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Merged
Icxolu merged 1 commit into from
Mar 17, 2026
Merged

Fix TypeError when converting Rust encoding errors to Python #5668

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33 changes: 33 additions & 0 deletions guide/src/migration.md
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Expand Up @@ -3,6 +3,39 @@
This guide can help you upgrade code through breaking changes from one PyO3 version to the next.
For a detailed list of all changes, see the [CHANGELOG](changelog.md).

## from 0.28.* to 0.29

### Removed implementations of `From<str::Utf8Error>`, `From<string::FromUtf16Error>`, and `From<char::DecodeUtf16Error>` for `PyErr`

Previously the implementations of `From<string::FromUtf8Error>`, `From<ffi::IntoStringError>`, `From<str::Utf8Error>`, `From<string::FromUtf16Error>`, and `From<char::DecodeUtf16Error>` failed to construct the correct Python exception class, as reported in <https://github.com/PyO3/pyo3/issues/5651>.
The implementations for `string::FromUtf8Error` and `ffi::IntoStringError` were fixed in this release.

For `str::Utf8Error`, the Rust error does not contain the source bytes required to construct the Python exception.
Instead, `PyUnicodeDecodeError::new_err_from_utf8` can be used to convert the error to a `PyErr`.

Before:

```rust,ignore
fn bytes_to_str(bytes: &[u8]) -> PyResult<&str> {
Ok(std::str::from_utf8(bytes)?)
}
```

After:

```rust
# use pyo3::prelude::*;
use pyo3::exceptions::PyUnicodeDecodeError;

# #[expect(dead_code)]
fn bytes_to_str<'a>(py: Python<'_>, bytes: &'a [u8]) -> PyResult<&'a str> {
std::str::from_utf8(bytes).map_err(|e| PyUnicodeDecodeError::new_err_from_utf8(py, bytes, e))
}
```

For `string::FromUtf16Error` and `char::DecodeUtf16Error` the Rust error types do not contain any of the information required to construct a `UnicodeDecodeError`.
To raise a Python `UnicodeDecodeError` a new error should be manually constructed by calling `PyUnicodeDecodeError::new_err(...)`.

## from 0.27.* to 0.28

### Default to supporting free-threaded Python
Expand Down
1 change: 1 addition & 0 deletions newsfragments/5668.added.md
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@@ -0,0 +1 @@
Added new `PyUnicodeDecodeError::new_err_from_utf8` API to create a `PyErr` from a `str::Utf8Error`
1 change: 1 addition & 0 deletions newsfragments/5668.fixed.md
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@@ -0,0 +1 @@
Fixed the implementations of `From<string::FromUtf8Error>` and `From<ffi::IntoStringError>` for `PyErr`.
1 change: 1 addition & 0 deletions newsfragments/5668.removed.md
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@@ -0,0 +1 @@
Removed the failing implementations of `From<str::Utf8Error>`, `From<string::FromUtf16Error>`, and `From<char::DecodeUtf16Error>` for `PyErr`.
17 changes: 10 additions & 7 deletions src/conversions/std/cstring.rs
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@@ -1,3 +1,4 @@
use crate::exceptions::PyUnicodeDecodeError;
#[cfg(feature = "experimental-inspect")]
use crate::inspect::PyStaticExpr;
#[cfg(feature = "experimental-inspect")]
Expand All @@ -6,7 +7,6 @@ use crate::types::PyString;
use crate::{Borrowed, Bound, FromPyObject, IntoPyObject, PyAny, PyErr, Python};
use std::borrow::Cow;
use std::ffi::{CStr, CString};
use std::str::Utf8Error;
#[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
use {
crate::{exceptions::PyValueError, ffi},
Expand All @@ -16,21 +16,24 @@ use {
impl<'py> IntoPyObject<'py> for &CStr {
type Target = PyString;
type Output = Bound<'py, Self::Target>;
type Error = Utf8Error;
type Error = PyErr;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = <&str>::OUTPUT_TYPE;

#[inline]
fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
self.to_str()?.into_pyobject(py).map_err(|err| match err {})
self.to_str()
.map_err(|e| PyUnicodeDecodeError::new_err_from_utf8(py, self.to_bytes(), e))?
.into_pyobject(py)
.map_err(|err| match err {})
}
}

impl<'py> IntoPyObject<'py> for CString {
type Target = PyString;
type Output = Bound<'py, Self::Target>;
type Error = Utf8Error;
type Error = PyErr;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = <&CStr>::OUTPUT_TYPE;
Expand All @@ -44,7 +47,7 @@ impl<'py> IntoPyObject<'py> for CString {
impl<'py> IntoPyObject<'py> for &CString {
type Target = PyString;
type Output = Bound<'py, Self::Target>;
type Error = Utf8Error;
type Error = PyErr;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = <&CStr>::OUTPUT_TYPE;
Expand All @@ -58,7 +61,7 @@ impl<'py> IntoPyObject<'py> for &CString {
impl<'py> IntoPyObject<'py> for Cow<'_, CStr> {
type Target = PyString;
type Output = Bound<'py, Self::Target>;
type Error = Utf8Error;
type Error = PyErr;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = <&CStr>::OUTPUT_TYPE;
Expand All @@ -71,7 +74,7 @@ impl<'py> IntoPyObject<'py> for Cow<'_, CStr> {
impl<'py> IntoPyObject<'py> for &Cow<'_, CStr> {
type Target = PyString;
type Output = Bound<'py, Self::Target>;
type Error = Utf8Error;
type Error = PyErr;

#[cfg(feature = "experimental-inspect")]
const OUTPUT_TYPE: PyStaticExpr = <&CStr>::OUTPUT_TYPE;
Expand Down
140 changes: 127 additions & 13 deletions src/err/impls.rs
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@@ -1,4 +1,4 @@
use crate::{err::PyErrArguments, exceptions, PyErr, Python};
use crate::{err::PyErrArguments, exceptions, types, PyErr, Python};
use crate::{IntoPyObject, Py, PyAny};
use std::io;

Expand Down Expand Up @@ -118,28 +118,78 @@ macro_rules! impl_to_pyerr {
};
}

struct Utf8ErrorWithBytes {
err: std::str::Utf8Error,
bytes: Vec<u8>,
}

impl PyErrArguments for Utf8ErrorWithBytes {
fn arguments(self, py: Python<'_>) -> Py<PyAny> {
let Self { err, bytes } = self;
let start = err.valid_up_to();
let end = err.error_len().map_or(bytes.len(), |l| start + l);

let encoding = types::PyString::new(py, "utf-8").into_any();
let bytes = types::PyBytes::new(py, &bytes).into_any();
let start = types::PyInt::new(py, start).into_any();
let end = types::PyInt::new(py, end).into_any();
let reason = types::PyString::new(py, "invalid utf-8").into_any();
Comment thread
davidhewitt marked this conversation as resolved.

// FIXME(icxolu) remove unwrap
types::PyTuple::new(py, &[encoding, bytes, start, end, reason])
.unwrap()
.into_any()
.unbind()
}
}

impl PyErrArguments for std::string::FromUtf8Error {
fn arguments(self, py: Python<'_>) -> Py<PyAny> {
Utf8ErrorWithBytes {
err: self.utf8_error(),
bytes: self.into_bytes(),
}
.arguments(py)
}
}

impl std::convert::From<std::string::FromUtf8Error> for PyErr {
fn from(err: std::string::FromUtf8Error) -> PyErr {
exceptions::PyUnicodeDecodeError::new_err(err)
}
}

impl PyErrArguments for std::ffi::IntoStringError {
fn arguments(self, py: Python<'_>) -> Py<PyAny> {
Utf8ErrorWithBytes {
err: self.utf8_error(),
bytes: self.into_cstring().into_bytes(),
}
.arguments(py)
}
}

impl std::convert::From<std::ffi::IntoStringError> for PyErr {
fn from(err: std::ffi::IntoStringError) -> PyErr {
exceptions::PyUnicodeDecodeError::new_err(err)
}
}

impl_to_pyerr!(std::array::TryFromSliceError, exceptions::PyValueError);
impl_to_pyerr!(std::num::ParseIntError, exceptions::PyValueError);
impl_to_pyerr!(std::num::ParseFloatError, exceptions::PyValueError);
impl_to_pyerr!(std::num::TryFromIntError, exceptions::PyValueError);
impl_to_pyerr!(std::str::ParseBoolError, exceptions::PyValueError);
impl_to_pyerr!(std::ffi::IntoStringError, exceptions::PyUnicodeDecodeError);
impl_to_pyerr!(std::ffi::NulError, exceptions::PyValueError);
impl_to_pyerr!(std::str::Utf8Error, exceptions::PyUnicodeDecodeError);
impl_to_pyerr!(std::string::FromUtf8Error, exceptions::PyUnicodeDecodeError);
impl_to_pyerr!(
std::string::FromUtf16Error,
exceptions::PyUnicodeDecodeError
);
impl_to_pyerr!(
std::char::DecodeUtf16Error,
exceptions::PyUnicodeDecodeError
);
impl_to_pyerr!(std::net::AddrParseError, exceptions::PyValueError);

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

use crate::exceptions::PyUnicodeDecodeError;
use crate::types::PyAnyMethods;
use crate::{IntoPyObjectExt as _, PyErr, Python};
use std::io;

#[test]
Expand Down Expand Up @@ -179,4 +229,68 @@ mod tests {
check_err(io::ErrorKind::IsADirectory, "IsADirectoryError");
check_err(io::ErrorKind::NotADirectory, "NotADirectoryError");
}

#[test]
#[allow(invalid_from_utf8)]
fn utf8_errors() {
let bytes = b"abc\xffdef".to_vec();

let check_err = |py_err: PyErr| {
Python::attach(|py| {
let py_err = py_err.into_bound_py_any(py).unwrap();

assert!(py_err.is_instance_of::<exceptions::PyUnicodeDecodeError>());
assert_eq!(
py_err
.getattr("encoding")
.unwrap()
.extract::<String>()
.unwrap(),
"utf-8"
);
assert_eq!(
py_err
.getattr("object")
.unwrap()
.extract::<Vec<u8>>()
.unwrap(),
&*bytes
);
assert_eq!(
py_err.getattr("start").unwrap().extract::<usize>().unwrap(),
3
);
assert_eq!(
py_err.getattr("end").unwrap().extract::<usize>().unwrap(),
4
);
assert_eq!(
py_err
.getattr("reason")
.unwrap()
.extract::<String>()
.unwrap(),
"invalid utf-8"
);
});
};

let utf8_err_with_bytes = PyUnicodeDecodeError::new_err(Utf8ErrorWithBytes {
err: std::str::from_utf8(&bytes).expect_err("\\xff is invalid utf-8"),
bytes: bytes.clone(),
});
check_err(utf8_err_with_bytes);

let from_utf8_err = String::from_utf8(bytes.clone())
.expect_err("\\xff is invalid utf-8")
.into();
check_err(from_utf8_err);

let from_utf8_err = std::ffi::CString::new(bytes.clone())
.unwrap()
.into_string()
.expect_err("\\xff is invalid utf-8")
.into();
check_err(from_utf8_err);
}
}
89 changes: 86 additions & 3 deletions src/exceptions.rs
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Expand Up @@ -776,8 +776,38 @@ impl PyUnicodeDecodeError {
input: &[u8],
err: std::str::Utf8Error,
) -> PyResult<Bound<'py, PyUnicodeDecodeError>> {
let pos = err.valid_up_to();
PyUnicodeDecodeError::new(py, c"utf-8", input, pos..(pos + 1), c"invalid utf-8")
let start = err.valid_up_to();
let end = err.error_len().map_or(input.len(), |l| start + l);
PyUnicodeDecodeError::new(py, c"utf-8", input, start..end, c"invalid utf-8")
}

/// Create a new [`PyErr`](crate::PyErr) of this type from a Rust UTF-8 decoding error.
///
/// This is equivalent to [`PyUnicodeDecodeError::new_utf8`], but returning a
/// [`PyErr`](crate::PyErr) instead of an exception object.
///
/// # Example
///
/// ```
/// use pyo3::prelude::*;
/// use pyo3::exceptions::PyUnicodeDecodeError;
///
/// Python::attach(|py| {
/// let invalid_utf8 = b"fo\xd8o";
/// # #[expect(invalid_from_utf8)]
/// let err = std::str::from_utf8(invalid_utf8).expect_err("should be invalid utf8");
/// let py_err = PyUnicodeDecodeError::new_err_from_utf8(py, invalid_utf8, err);
/// })
/// ```
pub fn new_err_from_utf8(
py: Python<'_>,
bytes: &[u8],
err: std::str::Utf8Error,
) -> crate::PyErr {
match Self::new_utf8(py, bytes, err) {
Ok(e) => crate::PyErr::from_value(e.into_any()),
Err(e) => e,
}
}
}

Expand Down Expand Up @@ -925,7 +955,7 @@ mod tests {
use super::*;
use crate::types::any::PyAnyMethods;
use crate::types::{IntoPyDict, PyDict};
use crate::PyErr;
use crate::{IntoPyObjectExt as _, PyErr};

import_exception!(socket, gaierror);
import_exception!(email.errors, MessageError);
Expand Down Expand Up @@ -1222,4 +1252,57 @@ mod tests {
test_exception!(PyBytesWarning);
#[cfg(Py_3_10)]
test_exception!(PyEncodingWarning);

#[test]
#[allow(invalid_from_utf8)]
fn unicode_decode_error_from_utf8() {
Python::attach(|py| {
let bytes = b"abc\xffdef".to_vec();

let check_err = |py_err: PyErr| {
let py_err = py_err.into_bound_py_any(py).unwrap();

assert!(py_err.is_instance_of::<PyUnicodeDecodeError>());
assert_eq!(
py_err
.getattr("encoding")
.unwrap()
.extract::<String>()
.unwrap(),
"utf-8"
);
assert_eq!(
py_err
.getattr("object")
.unwrap()
.extract::<Vec<u8>>()
.unwrap(),
&*bytes
);
assert_eq!(
py_err.getattr("start").unwrap().extract::<usize>().unwrap(),
3
);
assert_eq!(
py_err.getattr("end").unwrap().extract::<usize>().unwrap(),
4
);
assert_eq!(
py_err
.getattr("reason")
.unwrap()
.extract::<String>()
.unwrap(),
"invalid utf-8"
);
};

let utf8_err_with_bytes = PyUnicodeDecodeError::new_err_from_utf8(
py,
&bytes,
std::str::from_utf8(&bytes).expect_err("\\xff is invalid utf-8"),
);
check_err(utf8_err_with_bytes);
})
}
}
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