stow-cli 0.4.1

CLI that routes rustc invocations through the stow public artifact cache
Documentation 
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//! `CC`/`CXX` and `CMAKE_*_COMPILER_LAUNCHER` have different calling
//! conventions, and using one shim for both breaks every C build.
//!
//! A *launcher* receives the program to run as its first argument. `CC` and
//! `CXX` do not — they are invoked with compiler arguments only, so a
//! launcher-shaped shim tries to execute the first compiler flag. Under `CC`
//! that turns every cc-rs probe into `configure: error: C compiler cannot
//! create executables`.

use std::path::Path;
use std::process::Command;

fn setup_in(dir: &Path) -> toml::Value {
    let status = Command::new(env!("CARGO_BIN_EXE_stow-cli"))
        .arg("setup")
        .current_dir(dir)
        .status()
        .expect("run stow-cli setup");
    assert!(status.success(), "stow-cli setup failed");
    let config = std::fs::read_to_string(dir.join(".cargo").join("config.toml"))
        .expect("read generated .cargo/config.toml");
    toml::from_str(&config).expect("parse generated .cargo/config.toml")
}

/// Cargo's `[env]` entries are tables — the value lives under `.value`.
fn env_value<'a>(config: &'a toml::Value, key: &str) -> &'a str {
    config
        .get("env")
        .and_then(|env| env.get(key))
        .and_then(|entry| entry.get("value"))
        .and_then(toml::Value::as_str)
        .unwrap_or_else(|| panic!("generated config has no [env] entry for {key}"))
}

#[test]
fn cc_is_invoked_with_compiler_arguments_only() {
    // The shim execs `cc`; a host without one has nothing to probe.
    if let Err(error) = Command::new("cc").arg("--version").output() {
        if error.kind() == std::io::ErrorKind::NotFound {
            return;
        }
        panic!("spawn cc --version: {error}");
    }
    let dir = tempfile::tempdir().expect("temp dir");
    let config = setup_in(dir.path());

    std::fs::write(dir.path().join("probe.c"), "int main(void) { return 0; }\n")
        .expect("write probe source");
    let object = dir.path().join("probe.o");

    // Exactly how cc-rs calls it: no leading executable positional.
    let status = Command::new(env_value(&config, "CC"))
        .arg("-c")
        .arg("-o")
        .arg(&object)
        .arg("probe.c")
        .current_dir(dir.path())
        .env("STOW_REAL_CC", env_value(&config, "STOW_REAL_CC"))
        .status()
        .expect("run the CC shim");

    assert!(status.success(), "the CC shim failed to compile a probe");
    assert!(object.exists(), "the CC shim produced no object file");
}

#[test]
fn the_launcher_and_the_compilers_are_three_different_shims() {
    let dir = tempfile::tempdir().expect("temp dir");
    let config = setup_in(dir.path());

    let cc = env_value(&config, "CC");
    let cxx = env_value(&config, "CXX");
    let launcher = env_value(&config, "CMAKE_C_COMPILER_LAUNCHER");

    assert_ne!(cc, launcher, "CC must not be the launcher-shaped shim");
    assert_ne!(cxx, launcher, "CXX must not be the launcher-shaped shim");
    assert_ne!(cc, cxx, "CC and CXX must exec different real compilers");
    assert_eq!(
        launcher,
        env_value(&config, "CMAKE_CXX_COMPILER_LAUNCHER"),
        "both CMake launcher variables take the same launcher shim"
    );
}

#[test]
fn an_explicit_toolchain_survives_setup() {
    let dir = tempfile::tempdir().expect("temp dir");
    let status = Command::new(env!("CARGO_BIN_EXE_stow-cli"))
        .arg("setup")
        .current_dir(dir.path())
        .env("CC", "/usr/bin/clang")
        .env("CXX", "/usr/bin/clang++")
        .status()
        .expect("run stow-cli setup");
    assert!(status.success(), "stow-cli setup failed");
    let config: toml::Value = toml::from_str(
        &std::fs::read_to_string(dir.path().join(".cargo").join("config.toml"))
            .expect("read generated .cargo/config.toml"),
    )
    .expect("parse generated .cargo/config.toml");

    // Overwriting CC/CXX without recording them would silently drop the
    // caller's compiler choice.
    assert_eq!(env_value(&config, "STOW_REAL_CC"), "/usr/bin/clang");
    assert_eq!(env_value(&config, "STOW_REAL_CXX"), "/usr/bin/clang++");
}