denoland/deno · error · AnyError

unexpected argument '{name}' found

Error message

unexpected argument '{name}' found

What it means

`dcore`'s hand-rolled parser recognizes only `-h`/`--help`, the three `--inspect*` flags, `--strace-ops`, `--strace-ops-summary`, and `--v8-flags=<value>`. Any other token beginning with `-` (except the bare `-` marker) falls to the catch-all arm and bails as an unexpected argument.

Source

Thrown at libs/dcore/src/main.rs:221

          let addr = parse_addr(name, value)?;
          match name {
            "--inspect" => out.inspect = Some(addr),
            "--inspect-wait" => out.inspect_wait = Some(addr),
            // `--inspect-brk` is accepted but not wired up to the inspector
            // server, matching the previous clap-based behavior.
            _ => {}
          }
        }
        "--strace-ops" => out.strace_ops = true,
        "--strace-ops-summary" => out.strace_ops_summary = true,
        "--v8-flags" => {
          let Some(value) = value else {
            bail!("equal sign is needed when assigning values to '--v8-flags'");
          };
          out.v8_flags.extend(value.split(',').map(String::from));
        }
        _ if name.starts_with('-') && name != "-" => {
          bail!("unexpected argument '{name}' found");
        }
        _ => {
          if file_path.is_some() {
            bail!("unexpected argument '{arg}' found");
          }
          file_path = Some(arg);
        }
      }
    }

    let Some(file_path) = file_path else {
      bail!(
        "the following required arguments were not provided:\n  <file_path>"
      );
    };
    out.file_path = file_path;
    Ok(Some(out))
  }

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Remove flags dcore does not support — list them with `dcore -h`.
2. Use the full `deno` binary when you need permission/watch/reload flags; dcore is the minimal core runner with only inspect/strace/v8 flags.
3. Fix typos in supported flags (e.g. `--strace-ops`, not `--strace-op`).

Example fix

# before
dcore --allow-read --quiet app.js
# error: unexpected argument '--allow-read' found

# after: dcore has no permission system or quiet flag
dcore app.ts
# need those flags? use deno:
deno run --allow-read --quiet app.ts

# flag allowlist check for dcore invocations
for a in "$@"; do
  case "$a" in
    -h|--help|--inspect|--inspect-brk|--inspect-wait|--strace-ops|--strace-ops-summary|-) ;;
    --inspect=*|--inspect-brk=*|--inspect-wait=*|--v8-flags=*) ;;
    -*) echo "dcore does not support: $a" ;;
  esac
done

When it happens

Trigger: Passing full-Deno CLI flags to dcore: `dcore --allow-read app.js`, `--quiet`, `--reload`, `--watch`; or a typo like `--strace-op` (missing the s). Flags dcore does implement always parse via their exact names.

Common situations: Muscle memory from `deno run` flags (permissions, watch, reload); scripts or aliases originally written for the deno binary; docs copied between the two CLIs.

Related errors

• the argument '{previous}' cannot be used with '{name}'
• equal sign is needed when assigning values to '--v8-flags'
• unexpected argument '{arg}' found
• the following required arguments were not provided: <file_
• Invalid type for fetch: must be a function

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/6282d2e39fbae11a. Report an issue: GitHub.