fn run_buildrs()

in cargo/cargo_build_script_runner/bin.rs [26:172]
124 lines of code
14 McCabe index (conditional complexity)

fn run_buildrs() -> Result<(), String> {
    // We use exec_root.join rather than std::fs::canonicalize, to avoid resolving symlinks, as
    // some execution strategies and remote execution environments may use symlinks in ways which
    // canonicalizing them may break them, e.g. by having input files be symlinks into a /cas
    // directory - resolving these may cause tools which inspect $0, or try to resolve files
    // relative to themselves, to fail.
    let exec_root = env::current_dir().expect("Failed to get current directory");
    let manifest_dir_env = env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR was not set");
    let rustc_env = env::var("RUSTC").expect("RUSTC was not set");
    let manifest_dir = exec_root.join(&manifest_dir_env);
    let rustc = exec_root.join(&rustc_env);
    let Options {
        progname,
        crate_links,
        out_dir,
        env_file,
        compile_flags_file,
        link_flags_file,
        output_dep_env_path,
        stdout_path,
        stderr_path,
        input_dep_env_paths,
    } = parse_args()?;

    let out_dir_abs = exec_root.join(&out_dir);
    // For some reason Google's RBE does not create the output directory, force create it.
    create_dir_all(&out_dir_abs)
        .unwrap_or_else(|_| panic!("Failed to make output directory: {:?}", out_dir_abs));

    let target_env_vars =
        get_target_env_vars(&rustc_env).expect("Error getting target env vars from rustc");

    let mut command = Command::new(exec_root.join(&progname));
    command
        .current_dir(&manifest_dir)
        .envs(target_env_vars)
        .env("OUT_DIR", out_dir_abs)
        .env("CARGO_MANIFEST_DIR", manifest_dir)
        .env("RUSTC", rustc)
        .env("RUST_BACKTRACE", "full");

    for dep_env_path in input_dep_env_paths.iter() {
        if let Ok(contents) = read_to_string(dep_env_path) {
            for line in contents.split('\n') {
                // split on empty contents will still produce a single empty string in iterable.
                if line.is_empty() {
                    continue;
                }
                let mut key_val = line.splitn(2, '=');
                match (key_val.next(), key_val.next()) {
                    (Some(key), Some(value)) => {
                        command.env(key, value.replace("${pwd}", &exec_root.to_string_lossy()));
                    }
                    _ => {
                        return Err(
                            "error: Wrong environment file format, should not happen".to_owned()
                        )
                    }
                }
            }
        } else {
            return Err("error: Dependency environment file unreadable".to_owned());
        }
    }

    for compiler_env_var in &["CC", "CXX"] {
        if let Some(compiler_path) = env::var_os(compiler_env_var) {
            let mut compiler_path = exec_root.join(compiler_path).into_os_string();
            if let Some(sysroot_path) = env::var_os("SYSROOT") {
                compiler_path.push(" --sysroot=");
                compiler_path.push(&exec_root.join(sysroot_path));
            }
            command.env(compiler_env_var, compiler_path);
        }
    }

    if let Some(ar_path) = env::var_os("AR") {
        // The default OSX toolchain uses libtool as ar_executable not ar.
        // This doesn't work when used as $AR, so simply don't set it - tools will probably fall back to
        // /usr/bin/ar which is probably good enough.
        if Path::new(&ar_path).file_name() == Some("libtool".as_ref()) {
            command.env_remove("AR");
        } else {
            command.env("AR", exec_root.join(ar_path));
        }
    }

    if let Some(ld_path) = env::var_os("LD") {
        command.env("LD", exec_root.join(ld_path));
    }

    // replace env vars with a ${pwd} prefix with the exec_root
    for (key, value) in env::vars() {
        let exec_root_str = exec_root.to_str().expect("exec_root not in utf8");
        if value.contains("${pwd}") {
            env::set_var(key, value.replace("${pwd}", exec_root_str));
        }
    }

    let (buildrs_outputs, process_output) = BuildScriptOutput::outputs_from_command(&mut command)
        .map_err(|process_output| {
        format!(
            "Build script process failed{}\n--stdout:\n{}\n--stderr:\n{}",
            if let Some(exit_code) = process_output.status.code() {
                format!(" with exit code {}", exit_code)
            } else {
                String::new()
            },
            String::from_utf8(process_output.stdout)
                .expect("Failed to parse stdout of child process"),
            String::from_utf8(process_output.stderr)
                .expect("Failed to parse stdout of child process"),
        )
    })?;

    write(
        &env_file,
        BuildScriptOutput::outputs_to_env(&buildrs_outputs, &exec_root.to_string_lossy())
            .as_bytes(),
    )
    .unwrap_or_else(|_| panic!("Unable to write file {:?}", env_file));
    write(
        &output_dep_env_path,
        BuildScriptOutput::outputs_to_dep_env(
            &buildrs_outputs,
            &crate_links,
            &exec_root.to_string_lossy(),
        )
        .as_bytes(),
    )
    .unwrap_or_else(|_| panic!("Unable to write file {:?}", output_dep_env_path));
    write(&stdout_path, process_output.stdout)
        .unwrap_or_else(|_| panic!("Unable to write file {:?}", stdout_path));
    write(&stderr_path, process_output.stderr)
        .unwrap_or_else(|_| panic!("Unable to write file {:?}", stderr_path));

    let CompileAndLinkFlags {
        compile_flags,
        link_flags,
    } = BuildScriptOutput::outputs_to_flags(&buildrs_outputs, &exec_root.to_string_lossy());

    write(&compile_flags_file, compile_flags.as_bytes())
        .unwrap_or_else(|_| panic!("Unable to write file {:?}", compile_flags_file));
    write(&link_flags_file, link_flags.as_bytes())
        .unwrap_or_else(|_| panic!("Unable to write file {:?}", link_flags_file));
    Ok(())
}