Closed
Description
Why
While I am learning the source code, I found it challenging to understand asyncio. Taking this codebase as an example, I spend quite some time with the following method signature:
vllm/vllm/engine/async_llm_engine.py
Lines 394 to 399 in 7c60044
I realized there was a discrepancy in the return type hint. The original hint was:
-> RequestOutput:However, the correct hint should be:
-> typing.AsyncIterator[RequestOutput]:For a detailed demonstration of this issue, please see the appendix below.
Proposal
To enhance type checking with mypy, it's advisable to include the following options in mypy.ini, as suggested in this StackOverflow answer:
disallow_untyped_defs
disallow_incomplete_defs
disallow_untyped_calls
Appendix
Below is a complete example that illustrates the correct use of type hints for async iterators:
"""
For a full check including type hints, run the following command
mypy \
--disallow-untyped-defs \
--disallow-incomplete-defs \
--disallow-untyped-calls \
/tmp/a.py
"""
import asyncio
import typing
async def foo() -> typing.AsyncIterable[int]:
for i in range(3):
yield (i)
async def bar() -> typing.AsyncIterable[int]:
f = foo()
print(f"The type of foo is {type(foo)}") # <class 'function'>
print(f"The return type of foo is {type(f)}") # <class 'async_generator'>
async for i in f:
yield i
async def main() -> None:
b = bar()
print(f"The type of bar is {type(bar)}") # <class 'function'>
print(f"The return type of bar is {type(b)}") # <class 'async_generator'>
async for i in b:
print(i)
c = main()
print(f"The return type of main is {type(c)}") # <class 'coroutine'>
asyncio.run(c)