tests/test_exceptions.py

import pytest

from pybind11_tests import exceptions as m


def test_std_exception(msg):
    with pytest.raises(RuntimeError) as excinfo:
        m.throw_std_exception()
    assert msg(excinfo.value) == "This exception was intentionally thrown."


def test_error_already_set(msg):
    with pytest.raises(RuntimeError) as excinfo:
        m.throw_already_set(False)
    assert msg(excinfo.value) == "Unknown internal error occurred"

    with pytest.raises(ValueError) as excinfo:
        m.throw_already_set(True)
    assert msg(excinfo.value) == "foo"


def test_python_call_in_catch():
    d = {}
    assert m.python_call_in_destructor(d) is True
    assert d["good"] is True


def test_exception_matches():
    m.exception_matches()


def test_custom(msg):
    # Can we catch a MyException?
    with pytest.raises(m.MyException) as excinfo:
        m.throws1()
    assert msg(excinfo.value) == "this error should go to a custom type"

    # Can we translate to standard Python exceptions?
    with pytest.raises(RuntimeError) as excinfo:
        m.throws2()
    assert msg(excinfo.value) == "this error should go to a standard Python exception"

    # Can we handle unknown exceptions?
    with pytest.raises(RuntimeError) as excinfo:
        m.throws3()
    assert msg(excinfo.value) == "Caught an unknown exception!"

    # Can we delegate to another handler by rethrowing?
    with pytest.raises(m.MyException) as excinfo:
        m.throws4()
    assert msg(excinfo.value) == "this error is rethrown"

    # Can we fall-through to the default handler?
    with pytest.raises(RuntimeError) as excinfo:
        m.throws_logic_error()
    assert msg(excinfo.value) == "this error should fall through to the standard handler"

    # Can we handle a helper-declared exception?
    with pytest.raises(m.MyException5) as excinfo:
        m.throws5()
    assert msg(excinfo.value) == "this is a helper-defined translated exception"

    # Exception subclassing:
    with pytest.raises(m.MyException5) as excinfo:
        m.throws5_1()
    assert msg(excinfo.value) == "MyException5 subclass"
    assert isinstance(excinfo.value, m.MyException5_1)

    with pytest.raises(m.MyException5_1) as excinfo:
        m.throws5_1()
    assert msg(excinfo.value) == "MyException5 subclass"

    with pytest.raises(m.MyException5) as excinfo:
        try:
            m.throws5()
        except m.MyException5_1:
            raise RuntimeError("Exception error: caught child from parent")
    assert msg(excinfo.value) == "this is a helper-defined translated exception"


def test_nested_throws(capture):
    """Tests nested (e.g. C++ -> Python -> C++) exception handling"""

    def throw_myex():
        raise m.MyException("nested error")

    def throw_myex5():
        raise m.MyException5("nested error 5")

    # In the comments below, the exception is caught in the first step, thrown in the last step

    # C++ -> Python
    with capture:
        m.try_catch(m.MyException5, throw_myex5)
    assert str(capture).startswith("MyException5: nested error 5")

    # Python -> C++ -> Python
    with pytest.raises(m.MyException) as excinfo:
        m.try_catch(m.MyException5, throw_myex)
    assert str(excinfo.value) == "nested error"

    def pycatch(exctype, f, *args):
        try:
            f(*args)
        except m.MyException as e:
            print(e)

    # C++ -> Python -> C++ -> Python
    with capture:
        m.try_catch(
            m.MyException5, pycatch, m.MyException, m.try_catch, m.MyException, throw_myex5)
    assert str(capture).startswith("MyException5: nested error 5")

    # C++ -> Python -> C++
    with capture:
        m.try_catch(m.MyException, pycatch, m.MyException5, m.throws4)
    assert capture == "this error is rethrown"

    # Python -> C++ -> Python -> C++
    with pytest.raises(m.MyException5) as excinfo:
        m.try_catch(m.MyException, pycatch, m.MyException, m.throws5)
    assert str(excinfo.value) == "this is a helper-defined translated exception"