Store Sentinel parameters in reduce method

Additional data stored as a dict to ensure backwards and forwards compatibility

Author: HexDecimal

src/typing_extensions.py

@@ -4158,10 +4158,15 @@ def evaluate_forward_ref(
 
 _sentinel_registry = {}
 
-def _unpickle_fetch_sentinel(name: str, module_name: str):
-    """Stable Sentinel unpickling function, fetch Sentinel at 'module_name.name'."""
+def _unpickle_sentinel(
+    name: str,
+    module_name: str,
+    config: typing.Dict[str, typing.Any],
+    /,
+):
+    """Stable Sentinel unpickling function, get Sentinel at 'module_name.name'."""
     # Explicit repr=name because a saved module_name is known to be valid
-    return Sentinel(name, module_name, repr=name)
+    return Sentinel(name, module_name, repr=config.get("repr", name))
 
 class Sentinel:
     """A sentinel object.
@@ -4258,13 +4263,15 @@ def __ror__(self, other):
             return typing.Union[other, self]
 
     def __reduce__(self):
-        """Record where this sentinel is defined."""
+        """Record where this sentinel is defined and its current parameters."""
+        config = {"repr": self._repr}
         # Reduce callable must be at the top-level to be stable whenever Sentinel changes
         return (
-            _unpickle_fetch_sentinel,
-            (  # Only the location of the sentinel needs to be stored
+            _unpickle_sentinel,
+            (
                 self._name,
                 self._module_name,
+                config,
             ),
         )