@csabella, thanks for your PR! By analyzing the history of the files in this pull request, we identified @kbkaiser, @rhettinger and @terryjreedy to be potential reviewers.

@mlouielu I haven't made a separate PR yet, but I've made the other changes you suggested. I also added deletes for the mocks. One thing I wanted to ask is if you could help with the errors I'm getting when running the tests (warning: callback failed in WindowList <class '_tkinter.TclError'> : invalid command name ".!menu.windows"). I don't know enough to understand where to look to figure this out or what to change. Would you have any suggestions on what I can look at or how I can trace it? Thanks!

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I didn't expect the Spanish Inquisition!. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

And if you don't make the requested changes, you will be put in the comfy chair!

The test suite fails on both Appveyor and my system with
ERROR: setUpClass (idlelib.idle_test.test_outwin.OutputWindowTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\projects\cpython\lib\idlelib\idle_test\test_outwin.py", line 20, in setUpClass
    w = cls.window = outwin.OutputWindow(None, None, None, root)
  File "C:\projects\cpython\lib\idlelib\outwin.py", line 78, in __init__
    EditorWindow.__init__(self, *args)
  File "C:\projects\cpython\lib\idlelib\editor.py", line 269, in __init__
    self.askyesno = tkMessageBox.askyesno
AttributeError: module 'tkinter.messagebox' has no attribute 'askyesno'
----------------------------------------------------------------------

The problem in not with the messagebox import in outwin.py, as it persists with the import disabled. (This causes a later error when the above does not occur.) The test passes with line 269 commented out. Line 271 self.showerror = tkMessageBox.showerror is no problem.

from tkinter import messagebox; print(dir(messagebox)) prints a list that includes askyesno. If I put print(id(tkMessageBox), dir(tkMessageBox)) immediately before EditorWindowdef init and again at the top of init, it is the same object. askyesno is initially present but then missing (but nothing else is).

I believe that the problem is that we twice mocked askyesno in test_configdialog by replacing it and then deleting it. It is the same error as I reported above for showerrer here. The fix should save and restore. It can be a short PR for bpo-30780.

Added: I opened new issue bpo-31287. I fixed issue by localizing askyesno to classes and then masking with instance attribute in tests. Did same for outwin and showerror.

News blurb also needed

The update includes the fix from bpo-31287 that fixes the GUI test failure (no messagebox.askyesno). I added a new file. Unfortunately, it causes Appveyor to not run. Closing and opening did not either. A regular patch will trigger Appveyor.

Unless you post a patch first, I am going to make the fairly simple changes I requested.

Sorry, I was trying to figure out the whole thing with why messagebox.askyesno was disappearing. I still don't quite understand it. I guess if a function or class from another module is mocked, then it should be saved/restored instead of deleted?

Thanks for making the other changes.

The configdialog test replaced the original askyesno function in the messagebox module with a Mock and then deleted the mock. Some test imported editor before that, and editor imported the same module object. By the time outwin imported editor, the messagebox module referenced by editor was deficient. Test_idle is run in one process.

What puzzled me is that when outwin imported messagebox, it was not the same module object. (It had a different id().) I did not try to work out why. Python imports, with caching in sys.modules, is a tricky business sometimes.

Thanks for explaining. I played around some more (using mock.patch) and I think I have a better understanding of this.

There's a line in the mock.patch documentation, under the The patchers section, that says They [patchers] automatically handle the unpatching for you, even if exceptions are raised. . So I tried adding @mock.patch('idlelib.configdialog.tkMessageBox.askyesno') to the test functions in the old (broken) version of the code. Using the mock.patch decorator or context manager allowed it to work without having to del, save the original, or make it a function. I didn't really 'get it' before, but working through this helps me understand the why instead of just copying code.