Method _expect_state

lib/sqlalchemy/orm/state_changes.py:174–196

called within a method that changes states. method must also use the ``@declare_states()`` decorator.

(self, expected: _StateChangeState)

    @contextlib.contextmanager
    def _expect_state(self, expected: _StateChangeState) -> Iterator[Any]:
        """called within a method that changes states.

        method must also use the ``@declare_states()`` decorator.

        """
        assert self._next_state is _StateChangeStates.CHANGE_IN_PROGRESS, (
            "Unexpected call to _expect_state outside of "
            "state-changing method"
        )

        self._next_state = expected
        try:
            yield
        except:
            raise
        else:
            if self._state is not expected:
                raise sa_exc.IllegalStateChangeError(
                    f"Unexpected state change to {self._state!r}", code="isce"
                )
        finally:
            self._next_state = _StateChangeStates.CHANGE_IN_PROGRESS