mo.watch.file not supported on wasm #7956
Description
Describe the bug
I had a great time playing with mo.watch.file (like creating typst svg documents on the fly).
But after trying to package it on marimo.app to share it, I got this error:
Unsupported stream type <class 'marimo._pyodide.streams.PyodideStream'>
It makes sense that the Pyodide filesystem is not as powerful as the host, but this limitation was never documented.
IMO, the function should be able to read the contents in wasm, and just return a warning in the case where the pyodide filesystem is too limited to be reactive.
Thank's !
Will you submit a PR?
- Yes
Environment
Details
{
"marimo": "0.19.4",
"editable": false,
"location": "/var/mnt/data/Proj/marimo-website/.venv/lib/python3.13/site-packages/marimo",
"OS": "Linux",
"OS Version": "6.18.5-200.fc43.x86_64",
"Processor": "",
"Python Version": "3.13.9",
"Locale": "en_US",
"Binaries": {
"Browser": "--",
"Node": "v24.11.1"
},
"Dependencies": {
"click": "8.3.1",
"docutils": "0.22.4",
"itsdangerous": "2.2.0",
"jedi": "0.19.2",
"markdown": "3.10",
"narwhals": "2.15.0",
"packaging": "25.0",
"psutil": "7.2.1",
"pygments": "2.19.2",
"pymdown-extensions": "10.20",
"pyyaml": "6.0.3",
"starlette": "0.52.1",
"tomlkit": "0.14.0",
"typing-extensions": "4.15.0",
"uvicorn": "0.40.0",
"websockets": "16.0"
},
"Optional Dependencies": {
"altair": "6.0.0",
"loro": "1.10.3",
"openai": "2.15.0",
"polars": "1.37.1",
"ruff": "0.14.13",
"ty": "0.0.12",
"watchdog": "6.0.0"
},
"Experimental Flags": {}
}
Code to reproduce
import marimo as mo
mo.file.watch("file.txt")
Here is the entire stacktrace of the wasm execution:
Traceback (most recent call last):
File "/tmp/marimo_42/__marimo__cell_lcWz_.py", line 1, in <module>
mo.watch.file("file.txt")
File "/lib/python3.12/site-packages/marimo/_runtime/watch/_file.py", line 148, in file
return FileState(path, allow_self_loops=True)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lib/python3.12/site-packages/marimo/_runtime/watch/_file.py", line 67, in __init__
super().__init__(*args, **kwargs)
File "/lib/python3.12/site-packages/marimo/_runtime/watch/_path.py", line 74, in __init__
Thread(
File "/lib/python3.12/site-packages/marimo/_runtime/threads.py", line 101, in __init__
raise RuntimeError(
RuntimeError: Unsupported stream type <class 'marimo._pyodide.streams.PyodideStream'>