mongodb/node-mongodb-native · warning · MongoInvalidArgumentError

Invalid first parameter to count

Error message

Invalid first parameter to count

What it means

Thrown by the deprecated FindCursor.count() (MongoInvalidArgumentError) when its first argument is a boolean. The old cursor.count(applySkipLimit) signature accepted a boolean; the current signature accepts only CountOptions. Passing true/false (often copy-pasted from old examples) is rejected.

Source

Thrown at src/cursor/find_cursor.ts:156

      this.numReturned = this.numReturned + response.batchSize;

      return response;
    } finally {
      cleanup?.();
    }
  }

  /**
   * Get the count of documents for this cursor
   * @deprecated Use `collection.estimatedDocumentCount` or `collection.countDocuments` instead
   */
  async count(options?: CountOptions): Promise<number> {
    emitWarningOnce(
      'cursor.count is deprecated and will be removed in the next major version, please use `collection.estimatedDocumentCount` or `collection.countDocuments` instead '
    );
    if (typeof options === 'boolean') {
      throw new MongoInvalidArgumentError('Invalid first parameter to count');
    }
    return await executeOperation(
      this.client,
      new CountOperation(this.namespace, this.cursorFilter, {
        ...this.findOptions, // NOTE: order matters here, we may need to refine this
        ...this.cursorOptions,
        ...options
      })
    );
  }

  /** Execute the explain for the cursor */
  async explain(): Promise<Document>;
  async explain(verbosity: ExplainVerbosityLike | ExplainCommandOptions): Promise<Document>;
  async explain(options: { timeoutMS?: number }): Promise<Document>;
  async explain(
    verbosity: ExplainVerbosityLike | ExplainCommandOptions,
    options: { timeoutMS?: number }

View on GitHub (pinned to 3366c21a63)

Solutions

1. Replace cursor.count() with collection.countDocuments(filter) or collection.estimatedDocumentCount()
2. If you must use count(), pass an options object (e.g. { limit, skip }) or no argument
3. Remove the boolean argument entirely

Example fix

// before
const n = await coll.find({}).limit(10).count(true);
// after
const n = await coll.countDocuments({}, { limit: 10 });

// Before calling count(), ensure the arg is not a boolean
function safeCount(cursor, opts) {
  if (typeof opts === 'boolean') {
    console.warn('cursor.count(boolean) is unsupported; migrating to countDocuments');
    return cursor.client.db().collection('x').countDocuments({}, opts);
  }
  return cursor.count(opts);
}

const isCountOptions = (o) => o == null || typeof o === 'object';

When it happens

Trigger: cursor.count(true) or cursor.count(false). Most commonly from pre-4.0 tutorials where count took a boolean applySkipLimit flag.

Common situations: Upgrading from driver v3 or earlier; copying old StackOverflow snippets; automated migrations that left boolean count() calls in place.

Related errors

• ${optionWord} ${Array.from(unsupportedOptions).join(', ')} $
• Unable to make a writeConcern from fsync=${value}
• Unable to make a writeConcern from journal=${value}
• Cannot make WriteConcern from wtimeout
• Argument "iterator" must be a function

AI-assisted analysis of mongodb/node-mongodb-native@3366c21a63 (2026-08-04). Data as JSON: /data/errors/02917a6b38b21773.json. Report an issue: GitHub.