1  from __future__ import annotations
   2  
   3  import sys
   4  from contextlib import AbstractContextManager
   5  from types import TracebackType
   6  from typing import TYPE_CHECKING, Optional, Type, cast
   7  
   8  if sys.version_info < (3, 11):
   9      from ._exceptions import BaseExceptionGroup
  10  
  11  if TYPE_CHECKING:
  12      # requires python 3.9
  13      BaseClass = AbstractContextManager[None]
  14  else:
  15      BaseClass = AbstractContextManager
  16  
  17  
  18  class suppress(BaseClass):
  19      """Backport of :class:`contextlib.suppress` from Python 3.12.1."""
  20  
  21      def __init__(self, *exceptions: type[BaseException]):
  22          self._exceptions = exceptions
  23  
  24      def __enter__(self) -> None:
  25          pass
  26  
  27      def __exit__(
  28          self,
  29          exctype: Optional[Type[BaseException]],
  30          excinst: Optional[BaseException],
  31          exctb: Optional[TracebackType],
  32      ) -> bool:
  33          # Unlike isinstance and issubclass, CPython exception handling
  34          # currently only looks at the concrete type hierarchy (ignoring
  35          # the instance and subclass checking hooks). While Guido considers
  36          # that a bug rather than a feature, it's a fairly hard one to fix
  37          # due to various internal implementation details. suppress provides
  38          # the simpler issubclass based semantics, rather than trying to
  39          # exactly reproduce the limitations of the CPython interpreter.
  40          #
  41          # See http://bugs.python.org/issue12029 for more details
  42          if exctype is None:
  43              return False
  44  
  45          if issubclass(exctype, self._exceptions):
  46              return True
  47  
  48          if issubclass(exctype, BaseExceptionGroup):
  49              match, rest = cast(BaseExceptionGroup, excinst).split(self._exceptions)
  50              if rest is None:
  51                  return True
  52  
  53              raise rest
  54  
  55          return False
  56