self) -> None:
         reader_coro = self._bh_loop_forever(self._bh_recv_message, 'Reader')
         writer_coro = self._bh_loop_forever(self._bh_send_message, 'Writer')
 
-        self._reader_task = create_task(reader_coro)
-        self._writer_task = create_task(writer_coro)
+        self._reader_task = asyncio.create_task(reader_coro)
+        self._writer_task = asyncio.create_task(writer_coro)
 
         self._bh_tasks = asyncio.gather(
             self._reader_task,
@@ -708,7 +705,7 @@ def _schedule_disconnect(self) -> None:
         if not self._dc_task:
             self._set_state(Runstate.DISCONNECTING)
             self.logger.debug("Scheduling disconnect.")
-            self._dc_task = create_task(self._bh_disconnect())
+            self._dc_task = asyncio.create_task(self._bh_disconnect())
 
     @upper_half
     async def _wait_disconnect(self) -> None:
@@ -844,13 +841,13 @@ async def _bh_close_stream(self, error_pathway: bool = False) -> None:
         if not self._writer:
             return
 
-        if not is_closing(self._writer):
+        if not self._writer.is_closing():
             self.logger.debug("Closing StreamWriter.")
             self._writer.close()
 
         self.logger.debug("Waiting for StreamWriter to close ...")
         try:
-            await wait_closed(self._writer)
+            await self._writer.wait_closed()
         except Exception:  # pylint: disable=broad-except
             # It's hard to tell if the Stream is already closed or
             # not. Even if one of the tasks has failed, it may have
diff --git a/python/qemu/qmp/qmp_tui.py b/python/qemu/qmp/qmp_tui.py
index 2d9ebbd20bc..562be008d5e 100644
--- a/python/qemu/qmp/qmp_tui.py
+++ b/python/qemu/qmp/qmp_tui.py
@@ -40,7 +40,7 @@
 from .message import DeserializationError, Message, UnexpectedTypeError
 from .protocol import ConnectError, Runstate
 from .qmp_client import ExecInterruptedError, QMPClient
-from .util import create_task, pretty_traceback
+from .util import pretty_traceback
 
 
 # The name of the signal that is used to update the history list
@@ -225,7 +225,7 @@ def cb_send_to_server(self, raw_msg: str) -> None:
         """
         try:
             msg = Message(bytes(raw_msg, encoding='utf-8'))
-            create_task(self._send_to_server(msg))
+            asyncio.create_task(self._send_to_server(msg))
         except (DeserializationError, UnexpectedTypeError) as err:
             raw_msg = format_json(raw_msg)
             logging.info('Invalid message: %s', err.error_message)
@@ -246,7 +246,7 @@ def kill_app(self) -> None:
         Initiates killing of app. A bridge between asynchronous and synchronous
         code.
         """
-        create_task(self._kill_app())
+        asyncio.create_task(self._kill_app())
 
     async def _kill_app(self) -> None:
         """
@@ -393,7 +393,7 @@ def run(self, debug: bool = False) -> None:
                                    handle_mouse=True,
                                    event_loop=event_loop)
 
-        create_task(self.manage_connection(), self.aloop)
+        self.aloop.create_task(self.manage_connection())
         try:
             main_loop.run()
         except Exception as err:
diff --git a/python/qemu/qmp/util.py b/python/qemu/qmp/util.py
index ca6225e9cda..0b3e781373d 100644
--- a/python/qemu/qmp/util.py
+++ b/python/qemu/qmp/util.py
@@ -1,25 +1,15 @@
 """
 Miscellaneous Utilities
 
-This module provides asyncio utilities and compatibility wrappers for
-Python 3.6 to provide some features that otherwise become available in
-Python 3.7+.
-
-Various logging and debugging utilities are also provided, such as
-`exception_summary()` and `pretty_traceback()`, used primarily for
-adding information into the logging stream.
+This module provides asyncio and various logging and debugging
+utilities, such as `exception_summary()` and `pretty_traceback()`, used
+primarily for adding information into the logging stream.
 """
 
 import asyncio
 import sys
 import traceback
-from typing import (
-    Any,
-    Coroutine,
-    Optional,
-    TypeVar,
-    cast,
-)
+from typing import TypeVar, cast
 
 
 T = TypeVar('T')
@@ -79,95 +69,6 @@ def bottom_half(func: T) -> T:
     return func
 
 
-# -------------------------------
-# Section: Compatibility Wrappers
-# -------------------------------
-
-
-def create_task(coro: Coroutine[Any, Any, T],
-                loop: Optional[asyncio.AbstractEventLoop] = None
-                ) -> 'asyncio.Future[T]':
-    """
-    Python 3.6-compatible `asyncio.create_task` wrapper.
-
-    :param coro: The coroutine to execute in a task.
-    :param loop: Optionally, the loop to create the task in.
-
-    :return: An `asyncio.Future` object.
-    """
-    if sys.version_info >= (3, 7):
-        if loop is not None:
-            return loop.create_task(coro)
-        return asyncio.create_task(coro)  # pylint: disable=no-member
-
-    # Python 3.6:
-    return asyncio.ensure_future(coro, loop=loop)
-
-
-def is_closing(writer: asyncio.StreamWriter) -> bool:
-    """
-    Python 3.6-compatible `asyncio.StreamWriter.is_closing` wrapper.
-
-    :param writer: The `asyncio.StreamWriter` object.
-    :return: `True` if the writer is closing, or closed.
-    """
-    if sys.version_info >= (3, 7):
-        return writer.is_closing()
-
-    # Python 3.6:
-    transport = writer.transport
-    assert isinstance(transport, asyncio.WriteTransport)
-    return transport.is_closing()
-
-
-async def wait_closed(writer: asyncio.StreamWriter) -> None:
-    """
-    Python 3.6-compatible `asyncio.StreamWriter.wait_closed` wrapper.
-
-    :param writer: The `asyncio.StreamWriter` to wait on.
-    """
-    if sys.version_info >= (3, 7):
-        await writer.wait_closed()
-        return
-
-    # Python 3.6
-    transport = writer.transport
-    assert isinstance(transport, asyncio.WriteTransport)
-
-    while not transport.is_closing():
-        await asyncio.sleep(0)
-
-    # This is an ugly workaround, but it's the best I can come up with.
-    sock = transport.get_extra_info('socket')
-
-    if sock is None:
-        # Our transport doesn't have a socket? ...
-        # Nothing we can reasonably do.
-        return
-
-    while sock.fileno() != -1:
-        await asyncio.sleep(0)
-
-
-def asyncio_run(coro: Coroutine[Any, Any, T], *, debug: bool = False) -> T:
-    """
-    Python 3.6-compatible `asyncio.run` wrapper.
-
-    :param coro: A coroutine to execute now.
-    :return: The return value from the coroutine.
-    """
-    if sys.version_info >= (3, 7):
-        return asyncio.run(coro, debug=debug)
-
-    # Python 3.6
-    loop = asyncio.get_event_loop()
-    loop.set_debug(debug)
-    ret = loop.run_until_complete(coro)
-    loop.close()
-
-    return ret
-
-
 # ----------------------------
 # Section: Logging & Debugging
 # ----------------------------
diff --git a/python/tests/protocol.py b/python/tests/protocol.py
index 56c4d441f9c..c254c77b176 100644
--- a/python/tests/protocol.py
+++ b/python/tests/protocol.py
@@ -8,7 +8,6 @@
 
 from qemu.qmp import ConnectError, Runstate
 from qemu.qmp.protocol import AsyncProtocol, StateError
-from qemu.qmp.util import asyncio_run, create_task
 
 
 class NullProtocol(AsyncProtocol[None]):
@@ -124,7 +123,7 @@ async def _runner():
             if allow_cancellation:
                 return
             raise
-    return create_task(_runner())
+    return asyncio.create_task(_runner())
 
 
 @contextmanager
@@ -271,7 +270,7 @@ async def _watcher():
                     msg=f"Expected state '{state.name}'",
                 )
 
-        self.runstate_watcher = create_task(_watcher())
+        self.runstate_watcher = asyncio.create_task(_watcher())
         # Kick the loop and force the task to block on the event.
         await asyncio.sleep(0)
 
@@ -589,7 +588,8 @@ async def _asyncTearDown(self):
     async def testSmoke(self):
         with TemporaryDirectory(suffix='.qmp') as tmpdir:
             sock = os.path.join(tmpdir, type(self.proto).__name__ + ".sock")
-            server_task = create_task(self.server.start_server_and_accept(sock))
+            server_task = asyncio.create_task(
+                self.server.start_server_and_accept(sock))
 
             # give the server a chance to start listening [...]
             await asyncio.sleep(0)
-- 
2.50.1