build.rs

use std::env;

use pyo3_build_config::pyo3_build_script_impl::{cargo_env_var, errors::Result};
use pyo3_build_config::{bail, print_feature_cfgs, InterpreterConfig};

fn ensure_auto_initialize_ok(interpreter_config: &InterpreterConfig) -> Result<()> {
    if cargo_env_var("CARGO_FEATURE_AUTO_INITIALIZE").is_some() {
        if !interpreter_config.shared {
            bail!(
                "The `auto-initialize` feature is enabled, but your python installation only supports \
                embedding the Python interpreter statically. If you are attempting to run tests, or a \
                binary which is okay to link dynamically, install a Python distribution which ships \
                with the Python shared library.\n\
                \n\
                Embedding the Python interpreter statically does not yet have first-class support in \
                PyO3. If you are sure you intend to do this, disable the `auto-initialize` feature.\n\
                \n\
                For more information, see \
                https://pyo3.rs/v{pyo3_version}/\
                    building_and_distribution.html#embedding-python-in-rust",
                pyo3_version = env::var("CARGO_PKG_VERSION").unwrap()
            );
        }

        // TODO: PYO3_CI env is a hack to workaround CI with PyPy, where the `dev-dependencies`
        // currently cause `auto-initialize` to be enabled in CI.
        // Once MSRV is 1.51 or higher, use cargo's `resolver = "2"` instead.
        if interpreter_config.implementation.is_pypy() && env::var_os("PYO3_CI").is_none() {
            bail!("the `auto-initialize` feature is not supported with PyPy");
        }
    }
    Ok(())
}

/// Prepares the PyO3 crate for compilation.
///
/// This loads the config from pyo3-build-config and then makes some additional checks to improve UX
/// for users.
///
/// Emits the cargo configuration based on this config as well as a few checks of the Rust compiler
/// version to enable features which aren't supported on MSRV.
fn configure_pyo3() -> Result<()> {
    let interpreter_config = pyo3_build_config::get();

    interpreter_config.emit_pyo3_cfgs();

    ensure_auto_initialize_ok(interpreter_config)?;

    // Emit cfgs like `addr_of` and `min_const_generics`
    print_feature_cfgs();

    Ok(())
}

fn main() {
    if let Err(e) = configure_pyo3() {
        eprintln!("error: {}", e.report());
        std::process::exit(1)
    }
}