denoland/deno · error · TypeError

ERR_INVALID_ARG_TYPE

ERR_INVALID_ARG_TYPE

Error message

The "channel" argument must be one of type string or symbol. Received ${actual}

What it means

diagnostics_channel.channel(name) (and everything built on it: subscribe(), unsubscribe(), TracingChannel's string form) requires the channel identifier to be a string or a symbol. The WeakRefMap cache is consulted first, but a non-string/non-symbol name is never cached, so it always falls through to this ERR_INVALID_ARG_TYPE.

Source

Thrown at ext/node/polyfills/diagnostics_channel.js:254

  get hasSubscribers() {
    return false;
  }

  publish() {}

  runStores(_data, fn, thisArg, ...args) {
    return ReflectApply(fn, thisArg, args);
  }
}

const channels = new WeakRefMap();

function channel(name) {
  const ch = channels.get(name);
  if (ch) return ch;

  if (typeof name !== "string" && typeof name !== "symbol") {
    throw new ERR_INVALID_ARG_TYPE("channel", ["string", "symbol"], name);
  }

  return new Channel(name);
}

function subscribe(name, subscription) {
  return channel(name).subscribe(subscription);
}

function unsubscribe(name, subscription) {
  return channel(name).unsubscribe(subscription);
}

function hasSubscribers(name) {
  const ch = channels.get(name);
  if (!ch) return false;

  return ch.hasSubscribers;

View on GitHub (pinned to 89f33cbef2)

Solutions

1. Coerce to string explicitly: dc.channel(String(name))
2. Use Symbol.for('namespace:channel') for collision-free symbolic names
3. If you already hold a Channel instance, use it directly instead of calling channel() again

Example fix

// before
const name = 42; // from a numeric enum
const ch = dc.channel(name); // throws

// after
const ch = dc.channel(String(name));

const name2 = typeof name === 'symbol' ? name : String(name);
const ch = dc.channel(name2);

const isChannelName = (v) => typeof v === 'string' || typeof v === 'symbol';

When it happens

Trigger: dc.channel(42); dc.subscribe(['http'], fn); dc.unsubscribe(null, fn); new TracingChannel({ toString: () => 'x' }) paths that stringify late — anything where the name is not literally string or symbol.

Common situations: Names built from enums stored as numbers, values read from structured config, iterating object keys with a numeric index, or passing a channel object where the name is expected.

Related errors

• resolve hook must return { shortCircuit: true } or call next
• load hook must return { shortCircuit: true } or call nextLoa
• A file exists at the destination: ${destStr}
• ERR_MISSING_ARGS
• No callback function supplied

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/11f8d5f5579abf82. Report an issue: GitHub.