Set PYO3_PYTHON to run scripts for stable ABI builds

src/compile.rs

@@ -895,7 +895,7 @@ fn configure_pyo3_env(
     // Setup `PYO3_CONFIG_FILE` if we are cross compiling for pyo3 bindings
     if let Some(interpreter) = python_interpreter {
         // Target python interpreter isn't runnable when cross compiling
-        if interpreter.runnable && !force_target_abi {
+        if interpreter.runnable {
             if bridge_model.is_pyo3() {
                 debug!(
                     "Setting PYO3_PYTHON to {}",

test-crates/pyo3-cffi-build-script/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "pyo3-cffi-build-script"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+pyo3 = { version = "0.29.0", features = ["abi3"] }
+
+[lib]
+name = "pyo3_cffi_build_script"
+crate-type = ["cdylib"]

test-crates/pyo3-cffi-build-script/build.rs

@@ -0,0 +1,21 @@
+//! Models the `cryptography` project: a PyO3 extension whose build script shells
+//! out to the build interpreter to run cffi. maturin must hand us that
+//! interpreter via `PYO3_PYTHON`, even for abi3 builds.
+
+use std::env;
+use std::process::Command;
+
+fn main() {
+    println!("cargo:rerun-if-env-changed=PYO3_PYTHON");
+    let python = env::var("PYO3_PYTHON")
+        .expect("PYO3_PYTHON is not set; maturin must hand abi3 builds an interpreter");
+    let status = Command::new(&python)
+        .args([
+            "-c",
+            "import cffi; ffi = cffi.FFI(); ffi.cdef('int answer(void);'); \
+             ffi.set_source('_pyo3_cffi_demo', 'int answer(void) { return 42; }')",
+        ])
+        .status()
+        .expect("failed to run PYO3_PYTHON");
+    assert!(status.success(), "cffi codegen via PYO3_PYTHON failed");
+}

test-crates/pyo3-cffi-build-script/src/lib.rs

@@ -0,0 +1,7 @@
+use pyo3::prelude::*;
+
+#[pymodule]
+fn pyo3_cffi_build_script(m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add("answer", 42)?;
+    Ok(())
+}

tests/common/other.rs

@@ -489,6 +489,40 @@ pub fn abi3_without_version() -> Result<()> {
     Ok(())
 }
 
+pub fn pyo3_cffi_build_script() -> Result<()> {
+    let base = crate::common::test_python_path().map(PathBuf::from);
+    let venv_dir = crate::common::create_named_virtualenv("pyo3-cffi-build-script", base)?;
+    let venv_python = maturin::Target::from_target_triple(None)?.get_venv_python(&venv_dir);
+    crate::common::install_pip_packages(&venv_python, &["cffi"])?;
+    let python = venv_python
+        .to_str()
+        .context("venv python path is not utf-8")?;
+
+    // The first argument is ignored by clap
+    let cli = vec![
+        "build",
+        "--manifest-path",
+        "test-crates/pyo3-cffi-build-script/Cargo.toml",
+        "--quiet",
+        "--interpreter",
+        python,
+        "--target-dir",
+        "test-targets/wheels/pyo3_cffi_build_script",
+    ];
+
+    let options = BuildOptions::try_parse_from(cli)?;
+    let build_context = options
+        .into_build_context()
+        .strip(Some(cfg!(feature = "faster-tests")))
+        .editable(false)
+        .build()?;
+    // Actually build the wheel so the crate's build.rs runs.
+    let wheels = BuildOrchestrator::new(&build_context).build_wheels();
+    assert!(wheels.is_ok());
+
+    Ok(())
+}
+
 pub fn abi3t_without_version() -> Result<()> {
     let python = crate::common::test_python_path().unwrap_or_else(|| "python3".to_string());
     // The first argument is ignored by clap

tests/run/integration.rs

@@ -168,6 +168,11 @@ fn abi3_without_version() {
     handle_result(other::abi3_without_version())
 }
 
+#[test]
+fn pyo3_cffi_build_script() {
+    handle_result(other::pyo3_cffi_build_script())
+}
+
 #[test]
 fn abi3t_without_version() {
     // abi3t requires CPython >= 3.15 (PEP 803). On older runners the build