Use asyncio._get_running_loop() and _set_running_loop() when available

Author: 1st1

tests/test_base.py

@@ -530,3 +530,27 @@ def test_uvloop_policy(self):
                 loop.close()
         finally:
             asyncio.set_event_loop_policy(None)
+
+    @unittest.skipUnless(hasattr(asyncio, '_get_running_loop'),
+                         'No asyncio._get_running_loop')
+    def test_running_loop_within_a_loop(self):
+        @asyncio.coroutine
+        def runner(loop):
+            loop.run_forever()
+
+        try:
+            asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
+
+            loop = asyncio.new_event_loop()
+            outer_loop = asyncio.new_event_loop()
+
+            try:
+                with self.assertRaisesRegex(RuntimeError,
+                                            'while another loop is running'):
+                    outer_loop.run_until_complete(runner(loop))
+            finally:
+                loop.close()
+                outer_loop.close()
+
+        finally:
+            asyncio.set_event_loop_policy(None)

uvloop/includes/stdlib.pxi

@@ -38,6 +38,8 @@ cdef aio_Protocol = asyncio.Protocol
 cdef aio_SSLProtocol = asyncio.sslproto.SSLProtocol
 cdef aio_debug_wrapper = asyncio.coroutines.debug_wrapper
 cdef aio_isfuture = getattr(asyncio, 'isfuture', None)
+cdef aio_get_running_loop = getattr(asyncio, '_get_running_loop', None)
+cdef aio_set_running_loop = getattr(asyncio, '_set_running_loop', None)
 
 cdef col_deque = collections.deque
 cdef col_Iterable = collections.Iterable

uvloop/loop.pyx

@@ -322,7 +322,12 @@ cdef class Loop:
             raise RuntimeError('unable to start the loop; it was closed')
 
         if self._running == 1:
-            raise RuntimeError('Event loop is running.')
+            raise RuntimeError('this event loop is already running.')
+
+        if (aio_get_running_loop is not None and
+                aio_get_running_loop() is not None):
+            raise RuntimeError(
+                'Cannot run the event loop while another loop is running')
 
         if self._signal_handlers is None:
             self._setup_signals()
@@ -337,7 +342,13 @@ cdef class Loop:
         self.handler_check__exec_writes.start()
         self.handler_idle.start()
 
-        self.__run(mode)
+        if aio_set_running_loop is not None:
+            aio_set_running_loop(self)
+        try:
+            self.__run(mode)
+        finally:
+            if aio_set_running_loop is not None:
+                aio_set_running_loop(None)
 
         self.handler_check__exec_writes.stop()
         self.handler_idle.stop()