TST: add Rust extension module using PyO3

This requires nightly Rust and unreleased Meson.

Author: dnicolodi

tests/packages/rust-pyo3/Cargo.lock

@@ -0,0 +1,15 @@
+# SPDX-FileCopyrightText: 2026 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+[package]
+name = "rust-pyo3"
+version = "1.0.0"
+edition = "2024"
+
+[lib]
+name = "rust_pyo3"
+crate-type = ["cdylib"]
+
+[dependencies]
+pyo3 = "0.29.0"

tests/packages/rust-pyo3/Cargo.toml

@@ -0,0 +1,17 @@
+# SPDX-FileCopyrightText: 2026 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+project('rust-pyo3', 'rust', version: '1.0.0', meson_version: '>= 1.11.0', default_options: ['rust_std=2024'])
+
+py = import('python').find_installation(pure: false)
+pkg = import('rust').workspace().package()
+
+py.extension_module(
+    'rust_pyo3',
+    'src/lib.rs',
+    rust_dependency_map : pkg.rust_dependency_map(),
+    rust_args: pkg.rust_args(),
+    dependencies : pkg.dependencies(),
+    install: true,
+)

tests/packages/rust-pyo3/meson.build

@@ -0,0 +1,7 @@
+# SPDX-FileCopyrightText: 2021 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+[build-system]
+build-backend = "mesonpy"
+requires = ["meson-python"]

tests/packages/rust-pyo3/pyproject.toml

@@ -0,0 +1,16 @@
+// SPDX-FileCopyrightText: 2026 The meson-python developers
+//
+// SPDX-License-Identifier: MIT
+
+use pyo3::prelude::*;
+
+#[pymodule]
+mod rust_pyo3 {
+    use pyo3::prelude::*;
+
+    /// Sum two numbers.
+    #[pyfunction]
+    fn sum(a: i64, b: i64) -> PyResult<i64> {
+        Ok(a + b)
+    }
+}

tests/packages/rust-pyo3/src/lib.rs

@@ -413,3 +413,11 @@ def test_limited_api_free_threaded(wheel_limited_api_free_threaded):
     assert name.group('pyver') == INTERPRETER
     assert name.group('abi') == 'abi3.abi3t' if FREE_THREADED_BUILD else 'abi3'
     assert name.group('plat') == PLATFORM
+
+
+@pytest.mark.skipif(MESON_VERSION < (1, 12, 0), reason='meson too old')
+@pytest.mark.skipif(not shutil.which('rustc'), reason='rust compiler not found')
+def test_rust_pyo3(venv, wheel_rust_pyo3):
+    venv.pip('install', wheel_rust_pyo3)
+    output = venv.python('-c', 'import rust_pyo3; print(rust_pyo3.sum(1, 2))')
+    assert int(output) == 3