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v2.10.1: fails to start on Python 3.14

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
backend

Research direction

Start with src/e3sm_quickview/view_manager.py at the asyncio.get_event_loop() call identified in the report, then check how the server starts and how wslink handles loop setup. Reproduce on Python 3.14 using the reported startup command; done when quickview starts without the missing-loop error. Consider adding Python 3.14 to CI, as suggested.

Written by the indexing model from the issue text.

Description

We're testing e3sm-quickview 2.10.1 (from conda-forge) on Perlmutter, in the upcoming E3SM-Unified 1.14.0, which uses Python 3.14.7. Running quickview crashes on startup, before the server starts:

$ quickview
VTKStreaming Video encoding is NOT AVAILABLE (missing Python package)
Loading plugin :  .../e3sm_quickview/plugins/eam_gridlines.py
Loading plugin :  .../e3sm_quickview/plugins/eam_projection.py
Loading plugin :  .../e3sm_quickview/plugins/eam_reader.py
Loading plugin :  .../e3sm_quickview/plugins/eam_filters.py
Traceback (most recent call last):
  File ".../bin/quickview", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File ".../e3sm_quickview/app.py", line 802, in main
    app = EAMApp()
  File ".../e3sm_quickview/app.py", line 75, in __init__
    self.view_manager = ViewManager(self.server, self.source)
                        ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../e3sm_quickview/view_manager.py", line 100, in __init__
    self.loop = asyncio.get_event_loop()
                ~~~~~~~~~~~~~~~~~~~~~~^^
  File ".../python3.14/asyncio/events.py", line 718, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
                       % threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'MainThread'.

Cause: Starting with Python 3.14, asyncio.get_event_loop() raises RuntimeError when no loop is set, where earlier versions created one implicitly. ViewManager.__init__ (view_manager.py#L100) runs before trame/wslink have started a loop, so it fails. The same line is still on main.

Suggested fix: wslink 2.5.7 already handles this (wslink/core.py, wslink/server.py) with:

try:
    self.loop = asyncio.get_event_loop()
except RuntimeError:
    self.loop = asyncio.new_event_loop()
    asyncio.set_event_loop(self.loop)

wslink then picks up the same loop when the server starts. We checked this by setting a loop before calling main():

python -c "import asyncio, sys; asyncio.set_event_loop(asyncio.new_event_loop()); from e3sm_quickview.app import main; sys.argv[0]='quickview'; sys.exit(main())" --server

With that, the server starts normally and prints the connection URL. Since requires-python = ">=3.10" allows 3.14, it may also be worth adding Python 3.14 to CI.

This looks related to #111 (event loop missing in debounce) but affects a different code path.

Environment:

  • e3sm-quickview 2.10.1 (conda-forge, noarch)
  • Python 3.14.7
  • trame 4.0.0, trame-server 4.0.0, wslink 2.5.7
  • NERSC Perlmutter login node (pm-cpu)

Drafted by Claude Code and @xylar together.

Dominant language
JavaScript
Stars
3
Forks
4
Avg merge
10h 10m
Merged PRs (30d)
7

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