Drop Python 3.4 and switch to async / await syntax for asyncio. Fixes #1425

gns3server/utils/asyncio/__init__.py

@@ -25,8 +25,7 @@ import threading
 from asyncio.futures import CancelledError
 
 
-@asyncio.coroutine
-def wait_run_in_executor(func, *args, **kwargs):
+async def wait_run_in_executor(func, *args, **kwargs):
     """
     Run blocking code in a different thread and wait
     for the result.
@@ -39,12 +38,11 @@ def wait_run_in_executor(func, *args, **kwargs):
 
     loop = asyncio.get_event_loop()
     future = loop.run_in_executor(None, functools.partial(func, *args, **kwargs))
-    yield from asyncio.wait([future])
+    await asyncio.wait([future])
     return future.result()
 
 
-@asyncio.coroutine
-def cancellable_wait_run_in_executor(func, *args, **kwargs):
+async def cancellable_wait_run_in_executor(func, *args, **kwargs):
     """
     Run blocking code in a different thread and wait
     for the result. Support cancellation.
@@ -57,13 +55,12 @@ def cancellable_wait_run_in_executor(func, *args, **kwargs):
     stopped_event = threading.Event()
     kwargs['stopped_event'] = stopped_event
     try:
-        yield from wait_run_in_executor(func, *args, **kwargs)
+        await wait_run_in_executor(func, *args, **kwargs)
     except CancelledError:
         stopped_event.set()
 
 
-@asyncio.coroutine
-def subprocess_check_output(*args, cwd=None, env=None, stderr=False):
+async def subprocess_check_output(*args, cwd=None, env=None, stderr=False):
     """
     Run a command and capture output
 
@@ -75,11 +72,11 @@ def subprocess_check_output(*args, cwd=None, env=None, stderr=False):
     """
 
     if stderr:
-        proc = yield from asyncio.create_subprocess_exec(*args, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=env)
-        output = yield from proc.stderr.read()
+        proc = await asyncio.create_subprocess_exec(*args, stderr=asyncio.subprocess.PIPE, cwd=cwd, env=env)
+        output = await proc.stderr.read()
     else:
-        proc = yield from asyncio.create_subprocess_exec(*args, stdout=asyncio.subprocess.PIPE, cwd=cwd, env=env)
-        output = yield from proc.stdout.read()
+        proc = await asyncio.create_subprocess_exec(*args, stdout=asyncio.subprocess.PIPE, cwd=cwd, env=env)
+        output = await proc.stdout.read()
     if output is None:
         return ""
     # If we received garbage we ignore invalid characters
@@ -87,14 +84,13 @@ def subprocess_check_output(*args, cwd=None, env=None, stderr=False):
     # and the code of VPCS, dynamips... Will detect it's not the correct binary
     return output.decode("utf-8", errors="ignore")
 
-@asyncio.coroutine
-def wait_for_process_termination(process, timeout=10):
+async def wait_for_process_termination(process, timeout=10):
     """
     Wait for a process terminate, and raise asyncio.TimeoutError in case of
     timeout.
 
     In theory this can be implemented by just:
-    yield from asyncio.wait_for(self._iou_process.wait(), timeout=100)
+    await asyncio.wait_for(self._iou_process.wait(), timeout=100)
 
     But it's broken before Python 3.4:
     http://bugs.python.org/issue23140
@@ -105,24 +101,23 @@ def wait_for_process_termination(process, timeout=10):
 
     if sys.version_info >= (3, 5):
         try:
-            yield from asyncio.wait_for(process.wait(), timeout=timeout)
+            await asyncio.wait_for(process.wait(), timeout=timeout)
         except ProcessLookupError:
             return
     else:
         while timeout > 0:
             if process.returncode is not None:
                 return
-            yield from asyncio.sleep(0.1)
+            await asyncio.sleep(0.1)
             timeout -= 0.1
         raise asyncio.TimeoutError()
 
 
-@asyncio.coroutine
-def _check_process(process, termination_callback):
+async def _check_process(process, termination_callback):
     if not hasattr(sys, "_called_from_test") or not sys._called_from_test:
-        returncode = yield from process.wait()
+        returncode = await process.wait()
         if asyncio.iscoroutinefunction(termination_callback):
-            yield from termination_callback(returncode)
+            await termination_callback(returncode)
         else:
             termination_callback(returncode)
 
@@ -130,22 +125,20 @@ def _check_process(process, termination_callback):
 def monitor_process(process, termination_callback):
     """Call termination_callback when a process dies"""
 
-    asyncio_ensure_future(_check_process(process, termination_callback))
+    asyncio.ensure_future(_check_process(process, termination_callback))
 
 
-@asyncio.coroutine
-def wait_for_file_creation(path, timeout=10):
+async def wait_for_file_creation(path, timeout=10):
 
     while timeout > 0:
         if os.path.exists(path):
             return
-        yield from asyncio.sleep(0.5)
+        await asyncio.sleep(0.5)
         timeout -= 0.5
     raise asyncio.TimeoutError()
 
 
-@asyncio.coroutine
-def wait_for_named_pipe_creation(pipe_path, timeout=60):
+async def wait_for_named_pipe_creation(pipe_path, timeout=60):
 
     import win32pipe
     import pywintypes
@@ -154,38 +147,20 @@ def wait_for_named_pipe_creation(pipe_path, timeout=60):
         try:
             win32pipe.WaitNamedPipe(pipe_path, 1)
         except pywintypes.error:
-            yield from asyncio.sleep(0.5)
+            await asyncio.sleep(0.5)
             timeout -= 0.5
         else:
             return
     raise asyncio.TimeoutError()
 
-#FIXME: Use the following wrapper when we drop Python 3.4 and use the async def syntax
-# def locking(f):
-#
-#     @wraps(f)
-#     async def wrapper(oself, *args, **kwargs):
-#         lock_name = "__" + f.__name__ + "_lock"
-#         if not hasattr(oself, lock_name):
-#             setattr(oself, lock_name, asyncio.Lock())
-#         async with getattr(oself, lock_name):
-#             return await f(oself, *args, **kwargs)
-#     return wrapper
 
 def locking(f):
 
     @functools.wraps(f)
-    def wrapper(oself, *args, **kwargs):
+    async def wrapper(oself, *args, **kwargs):
         lock_name = "__" + f.__name__ + "_lock"
         if not hasattr(oself, lock_name):
             setattr(oself, lock_name, asyncio.Lock())
-        with (yield from getattr(oself, lock_name)):
-            return (yield from f(oself, *args, **kwargs))
+        async with getattr(oself, lock_name):
+            return await f(oself, *args, **kwargs)
     return wrapper
-
-#FIXME: conservative approach to supported versions, please remove it when we drop the support to Python < 3.4.4
-try:
-    from asyncio import ensure_future
-    asyncio_ensure_future = asyncio.ensure_future
-except ImportError:
-    asyncio_ensure_future = getattr(asyncio, 'async')