padrino/padrino-framework · error · Padrino::Mounter::MounterException

Unable to locate source file for app '#{app_class}', try wit

Error message

Unable to locate source file for app '#{app_class}', try with app_file: '/path/app.rb'

What it means

Error "Unable to locate source file for app '#{app_class}', try with app_file: '/path/app.rb'" thrown in padrino/padrino-framework.

Source

Thrown at padrino-core/lib/padrino-core/mounter.rb:215

      candidates  = []
      candidates << app_const.app_file if app_const.respond_to?(:app_file)
      candidates << Padrino.first_caller if File.identical?(Padrino.first_caller.to_s, Padrino.called_from.to_s)
      candidates << Padrino.mounted_root(name.downcase, 'app.rb')

      simple_name = name.split('::').last.downcase
      mod_name = name.split('::')[0..-2].join('::')

      Padrino.modules.each { |mod| candidates << mod.root(simple_name, 'app.rb') if mod.name == mod_name }
      candidates << Padrino.root('app', 'app.rb')
      candidates.find { |candidate| File.exist?(candidate) }
    end

    ###
    # Raises an exception unless app_file is located properly.
    #
    def ensure_app_file!
      message = "Unable to locate source file for app '#{app_class}', try with app_file: '/path/app.rb'"
      raise MounterException, message unless @app_file
    end

    ###
    # Raises an exception unless app_obj is defined properly.
    #
    def ensure_app_object!
      message = "Unable to locate app for '#{app_class}', try with app_class: 'MyAppClass'"
      raise MounterException, message unless @app_obj
    end
  end

  class << self
    attr_writer :mounted_root # Set root directory where padrino searches mounted apps

    ##
    # @param [Array] args
    #
    # @return [String]

View on GitHub (pinned to 167044f3d5)

When it happens

Trigger: Thrown at padrino-core/lib/padrino-core/mounter.rb:215 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of padrino/padrino-framework@167044f3d5 (2026-08-23). Data as JSON: /api/errors/bda8414ecb4e986e. Report an issue: GitHub.