swc-project/swc · error

failed to create directory ({}) for writing data of the fail

Error message

failed to create directory ({}) for writing data of the failed assertion: {}

What it means

Raised in print_left_right (crates/testing/src/lib.rs:270). After a failed assert_eq_ignore_span, the harness builds ./target/swc-test-results/<test name components>/ via create_dir_all; if directory creation fails (permissions, disk full, invalid path, sandbox), the panic fires and masks the underlying assertion failure. The failing create_dir_all result for the per-test results directory is the fault.

Source

Thrown at crates/testing/src/lib.rs:270

        s.into()
    }

    let (left, right) = (print(left), print(right));

    let cur = thread::current();
    let test_name = cur
        .name()
        .expect("rustc sets test name as the name of thread");

    // ./target/debug/tests/${test_name}/
    let target_dir = {
        let mut buf = paths::test_results_dir().to_path_buf();
        for m in test_name.split("::") {
            buf.push(m)
        }

        create_dir_all(&buf).unwrap_or_else(|err| {
            panic!(
                "failed to create directory ({}) for writing data of the failed assertion: {}",
                buf.display(),
                err
            )
        });

        buf
    };

    write_to_file(&target_dir.join("left"), &left);
    write_to_file(&target_dir.join("right"), &right);

    format!("----- {test_name}\n    left:\n{left}\n    right:\n{right}")
}

#[macro_export]
macro_rules! assert_eq_ignore_span {
    ($l:expr, $r:expr) => {{

View on GitHub (pinned to 5176682b65)

Solutions

1. Pre-create or verify writability of target/swc-test-results before running the test suite
2. Run tests outside read-only/sandboxed filesystems, or point the results dir at a writable location
3. Fall back to printing left/right to stdout if directory creation fails, preserving the assertion output

When it happens

Trigger: Thrown at crates/testing/src/lib.rs:270 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/0f9fc8430bd7828b. Report an issue: GitHub.