rust: upgrade PyO3 from 0.25 to 0.29

.github/workflows/external-zstd.yml

@@ -61,4 +61,11 @@ jobs:
 
       - name: Build
         run: |
+          # Homebrew's prefix (/opt/homebrew on Apple Silicon) isn't on the
+          # default compiler search paths, and its libzstd is arm64 only, so
+          # don't build the universal2 binary the Python framework asks for.
+          ZSTD_PREFIX="$(brew --prefix zstd)"
+          export CFLAGS="-I${ZSTD_PREFIX}/include"
+          export LDFLAGS="-L${ZSTD_PREFIX}/lib"
+          export ARCHFLAGS="-arch arm64"
           python -m pip install --config-settings=--global-option=--system-zstd .

Cargo.toml

@@ -26,5 +26,5 @@ version = "2.0.16"
 features = ["experimental", "legacy", "zstdmt"]
 
 [dependencies.pyo3]
-version = "0.25.1"
+version = "0.29.3"
 features = ["extension-module"]

ci/conda/meta.yaml

@@ -1,8 +1,12 @@
-{% set data = load_setup_py_data() %}
+# Don't use load_setup_py_data(): it runs setup.py inside the conda-build
+# process, and setup.py's sys.path.insert(0, ".") then makes the unbuilt
+# zstandard package in the source tree shadow the zstandard bindings that
+# conda-package-handling needs for .conda support.
+{% set version_match = load_file_regex(load_file="../../c-ext/python-zstandard.h", regex_pattern='PYTHON_ZSTANDARD_VERSION "([^"]+)"', from_recipe_dir=True) %}
 
 package:
   name: zstandard
-  version: "{{ data.get('version') }}"
+  version: "{{ version_match.group(1) }}"
 
 source:
   path: ../../

docs/news.rst

@@ -17,6 +17,11 @@ Backwards Compatibility Notes
 * cibuildwheel upgrade required us to drop generating the CPython 3.13 free-threaded
   wheels.
 
+Changes
+-------
+
+* PyO3 Rust crate upgraded from 0.25 to 0.29.
+
 0.25.0 (released 2025-09-14)
 ============================
 

pyproject.toml

@@ -42,14 +42,20 @@ requires = [
 build-backend = "setuptools.build_meta"
 
 [dependency-groups]
-dev = [
+# Dependencies needed to run the test suite. cibuildwheel installs this group
+# unlocked inside its build containers, so keep it free of packages (like mypy)
+# without wheels for every platform we build.
+test = [
     "cffi~=1.17; platform_python_implementation != 'PyPy' and python_version < '3.14'",
     "cffi>=2.0.0b; platform_python_implementation != 'PyPy' and python_version >= '3.14'",
     "hypothesis==6.111.0",
-    "mypy>=1.17.1",
     "pytest>=8.4.1",
     "pytest-xdist>=3.8.0",
 ]
+dev = [
+    { include-group = "test" },
+    "mypy>=1.17.1",
+]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
@@ -71,7 +77,7 @@ test-command = [
     "pytest -v --numprocesses=auto",
     "PYTHON_ZSTANDARD_IMPORT_POLICY=cffi pytest -v --numprocesses=auto",
 ]
-test-groups = ["dev"]
+test-groups = ["test"]
 test-sources = ["tests"]
 
 [tool.cibuildwheel.linux]

rust-ext/src/buffers.rs

@@ -26,7 +26,7 @@ pub(crate) struct BufferSegment {
 #[pyclass(module = "zstandard.backend_rust", name = "BufferSegment")]
 pub struct ZstdBufferSegment {
     /// The object backing storage. For reference counting.
-    _parent: PyObject,
+    _parent: Py<PyAny>,
     /// PyBuffer into parent object.
     buffer: PyBuffer<u8>,
     /// Offset of segment within data.
@@ -53,7 +53,7 @@ impl ZstdBufferSegment {
     }
 
     // PyBufferProtocol.
-    fn bf_getbuffer(slf: PyRefMut<Self>, view: PyObject, flags: i32) -> PyResult<()> {
+    fn bf_getbuffer(slf: PyRefMut<Self>, view: Py<PyAny>, flags: i32) -> PyResult<()> {
         let slice = slf.as_slice();
 
         if unsafe {
@@ -74,7 +74,7 @@ impl ZstdBufferSegment {
     }
 
     #[allow(unused_variables)]
-    fn bf_releasebuffer(slf: PyRefMut<Self>, view: PyObject) {}
+    fn bf_releasebuffer(slf: PyRefMut<Self>, view: Py<PyAny>) {}
 
     // Our methods.
 
@@ -90,18 +90,18 @@ impl ZstdBufferSegment {
 
 #[pyclass(module = "zstandard.backend_rust", name = "BufferSegments")]
 pub struct ZstdBufferSegments {
-    parent: PyObject,
+    parent: Py<PyAny>,
 }
 
 unsafe impl Sync for ZstdBufferSegments {}
 
 #[pymethods]
 impl ZstdBufferSegments {
     // PyBufferProtocol.
-    fn bf_getbuffer(slf: PyRefMut<Self>, view: PyObject, flags: i32) -> PyResult<()> {
+    fn bf_getbuffer(slf: PyRefMut<Self>, view: Py<PyAny>, flags: i32) -> PyResult<()> {
         let py = slf.py();
 
-        let parent = slf.parent.downcast_bound::<ZstdBufferWithSegments>(py)?;
+        let parent = slf.parent.cast_bound::<ZstdBufferWithSegments>(py)?;
 
         if unsafe {
             pyo3::ffi::PyBuffer_FillInfo(
@@ -121,12 +121,12 @@ impl ZstdBufferSegments {
     }
 
     #[allow(unused_variables)]
-    fn bf_releasebuffer(slf: PyRefMut<Self>, view: PyObject) {}
+    fn bf_releasebuffer(slf: PyRefMut<Self>, view: Py<PyAny>) {}
 }
 
 #[pyclass(module = "zstandard.backend_rust", name = "BufferWithSegments")]
 pub struct ZstdBufferWithSegments {
-    source: PyObject,
+    source: Py<PyAny>,
     pub(crate) buffer: PyBuffer<u8>,
     pub(crate) segments: Vec<BufferSegment>,
 }
@@ -161,7 +161,7 @@ impl ZstdBufferWithSegments {
     }
 
     fn __getitem__(&self, key: isize) -> PyResult<ZstdBufferSegment> {
-        let py = unsafe { Python::assume_gil_acquired() };
+        let py = unsafe { Python::assume_attached() };
 
         if key < 0 {
             return Err(PyIndexError::new_err("offset must be non-negative"));
@@ -180,14 +180,14 @@ impl ZstdBufferWithSegments {
 
         Ok(ZstdBufferSegment {
             _parent: self.source.clone_ref(py),
-            buffer: PyBuffer::get(self.source.downcast_bound(py)?)?,
+            buffer: PyBuffer::get(self.source.cast_bound(py)?)?,
             offset: segment.offset as _,
             len: segment.length as _,
         })
     }
 
     // PyBufferProtocol.
-    fn bf_getbuffer(slf: PyRefMut<Self>, view: PyObject, flags: i32) -> PyResult<()> {
+    fn bf_getbuffer(slf: PyRefMut<Self>, view: Py<PyAny>, flags: i32) -> PyResult<()> {
         if unsafe {
             pyo3::ffi::PyBuffer_FillInfo(
                 view.as_ptr() as *mut Py_buffer,
@@ -206,7 +206,7 @@ impl ZstdBufferWithSegments {
     }
 
     #[allow(unused_variables)]
-    fn bf_releasebuffer(slf: PyRefMut<Self>, view: PyObject) {}
+    fn bf_releasebuffer(slf: PyRefMut<Self>, view: Py<PyAny>) {}
 
     // Our methods.
 
@@ -256,8 +256,7 @@ impl ZstdBufferWithSegments {
 
     fn segments(slf: PyRef<Self>, py: Python) -> PyResult<ZstdBufferSegments> {
         Ok(ZstdBufferSegments {
-            // TODO surely there is a better way to cast self to PyObject?
-            parent: unsafe { Py::from_borrowed_ptr(py, slf.as_ptr()) },
+            parent: slf.into_pyobject(py)?.into_any().unbind(),
         })
     }
 
@@ -272,7 +271,7 @@ impl ZstdBufferWithSegments {
 )]
 pub struct ZstdBufferWithSegmentsCollection {
     // Py<ZstdBufferWithSegments>.
-    pub(crate) buffers: Vec<PyObject>,
+    pub(crate) buffers: Vec<Py<PyAny>>,
     first_elements: Vec<usize>,
 }
 
@@ -287,7 +286,7 @@ impl ZstdBufferWithSegmentsCollection {
     }
 
     fn __getitem__(&self, key: isize) -> PyResult<ZstdBufferSegment> {
-        let py = unsafe { Python::assume_gil_acquired() };
+        let py = unsafe { Python::assume_attached() };
 
         if key < 0 {
             return Err(PyIndexError::new_err("offset must be non-negative"));
@@ -309,7 +308,7 @@ impl ZstdBufferWithSegmentsCollection {
                     offset = self.first_elements[buffer_index - 1];
                 }
 
-                let item = segment.downcast_bound::<ZstdBufferWithSegments>(py)?;
+                let item = segment.cast_bound::<ZstdBufferWithSegments>(py)?;
 
                 return item.borrow().__getitem__((key - offset) as isize);
             }
@@ -332,7 +331,7 @@ impl ZstdBufferWithSegmentsCollection {
         let mut offset = 0;
 
         for item in py_args {
-            let item = item.downcast::<ZstdBufferWithSegments>().map_err(|_| {
+            let item = item.cast::<ZstdBufferWithSegments>().map_err(|_| {
                 PyTypeError::new_err("arguments must be BufferWithSegments instances")
             })?;
             let segment = item.borrow();
@@ -359,7 +358,7 @@ impl ZstdBufferWithSegmentsCollection {
         let mut size = 0;
 
         for buffer in &self.buffers {
-            let item = buffer.downcast_bound::<ZstdBufferWithSegments>(py)?;
+            let item = buffer.cast_bound::<ZstdBufferWithSegments>(py)?;
 
             for segment in &item.borrow().segments {
                 size += segment.length as usize;

rust-ext/src/compression_chunker.rs

@@ -196,12 +196,12 @@ impl ZstdCompressionChunkerIterator {
         slf
     }
 
-    fn __next__(mut slf: PyRefMut<Self>) -> PyResult<Option<PyObject>> {
+    fn __next__(mut slf: PyRefMut<Self>) -> PyResult<Option<Py<PyAny>>> {
         if slf.finished {
             return Ok(None);
         }
 
-        let py = unsafe { Python::assume_gil_acquired() };
+        let py = unsafe { Python::assume_attached() };
 
         // Consume any data left in the input.
         while let Some(mut in_buffer) = slf.source.input_buffer(py)? {

rust-ext/src/compression_dict.rs

@@ -257,7 +257,7 @@ fn train_dictionary(
     // validated to be PyBytes.
     for sample in samples.iter() {
         let bytes = sample
-            .downcast::<PyBytes>()
+            .cast::<PyBytes>()
             .or_else(|_| Err(PyValueError::new_err("samples must be bytes")))?;
 
         samples_len += bytes.as_bytes().len();
@@ -267,7 +267,7 @@ fn train_dictionary(
     let mut sample_sizes: Vec<libc::size_t> = Vec::with_capacity(samples.len());
 
     for sample in samples.iter() {
-        let bytes = sample.downcast::<PyBytes>()?;
+        let bytes = sample.cast::<PyBytes>()?;
         let data = bytes.as_bytes();
         sample_sizes.push(data.len());
         samples_buffer.extend_from_slice(data);