Add _close() method that does the actual cleanup (close() asks the

user what they want first if there's unsaved stuff, and may cancel).
It closes more than before.

Add unload_extensions() method to unload all extensions; called from
_close().  It calls an extension's close() method if it has one.

Tools/idle/EditorWindow.py

@@ -462,22 +462,38 @@ class EditorWindow:
         self.top.tkraise()
         reply = self.maybesave()
         if reply != "cancel":
+            self._close()
+        return reply
+
+    def _close(self):
         WindowList.unregister_callback(self.postwindowsmenu)
         if self.close_hook:
             self.close_hook()
+        self.flist = None
         colorizing = 0
+        self.unload_extensions()
+        self.io.close(); self.io = None
+        self.undo = None # XXX
         if self.color:
             colorizing = self.color.colorizing
             doh = colorizing and self.top
             self.color.close(doh) # Cancel colorization
+        self.text = None
+        self.vars = None
+        self.per.close(); self.per = None
         if not colorizing:
             self.top.destroy()
-        return reply
 
     def load_extensions(self):
         self.extensions = {}
         self.load_standard_extensions()
 
+    def unload_extensions(self):
+        for ins in self.extensions.values():
+            if hasattr(ins, "close"):
+                ins.close()
+        self.extensions = {}
+
     def load_standard_extensions(self):
         for name in self.get_standard_extension_names():
             try: