# mod.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pyo3-0.13.2/src/err/mod.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright (c) 2017-present PyO3 Project and Contributors

    use crate::panic::PanicException;
    use crate::type_object::PyTypeObject;
    use crate::types::PyType;
    use crate::{
        exceptions::{self, PyBaseException},
        ffi,
    };
    use crate::{
        AsPyPointer, FromPyPointer, IntoPy, Py, PyAny, PyNativeType, PyObject, Python,
        ToBorrowedObject, ToPyObject,
    };
    use std::borrow::Cow;
    use std::cell::UnsafeCell;
    use std::ffi::CString;
    use std::os::raw::c_char;
    use std::os::raw::c_int;
    use std::ptr::NonNull;

    mod err_state;
    mod impls;

    pub use err_state::PyErrArguments;
    use err_state::{boxed_args, PyErrState, PyErrStateNormalized};

    /// Represents a Python exception that was raised.
    pub struct PyErr {
        // Safety: can only hand out references when in the "normalized" state. Will never change
        // after normalization.
        //
        // The state is temporarily removed from the PyErr during normalization, to avoid
        // concurrent modifications.
        state: UnsafeCell<Option<PyErrState>>,
    }

    unsafe impl Send for PyErr {}
    unsafe impl Sync for PyErr {}

    /// Represents the result of a Python call.
    pub type PyResult<T> = Result<T, PyErr>;

    /// Error that indicates a failure to convert a PyAny to a more specific Python type.
    #[derive(Debug)]
    pub struct PyDowncastError<'a> {
        from: &'a PyAny,
        to: Cow<'static, str>,
    }

    impl<'a> PyDowncastError<'a> {
        pub fn new(from: &'a PyAny, to: impl Into<Cow<'static, str>>) -> Self {
            PyDowncastError {
                from,
                to: to.into(),
            }
        }
    }

    impl PyErr {
        /// Creates a new PyErr of type `T`.
        ///
        /// `value` can be:
        /// * a tuple: the exception instance will be created using Python `T(*tuple)`
        /// * any other value: the exception instance will be created using Python `T(value)`
        ///
        /// Note: if `value` is not `Send` or `Sync`, consider using `PyErr::from_instance` instead.
        ///
        /// Panics if `T` is not a Python class derived from `BaseException`.
        ///
        /// Example:
        /// ```ignore
        /// return Err(PyErr::new::<exceptions::PyTypeError, _>("Error message"));
        /// ```
        ///
        /// In most cases, you can use a concrete exception's constructor instead, which is equivalent:
        /// ```ignore
        /// return Err(exceptions::PyTypeError::new_err("Error message"));
        /// ```
        pub fn new<T, A>(args: A) -> PyErr
        where
            T: PyTypeObject,
            A: PyErrArguments + Send + Sync + 'static,
        {
            Python::with_gil(|py| PyErr::from_type(T::type_object(py), args))
        }

        /// Constructs a new error, with the usual lazy initialization of Python exceptions.
        ///
        /// `exc` is the exception type; usually one of the standard exceptions
        /// like `exceptions::PyRuntimeError`.
        /// `args` is the a tuple of arguments to pass to the exception constructor.
        pub fn from_type<A>(ty: &PyType, args: A) -> PyErr
        where
            A: PyErrArguments + Send + Sync + 'static,
        {
            if unsafe { ffi::PyExceptionClass_Check(ty.as_ptr()) } == 0 {
                return exceptions_must_derive_from_base_exception(ty.py());
            }

            PyErr::from_state(PyErrState::Lazy {
                ptype: ty.into(),
                pvalue: boxed_args(args),
            })
        }

        /// Creates a new PyErr.
        ///
        /// `obj` must be an Python exception instance, the PyErr will use that instance.
        /// If `obj` is a Python exception type object, the PyErr will (lazily) create a new
        /// instance of that type.
        /// Otherwise, a `TypeError` is created instead.
        ///
        /// # Example
        /// ```rust
        /// use pyo3::{Python, PyErr, IntoPy, exceptions::PyTypeError, types::PyType};
        /// Python::with_gil(|py| {
        ///     // Case #1: Exception instance
        ///     let err = PyErr::from_instance(PyTypeError::new_err("some type error",).instance(py));
        ///     assert_eq!(err.to_string(), "TypeError: some type error");
        ///
        ///     // Case #2: Exception type
        ///     let err = PyErr::from_instance(PyType::new::<PyTypeError>(py));
        ///     assert_eq!(err.to_string(), "TypeError: ");
        ///
        ///     // Case #3: Invalid exception value
        ///     let err = PyErr::from_instance("foo".into_py(py).as_ref(py));
        ///     assert_eq!(err.to_string(), "TypeError: exceptions must derive from BaseException");
        /// });
        /// ```
        pub fn from_instance(obj: &PyAny) -> PyErr {
            let ptr = obj.as_ptr();

            let state = if unsafe { ffi::PyExceptionInstance_Check(ptr) } != 0 {
                PyErrState::Normalized(PyErrStateNormalized {
                    ptype: unsafe {
                        Py::from_borrowed_ptr(obj.py(), ffi::PyExceptionInstance_Class(ptr))
                    },
                    pvalue: unsafe { Py::from_borrowed_ptr(obj.py(), obj.as_ptr()) },
                    ptraceback: None,
                })
            } else if unsafe { ffi::PyExceptionClass_Check(obj.as_ptr()) } != 0 {
                PyErrState::FfiTuple {
                    ptype: unsafe { Some(Py::from_borrowed_ptr(obj.py(), ptr)) },
                    pvalue: None,
                    ptraceback: None,
                }
            } else {
                return exceptions_must_derive_from_base_exception(obj.py());
            };

            PyErr::from_state(state)
        }

        /// Get the type of this exception object.
        ///
        /// The object will be normalized first if needed.
        ///
        /// # Example
        /// ```rust
        /// use pyo3::{Python, PyErr, exceptions::PyTypeError, types::PyType};
        /// Python::with_gil(|py| {
        ///     let err = PyTypeError::new_err(("some type error",));
        ///     assert_eq!(err.ptype(py), PyType::new::<PyTypeError>(py));
        /// });
        /// ```
        pub fn ptype<'py>(&'py self, py: Python<'py>) -> &'py PyType {
            self.normalized(py).ptype.as_ref(py)
        }

        /// Get the value of this exception object.
        ///
        /// The object will be normalized first if needed.
        ///
        /// # Example
        /// ```rust
        /// use pyo3::{Python, PyErr, exceptions::PyTypeError, types::PyType};
        /// Python::with_gil(|py| {
        ///     let err = PyTypeError::new_err(("some type error",));
        ///     assert!(err.is_instance::<PyTypeError>(py));
        ///     assert_eq!(err.pvalue(py).to_string(), "some type error");
        /// });
        /// ```
        pub fn pvalue<'py>(&'py self, py: Python<'py>) -> &'py PyBaseException {
            self.normalized(py).pvalue.as_ref(py)
        }

        /// Get the value of this exception object.
        ///
        /// The object will be normalized first if needed.
        ///
        /// # Example
        /// ```rust
        /// use pyo3::{Python, PyErr, exceptions::PyTypeError, types::PyType};
        /// Python::with_gil(|py| {
        ///     let err = PyTypeError::new_err(("some type error",));
        ///     assert_eq!(err.ptraceback(py), None);
        /// });
        /// ```
        pub fn ptraceback<'py>(&'py self, py: Python<'py>) -> Option<&'py PyAny> {
            self.normalized(py)
                .ptraceback
                .as_ref()
                .map(|obj| obj.as_ref(py))
        }

        /// Gets whether an error is present in the Python interpreter's global state.
        #[inline]
        pub fn occurred(_: Python) -> bool {
            unsafe { !ffi::PyErr_Occurred().is_null() }
        }

        /// Retrieves the current error from the Python interpreter's global state.
        ///
        /// The error is cleared from the Python interpreter.
        /// If no error is set, returns a `SystemError`.
        ///
        /// If the error fetched is a `PanicException` (which would have originated from a panic in a
        /// pyo3 callback) then this function will resume the panic.
        pub fn fetch(py: Python) -> PyErr {
            unsafe {
                let mut ptype: *mut ffi::PyObject = std::ptr::null_mut();
                let mut pvalue: *mut ffi::PyObject = std::ptr::null_mut();
                let mut ptraceback: *mut ffi::PyObject = std::ptr::null_mut();
                ffi::PyErr_Fetch(&mut ptype, &mut pvalue, &mut ptraceback);

                let err = PyErr::new_from_ffi_tuple(py, ptype, pvalue, ptraceback);

                if ptype == PanicException::type_object(py).as_ptr() {
                    let msg: String = PyAny::from_borrowed_ptr_or_opt(py, pvalue)
                        .and_then(|obj| obj.extract().ok())
                        .unwrap_or_else(|| String::from("Unwrapped panic from Python code"));

                    eprintln!(
                        "--- PyO3 is resuming a panic after fetching a PanicException from Python. ---"
                    );
                    eprintln!("Python stack trace below:");
                    err.print(py);

                    std::panic::resume_unwind(Box::new(msg))
                }

                err
            }
        }

        /// Creates a new exception type with the given name, which must be of the form
        /// `<module>.<ExceptionName>`, as required by `PyErr_NewException`.
        ///
        /// `base` can be an existing exception type to subclass, or a tuple of classes
        /// `dict` specifies an optional dictionary of class variables and methods
        pub fn new_type<'p>(
            _: Python<'p>,
            name: &str,
            base: Option<&PyType>,
            dict: Option<PyObject>,
        ) -> NonNull<ffi::PyTypeObject> {
            let base: *mut ffi::PyObject = match base {
                None => std::ptr::null_mut(),
                Some(obj) => obj.as_ptr(),
            };

            let dict: *mut ffi::PyObject = match dict {
                None => std::ptr::null_mut(),
                Some(obj) => obj.as_ptr(),
            };

            unsafe {
                let null_terminated_name =
                    CString::new(name).expect("Failed to initialize nul terminated exception name");

                NonNull::new_unchecked(ffi::PyErr_NewException(
                    null_terminated_name.as_ptr() as *mut c_char,
                    base,
                    dict,
                ) as *mut ffi::PyTypeObject)
            }
        }

        /// Create a PyErr from an ffi tuple
        ///
        /// # Safety
        /// - `ptype` must be a pointer to valid Python exception type object.
        /// - `pvalue` must be a pointer to a valid Python object, or NULL.
        /// - `ptraceback` must be a pointer to a valid Python traceback object, or NULL.
        unsafe fn new_from_ffi_tuple(
            py: Python,
            ptype: *mut ffi::PyObject,
            pvalue: *mut ffi::PyObject,
            ptraceback: *mut ffi::PyObject,
        ) -> PyErr {
            // Note: must not panic to ensure all owned pointers get acquired correctly,
            // and because we mustn't panic in normalize().
            PyErr::from_state(PyErrState::FfiTuple {
                ptype: Py::from_owned_ptr_or_opt(py, ptype),
                pvalue: Py::from_owned_ptr_or_opt(py, pvalue),
                ptraceback: Py::from_owned_ptr_or_opt(py, ptraceback),
            })
        }

        /// Prints a standard traceback to `sys.stderr`.
        pub fn print(&self, py: Python) {
            self.clone_ref(py).restore(py);
            unsafe { ffi::PyErr_PrintEx(0) }
        }

        /// Prints a standard traceback to `sys.stderr`, and sets
        /// `sys.last_{type,value,traceback}` attributes to this exception's data.
        pub fn print_and_set_sys_last_vars(&self, py: Python) {
            self.clone_ref(py).restore(py);
            unsafe { ffi::PyErr_PrintEx(1) }
        }

        /// Returns true if the current exception matches the exception in `exc`.
        ///
        /// If `exc` is a class object, this also returns `true` when `self` is an instance of a subclass.
        /// If `exc` is a tuple, all exceptions in the tuple (and recursively in subtuples) are searched for a match.
        pub fn matches<T>(&self, py: Python, exc: T) -> bool
        where
            T: ToBorrowedObject,
        {
            exc.with_borrowed_ptr(py, |exc| unsafe {
                ffi::PyErr_GivenExceptionMatches(self.ptype_ptr(), exc) != 0
            })
        }

        /// Returns true if the current exception is instance of `T`.
        pub fn is_instance<T>(&self, py: Python) -> bool
        where
            T: PyTypeObject,
        {
            unsafe {
                ffi::PyErr_GivenExceptionMatches(self.ptype_ptr(), T::type_object(py).as_ptr()) != 0
            }
        }

        /// Retrieves the exception instance for this error.
        pub fn instance<'py>(&'py self, py: Python<'py>) -> &'py PyBaseException {
            self.normalized(py).pvalue.as_ref(py)
        }

        /// Consumes self to take ownership of the exception instance for this error.
        pub fn into_instance(self, py: Python) -> Py<PyBaseException> {
            let out = self.normalized(py).pvalue.as_ref(py).into();
            std::mem::forget(self);
            out
        }

        /// Writes the error back to the Python interpreter's global state.
        /// This is the opposite of `PyErr::fetch()`.
        #[inline]
        pub fn restore(self, py: Python) {
            let (ptype, pvalue, ptraceback) = self
                .state
                .into_inner()
                .expect("Cannot restore a PyErr while normalizing it")
                .into_ffi_tuple(py);
            unsafe { ffi::PyErr_Restore(ptype, pvalue, ptraceback) }
        }

        /// Issues a warning message.
        /// May return a `PyErr` if warnings-as-errors is enabled.
        pub fn warn(py: Python, category: &PyAny, message: &str, stacklevel: i32) -> PyResult<()> {
            let message = CString::new(message)?;
            unsafe {
                error_on_minusone(
                    py,
                    ffi::PyErr_WarnEx(
                        category.as_ptr(),
                        message.as_ptr(),
                        stacklevel as ffi::Py_ssize_t,
                    ),
                )
            }
        }

        /// Clone the PyErr. This requires the GIL, which is why PyErr does not implement Clone.
        ///
        /// # Example
        /// ```rust
        /// use pyo3::{Python, PyErr, exceptions::PyTypeError, types::PyType};
        /// Python::with_gil(|py| {
        ///     let err = PyTypeError::new_err(("some type error",));
        ///     let err_clone = err.clone_ref(py);
        ///     assert_eq!(err.ptype(py), err_clone.ptype(py));
        ///     assert_eq!(err.pvalue(py), err_clone.pvalue(py));
        ///     assert_eq!(err.ptraceback(py), err_clone.ptraceback(py));
        /// });
        /// ```
        pub fn clone_ref(&self, py: Python) -> PyErr {
            PyErr::from_state(PyErrState::Normalized(self.normalized(py).clone()))
        }

        fn from_state(state: PyErrState) -> PyErr {
            PyErr {
                state: UnsafeCell::new(Some(state)),
            }
        }

        /// Returns borrowed reference to this Err's type
        fn ptype_ptr(&self) -> *mut ffi::PyObject {
            match unsafe { &*self.state.get() } {
                Some(PyErrState::Lazy { ptype, .. }) => ptype.as_ptr(),
                Some(PyErrState::FfiTuple { ptype, .. }) => ptype.as_ptr(),
                Some(PyErrState::Normalized(n)) => n.ptype.as_ptr(),
                None => panic!("Cannot access exception type while normalizing"),
            }
        }

        fn normalized(&self, py: Python) -> &PyErrStateNormalized {
            // This process is safe because:
            // - Access is guaranteed not to be concurrent thanks to `Python` GIL token
            // - Write happens only once, and then never will change again.
            // - State is set to None during the normalization process, so that a second
            //   concurrent normalization attempt will panic before changing anything.

            if let Some(PyErrState::Normalized(n)) = unsafe { &*self.state.get() } {
                return n;
            }

            let state = unsafe {
                (*self.state.get())
                    .take()
                    .expect("Cannot normalize a PyErr while already normalizing it.")
            };
            let (mut ptype, mut pvalue, mut ptraceback) = state.into_ffi_tuple(py);

            unsafe {
                ffi::PyErr_NormalizeException(&mut ptype, &mut pvalue, &mut ptraceback);
                let self_state = &mut *self.state.get();
                *self_state = Some(PyErrState::Normalized(PyErrStateNormalized {
                    ptype: Py::from_owned_ptr_or_opt(py, ptype)
                        .unwrap_or_else(|| exceptions::PySystemError::type_object(py).into()),
                    pvalue: Py::from_owned_ptr_or_opt(py, pvalue).unwrap_or_else(|| {
                        exceptions::PySystemError::new_err("Exception value missing")
                            .instance(py)
                            .into_py(py)
                    }),
                    ptraceback: PyObject::from_owned_ptr_or_opt(py, ptraceback),
                }));

                match self_state {
                    Some(PyErrState::Normalized(n)) => n,
                    _ => unreachable!(),
                }
            }
        }
    }

    impl std::fmt::Debug for PyErr {
        fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
            Python::with_gil(|py| {
                f.debug_struct("PyErr")
                    .field("type", self.ptype(py))
                    .field("value", self.pvalue(py))
                    .field("traceback", &self.ptraceback(py))
                    .finish()
            })
        }
    }

    impl std::fmt::Display for PyErr {
        fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
            Python::with_gil(|py| {
                let instance = self.instance(py);
                let type_name = instance.get_type().name().map_err(|_| std::fmt::Error)?;
                write!(f, "{}", type_name)?;
                if let Ok(s) = instance.str() {
                    write!(f, ": {}", &s.to_string_lossy())
                } else {
                    write!(f, ": <exception str() failed>")
                }
            })
        }
    }

    impl std::error::Error for PyErr {}

    impl IntoPy<PyObject> for PyErr {
        fn into_py(self, py: Python) -> PyObject {
            self.into_instance(py).into()
        }
    }

    impl ToPyObject for PyErr {
        fn to_object(&self, py: Python) -> PyObject {
            self.clone_ref(py).into_py(py)
        }
    }

    impl<'a> IntoPy<PyObject> for &'a PyErr {
        fn into_py(self, py: Python) -> PyObject {
            self.clone_ref(py).into_py(py)
        }
    }

    /// Convert `PyDowncastError` to Python `TypeError`.
    impl<'a> std::convert::From<PyDowncastError<'a>> for PyErr {
        fn from(err: PyDowncastError) -> PyErr {
            exceptions::PyTypeError::new_err(err.to_string())
        }
    }

    impl<'a> std::error::Error for PyDowncastError<'a> {}

    impl<'a> std::fmt::Display for PyDowncastError<'a> {
        fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
            write!(
                f,
                "'{}' object cannot be converted to '{}'",
                self.from.get_type().name().map_err(|_| std::fmt::Error)?,
                self.to
            )
        }
    }

    pub fn panic_after_error(_py: Python) -> ! {
        unsafe {
            ffi::PyErr_Print();
        }
        panic!("Python API call failed");
    }

    /// Returns Ok if the error code is not -1.
    #[inline]
    pub fn error_on_minusone(py: Python, result: c_int) -> PyResult<()> {
        if result != -1 {
            Ok(())
        } else {
            Err(PyErr::fetch(py))
        }
    }

    #[inline]
    fn exceptions_must_derive_from_base_exception(py: Python) -> PyErr {
        PyErr::from_state(PyErrState::Lazy {
            ptype: exceptions::PyTypeError::type_object(py).into(),
            pvalue: boxed_args("exceptions must derive from BaseException"),
        })
    }

    #[cfg(test)]
    mod tests {
        use super::PyErrState;
        use crate::exceptions;
        use crate::{PyErr, Python};

        #[test]
        fn set_typeerror() {
            let gil = Python::acquire_gil();
            let py = gil.python();
            let err: PyErr = exceptions::PyTypeError::new_err(());
            err.restore(py);
            assert!(PyErr::occurred(py));
            drop(PyErr::fetch(py));
        }

        #[test]
        #[should_panic(expected = "new panic")]
        fn fetching_panic_exception_resumes_unwind() {
            // TODO replace with #[cfg(panic = "unwind")] once stable
            if !crate::cfg_panic_unwind() {
                // panic to meet the expected abort in panic=abort :-/
                panic!("new panic");
            }

            use crate::panic::PanicException;

            let gil = Python::acquire_gil();
            let py = gil.python();
            let err: PyErr = PanicException::new_err("new panic");
            err.restore(py);
            assert!(PyErr::occurred(py));

            // should resume unwind
            let _ = PyErr::fetch(py);
        }

        #[test]
        fn err_debug() {
            // Debug representation should be like the following (without the newlines):
            // PyErr {
            //     type: <class 'Exception'>,
            //     value: Exception('banana'),
            //     traceback: Some(<traceback object at 0x..)"
            // }

            let gil = Python::acquire_gil();
            let py = gil.python();
            let err = py
                .run("raise Exception('banana')", None, None)
                .expect_err("raising should have given us an error");

            let debug_str = format!("{:?}", err);
            assert!(debug_str.starts_with("PyErr { "));
            assert!(debug_str.ends_with(" }"));

            // strip "PyErr { " and " }"
            let mut fields = debug_str["PyErr { ".len()..debug_str.len() - 2].split(", ");

            assert_eq!(fields.next().unwrap(), "type: <class 'Exception'>");
            if py.version_info() >= (3, 7) {
                assert_eq!(fields.next().unwrap(), "value: Exception('banana')");
            } else {
                // Python 3.6 and below formats the repr differently
                assert_eq!(fields.next().unwrap(), ("value: Exception('banana',)"));
            }

            let traceback = fields.next().unwrap();
            assert!(traceback.starts_with("traceback: Some(<traceback object at 0x"));
            assert!(traceback.ends_with(">)"));

            assert!(fields.next().is_none());
        }

        #[test]
        fn err_display() {
            let gil = Python::acquire_gil();
            let py = gil.python();
            let err = py
                .run("raise Exception('banana')", None, None)
                .expect_err("raising should have given us an error");
            assert_eq!(err.to_string(), "Exception: banana");
        }

        #[test]
        fn test_pyerr_send_sync() {
            fn is_send<T: Send>() {}
            fn is_sync<T: Sync>() {}

            is_send::<PyErr>();
            is_sync::<PyErr>();

            is_send::<PyErrState>();
            is_sync::<PyErrState>();
        }
    }