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.