Automattic/mongoose · error · MongooseError

Connection.prototype.dropCollection() no longer accepts a…

Error message

Connection.prototype.dropCollection() no longer accepts a callback

What it means

Mongoose 7 removed all callback-style APIs; dropCollection() is async and returns a Promise that resolves once the collection (documents and indexes) is deleted. A function in the second argument position (after the collection name) trips an explicit guard so legacy callback code fails loudly instead of the callback being silently dropped.

Solutions

1. Remove the callback and await: await conn.dropCollection('users')
2. Move the old callback body into try/catch around the awaited call

Example fix

// before
conn.dropCollection('users', (err) => { done(err); });

// after
await conn.dropCollection('users');

function dropCollectionSafe(name) {
  if (typeof name !== 'string') {
    throw new TypeError('dropCollection expects a collection name string');
  }
  return conn.dropCollection(name);
}

const isCollectionName = (v) => typeof v === 'string' && v.length > 0;

When it happens

Trigger: conn.dropCollection('users', (err) => { ... }) — a collection name followed by a callback function.

Common situations: Test teardown helpers written against mongoose 6 or earlier; migrating an old suite to mongoose 7/8/9 without rewriting cleanup code; copied legacy snippets.

Related errors

• Connection.prototype.close() no longer accepts a callback
• Connection.prototype.destroy() no longer accepts a callback
• Connection.prototype.dropDatabase() no longer accepts a…
• Connection.prototype.openUri() no longer accepts a callback
• Connection.prototype.startSession() no longer accepts a…

AI-assisted analysis of Automattic/mongoose@49cdab0136 (2026-08-21). Data as JSON: /api/errors/06741011d95ec233. Report an issue: GitHub.

Appendix: source

Thrown at lib/connection.js:811

      }
      val[arrayAtomicsSymbol] = state.atomics.get(path);
    }
  }
}

/**
 * Helper for `dropCollection()`. Will delete the given collection, including
 * all documents and indexes.
 *
 * @method dropCollection
 * @param {string} collection The collection to delete
 * @return {Promise}
 * @api public
 */

Connection.prototype.dropCollection = async function dropCollection(collection) {
  if (arguments.length >= 2 && typeof arguments[1] === 'function') {
    throw new MongooseError('Connection.prototype.dropCollection() no longer accepts a callback');
  }

  await this._waitForConnect();

  return this.db.dropCollection(collection);
};

/**
 * Waits for connection to be established, so the connection has a `client`
 *
 * @param {boolean} [noTimeout=false] if set, don't put a timeout on the operation. Used internally so `mongoose.model()` doesn't leave open handles.
 * @return {Promise}
 * @api private
 */

Connection.prototype._waitForConnect = async function _waitForConnect(noTimeout) {
  if ((this.readyState === STATES.connecting || this.readyState === STATES.disconnected) && this._shouldBufferCommands()) {
    const bufferTimeoutMS = this._getBufferTimeoutMS();

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