Description

vstinner

opened on Oct 16, 2026

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Tcl/Tk was recently upgraded from Tcl 9.0/Tk 9.0 to Tcl 9.1/Tk 9.1 on macOS GitHub Action. Since this update, many tests of test_idle and test_tkinter started to fail on "macOS (free-threading) / build and test (macos-26)" (GHA CI) with _tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle".

Example of failed build: https://github.com/python/cpython/actions/runs/38874850453/job/116887409891?pr=159515.

test.pythoninfo after:

tkinter.TCL_VERSION: 9.1
tkinter.TK_VERSION: 9.1
tkinter.info_patchlevel: 9.1.0

---

Previous build when the tests passed: https://github.com/python/cpython/actions/runs/38680918836/job/116256273820

test.pythoninfo before:

tkinter.TCL_VERSION: 9.0
tkinter.TK_VERSION: 9.0
tkinter.info_patchlevel: 9.0.4

Linked PRs

• [3.15] gh-159517: Modernize tkinter.simpledialog #159518
• [3.14] gh-159517: Modernize tkinter.simpledialog (GH-159518) #159522
• gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDLE on Tk 9.1 #159527
• [3.15] gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDLE on Tk 9.1 (GH-159527) #159624
• [3.14] gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDLE on Tk 9.1 (GH-159527) #159625

Activity

1. vstinner

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   testsTests in the Lib/test dirTests in the Lib/test dir

   OS-mac

   topic-tkinter

   on Oct 16, 2026
2. vstinner commented on Oct 16, 2026

   

   vstinner

   on Oct 16, 2026

   MemberAuthor

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   Example of failure:

   ERROR: test_open_and_close (idlelib.idle_test.test_searchbase.SearchDialogBaseTest.test_open_and_close)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "/Users/runner/work/cpython/cpython/Lib/idlelib/idle_test/test_searchbase.py", line 52, in test_open_and_close
       self.dialog.open(text)
       ~~~~~~~~~~~~~~~~^^^^^^
     File "/Users/runner/work/cpython/cpython/Lib/idlelib/searchbase.py", line 55, in open
       self.create_widgets()
       ~~~~~~~~~~~~~~~~~~~^^
     File "/Users/runner/work/cpython/cpython/Lib/idlelib/searchbase.py", line 103, in create_widgets
       _setup_dialog(top)
       ~~~~~~~~~~~~~^^^^^
     File "/Users/runner/work/cpython/cpython/Lib/tkinter/simpledialog.py", line 265, in _setup_dialog
       w.tk.call("::tk::unsupported::MacWindowStyle", "style",
       ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                 w, "moveableModal", "")
                 ^^^^^^^^^^^^^^^^^^^^^^^
   _tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle"
   

   cc @terryjreedy @serhiy-storchaka
3. vstinner

   changed the title [-]test_idle and test_tkinter fail with `_tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle"` on Tk 9.1/Tcl 9.1[/-] [+]On macOS, test_idle and test_tkinter fail with `_tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle"` on Tk/Tcl 9.1[/+] on Oct 16, 2026
4. vstinner

   changed the title [-]On macOS, test_idle and test_tkinter fail with `_tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle"` on Tk/Tcl 9.1[/-] [+]On macOS with Python 3.15, test_idle and test_tkinter fail with `_tkinter.TclError: invalid command name "::tk::unsupported::MacWindowStyle"` on Tk/Tcl 9.1[/+] on Oct 16, 2026
5. vstinner

   added 3 commits that reference this issue on Oct 16, 2026

   pythongh-159517: Modernize tkinter.simpledialog

   b25326b

   [3.15] gh-159517: Modernize tkinter.simpledialog (#159518)

   173dabe

   [3.14] gh-159517: Modernize tkinter.simpledialog (GH-159518) (#159522)

   8c27786
6. serhiy-storchaka commented on Oct 16, 2026

   

   serhiy-storchaka

   on Oct 16, 2026

   Member

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   Thank you, @vstinner. I did not expect CI will use Tcl 9.1/Tk 9.1 so soon, especially on non-main branches. I do not recommend to use 9.1.0. It has many bugs in new features. The next bugfix release will came with their fixes, and also with many fixes of old bugs and important macOS fixes.

   #159527 fixes other use of ::tk::unsupported::MacWindowStyle in IDLE.
7. vstinner commented on Oct 16, 2026

   

   vstinner

   on Oct 16, 2026

   MemberAuthor

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   Thank you, @vstinner.

   You're welcome.

   I did not expect CI will use Tcl 9.1/Tk 9.1 so soon, especially on non-main branches. I do not recommend to use 9.1.0. It has many bugs in new features. The next bugfix release will came with their fixes, and also with many fixes of old bugs and important macOS fixes.

   The failed 3.15 job uses macOS 26 arm image. The surprising thing is that https://github.com/actions/runner-images/blob/main/images/macos/macos-26-arm64-Readme.md still mentions "Tcl/Tk 8.6.18" whereas it was "Tcl/Tk 9.0" a few hours ago, and it's now "Tcl/Tk 9.1". The README is outdated, and I looked at the wrong README :-)
8. serhiy-storchaka

   added 3 commits that reference this issue on Oct 17, 2026

   gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDLE on Tk…

   e5ef47e

   [3.14] gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDL…

   2261a3e

   [3.15] gh-159517: Do not use ::tk::unsupported::MacWindowStyle in IDL…

   b4031e0
9. vstinner commented on Oct 18, 2026

   

   vstinner

   on Oct 18, 2026

   MemberAuthor

   More actions

   Both changes have been merged and backported to stable versions, I close the issue.
10. vstinner

    closed this as completedon Oct 18, 2026

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