denoland/deno · error

dev server exited without printing a URL

Error message

dev server exited without printing a URL

What it means

Error "dev server exited without printing a URL" thrown in denoland/deno.

Source

Thrown at cli/tools/desktop.rs:1222

      format!("failed to spawn HMR dev server: {:?}", cmd_args)
    })?;

  let stdout = child.stdout.take().ok_or_else(|| {
    deno_core::anyhow::anyhow!("failed to capture HMR dev server stdout")
  })?;
  let mut lines = BufReader::new(stdout).lines();

  let url = tokio::time::timeout(std::time::Duration::from_secs(15), async {
    while let Ok(Some(line)) = lines.next_line().await {
      let url = parse_dev_server_url(&line);
      // Echo the dev server's own startup output (banner, URL, warnings) so
      // it isn't swallowed while we scan for the URL.
      log::info!("{line}");
      if let Some(url) = url {
        return Ok(url);
      }
    }
    deno_core::anyhow::bail!("dev server exited without printing a URL")
  })
  .await
  .map_err(|_| {
    deno_core::anyhow::anyhow!(
      "{name} dev server with HMR did not start within 15s"
    )
  })??;

  // Keep forwarding the dev server's stdout so its HMR/compile logs stay
  // visible after startup instead of being silently swallowed. The task ends
  // on its own once the child is killed (on drop) and the pipe closes.
  tokio::spawn(async move {
    while let Ok(Some(line)) = lines.next_line().await {
      log::info!("{line}");
    }
  });

  Ok((url, child))

View on GitHub (pinned to 89f33cbef2)

When it happens

Trigger: Thrown at cli/tools/desktop.rs:1222 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/68af13132e80f5cf. Report an issue: GitHub.