facebook/flow · warning

failed to clear spinner line

Error message

failed to clear spinner line

What it means

When the server tells the client to hold (PleaseHold) or otherwise returns a retryable state, the client clears the spinner line on stderr before returning; if print_clear_line fails, it panics with this message. Like other spinner panics, it indicates stderr became unwritable mid-command.

Source

Thrown at rust_port/crates/flow_command_utils/src/lib.rs:2959

                        bincode::config::legacy()
                            .with_limit::<{ flow_commands_connect::command_connect_simple::MAX_FRAME_BYTES }>(),
                    )
                });
            let response = match response {
                Ok(r) => r,
                Err(bincode::error::DecodeError::Io { inner, .. })
                    if matches!(
                        inner.kind(),
                        std::io::ErrorKind::BrokenPipe
                            | std::io::ErrorKind::ConnectionReset
                            | std::io::ErrorKind::UnexpectedEof
                    ) =>
                {
                    if show_progress && flow_utils_tty::spinner_used() {
                        let stderr = std::io::stderr();
                        let mut stderr = stderr.lock();
                        flow_utils_tty::print_clear_line(&mut stderr)
                            .expect("failed to clear spinner line");
                    }
                    return Err(());
                }
                Err(e) => {
                    if show_progress && flow_utils_tty::spinner_used() {
                        let stderr = std::io::stderr();
                        let mut stderr = stderr.lock();
                        flow_utils_tty::print_clear_line(&mut stderr)
                            .expect("failed to clear spinner line");
                    }
                    panic!("Unknown exception reading from the server: {}", e)
                }
            };
            match response {
                MonitorToClientMessage::PleaseHold(server_status, watcher_status) => {
                    let status_string = {
                        if server_status::is_free(&server_status) {
                            // Let's ignore messages from the server that it is free.

View on GitHub (pinned to 5c86586199)

Solutions

1. Keep stderr attached and open for the whole flow command; avoid early-exiting pipe consumers.
2. Run without a TTY/spinner (redirect output, or disable progress) so the clear-line path is skipped.
3. Free disk space / fix permissions on the stderr target file.

Example fix

// before
flow status | grep -m1 ready   # grep exits, pipe closes
// after
flow status > out.log 2>&1; grep -m1 ready out.log

[ -t 2 ] || [ -w /dev/stderr ] || echo 'stderr unusable; run without progress output'

flow status > status.log 2>&1 || { cat status.log; exit 1; }

When it happens

Trigger: During a server command with show_progress enabled and a spinner in use, the PleaseHold/Err(()) branch calls flow_utils_tty::print_clear_line on locked stderr and the write fails (closed pipe, unwritable target).

Common situations: Long `flow check`/IDE-status commands whose stderr pipe is closed by a supervisor, or output redirected to a file that became unwritable (disk full).

Related errors

• failed to flush spinner status
• failed to flush spinner status
• failed to clear spinner line
• failed to clear spinner line
• failed to write spinner status

AI-assisted analysis of facebook/flow@5c86586199 (2026-09-08). Data as JSON: /api/errors/d89ec523ae3e8426. Report an issue: GitHub.