roc/crates/compiler/builtins/bitcode/build.rs

use roc_command_utils::{pretty_command_string, zig};
use roc_error_macros::internal_error;
use std::fs;
use std::io;
use std::path::Path;
use std::str;
use std::{env, path::PathBuf, process::Command};

#[cfg(target_os = "macos")]
use tempfile::tempdir;

/// To debug the zig code with debug prints, we need to disable the wasm code gen
const DEBUG: bool = false;

fn main() {
    println!("cargo:rerun-if-changed=build.rs");

    // "." is relative to where "build.rs" is
    // dunce can be removed once ziglang/zig#5109 is fixed
    let bitcode_path = dunce::canonicalize(Path::new(".")).unwrap();

    // workaround for github.com/ziglang/zig/issues/20501
    #[cfg(target_os = "macos")]
    let zig_cache_dir = tempdir().expect("Failed to create temp directory for zig cache");
    #[cfg(target_os = "macos")]
    std::env::set_var("ZIG_GLOBAL_CACHE_DIR", zig_cache_dir.path().as_os_str());

    // OBJECT FILES
    #[cfg(windows)]
    const BUILTINS_HOST_FILE: &str = "builtins-host.obj";

    #[cfg(not(windows))]
    const BUILTINS_HOST_FILE: &str = "builtins-host.o";

    generate_object_file(&bitcode_path, "object", BUILTINS_HOST_FILE);

    generate_object_file(
        &bitcode_path,
        "windows-x86_64-object",
        "builtins-windows-x86_64.obj",
    );

    if !DEBUG {
        generate_object_file(&bitcode_path, "wasm32-object", "builtins-wasm32.o");
    }

    copy_zig_builtins_to_target_dir(&bitcode_path);

    get_zig_files(bitcode_path.as_path(), &|path| {
        let path: &Path = path;
        println!(
            "cargo:rerun-if-changed={}",
            path.to_str().expect("Failed to convert path to str")
        );
    })
    .unwrap();

    #[cfg(target_os = "macos")]
    zig_cache_dir
        .close()
        .expect("Failed to delete temp dir zig_cache_dir.");
}

fn generate_object_file(bitcode_path: &Path, zig_object: &str, object_file_name: &str) {
    let dest_obj_path = get_lib_dir().join(object_file_name);
    let dest_obj = dest_obj_path.to_str().expect("Invalid dest object path");

    let src_obj_path = bitcode_path.join("zig-out").join(object_file_name);
    let src_obj = src_obj_path.to_str().expect("Invalid src object path");

    println!("Compiling zig object `{zig_object}` to: {src_obj}");

    // workaround for github.com/ziglang/zig/issues/20501
    #[cfg(target_os = "macos")]
    let _ = fs::remove_dir_all("./.zig-cache");

    let mut zig_cmd = zig();

    zig_cmd
        .current_dir(bitcode_path)
        .args(["build", zig_object, "-Drelease=true"]);

    run_command(zig_cmd, 0);

    println!("Moving zig object `{zig_object}` to: {dest_obj}");

    // we store this .o file in rust's `target` folder (for wasm we need to leave a copy here too)
    fs::copy(src_obj, dest_obj).unwrap_or_else(|err| {
        internal_error!(
            "Failed to copy object file {} to {}: {:?}",
            src_obj,
            dest_obj,
            err
        );
    });
}

pub fn get_lib_dir() -> PathBuf {
    // Currently we have the OUT_DIR variable which points to `/target/debug/build/roc_builtins-*/out/`.
    // So we just need to add "/bitcode" to that.
    let dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());

    // create dir if it does not exist
    fs::create_dir_all(&dir).expect("Failed to make $OUT_DIR/ dir.");

    dir
}

fn copy_zig_builtins_to_target_dir(bitcode_path: &Path) {
    // To enable roc to find the zig builtins, we want them to be moved to a folder next to the roc executable.
    // So if <roc_folder>/roc is the executable. The zig files will be in <roc_folder>/lib/*.zig
    let target_profile_dir = get_lib_dir();

    let zig_src_dir = bitcode_path.join("src");

    cp_unless_zig_cache(&zig_src_dir, &target_profile_dir).unwrap_or_else(|err| {
        internal_error!(
            "Failed to copy zig bitcode files {:?} to {:?}: {:?}",
            zig_src_dir,
            target_profile_dir,
            err
        );
    });
}

// recursively copy all the .zig files from this directory, but do *not* recurse into .zig-cache/
fn cp_unless_zig_cache(src_dir: &Path, target_dir: &Path) -> io::Result<()> {
    // Make sure the destination directory exists before we try to copy anything into it.
    std::fs::create_dir_all(target_dir).unwrap_or_else(|err| {
        internal_error!(
            "Failed to create output library directory for zig bitcode {:?}: {:?}",
            target_dir,
            err
        );
    });

    for entry in fs::read_dir(src_dir)? {
        let src_path = entry?.path();
        let src_filename = src_path.file_name().unwrap();

        // Only copy individual files if they have the .zig extension
        if src_path.extension().unwrap_or_default() == "zig" {
            let dest = target_dir.join(src_filename);

            fs::copy(&src_path, &dest).unwrap_or_else(|err| {
                internal_error!(
                    "Failed to copy zig bitcode file {:?} to {:?}: {:?}",
                    src_path,
                    dest,
                    err
                );
            });
        } else if src_path.is_dir() && src_filename != ".zig-cache" {
            // Recursively copy all directories except .zig-cache
            cp_unless_zig_cache(&src_path, &target_dir.join(src_filename))?;
        }
    }

    Ok(())
}

fn run_command(mut command: Command, flaky_fail_counter: usize) {
    let command_str = pretty_command_string(&command);
    let command_str = command_str.to_string_lossy();

    let output_result = command.output();

    match output_result {
        Ok(output) => match output.status.success() {
            true => (),
            false => {
                let error_str = match str::from_utf8(&output.stderr) {
                    Ok(stderr) => stderr.to_string(),
                    Err(_) => format!("Failed to run \"{command_str}\""),
                };

                if error_str
                    .contains("lld-link: error: failed to write the output file: Permission denied")
                {
                    internal_error!("{} failed with:\n\n  {}\n\nWorkaround:\n\n  Re-run the cargo command that triggered this build.\n\n", command_str, error_str);
                } else {
                    // We have bunch of flaky failures here on macos, particularly since upgrading to zig 13 github.com/roc-lang/roc/pull/6921
                    if cfg!(target_os = "macos") {
                        if flaky_fail_counter == 10 {
                            internal_error!("{} failed 10 times in a row. The following error is unlikely to be a flaky error: {}", command_str, error_str);
                        } else {
                            run_command(command, flaky_fail_counter + 1)
                        }
                    } else {
                        internal_error!("{} failed with:\n\n  {}\n", command_str, error_str);
                    }
                }
            }
        },
        Err(reason) => internal_error!("{} failed: {}", command_str, reason),
    }
}

fn get_zig_files(dir: &Path, cb: &dyn Fn(&Path)) -> io::Result<()> {
    if dir.is_dir() {
        for entry in fs::read_dir(dir)? {
            let entry = entry?;
            let path_buf = entry.path();
            if path_buf.is_dir() {
                if !path_buf.ends_with(".zig-cache") {
                    get_zig_files(&path_buf, cb).unwrap();
                }
            } else {
                let path = path_buf.as_path();

                match path.extension() {
                    Some(osstr) if osstr == "zig" => {
                        cb(path);
                    }
                    _ => {}
                }
            }
        }
    }
    Ok(())
}