Hello,
I’m planning to work on fixing this issue, and I noticed this part of the code:

        if use_subprocess:
            ms = self.menu_specs
            if ms[2][0] != "shell":
                ms.insert(2, ("shell", "She_ll"))

Would it be feasible to simply remove the if use_subprocess: condition? I'm unsure if this change could cause other issues and would appreciate your input.

Thank you!

@terryjreedy, I dug through past code to find the cause of the issue and tried to fix it, and I'll create a PR in a while.

First of all, I found out that this issue was artificially introduced, which was brought up by kbkaiser in a commit 21 years ago (8f570a7):

And the changes are as follows:

1. Add a command line switch to run without the subprocess
2. Remove the shell menu and associated bindings when running
   without the subprocess.
3. Update the IDLE Help and usage text.
4. Update display_port_binding_error to suggest using -n

The key lies in the second point. And it's IMPORTANT to note that at that time there were only two options for the menu "shell":

After testing, these two functions are not available when using the parameter "-n" and cause some errors. So I'm guessing that's why kbkaiser disabled the menu "shell" at that time.

But from the image above, we can clearly see that more features have been added to the menu "shell" since then. After testing, the rest of the functions work correctly when using the parameter "-n".

So I think the appropriate fix would be to restore the menu "shell" while disabling the two previously mentioned options that can't be used when using the "-n" parameter.

The final effect is as follows:

Maybe there is some problem with my idea, if there is, please help me point it out, thanks!

The basic idea is like that, but I'm not very clear as to why those two features cause errors in single-process mode. Perhaps we should address this issue in detail in the documentation?

In single process mode, the GUI and the user program are ran in the same process. What are you going to restart?

In single process mode, the GUI and the user program are ran in the same process. What are you going to restart?

Yes! It makes so much sense, how I didn't think of this question!

Thank you all for the research, fix, and merge. I somehow missed the posting of the PR. I added 2 draft follow-up issues to the Restart topic of the IDLE issues Project page.

1. View Restart should consider the initial start a restart, making it applicable in -n mode.
2. The documented purpose of Restart is to 'clean the environment'. This is applicable and I believe easily done in -n mode. Restarting a dead or stuck subprocess as a super-interrupt to regain control when ^-C fails would remain normal-mode only.

The user code shares the environment (e.g. imported modules, sys settings, opened file descriptors, Tkinter widgets) with IDLE. It cannot be cleaned.