[3.9] bpo-42248: [Enum] ensure exceptions raised in ``_missing_`` are released (GH-25350). (GH-25370)

(cherry picked from commit 8c14f5a787b21d5a1eae5d5ee981431d1c0e055f)

Co-authored-by: Ethan Furman <ethan@stoneleaf.us>

1 files changed, 18 insertions, 13 deletions

diff --git a/Lib/enum.py b/Lib/enum.py
index 1fddb1c..be74796 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -669,19 +669,24 @@ class Enum(metaclass=EnumMeta):
         except Exception as e:
             exc = e
             result = None
-        if isinstance(result, cls):
-            return result
-        else:
-            ve_exc = ValueError("%r is not a valid %s" % (value, cls.__qualname__))
-            if result is None and exc is None:
-                raise ve_exc
-            elif exc is None:
-                exc = TypeError(
-                        'error in %s._missing_: returned %r instead of None or a valid member'
-                        % (cls.__name__, result)
-                        )
-            exc.__context__ = ve_exc
-            raise exc
+        try:
+            if isinstance(result, cls):
+                return result
+            else:
+                ve_exc = ValueError("%r is not a valid %s" % (value, cls.__qualname__))
+                if result is None and exc is None:
+                    raise ve_exc
+                elif exc is None:
+                    exc = TypeError(
+                            'error in %s._missing_: returned %r instead of None or a valid member'
+                            % (cls.__name__, result)
+                            )
+                exc.__context__ = ve_exc
+                raise exc
+        finally:
+            # ensure all variables that could hold an exception are destroyed
+            exc = None
+            ve_exc = None
 
     def _generate_next_value_(name, start, count, last_values):
         """