denoland/deno · error

Invalid arguments

Error message

Invalid arguments

What it means

spawn() validates SpawnOptions before touching CreateProcessW: the executable path (options.file) and the argv vector (options.args) must both be non-empty, because the Windows command line is assembled from at least the program name. An empty program string or empty argv is rejected immediately with ErrorKind::InvalidInput 'Invalid arguments'.

Source

Thrown at runtime/subprocess_windows/src/process.rs:530

        let err = io::Error::last_os_error();
        drop(unsafe { Box::from_raw(ptr) });
        return Poll::Ready(Err(err));
      }
      inner.waiting = Some(Waiting {
        rx,
        wait_object,
        tx: ptr,
      });
    }
  }
}

pub fn spawn(options: &SpawnOptions) -> Result<ChildProcess, std::io::Error> {
  let mut startup = unsafe { mem::zeroed::<STARTUPINFOW>() };
  let mut info = unsafe { mem::zeroed::<PROCESS_INFORMATION>() };

  if options.file.is_empty() || options.args.is_empty() {
    return Err(std::io::Error::new(
      std::io::ErrorKind::InvalidInput,
      "Invalid arguments",
    ));
  }

  // Convert file path to UTF-16
  let application = WCString::new(&options.file);

  // Create environment block if provided
  let env_saw_path = options.env.have_changed_path();
  let maybe_env = options.env.capture_if_changed();

  let child_paths = if env_saw_path {
    if let Some(env) = maybe_env.as_ref() {
      env.get(&EnvKey::new("PATH")).map(|s| s.as_os_str())
    } else {
      None
    }

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Validate the command string is non-empty before constructing Deno.Command
2. Fix the source of the empty string: required env var, config field, or CLI argument
3. Fail fast with a clear app-level error or provide a sensible default program

Example fix

// before
const cmd = new Deno.Command(Deno.env.get("PAGER") ?? "");

// after
const pager = Deno.env.get("PAGER");
if (!pager) throw new Error("PAGER environment variable is required");
const cmd = new Deno.Command(pager);

if (typeof prog !== "string" || prog.length === 0) {
  throw new Error("command must be a non-empty string");
}
const cmd = new Deno.Command(prog);

const isNonEmptyString = (v: unknown): v is string =>
  typeof v === "string" && v.length > 0;

When it happens

Trigger: new Deno.Command("") on Windows (empty command string), or any API path such as Node-compat child_process or internal tooling that reaches spawn with an empty argv vector.

Common situations: Command name read from an unset env var or missing config field (resolving to an empty string); template strings that trim to empty; CLI wrappers forwarding an optional command that was never provided.

Related errors

• ERR_FS_INVALID_SYMLINK_TYPE
• {}: ({}) {}
• failed to unregister: {}
• nul byte found in provided data
• Process not found

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/9fc432478a24c0b8. Report an issue: GitHub.