mercurial-scm/hg: rust/hg-pyo3/src/convert

comparison rust/hg-pyo3/src/convert_cpython.rs @ 52529:bd65cb043aa5

rust-pyo3: error propagation for UnsafePyLeaked wrapping a result This `py_leaked_or_map_err` is the PyO3 version of the function of the same name in `hg-cpython/src/ancestors.rs`.

author	Georges Racinet <georges.racinet@cloudcrane.io>
date	Sat, 07 Dec 2024 18:18:09 +0100
parents	1dd673c1ab3b
children	736551565871

comparison

equal deleted inserted replaced

-:1dd673c1ab3b
+:bd65cb043aa5
 .try_borrow(py)
 .map_err(|e| from_cpython_pyerr(py, e))?
 };
 Ok(py_shared.inner)
 }
+/// Error propagation for an [`UnsafePyLeaked`] wrapping a [`Result`]
+///
+/// TODO (will consider when implementing UnsafePyLeaked in PyO3):
+/// It would be nice for UnsafePyLeaked to provide this directly as a variant
+/// of the `map` method with a signature such as:
+///
+/// ```
+///   unsafe fn map_or_err(&self,
+///                        py: Python,
+///                        f: impl FnOnce(T) -> Result(U, E),
+///                        convert_err: impl FnOnce(E) -> PyErr)
+/// ```
+///
+/// This would spare users of the `cpython` crate the additional `unsafe` deref
+/// to inspect the error and return it outside `UnsafePyLeaked`, and the
+/// subsequent unwrapping that this function performs.
+#[allow(dead_code)]
+pub(crate) fn py_leaked_or_map_err<T, E: std::fmt::Debug + Copy>(
+py: cpython::Python,
+leaked: cpython::UnsafePyLeaked<Result<T, E>>,
+convert_err: impl FnOnce(E) -> PyErr,
+) -> PyResult<cpython::UnsafePyLeaked<T>> {
+// Safety: we don't leak the "faked" reference out of `UnsafePyLeaked`
+if let Err(e) = *unsafe {
+leaked
+.try_borrow(py)
+.map_err(|e| from_cpython_pyerr(py, e))?
+} {
+return Err(convert_err(e));
+}
+// Safety: we don't leak the "faked" reference out of `UnsafePyLeaked`
+Ok(unsafe {
+leaked.map(py, |res| {
+res.expect("Error case should have already be treated")
+})
+})
+}

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comparison rust/hg-pyo3/src/convert_cpython.rs @ 52529:bd65cb043aa5