Different behaviour between `nbqa black` and `nbqa black --check`

Hello,

Thanks for making this awesome tool.

I’ve been having some problems related to nbqa black --check raising problems but nbqa black not doing anything to change it. I’ve managed to recreate this with the following minimal example. It appears to be related to how the configuration is parsed.

.
├── notebook.ipynb
└── pyproject.toml

My project has something like the following configuration. We set the line length to be 79 for source code but are happy with longer lines inside notebooks.

# pyproject.toml
[tool.black]
line-length = 79

[tool.nbqa.addopts]
# use longer lines in notebooks
black = [
    "--line-length=88",
]

notebook.ipynb has a single cell with the following contents

result = function_name(xxxxxxxxxxxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx)

The exact contents are not so important, the important thing is that the line length is more than 79 but less than 88. Running

nbqa black notebook.ipynb

results in no changes, but running

nbqa black --check notebook.ipynb

indicates that the notebook would be reformatted.

To avoid any ambiguity, here’s the notebook JSON

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "77402ebb-99fc-4232-9f9a-d46bb0d3aa3d",
   "metadata": {},
   "outputs": [],
   "source": [
    "result = function_name(xxxxxxxxxxxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx)"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "nbqa",
   "language": "python",
   "name": "nbqa"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.9.5"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}

[MarcoGorelli]

@tcbegley I’ve made a new release (it’s been about a year since the first version, so I’ve finally made a 1.0.0 release 🎉), if you could try it out and let me know if this doesn’t work for you, that’d be much appreciated

As an aside, --nbqa-mutate is no longer necessary (it won’t error if you pass it, but it won’t do anything anymore)

[tcbegley]

Thanks @MarcoGorelli! Updated our CI and it all seems to be working like a charm.