vscode-jupyter changes cells that were not modified: removes \n at the end of every "image/png" field

Environment data

• VS Code version: Version: 1.61.1, commit c13f1abb110fc756f9b3a6f16670df9cd9d4cf63
• Jupyter Extension version (available under the Extensions sidebar): v2021.9.1101343141
• Python Extension version (available under the Extensions sidebar): v2021.10.1336267007
• OS (Windows | Mac | Linux distro) and version: OS: Darwin x64 19.6.0
• Python and/or Anaconda version: 3.8.12
• Type of virtual environment used (N/A | venv | virtualenv | conda | …): conda
• Jupyter server running: Local

Expected behaviour

When opening in VSCode a Jupyter notebook created using Jupyter Notebook or Jupyter Lab and making a tiny change to one cell, then saving the notebook, the other cells in the notebook should not be modified.

Actual behaviour

Every cell that outputs an image (e.g., using Matplotlib) is modified. Specifically, the \n at the end of every "image/png" field is removed. This makes switching between VSCode and Jupyter Notebook/Lab very painful, especially when working with git, as even minor changes lead to large diffs.

Steps to reproduce:

1. Create a notebook with Jupyter Notebook or Jupyter Lab, and run the following code:

import matplotlib.pyplot as plt

plt.plot([1,2,3], [3, 1, 2])
plt.show()

1. Save the notebook. You can verify that the "image/png" field has a \n at the end.
2. Open the notebook in VScode, make a tiny modification without running the notebook or modifying the existing cells (e.g., add a markdown cell).
3. Save the notebook. You can verify that the "image/png" field no longer has a \n at the end. It was modified even though we didn’t touch it.

[rchiodo]

I was looking at it because it was unassigned. Here’s a start: https://github.com/rchiodo/vscode/commit/8acd26407529bfa338732e5e3664e39723e1d795

[DonJayamanne]

Thanks for filing this issue, i’ll look into this and am certain we can get this sorted out. Apologies this causes issues with your workflow.