- debugger.py: use Watches.remove and .add to update an edited expres…

…sion

pudb/debugger.py

@@ -1166,7 +1166,11 @@ def edit_inspector_detail(w, size, key):
                     iinfo.access_level = "all"
 
                 if var.watch_expr is not None:
-                    var.watch_expr.expression = watch_edit.get_edit_text()
+                    # Remove old expression and add new one, to avoid rehashing
+                    Watches.remove(var.watch_expr)
+                    var.watch_expr = WatchExpression(
+                        watch_edit.get_edit_text())
+                    Watches.add(var.watch_expr)
 
             elif result == "del":
                 # Remove saved expression

pudb/test/test_var_view.py

@@ -5,6 +5,8 @@
 
 from unittest.mock import patch, mock_open
 
+import pytest
+
 from pudb.var_view import (
     STRINGIFIERS,
     BasicValueWalker,
@@ -473,6 +475,12 @@ def test_set(self):
         test_set2.add(WatchExpression("a"))
         self.assertEqual(test_set1, test_set2)
 
+    def test_immutability(self):
+        Watches.clear()
+        we_a = WatchExpression("a")
+        with pytest.raises(AttributeError):
+            we_a.expression = "b"
+
 
 class WatchesTests(unittest.TestCase):
     """