Merge pull request #11990 from jonathanslenders/asyncio-inputhook-improvements

Improve cleanup of asyncio input hook.

IPython/terminal/pt_inputhooks/asyncio.py

@@ -1,43 +1,46 b''
 """
 Inputhook for running the original asyncio event loop while we're waiting for
 input.
 
 By default, in IPython, we run the prompt with a different asyncio event loop,
 because otherwise we risk that people are freezing the prompt by scheduling bad
 coroutines. E.g., a coroutine that does a while/true and never yield back
 control to the loop. We can't cancel that.
 
 However, sometimes we want the asyncio loop to keep running while waiting for
 a prompt.
 
 The following example will print the numbers from 1 to 10 above the prompt,
 while we are waiting for input. (This works also because we use
 prompt_toolkit`s `patch_stdout`)::
 
     In [1]: import asyncio
 
     In [2]: %gui asyncio
 
     In [3]: async def f():
        ...:     for i in range(10):
        ...:         await asyncio.sleep(1)
        ...:         print(i)
 
 
     In [4]: asyncio.ensure_future(f())
 
 """
 import asyncio
 
 # Keep reference to the original asyncio loop, because getting the event loop
 # within the input hook would return the other loop.
 loop = asyncio.get_event_loop()
 
 
 def inputhook(context):
     def stop():
         loop.stop()
 
-    loop.add_reader(context.fileno(), stop)
-    context.fileno()
-    loop.run_forever()
+    fileno = context.fileno()
+    loop.add_reader(fileno, stop)
+    try:
+        loop.run_forever()
+    finally:
+        loop.remove_reader(fileno)