gh-97527: IDLE - fix buggy macosx patch (GH-98313)

GH-97530 fixed IDLE tests possibly crashing on a Mac without a GUI.
But it resulted in IDLE not starting in 3.10.8, 3.12.0a1, and
Microsoft Python 3.10.2288.0 when test/* is not installed.
After this patch, test.* is only imported when testing on Mac.
(cherry picked from commit 35fa5d5)

Co-authored-by: Terry Jan Reedy <[email protected]>

Lib/idlelib/NEWS.txt

@@ -4,6 +4,11 @@ Released on 2022-10-03
 =========================
 
 
+gh-97527: Fix a bug in the previous bugfix that caused IDLE to not
+start when run with 3.10.8, 3.12.0a1, and at least Microsoft Python
+3.10.2288.0 installed without the Lib/test package.  3.11.0 was never
+affected.
+
 gh-65802: Document handling of extensions in Save As dialogs.
 
 gh-95191: Include prompts when saving Shell (interactive input/output).

Lib/idlelib/macosx.py

@@ -4,7 +4,6 @@
 from os.path import expanduser
 import plistlib
 from sys import platform  # Used in _init_tk_type, changed by test.
-from test.support import requires, ResourceDenied
 
 import tkinter
 
@@ -16,27 +15,38 @@
 
 def _init_tk_type():
     """ Initialize _tk_type for isXyzTk functions.
+
+    This function is only called once, when _tk_type is still None.
     """
     global _tk_type
     if platform == 'darwin':
-        try:
-            requires('gui')
-        except ResourceDenied:  # Possible when testing.
-            _tk_type = "cocoa"  # Newest and most common.
-        else:
-            root = tkinter.Tk()
-            ws = root.tk.call('tk', 'windowingsystem')
-            if 'x11' in ws:
-                _tk_type = "xquartz"
-            elif 'aqua' not in ws:
-                _tk_type = "other"
-            elif 'AppKit' in root.tk.call('winfo', 'server', '.'):
+
+        # When running IDLE, GUI is present, test/* may not be.
+        # When running tests, test/* is present, GUI may not be.
+        # If not, guess most common.  Does not matter for testing.
+        from idlelib.__init__ import testing
+        if testing:
+            from test.support import requires, ResourceDenied
+            try:
+                requires('gui')
+            except ResourceDenied:
                 _tk_type = "cocoa"
-            else:
-                _tk_type = "carbon"
-            root.destroy()
+                return
+
+        root = tkinter.Tk()
+        ws = root.tk.call('tk', 'windowingsystem')
+        if 'x11' in ws:
+            _tk_type = "xquartz"
+        elif 'aqua' not in ws:
+            _tk_type = "other"
+        elif 'AppKit' in root.tk.call('winfo', 'server', '.'):
+            _tk_type = "cocoa"
+        else:
+            _tk_type = "carbon"
+        root.destroy()
     else:
         _tk_type = "other"
+    return
 
 def isAquaTk():
     """

Misc/NEWS.d/next/IDLE/2022-10-15-21-20-40.gh-issue-97527.otAHJM.rst

@@ -0,0 +1,3 @@
+Fix a bug in the previous bugfix that caused IDLE to not start when run with
+3.10.8, 3.12.0a1, and at least Microsoft Python 3.10.2288.0 installed
+without the Lib/test package.  3.11.0 was never affected.