Ruff emits a W391 error, a spurious one as far as I can see, and --fix doesn't modify the file:

$ ruff check --isolated --no-cache --extend-select W --preview --fix file.ipynb
Found 1 error (1 fixed, 0 remaining).
$ 
$ ruff check --isolated --no-cache --extend-select W --preview --fix file.ipynb
Found 1 error (1 fixed, 0 remaining).
$ 

The issue is associated to this line in the Jupyter Notebook:

   "source": []

• List of keywords you searched for before creating this issue: "W391"

• A minimal code snippet that reproduces the bug.

  code snippet

  {
   "cells": [
    {
     "cell_type": "code",
     "execution_count": null,
     "metadata": {},
     "outputs": [
      {
       "name": "stdout",
       "output_type": "stream",
       "text": [
        "True\n"
       ]
      }
     ],
     "source": [
      "True"
     ]
    },
    {
     "cell_type": "code",
     "execution_count": null,
     "metadata": {},
     "outputs": [],
     "source": []
    }
   ],
   "metadata": {
    "kernelspec": {
     "display_name": "Python 3 (ipykernel)",
     "language": "python",
     "name": "python3"
    }
   },
   "nbformat": 4,
   "nbformat_minor": 2
  }
  

• The command you invoked (e.g., ruff /path/to/file.py --fix), ideally including the --isolated flag.

   ruff check --isolated --no-cache --extend-select W --preview --fix file.ipynb
  

• The current Ruff settings (any relevant sections from your pyproject.toml).

• The current Ruff version (ruff --version).

  ruff 0.6.9