Keyword arguments to functions in web worker are not passed properly #2398
Description
Checklist
- I added a descriptive title
- I searched for other issues and couldn't find a solution or duplication
- I already searched in Google and didn't find any good information or help
What happened?
I tried calling a function in web worker with keyword arguments but it got stuck. It looks like keyword arguments are not passed properly between main thread and web worker and end up being passed as some kind of object as positional argument. Below I pasted example code so you can reproduce (I tested with 2025.10.3 as well with the same result).
What browsers are you seeing the problem on? (if applicable)
Firefox
Console info
This call:
`await my_worker.some_function(2, 3, 10, x=20)`
Results in:
`some_function called with a=2, b=3, args=(10, [object Object]), kwargs={}`Additional Context
Repro:
<!doctype html>
<html>
<head>
<!-- https://docs.pyscript.net/2025.7.1/user-guide/workers/ -->
<script src="./mini-coi.js" scope="./"></script>
<!-- Recommended meta tags -->
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<!-- PyScript CSS -->
<link rel="stylesheet" href="https://pyscript.net/releases/2025.7.1/core.css">
<!-- This script tag bootstraps PyScript -->
<script type="module" src="https://pyscript.net/releases/2025.7.1/core.js"></script>
</head>
<body>
<py-script type="py" worker name="my-worker">
from pyscript import window
def some_function(a: int, b: int, *args, **kwargs) -> int:
window.console.log(f"some_function called with a={a}, b={b}, args={args}, kwargs={kwargs}")
return a + b
__export__ = ["some_function"]
</py-script>
<py-script type="py">
from pyscript import workers
from pyscript import display
my_worker = await workers["my-worker"]
async def run(_event):
result_positional = await my_worker.some_function(2, 3, 10, x=20)
display(f"Result with positional arguments: {result_positional}")
result_keyword = await my_worker.some_function(a=5, b=7, c=10)
display(f"Result with keyword arguments: {result_keyword}")
</py-script>
<button py-click="run">Run</button>
</body>
</html>