Strange behaviour for --set-formats after --to py:percent

[MPKonst]

I am having the following issue when I use the CLI for jupytext.
While in a folder notebooks containing a single file notebook_first.ipynb the following:

jupytext --to py:percent notebook_first.ipynb # works fine, notebook_first.py is created
jupytext --set-formats ipynb,py:percent notebook_first.ipynb

thows a KeyError: 'formats'. If I only run the second command, things work fine, that is, notebook_first.py is created and the formats are set.

I noticed also that in the opposite direction there is no such problem. That is, if I start with a python file script_first.py, then running

jupytext --to notebook script_first.py 
jupytext --set-formats ipynb,py:percent script_first.ipynb

works as expected.

[mwouts]

Thank you @MPKonst for reporting this. I'll have a look soon!

[mwouts]

At #407 we have one test that reproduces this, together with the fix. Thanks @MPKonst for your feedback!

[MPKonst]

Thanks for addressing this, Marc. Happy holidays!