flippercloud/flipper · error · ArgumentError

#{object.inspect} cannot be converted into an expression

Error message

#{object.inspect} cannot be converted into an expression

What it means

Error "#{object.inspect} cannot be converted into an expression" thrown in flippercloud/flipper.

Source

Thrown at lib/flipper/expression.rb:19

require "flipper/expression/builder"
require "flipper/expression/constant"

module Flipper
  class Expression
    include Builder

    PruneResult = Struct.new(:expression, :constant_value, keyword_init: true)
    private_constant :PruneResult

    def self.build(object)
      return object if object.is_a?(self) || object.is_a?(Constant)

      case object
      when Hash
        name = object.keys.first
        args = object.values.first
        unless name
          raise ArgumentError, "#{object.inspect} cannot be converted into an expression"
        end

        new(name, Array(args).map { |o| build(o) })
      when String, Numeric, FalseClass, TrueClass
        Expression::Constant.new(object)
      when Symbol
        Expression::Constant.new(object.to_s)
      else
        raise ArgumentError, "#{object.inspect} cannot be converted into an expression"
      end
    end

    # Use #build
    private_class_method :new

    attr_reader :name, :function, :args

    def initialize(name, args = [])

View on GitHub (pinned to 1f86de3ec9)

Solutions

1. Build the expression with Flipper::Expression builders (e.g. Flipper.expression(...)) or a supported Hash form
2. Use the documented expression DSL instead of passing arbitrary objects
3. Check the value type: only Hashes with valid operator keys and Expression objects are convertible

When it happens

Trigger: Thrown at lib/flipper/expression.rb:19 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of flippercloud/flipper@1f86de3ec9 (2026-08-23). Data as JSON: /api/errors/9d9f39aa8392ff97. Report an issue: GitHub.