In EditorWindow.open_module... once switch to querydialog, display errors (e.g. module not found) in askstring dialog itself, not open up subsequent 'showerror' dialog

I see this as two related changes:

a) Leave the module name query box open when there is a error, so the user can either correct a mistake (or hit Cancel) without reopening the box and re-entering the module name.  Good idea.

b) Put the error message in the box itself, perhaps with a beep.  I presume there would be no [OK] button, but rather the cursor would remain in the entry box.  Nice simplification.

I believe 'not a source-based module' means 'not a python-coded module', which seems a little clearer. We could check the importlib doc.

Exactly. The "querydialog" code (which will replace the simpledialog askstring/askinteger calls) displays errors as shown in querydialog.png, with the error messages disappearing as soon as you hit another key.

You can also pass in a 'validator' to check if the input is ok, so in this case it would check if the module could be loaded and return the appropriate message if not.

Where is querydialog? (It looks like something than should be in tkinter ;-).

Work in progress, have a few more tweaks to make, but here's a snapshot...

The patch is mostly obsolete.  I added query.py a year ago, which replaced the open-module box and those used in configdialog.  The code began with one of the existing boxes, but it has the two improvements listed above: a) stay open on error (really helpful if I type 'idlelib.run' and only need to correct one letter) and b) put error message below entry box.

I am leaving this open temporarily to see if there is anything in this patch needed in Query.

Thanks for the push.  query.py now has several subclasses which I believe covers all simple queries.