What causes "failed to capture stderr" in nikivdev/code?

Do not set stderr on the Command before passing it to run_command_with_output

failed to capture stderr

Error message

failed to capture stderr

What it means

Identical guard to the stdout case but for stderr: run_command_with_output pipes stderr and take()s it; if the handle is absent it throws 'failed to capture stderr'. With Stdio::piped() applied before spawn, this should never trigger.

Source

Thrown at src/storage.rs:398

fn resolve_jazz_tools_package_spec(raw: Option<&str>) -> String {
    raw.map(str::trim)
        .filter(|value| !value.is_empty())
        .unwrap_or(DEFAULT_JAZZ_TOOLS_NPX_SPEC)
        .to_string()
}

fn run_command_with_output(mut cmd: Command) -> Result<Output> {
    let mut child = cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).spawn()?;

    let mut stdout = child
        .stdout
        .take()
        .ok_or_else(|| anyhow::anyhow!("failed to capture stdout"))?;
    let mut stderr = child
        .stderr
        .take()
        .ok_or_else(|| anyhow::anyhow!("failed to capture stderr"))?;

    let stdout_handle = thread::spawn(move || {
        let mut buf = Vec::new();
        let _ = stdout.read_to_end(&mut buf);
        buf
    });
    let stderr_handle = thread::spawn(move || {
        let mut buf = Vec::new();
        let _ = stderr.read_to_end(&mut buf);
        buf
    });

    let start = Instant::now();
    let mut next_log = Duration::from_secs(10);
    let status = loop {
        if let Some(status) = child.try_wait()? {
            break status;
        }

View on GitHub (pinned to a747e741ae)

Solutions

Do not set stderr on the Command before passing it to run_command_with_output
Keep the .stderr(Stdio::piped()) call immediately before spawn()
If triggered, capture the error anyway by falling back to an empty buffer instead of failing

Example fix

// before
.take()
.ok_or_else(|| anyhow::anyhow!("failed to capture stderr"))?;
// after
.take().unwrap_or_default(); // or fail with context including the command name

Defensive patterns

Strategy: try-catch

Try / catch

match run_command_with_output(cmd) {
    Ok(out) => out,
    Err(e) if e.to_string().contains("failed to capture stderr") => {
        // stderr pipe missing; degrade gracefully by ignoring stderr
        eprintln!("stderr unavailable: {}", e);
        // proceed without stderr contents
    }
    Err(e) => return Err(e),
}

Prevention

Do not pre-set stderr on the Command at call sites
Keep .stderr(Stdio::piped()) in the helper itself
Prefer unwrap_or_default over hard error for non-critical streams

When it happens

Trigger: Calling run_command_with_output (via create_jazz_app_credentials) when the child's stderr pipe was not established — only possible if stdio configuration conflicts so child.stderr is None after spawn.

Common situations: Effectively unreachable in current code; would appear only after modifications that remove .stderr(Stdio::piped()) or pre-set stderr to inherit/null in the caller.

Related errors

AI-assisted analysis of nikivdev/code@a747e741ae (2026-09-01). Data as JSON: /api/errors/c0c4e141fa0b47d9. Report an issue: GitHub.