extmod/uasyncio: Add Loop.new_event_loop method.

This commit adds Loop.new_event_loop() which is used to reset the singleton
event loop.  This functionality is put here instead of in Loop.close() to
make it possible to write code that is compatible with CPython.

4 files changed, 62 insertions, 7 deletions

diff --git a/docs/library/uasyncio.rst b/docs/library/uasyncio.rst
index 9cb0ca9bb9..0f363a076e 100644
--- a/docs/library/uasyncio.rst
+++ b/docs/library/uasyncio.rst
@@ -244,6 +244,13 @@ Event Loop
 
     Return the event loop used to schedule and run tasks.  See `Loop`.
 
+.. function:: new_event_loop()
+
+    Reset the event loop and return it.
+
+    Note: since MicroPython only has a single event loop this function just
+    resets the loop's state, it does not create a new one.
+
 .. class:: Loop()
 
     This represents the object which schedules and runs tasks.  It cannot be
diff --git a/extmod/uasyncio/core.py b/extmod/uasyncio/core.py
index e2f64119c5..689487d36a 100644
--- a/extmod/uasyncio/core.py
+++ b/extmod/uasyncio/core.py
@@ -132,13 +132,6 @@ class IOQueue:
 ################################################################################
 # Main run loop
 
-# TaskQueue of Task instances
-_task_queue = TaskQueue()
-
-# Task queue and poller for stream IO
-_io_queue = IOQueue()
-
-
 # Ensure the awaitable is a task
 def _promote_to_task(aw):
     return aw if isinstance(aw, Task) else create_task(aw)
@@ -269,3 +262,16 @@ class Loop:
 # The runq_len and waitq_len arguments are for legacy uasyncio compatibility
 def get_event_loop(runq_len=0, waitq_len=0):
     return Loop
+
+
+def new_event_loop():
+    global _task_queue, _io_queue
+    # TaskQueue of Task instances
+    _task_queue = TaskQueue()
+    # Task queue and poller for stream IO
+    _io_queue = IOQueue()
+    return Loop
+
+
+# Initialise default event loop
+new_event_loop()
diff --git a/tests/extmod/uasyncio_new_event_loop.py b/tests/extmod/uasyncio_new_event_loop.py
new file mode 100644
index 0000000000..b711befba9
--- /dev/null
+++ b/tests/extmod/uasyncio_new_event_loop.py
@@ -0,0 +1,36 @@
+# Test Loop.new_event_loop()
+
+try:
+    import uasyncio as asyncio
+except ImportError:
+    try:
+        import asyncio
+    except ImportError:
+        print("SKIP")
+        raise SystemExit
+
+
+async def task():
+    for i in range(4):
+        print("task", i)
+        await asyncio.sleep(0)
+        await asyncio.sleep(0)
+
+
+async def main():
+    print("start")
+    loop.create_task(task())
+    await asyncio.sleep(0)
+    print("stop")
+    loop.stop()
+
+
+# Use default event loop to run some tasks
+loop = asyncio.get_event_loop()
+loop.create_task(main())
+loop.run_forever()
+
+# Create new event loop, old one should not keep running
+loop = asyncio.new_event_loop()
+loop.create_task(main())
+loop.run_forever()
diff --git a/tests/extmod/uasyncio_new_event_loop.py.exp b/tests/extmod/uasyncio_new_event_loop.py.exp
new file mode 100644
index 0000000000..9e104fda39
--- /dev/null
+++ b/tests/extmod/uasyncio_new_event_loop.py.exp
@@ -0,0 +1,6 @@
+start
+task 0
+stop
+start
+task 0
+stop