gh-112938: IDLE - Fix uninteruptable hang when Shell gets rapid continuous output.

Lib/idlelib/idle_test/test_outwin.py

@@ -1,6 +1,7 @@
 "Test outwin, coverage 76%."
 
 from idlelib import outwin
+import sys
 import unittest
 from test.support import requires
 from tkinter import Tk, Text
@@ -18,6 +19,10 @@ def setUpClass(cls):
         root.withdraw()
         w = cls.window = outwin.OutputWindow(None, None, None, root)
         cls.text = w.text = Text(root)
+        if sys.platform == 'darwin':  # Issue 112938
+            cls.text.update = cls.text.update_idletasks
+            # Without this, test write, writelines, and goto... fail.
+            # The reasons and why macOS-specific are unclear.
 
     @classmethod
     def tearDownClass(cls):

Lib/idlelib/outwin.py

@@ -112,7 +112,7 @@ def write(self, s, tags=(), mark="insert"):
         assert isinstance(s, str)
         self.text.insert(mark, s, tags)
         self.text.see(mark)
-        self.text.update_idletasks()
+        self.text.update()
         return len(s)
 
     def writelines(self, lines):

Misc/NEWS.d/next/IDLE/2024-09-21-23-12-18.gh-issue-112938.OeiDru.rst

@@ -0,0 +1 @@
+Fix uninteruptable hang when Shell gets rapid continuous output.