mongodb/mongoid · error · Mongoid::Errors::InvalidQuery

$in argument must be an array: #{Errors::InvalidQuery.trunca

Error message

$in argument must be an array: #{Errors::InvalidQuery.truncate_expr(condition)}

What it means

Error "$in argument must be an array: #{Errors::InvalidQuery.truncate_expr(condition)}" thrown in mongodb/mongoid.

Source

Thrown at lib/mongoid/matcher/in.rb:20

  module Matcher
    # In-memory matcher for $in expression.
    #
    # @see https://www.mongodb.com/docs/manual/reference/operator/query/in/
    #
    # @api private
    module In
      # Returns whether a value satisfies an $in expression.
      #
      # @param [ true | false ] exists Not used.
      # @param [ Object ] value The value to check.
      # @param [ Array<Object> ] condition The $in condition predicate.
      #
      # @return [ true | false ] Whether the value matches.
      #
      # @api private
      module_function def matches?(_exists, value, condition)
        unless condition.is_a?(Array)
          raise Errors::InvalidQuery, "$in argument must be an array: #{Errors::InvalidQuery.truncate_expr(condition)}"
        end

        if value.is_a?(Array) && value.any? do |v|
          condition.any? do |c|
            EqImplWithRegexp.matches?('$in', v, c)
          end
        end
          return true
        end

        condition.any? do |c|
          EqImplWithRegexp.matches?('$in', value, c)
        end
      end
    end
  end
end

View on GitHub (pinned to 0da0e23d71)

When it happens

Trigger: Thrown at lib/mongoid/matcher/in.rb:20 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mongodb/mongoid@0da0e23d71 (2026-08-23). Data as JSON: /api/errors/49d3c075936c1072. Report an issue: GitHub.