OS X test for Tk availability doesn't work

[alex]

BPO	17496
Nosy	@ronaldoussoren, @ned-deily, @glyph, @alex, @roseman
Files	tk-cond.diff issue-17496.txt

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/ronaldoussoren'
closed_at = None
created_at = <Date 2013-03-20.19:50:05.038>
labels = ['OS-mac', 'type-bug', 'expert-tkinter', '3.8', '3.7', 'tests']
title = "OS X test for Tk availability in runtktests.py doesn't work"
updated_at = <Date 2018-06-27.07:17:07.088>
user = 'https://github.com/alex'

bugs.python.org fields:

activity = <Date 2018-06-27.07:17:07.088>
actor = 'ronaldoussoren'
assignee = 'ronaldoussoren'
closed = False
closed_date = None
closer = None
components = ['macOS', 'Tests', 'Tkinter']
creation = <Date 2013-03-20.19:50:05.038>
creator = 'alex'
dependencies = []
files = ['29510', '29990']
hgrepos = []
issue_num = 17496
keywords = ['patch']
message_count = 14.0
messages = ['184784', '184843', '184844', '184845', '184846', '184850', '184851', '184862', '187632', '193592', '219025', '219028', '320500', '320551']
nosy_count = 6.0
nosy_names = ['ronaldoussoren', 'ned.deily', 'glyph', 'alex', 'markroseman', 'jesstess']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue17496'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5', 'Python 3.6', 'Python 3.7', 'Python 3.8']

Linked PRs

• gh-61698: Use launchctl to detect macOS window manager in tests #118390
• [3.13] gh-61698: Use launchctl to detect macOS window manager in tests (GH-118390) #125392
• [3.12] gh-61698: Use launchctl to detect macOS window manager in tests (GH-118390) #125393

[alex]

If I run:

$ python -mtest.test_tk

I get a skip, after speaking with people familiar with OS X, it appears that the condition for the skip uses old Carbon APIs, which are totally deprecated under 64-bit. Attached is a patch which should work.

[ned-deily]

The test for the condition was added to solve the problem reported in bpo-8716. The Tk crash for test_ttk_guionly reported there still occurs on a current 10.8 system with the Apple-supplied Cocoa Tk under the same conditions, that is, when running the tests from a process without a window manager connection, like an ssh or buildbot process where the user is not also currently logged in as the main "GUI user". And the skip test code in question does prevent that crash. The skip test also works correctly when using a 64-bit framework Python build (./configure --enable-framework), i.e. it does not skip the tests in a normal terminal session. A side effect of a framework build is that the Python interpreter runs within an OS X app bundle, which gives it magic GUI powers.

But if run from a non-framework (standard unix) build, the tests are skipped with a "cannot run without OS X gui process" skip although stubbing out the check, as your patch does, shows that test_tk and test_ttk_guionly appear to run without error. So it seems that the skip test is too restrictive but it shouldn't be unilaterally deleted.

[glyph]

Hi Ned,

It seems from your comment that you didn't read the patch. Alex added a simpler check via launchctl, rather than by framework symbol groveling :). He didn't remove the check.

It should be functionally identical to what's there now, but much shorter and without having to depend on ctypes.

-glyph

[ned-deily]

Um, yes, my tired eyes did skip over those added lines. Thanks, Glyph, and sorry, Alex.

While the suggested change solves the issue for the non-framework build case, it appears to introduce new problems. For one, with the current skip test, it is possible to run the tests from a buildbot or ssh process as long as the user name is logged in. That no longer works with the proposed change. Also, "launchctl managername" does not appear to be available on releases prior to 10.6, releases we still support.

[ned-deily]

Granted, the current test is a kludge. We could make it a bigger kludge by trying launchctl first and if it fails move on to the current ctypes-based tests. Any better options?

[ronaldoussoren]

A small helper program that does the equavalent of this should also work:

import Cocoa
Cocoa.NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(((10, 10), (100, 100)), 0, 0, 0)

If this code raises an exception you cannot create windows, if it doesn't you can. This doesn't actually show the window and shouldn't mess up the users desktop when running the testsuite interactively.

[ronaldoussoren]

Wouldn't it be better to check for the actual problem, that is use subprocess to start a small Tcl script that creates a window and check if that crashes?

That way the code for disabling the test doesn't have to try to guess whether or not Tk will crash in the current environment, and tests won't get skipped when the Tk folks get their act together and don't crash when the window manager isn't available.

[glyph]

Wouldn't it be better to check for the actual problem, that is use subprocess to start a small Tcl script that creates a window and check if that crashes?

Yes, this sounds great. Doing it with Tcl means that we're not invoking any of the problematic code in question. It sounds like this check could be done on other platforms as well, in lieu of looking for e.g. $DISPLAY. If a tcl script can make tk windows, so should a Python script be able to.

[ronaldoussoren]

The attached patch start wish and stops it by sending the 'exit' command. With the patch I can run the tk tests without getting a skip. I cannot easily test if the patch also does the right thing on buildbots, but have high hopes. I did check that just starting 'wish' on a machine where I don't have console access causes a crash (OSX 10.5, nobody on the console, I logged on through SSH).

Open issues with my patch:

• The check uses whatever version wish is on the PATH, which may or may
  not be related to the version of Tk that python is linked to.

  It might be better to explicitly use /usr/bin/wish, as that one is
  known to be native port of Tk (not X11) and is known to crash.

• Not tested if the patch causes a Skip when running tests without
  GUI access.