Mercurial > public > mercurial-scm > hg-stable
diff rust/hg-cpython/src/lib.rs @ 50990:4c5f6e95df84
rust: make `Revision` a newtype
This change is the one we've been building towards during this series.
The aim is to make `Revision` mean more than a simple integer, holding
the information that it is valid for a given revlog index.
While this still allows for programmer error, since creating a revision
directly and querying a different index with a "checked" revision are
still possible, the friction created by the newtype will hopefully make
us think twice about which type to use.
Enough of the Rust ecosystem relies on the newtype pattern to be
efficiently optimized away (even compiler in codegen tests?), so I'm not
worried about this being a fundamental problem.
[1] https://github.com/rust-lang/rust/blob/7a70647f195f6b0a0f1ebd72b1542ba91a32f43a/tests/codegen/vec-in-place.rs#L47
| author | Rapha?l Gom?s <rgomes@octobus.net> |
|---|---|
| date | Fri, 18 Aug 2023 14:34:29 +0200 |
| parents | 136aa80aa8b2 |
| children | 8b7123c8947b |
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--- a/rust/hg-cpython/src/lib.rs Thu Aug 10 11:01:07 2023 +0200 +++ b/rust/hg-cpython/src/lib.rs Fri Aug 18 14:34:29 2023 +0200 @@ -24,6 +24,9 @@ #![allow(clippy::manual_strip)] // rust-cpython macros #![allow(clippy::type_complexity)] // rust-cpython macros +use cpython::{FromPyObject, PyInt, Python, ToPyObject}; +use hg::{BaseRevision, Revision}; + /// This crate uses nested private macros, `extern crate` is still needed in /// 2018 edition. #[macro_use] @@ -44,6 +47,40 @@ pub mod revlog; pub mod utils; +/// Revision as exposed to/from the Python layer. +/// +/// We need this indirection because of the orphan rule, meaning we can't +/// implement a foreign trait (like [`cpython::ToPyObject`]) +/// for a foreign type (like [`hg::UncheckedRevision`]). +/// +/// This also acts as a deterrent against blindly trusting Python to send +/// us valid revision numbers. +#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] +pub struct PyRevision(BaseRevision); + +impl From<Revision> for PyRevision { + fn from(r: Revision) -> Self { + PyRevision(r.0) + } +} + +impl<'s> FromPyObject<'s> for PyRevision { + fn extract( + py: Python, + obj: &'s cpython::PyObject, + ) -> cpython::PyResult<Self> { + Ok(Self(obj.extract::<BaseRevision>(py)?)) + } +} + +impl ToPyObject for PyRevision { + type ObjectType = PyInt; + + fn to_py_object(&self, py: Python) -> Self::ObjectType { + self.0.to_py_object(py) + } +} + py_module_initializer!(rustext, initrustext, PyInit_rustext, |py, m| { m.add( py,