swc-project/swc · error

failed to create a temp directory

Error message

failed to create a temp directory

What it means

After ensuring the scratch root exists, `exec_with_node_test_runner` creates a temp directory inside it with `tempdir_in(&root)`. The `expect("failed to create a temp directory")` panics when tempfile cannot create that directory: permission denied on the parent, disk/inode exhaustion, or platform temp-creation limits (e.g. name collisions or EMFILE on some systems).

Source

Thrown at crates/swc_ecma_transforms_testing/src/lib.rs:653

fn exec_with_node_test_runner(src: &str) -> Result<(), ()> {
    let root = CARGO_TARGET_DIR.join("swc-es-exec-testing");

    create_dir_all(&root).expect("failed to create parent directory for temp directory");

    let hash = calc_hash(src);
    let success_cache = root.join(format!("{hash}.success"));

    if env::var("SWC_CACHE_TEST").unwrap_or_default() == "1" {
        println!("Trying cache as `SWC_CACHE_TEST` is `1`");

        if success_cache.exists() {
            println!("Cache: success");
            return Ok(());
        }
    }

    let tmp_dir = tempdir_in(&root).expect("failed to create a temp directory");
    create_dir_all(&tmp_dir).unwrap();

    let path = tmp_dir.path().join(format!("{hash}.test.js"));

    let mut tmp = OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .open(&path)
        .expect("failed to create a temp file");
    write!(tmp, "{src}").expect("failed to write to temp file");
    tmp.flush().unwrap();

    let test_runner_path = find_executable("mocha").expect("failed to find `mocha` from path");

    let mut base_cmd = if cfg!(target_os = "windows") {
        let mut c = Command::new("cmd");
        c.arg("/C").arg(&test_runner_path);

View on GitHub (pinned to 5176682b65)

Solutions

1. Fix permissions/ownership of `$CARGO_TARGET_DIR/swc-es-exec-testing` so the test user can create directories.
2. Check free space and inodes (`df -h`, `df -i`) and clean the build disk.
3. Reduce test parallelism if fd/inode exhaustion is implicated, or raise ulimits in the CI job.
4. As a workaround for constrained envs, disable execution tests with `EXEC=0`.

fn can_create_dirs_under(p: &std::path::Path) -> bool {
    let probe = p.join(".dir-probe");
    std::fs::create_dir(&probe).is_ok() && {
        let _ = std::fs::remove_dir(&probe);
        true
    }
}

When it happens

Trigger: Execution tests running with a read-only or root-owned `$CARGO_TARGET_DIR/swc-es-exec-testing`, out-of-space or out-of-inode filesystems, or heavy parallel test execution hitting file-descriptor limits.

Common situations: Same environments as the directory-creation failure: locked-down CI sandboxes, mixed-ownership target dirs after sudo runs, full build disks.

Related errors

• failed to create parent directory for temp directory
• failed to create a temp file
• failed to read file
• failed to run mocha
• Fallback bindings does not support filesystem access.

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/c100a721dec58c58. Report an issue: GitHub.