pythongh-103791: handle BaseExceptionGroup in contextlib.suppress() (python#111910)

Author: Zac-HD

Doc/library/contextlib.rst

@@ -304,15 +304,15 @@ Functions and classes provided:
 
  This context manager is :ref:`reentrant <reentrant-cms>`.
 
- If the code within the :keyword:`!with` block raises an
- :exc:`ExceptionGroup`, suppressed exceptions are removed from the
+ If the code within the :keyword:`!with` block raises a
+ :exc:`BaseExceptionGroup`, suppressed exceptions are removed from the
  group. If any exceptions in the group are not suppressed, a group containing them is re-raised.
 
  .. versionadded:: 3.4
 
  .. versionchanged:: 3.12
  ``suppress`` now supports suppressing exceptions raised as
- part of an :exc:`ExceptionGroup`.
+ part of an :exc:`BaseExceptionGroup`.
 
 .. function:: redirect_stdout(new_target)
 

Lib/contextlib.py

@@ -461,7 +461,7 @@ def __exit__(self, exctype, excinst, exctb):
  return
  if issubclass(exctype, self._exceptions):
  return True
- if issubclass(exctype, ExceptionGroup):
+ if issubclass(exctype, BaseExceptionGroup):
  match, rest = excinst.split(self._exceptions)
  if rest is None:
  return True

Lib/test/test_contextlib.py

@@ -1297,6 +1297,24 @@ def test_exception_groups(self):
  [KeyError("ke1"), KeyError("ke2")],
  ),
  )
+ # Check handling of BaseExceptionGroup, using GeneratorExit so that
+ # we don't accidentally discard a ctrl-c with KeyboardInterrupt.
+ with suppress(GeneratorExit):
+ raise BaseExceptionGroup("message", [GeneratorExit()])
+ # If we raise a BaseException group, we can still suppress parts
+ with self.assertRaises(BaseExceptionGroup) as eg1:
+ with suppress(KeyError):
+ raise BaseExceptionGroup("message", [GeneratorExit("g"), KeyError("k")])
+ self.assertExceptionIsLike(
+ eg1.exception, BaseExceptionGroup("message", [GeneratorExit("g")]),
+ )
+ # If we suppress all the leaf BaseExceptions, we get a non-base ExceptionGroup
+ with self.assertRaises(ExceptionGroup) as eg1:
+ with suppress(GeneratorExit):
+ raise BaseExceptionGroup("message", [GeneratorExit("g"), KeyError("k")])
+ self.assertExceptionIsLike(
+ eg1.exception, ExceptionGroup("message", [KeyError("k")]),
+ )
 
 
 class TestChdir(unittest.TestCase):

Misc/NEWS.d/next/Library/2023-11-09-10-45-56.gh-issue-103791.sdfkja.rst

@@ -0,0 +1,3 @@
+:class:`contextlib.suppress` now supports suppressing exceptions raised as
+part of a :exc:`BaseExceptionGroup`, in addition to the recent support for
+:exc:`ExceptionGroup`.