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# Test asyncio.gather() when a task is already finished before the gather starts.
try:
import asyncio
except ImportError:
print("SKIP")
raise SystemExit
# CPython and MicroPython differ in when they signal (and print) that a task raised an
# uncaught exception. So define an empty custom_handler() to suppress this output.
def custom_handler(loop, context):
pass
async def task_that_finishes_early(id, event, fail):
print("task_that_finishes_early", id)
event.set()
if fail:
raise ValueError("intentional exception", id)
async def task_that_runs():
for i in range(5):
print("task_that_runs", i)
await asyncio.sleep(0)
async def main(start_task_that_runs, task_fail, return_exceptions):
print("== start", start_task_that_runs, task_fail, return_exceptions)
# Set exception handler to suppress exception output.
loop = asyncio.get_event_loop()
loop.set_exception_handler(custom_handler)
# Create tasks.
event_a = asyncio.Event()
event_b = asyncio.Event()
tasks = []
if start_task_that_runs:
tasks.append(asyncio.create_task(task_that_runs()))
tasks.append(asyncio.create_task(task_that_finishes_early("a", event_a, task_fail)))
tasks.append(asyncio.create_task(task_that_finishes_early("b", event_b, task_fail)))
# Make sure task_that_finishes_early() are both done, before calling gather().
await event_a.wait()
await event_b.wait()
# Gather the tasks.
try:
result = "complete", await asyncio.gather(*tasks, return_exceptions=return_exceptions)
except Exception as er:
result = "exception", er, start_task_that_runs and tasks[0].done()
# Wait for the final task to finish (if it was started).
if start_task_that_runs:
await tasks[0]
# Print results.
print(result)
# Run the test in the 8 different combinations of its arguments.
for i in range(8):
asyncio.run(main(bool(i & 4), bool(i & 2), bool(i & 1)))
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