active-py mode strips leading # from comments

[kerrickstaley]

Summary

When I load a file that has a cell tagged with active-py and then save it, Jupytext strips the leading # on comments in the cell, making the cell no longer run correctly in the .py file.

To reproduce

1. Save this as foo.py:

# ---
# jupyter:
#   jupytext:
#     text_representation:
#       extension: .py
#       format_name: percent
#       format_version: '1.3'
#       jupytext_version: 1.15.2
#   kernelspec:
#     display_name: Python 3 (ipykernel)
#     language: python
#     name: python3
# ---

# %%
print('hello')

# %% tags=["active-py"]
# Print goodbye
print('goodbye')

2. Run jupyter notebook in the directory where you saved foo.py and open foo.py.
3. Hit Ctrl+S or Cmd+S to save the file.

Expected behavior

The file foo.py is unchanged.

Actual behavior

The line

# Print goodbye

in foo.py changes to

Print goodbye

which makes the file no longer runnable (not valid Python code).

System info

macOS 13.3.1
Python 3.11.5
jupytext 1.15.2

Also repros on:
Rocky Linux 8.8
Python 3.8.17
jupytext 1.5.2

[mwouts]

I see! Thank you @kerrickstaley for reporting this. I will have a look.