I never use (in other situations and letters) the Reply to all button, so I may sometimes forget to press it instead of a usual answer. Sorry. But I'm trying ^_^

>>Saving TUTORIAL is a strange thing to do. What is the purpose?

I suppose there are two main reasons:

1. Correcting mistakes. Eg. I saw "vv" on a new line where it was not supposed to be. Or there was a mistake in a "homework" section in the command, I don't remember where exectly.

2. Making notes for oneself. To explain something better (more clear to an exact learner).

*3. Or maybe even to argue. If I see some information which I completely disagree with, but I don't want to disturb the support team or waste time, I could just write a couple of sentences right in the Tutorial, kindof a comment, - and feel better ^_^

Eli Zaretskii <eliz@gnu.org> writes:

Cc: 74364@debbugs.gnu.org
Date: Mon, 25 Nov 2024 20:10:49 +0100
From:  Manuel Giraud via "Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>

Tatsu Takamaro <tatsu.takamaro@gmail.com> writes:

[...]

Ok, now your recipe is more precise and I can reproduce it.

3. Put some changes into the Tutorial. Say, just add a new line.

4. Press C-x-s to save. Emacs asks me to write a filename, I write
TUTORIAL, because the full path is alredy shown. Then Emacs asks me
whether I want to overwrite the file. I anser Yes (type y).

After this 'C-x C-s', you have saved the content of the (modified)
TUTORIAL into a file named "TUTORIAL" somewhere on your hard drive.
Now, in this buffer, `tutorial--lang' is set to nil (which cause the
error you saw) and Emacs still wants to save your progression in the
tutorial and that's why it asks the question when you tried to quit.

This is indeed a bug but maybe saving the TUTORIAL buffer is not
supported.  Or we should remap `save-buffer' to save tutorial
progression here?

Saving TUTORIAL is a strange thing to do.  What is the purpose?  The
file produced that way cannot be used as a tutorial, AFAIU, because
Emacs doesn't let users specify the tutorial's file name.

It seems that at some point of the tutorial, the user is expected to do
it.

[...]

So my suggestion would be to modify tutorial--save-tutorial and
tutorial--save-on-kill such that of tutorial--lang is nil, they will
do nothing.  Because there's no point of trying to save the tutorial
in that case.

I could try to come up with a patch like this.