nbdiff-web gets stuck on particular input

[jamesb6626]

I am running nbdime version 4.0.2, on python 3.13.3, in a virtual environment where I have installed nbdime and jupyterlab through pip.

The nbdiff-web tool refused to produce a full diff on a particular pair of notebooks. It produced a diff up to a certain point, but ignored everything past a certain offending cell, instead getting stuck and showing a spinning loading indicator. I should note here that the terminal-based nbdiff does not have the same problem, and gives a correct diff.

I've stripped down the offending files as much as I could while still reproducing the problem, hopefully this helps to identify the problem.

Steps to reproduce: Paste the contents cell-by-cell into fresh jupyterlab python notebooks, then run nbdiff-web File1.ipynb File2.ipynb. Only the first cell gets a correct diff.
Seemingly only the second cell in each causes a problem, though I've included the extra ones for demonstration.

Cells of File1.ipynb (2 cells, though first can be deleted and still reproduces):

This Works

# Offending Cell:
    - np.array([1, 0])[:, None, None]
Shared Line

Cells of File2.ipynb (3 cells, though first and last can be deleted and still reproduces):

This Too

# Offending Cell:
    - np.array([1, 0])[:, *(None,)*xs.ndim]
Shared Line

another line

Uh oh, no diff for cells after the problem

[jamesb6626]

Just in case my jupyterlab setup or version or something is causing the issue on my end, I'll paste the verbatim notebook files here. I don't think the jupyterlab which created the files is the absolute most up-to-date it could be.

File1.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "79a38947-364e-408a-9397-70777236b7d4",
   "metadata": {},
   "outputs": [],
   "source": [
    "This Works"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "91853a62-f565-46cb-ba9a-3f2090d084fa",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Offending Cell:\n",
    "    - np.array([1, 0])[:, None, None]\n",
    "Shared Line"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "",
   "name": ""
  },
  "language_info": {
   "name": ""
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}

File2.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "c10208c8-1c03-4b04-b657-559825a7bf38",
   "metadata": {},
   "outputs": [],
   "source": [
    "This Too"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3779e42e-a8f0-46ed-8b62-84cf00406270",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Offending Cell:\n",
    "    - np.array([1, 0])[:, *(None,)*xs.ndim]\n",
    "Shared Line\n",
    "\n",
    "another line"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6d17862f-8ad1-4214-ae9c-ec70d5c32841",
   "metadata": {},
   "outputs": [],
   "source": [
    "Uh oh, no diff for cells after the problem"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "",
   "name": ""
  },
  "language_info": {
   "name": ""
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}