Issue #22115: Fixed tracing Tkinter variables.

* trace_vdelete() with wrong mode no longer break tracing
* trace_vinfo() now always returns a list of pairs of strings

3 files changed, 65 insertions, 7 deletions

diff --git a/Lib/lib-tk/Tkinter.py b/Lib/lib-tk/Tkinter.py
index e825afa..64e9924 100644
--- a/Lib/lib-tk/Tkinter.py
+++ b/Lib/lib-tk/Tkinter.py
@@ -302,14 +302,19 @@ class Variable:
         CBNAME is the name of the callback returned from trace_variable or trace.
         """
         self._tk.call("trace", "vdelete", self._name, mode, cbname)
-        self._tk.deletecommand(cbname)
-        try:
-            self._tclCommands.remove(cbname)
-        except ValueError:
-            pass
+        cbname = self._tk.splitlist(cbname)[0]
+        for m, ca in self.trace_vinfo():
+            if self._tk.splitlist(ca)[0] == cbname:
+                break
+        else:
+            self._tk.deletecommand(cbname)
+            try:
+                self._tclCommands.remove(cbname)
+            except ValueError:
+                pass
     def trace_vinfo(self):
         """Return all trace callback information."""
-        return map(self._tk.split, self._tk.splitlist(
+        return map(self._tk.splitlist, self._tk.splitlist(
             self._tk.call("trace", "vinfo", self._name)))
     def __eq__(self, other):
         """Comparison for equality (==).
diff --git a/Lib/lib-tk/test/test_tkinter/test_variables.py b/Lib/lib-tk/test/test_tkinter/test_variables.py
index 5e07528..11f9414 100644
--- a/Lib/lib-tk/test/test_tkinter/test_variables.py
+++ b/Lib/lib-tk/test/test_tkinter/test_variables.py
@@ -1,5 +1,5 @@
 import unittest
-
+import gc
 from Tkinter import (Variable, StringVar, IntVar, DoubleVar, BooleanVar, Tcl,
                      TclError)
 
@@ -67,6 +67,55 @@ class TestVariable(TestBase):
         with self.assertRaises(ValueError):
             self.root.setvar('var\x00name', "value")
 
+    def test_trace(self):
+        v = Variable(self.root)
+        vname = str(v)
+        trace = []
+        def read_tracer(*args):
+            trace.append(('read',) + args)
+        def write_tracer(*args):
+            trace.append(('write',) + args)
+        cb1 = v.trace_variable('r', read_tracer)
+        cb2 = v.trace_variable('wu', write_tracer)
+        self.assertEqual(sorted(v.trace_vinfo()), [('r', cb1), ('wu', cb2)])
+        self.assertEqual(trace, [])
+
+        v.set('spam')
+        self.assertEqual(trace, [('write', vname, '', 'w')])
+
+        trace = []
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'r')])
+
+        trace = []
+        info = sorted(v.trace_vinfo())
+        v.trace_vdelete('w', cb1)  # Wrong mode
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        with self.assertRaises(TclError):
+            v.trace_vdelete('r', 'spam')  # Wrong command name
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        v.trace_vdelete('r', (cb1, 43)) # Wrong arguments
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'r')])
+
+        trace = []
+        v.trace_vdelete('r', cb1)
+        self.assertEqual(v.trace_vinfo(), [('wu', cb2)])
+        v.get()
+        self.assertEqual(trace, [])
+
+        trace = []
+        del write_tracer
+        gc.collect()
+        v.set('eggs')
+        self.assertEqual(trace, [('write', vname, '', 'w')])
+
+        #trace = []
+        #del v
+        #gc.collect()
+        #self.assertEqual(trace, [('write', vname, '', 'u')])
+
 
 class TestStringVar(TestBase):
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 5344813..8200327 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -13,6 +13,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #22115: Fixed tracing Tkinter variables: trace_vdelete() with wrong
+  mode no longer break tracing, trace_vinfo() now always returns a list of
+  pairs of strings.
+
 - Issue #27079: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().
 
 - Issue #22636: Avoid shell injection problems with