Fixed bare raise in a handler not raising an exception group

Author: agronholm

CHANGES.rst

@@ -8,6 +8,9 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
 - Added special monkeypatching if `Apport <https://github.com/canonical/apport>`_ has
   overridden ``sys.excepthook`` so it will format exception groups correctly
   (PR by John Litborn)
+- Fixed bare ``raise`` in a handler reraising the original naked exception rather than
+  an exception group which is what is raised when you do a ``raise`` in an ``except*``
+  handler
 
 **1.1.3**
 

src/exceptiongroup/_catch.py

@@ -64,7 +64,10 @@ def handle_exception(self, exc: BaseException) -> BaseException | None:
                     except BaseExceptionGroup:
                         result = handler(matched)
                 except BaseExceptionGroup as new_exc:
-                    new_exceptions.extend(new_exc.exceptions)
+                    if new_exc is matched:
+                        new_exceptions.append(new_exc)
+                    else:
+                        new_exceptions.extend(new_exc.exceptions)
                 except BaseException as new_exc:
                     new_exceptions.append(new_exc)
                 else:

tests/test_catch.py

@@ -208,3 +208,15 @@ def delegate(eg):
     with pytest.raises(TypeError, match="Exception handler must be a sync function."):
         with catch({TypeError: delegate}):
             raise ExceptionGroup("message", [TypeError("uh-oh")])
+
+
+def test_bare_reraise_from_naked_exception():
+    def handler(eg):
+        raise
+
+    with pytest.raises(ExceptionGroup) as excgrp, catch({Exception: handler}):
+        raise KeyError("foo")
+
+    assert len(excgrp.value.exceptions) == 1
+    assert isinstance(excgrp.value.exceptions[0], KeyError)
+    assert str(excgrp.value.exceptions[0]) == "'foo'"

tests/test_catch_py311.py

@@ -176,3 +176,15 @@ def test_bare_raise_in_handler():
     assert excgrp.value is not middle_exc
     assert excgrp.value.__cause__ is first_exc
     assert excgrp.value.__context__ is first_exc
+
+
+def test_bare_reraise_from_naked_exception():
+    with pytest.raises(ExceptionGroup) as excgrp:
+        try:
+            raise KeyError("foo")
+        except* KeyError:
+            raise
+
+    assert len(excgrp.value.exceptions) == 1
+    assert isinstance(excgrp.value.exceptions[0], KeyError)
+    assert str(excgrp.value.exceptions[0]) == "'foo'"