pybind11/tests/test_exceptions.cpp

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/*
tests/test_custom-exceptions.cpp -- exception translation
Copyright (c) 2016 Pim Schellart <P.Schellart@princeton.edu>
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#include "pybind11_tests.h"
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// A type that should be raised as an exception in Python
class MyException : public std::exception {
public:
explicit MyException(const char * m) : message{m} {}
virtual const char * what() const noexcept override {return message.c_str();}
private:
std::string message = "";
};
// A type that should be translated to a standard Python exception
class MyException2 : public std::exception {
public:
explicit MyException2(const char * m) : message{m} {}
virtual const char * what() const noexcept override {return message.c_str();}
private:
std::string message = "";
};
// A type that is not derived from std::exception (and is thus unknown)
class MyException3 {
public:
explicit MyException3(const char * m) : message{m} {}
virtual const char * what() const noexcept {return message.c_str();}
private:
std::string message = "";
};
// A type that should be translated to MyException
// and delegated to its exception translator
class MyException4 : public std::exception {
public:
explicit MyException4(const char * m) : message{m} {}
virtual const char * what() const noexcept override {return message.c_str();}
private:
std::string message = "";
};
// Like the above, but declared via the helper function
class MyException5 : public std::logic_error {
public:
explicit MyException5(const std::string &what) : std::logic_error(what) {}
};
// Inherits from MyException5
class MyException5_1 : public MyException5 {
using MyException5::MyException5;
};
struct PythonCallInDestructor {
PythonCallInDestructor(const py::dict &d) : d(d) {}
~PythonCallInDestructor() { d["good"] = true; }
py::dict d;
};
TEST_SUBMODULE(exceptions, m) {
m.def("throw_std_exception", []() {
throw std::runtime_error("This exception was intentionally thrown.");
});
// make a new custom exception and use it as a translation target
static py::exception<MyException> ex(m, "MyException");
py::register_exception_translator([](std::exception_ptr p) {
try {
if (p) std::rethrow_exception(p);
} catch (const MyException &e) {
// Set MyException as the active python error
ex(e.what());
}
});
// register new translator for MyException2
// no need to store anything here because this type will
// never by visible from Python
py::register_exception_translator([](std::exception_ptr p) {
try {
if (p) std::rethrow_exception(p);
} catch (const MyException2 &e) {
// Translate this exception to a standard RuntimeError
PyErr_SetString(PyExc_RuntimeError, e.what());
}
});
// register new translator for MyException4
// which will catch it and delegate to the previously registered
// translator for MyException by throwing a new exception
py::register_exception_translator([](std::exception_ptr p) {
try {
if (p) std::rethrow_exception(p);
} catch (const MyException4 &e) {
throw MyException(e.what());
}
});
// A simple exception translation:
auto ex5 = py::register_exception<MyException5>(m, "MyException5");
// A slightly more complicated one that declares MyException5_1 as a subclass of MyException5
py::register_exception<MyException5_1>(m, "MyException5_1", ex5.ptr());
m.def("throws1", []() { throw MyException("this error should go to a custom type"); });
m.def("throws2", []() { throw MyException2("this error should go to a standard Python exception"); });
m.def("throws3", []() { throw MyException3("this error cannot be translated"); });
m.def("throws4", []() { throw MyException4("this error is rethrown"); });
m.def("throws5", []() { throw MyException5("this is a helper-defined translated exception"); });
m.def("throws5_1", []() { throw MyException5_1("MyException5 subclass"); });
m.def("throws_logic_error", []() { throw std::logic_error("this error should fall through to the standard handler"); });
m.def("throws_overflow_error", []() {throw std::overflow_error(""); });
m.def("exception_matches", []() {
py::dict foo;
try {
// Assign to a py::object to force read access of nonexistent dict entry
py::object o = foo["bar"];
}
catch (py::error_already_set& ex) {
Simplify error_already_set `error_already_set` is more complicated than it needs to be, partly because it manages reference counts itself rather than using `py::object`, and partly because it tries to do more exception clearing than is needed. This commit greatly simplifies it, and fixes #927. Using `py::object` instead of `PyObject *` means we can rely on implicit copy/move constructors. The current logic did both a `PyErr_Clear` on deletion *and* a `PyErr_Fetch` on creation. I can't see how the `PyErr_Clear` on deletion is ever useful: the `Fetch` on creation itself clears the error, so the only way doing a `PyErr_Clear` on deletion could do anything if is some *other* exception was raised while the `error_already_set` object was alive--but in that case, clearing some other exception seems wrong. (Code that is worried about an exception handler raising another exception would already catch a second `error_already_set` from exception code). The destructor itself called `clear()`, but `clear()` was a little bit more paranoid that needed: it called `restore()` to restore the currently captured error, but then immediately cleared it, using the `PyErr_Restore` to release the references. That's unnecessary: it's valid for us to release the references manually. This updates the code to simply release the references on the three objects (preserving the gil acquire). `clear()`, however, also had the side effect of clearing the current error, even if the current `error_already_set` didn't have a current error (e.g. because of a previous `restore()` or `clear()` call). I don't really see how clearing the error here can ever actually be useful: the only way the current error could be set is if you called `restore()` (in which case the current stored error-related members have already been released), or if some *other* code raised the error, in which case `clear()` on *this* object is clearing an error for which it shouldn't be responsible. Neither of those seem like intentional or desirable features, and manually requesting deletion of the stored references similarly seems pointless, so I've just made `clear()` an empty method and marked it deprecated. This also fixes a minor potential issue with the destruction: it is technically possible for `value` to be null (though this seems likely to be rare in practice); this updates the check to look at `type` which will always be non-null for a `Fetch`ed exception. This also adds error_already_set round-trip throw tests to the test suite.
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if (!ex.matches(PyExc_KeyError)) throw;
return true;
}
return false;
});
m.def("exception_matches_base", []() {
py::dict foo;
try {
// Assign to a py::object to force read access of nonexistent dict entry
py::object o = foo["bar"];
}
catch (py::error_already_set &ex) {
if (!ex.matches(PyExc_Exception)) throw;
return true;
}
return false;
});
m.def("modulenotfound_exception_matches_base", []() {
try {
// On Python >= 3.6, this raises a ModuleNotFoundError, a subclass of ImportError
py::module::import("nonexistent");
}
catch (py::error_already_set &ex) {
if (!ex.matches(PyExc_ImportError)) throw;
return true;
}
return false;
});
m.def("throw_already_set", [](bool err) {
if (err)
PyErr_SetString(PyExc_ValueError, "foo");
try {
throw py::error_already_set();
} catch (const std::runtime_error& e) {
if ((err && e.what() != std::string("ValueError: foo")) ||
(!err && e.what() != std::string("Unknown internal error occurred")))
{
PyErr_Clear();
throw std::runtime_error("error message mismatch");
}
}
PyErr_Clear();
if (err)
PyErr_SetString(PyExc_ValueError, "foo");
throw py::error_already_set();
});
m.def("python_call_in_destructor", [](py::dict d) {
try {
PythonCallInDestructor set_dict_in_destructor(d);
PyErr_SetString(PyExc_ValueError, "foo");
throw py::error_already_set();
} catch (const py::error_already_set&) {
return true;
}
return false;
});
Simplify error_already_set `error_already_set` is more complicated than it needs to be, partly because it manages reference counts itself rather than using `py::object`, and partly because it tries to do more exception clearing than is needed. This commit greatly simplifies it, and fixes #927. Using `py::object` instead of `PyObject *` means we can rely on implicit copy/move constructors. The current logic did both a `PyErr_Clear` on deletion *and* a `PyErr_Fetch` on creation. I can't see how the `PyErr_Clear` on deletion is ever useful: the `Fetch` on creation itself clears the error, so the only way doing a `PyErr_Clear` on deletion could do anything if is some *other* exception was raised while the `error_already_set` object was alive--but in that case, clearing some other exception seems wrong. (Code that is worried about an exception handler raising another exception would already catch a second `error_already_set` from exception code). The destructor itself called `clear()`, but `clear()` was a little bit more paranoid that needed: it called `restore()` to restore the currently captured error, but then immediately cleared it, using the `PyErr_Restore` to release the references. That's unnecessary: it's valid for us to release the references manually. This updates the code to simply release the references on the three objects (preserving the gil acquire). `clear()`, however, also had the side effect of clearing the current error, even if the current `error_already_set` didn't have a current error (e.g. because of a previous `restore()` or `clear()` call). I don't really see how clearing the error here can ever actually be useful: the only way the current error could be set is if you called `restore()` (in which case the current stored error-related members have already been released), or if some *other* code raised the error, in which case `clear()` on *this* object is clearing an error for which it shouldn't be responsible. Neither of those seem like intentional or desirable features, and manually requesting deletion of the stored references similarly seems pointless, so I've just made `clear()` an empty method and marked it deprecated. This also fixes a minor potential issue with the destruction: it is technically possible for `value` to be null (though this seems likely to be rare in practice); this updates the check to look at `type` which will always be non-null for a `Fetch`ed exception. This also adds error_already_set round-trip throw tests to the test suite.
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// test_nested_throws
m.def("try_catch", [m](py::object exc_type, py::function f, py::args args) {
try { f(*args); }
catch (py::error_already_set &ex) {
if (ex.matches(exc_type))
py::print(ex.what());
else
throw;
}
});
}