Bug: Async JS Promise cannot find running Python event loop on Python 3.13 (Windows)

[LetuGitHub]

Issue type

Bug

How did you install PythonMonkey?

None

OS platform and distribution

Windows 11 x64

Python version (python --version)

3.13.0

PythonMonkey version (pip show pythonmonkey)

1.3.1

Bug Description

When awaiting a JavaScript async function from Python using asyncio.run(), PythonMonkey raises:

RuntimeError: PythonMonkey cannot find a running Python event-loop to make asynchronous calls.

However, a Python event loop is clearly running and can be retrieved with:

print(asyncio.get_running_loop())

which outputs:

<ProactorEventLoop running=True closed=False debug=False>

This suggests that PythonMonkey is unable to access the currently running event loop internally, even though one exists.

Standalone code to reproduce the issue

import asyncio
import pythonmonkey as pm

async def async_fn():
    print(asyncio.get_running_loop())

    await pm.eval("""
        new Promise((resolve) => setTimeout((...args) => {
            console.log(args);
            resolve();
        }, 1000, 42, "abc")
        )
    """)
    await pm.eval("async (x) => await x")(asyncio.sleep(0.5))

asyncio.run(async_fn())

Relevant log output or backtrace

await pm.eval("""
          ~~~~~~~^^^^
        new Promise((resolve) => setTimeout((...args) => {
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
        )
        ^
    """)
    ^^^^
RuntimeError: PythonMonkey cannot find a running Python event-loop to make asynchronous calls

Additional info if applicable

What branch of PythonMonkey were you developing on? (If applicable)

No response

[wiwichips]

I assume changing it to the following would make it work?

await pm.eval("""
      () => {
        new Promise((resolve) => setTimeout((...args) => {
            console.log(args);
            resolve();
        }, 1000, 42, "abc")
        )
      }
    """)()

lmk if I'm wrong, I didn't test it...

[LetuGitHub]

我猜改成以下内容会让它正常工作？

await pm.eval("""
() => {
new Promise((resolve) => setTimeout((...args) => {
console.log(args);
resolve();
}, 1000, 42, "abc")
)
}
""")()
如果我错了请告诉我，我没测试过......

Thanks. I tested the snippet you provided, but I still get the same error.

    await pm.eval("""
          ~~~~~~~~~~~
    ...<6 lines>...
      }
      ~
    """)()
    ~~~~^^
RuntimeError: PythonMonkey cannot find a running Python event-loop to make asynchronous calls.

[wiwichips]

FWIW - I can't reproduce this issue with python 3.12.8 and pm 1.3.1 on macos

wkp@m2~$ cat ex.py 
import pythonmonkey as pm
import asyncio

async def async_fn():
    print(asyncio.get_running_loop())

    # initial bug report repro
    await pm.eval("""
        new Promise((resolve) => setTimeout((...args) => {
            console.log(args);
            resolve();
        }, 1000, 42, "abc")
        )
    """)
    await pm.eval("async (x) => await x")(asyncio.sleep(0.5))


    # other way
    await pm.eval("""
      () => {
        return new Promise((resolve) => setTimeout((...args) => {
            console.log(args);
            resolve();
        }, 1000, 42, "abc")
        )
      }
    """)()

asyncio.run(async_fn())


wkp@m2~$ python3 ex.py 
<_UnixSelectorEventLoop running=True closed=False debug=False>
[ 42, 'abc' ]
[ 42, 'abc' ]


wkp@m2~$ python3 --version 
Python 3.12.8


wkp@m2~$ pip show pythonmonkey
Name: pythonmonkey
Version: 1.3.1
Summary: Seamless interop between Python and JavaScript.
Home-page: https://pythonmonkey.io/
Author: Distributive Corp.
Author-email: pm@distributive.network
License: MIT
Location: /Users/wkp/.local/share/mise/installs/python/3.12.8/lib/python3.12/site-packages
Requires: aiohttp, pminit
Required-by:

Will try 3.13 on windows later...

[LetuGitHub]

FWIW - I can't reproduce this issue with python 3.12.8 and pm 1.3.1 on macos

wkp@m2~$ cat ex.py
import pythonmonkey as pm
import asyncio

async def async_fn():
print(asyncio.get_running_loop())

# initial bug report repro
await pm.eval("""
    new Promise((resolve) => setTimeout((...args) => {
        console.log(args);
        resolve();
    }, 1000, 42, "abc")
    )
""")
await pm.eval("async (x) => await x")(asyncio.sleep(0.5))


# other way
await pm.eval("""
  () => {
    return new Promise((resolve) => setTimeout((...args) => {
        console.log(args);
        resolve();
    }, 1000, 42, "abc")
    )
  }
""")()

asyncio.run(async_fn())

wkp@m2~$ python3 ex.py
<_UnixSelectorEventLoop running=True closed=False debug=False>
[ 42, 'abc' ]
[ 42, 'abc' ]

wkp@m2~$ python3 --version
Python 3.12.8

wkp@m2~$ pip show pythonmonkey
Name: pythonmonkey
Version: 1.3.1
Summary: Seamless interop between Python and JavaScript.
Home-page: https://pythonmonkey.io/
Author: Distributive Corp.
Author-email: pm@distributive.network
License: MIT
Location: /Users/wkp/.local/share/mise/installs/python/3.12.8/lib/python3.12/site-packages
Requires: aiohttp, pminit
Required-by:
Will try 3.13 on windows later...

Thanks for looking into this. I'm currently waiting for the Windows test results. Please let me know what you find.

[LetuGitHub]

After switching to Python 3.13.13, the issue disappeared and it now returns the results correctly.

import asyncio
import pythonmonkey as pm

async def async_fn():
    await pm.eval("""
        new Promise((resolve) => setTimeout((...args) => {
            console.log(args);
            resolve();
        }, 1000, 42, "abc"))
    """)

asyncio.run(async_fn())

$ python --version
Python 3.13.13

$ python .\demo.py
[ 42, 'abc' ]

$ pip show pythonmonkey

Name: pythonmonkey
Version: 1.3.1
Summary: Seamless interop between Python and JavaScript.
Home-page: https://pythonmonkey.io/
Author: Distributive Corp.
Author-email: pm@distributive.network
License: MIT
Location: c:\Users\13944\Desktop\program\python\Lecourt\.venv\Lib\site-packages
Requires: aiohttp, pminit, pyreadline3
Required-by: