Class: RuboCop::Cop::Style::MissingRespondToMissing

Inherits:
Base
  • Object
show all
Defined in:
lib/rubocop/cop/style/missing_respond_to_missing.rb

Overview

Checks for the presence of ‘method_missing` without also defining `respond_to_missing?`.

Not defining ‘respond_to_missing?` will cause metaprogramming methods like `respond_to?` to behave unexpectedly:

source,ruby

class StringDelegator

def initialize(string)
  @string = string
end

def method_missing(name, *args)
  @string.send(name, *args)
end

end

delegator = StringDelegator.new(“foo”) # Claims to not respond to ‘upcase`. delegator.respond_to?(:upcase) # => false # But you can call it. delegator.upcase # => FOO

Examples:

# bad
def method_missing(name, *args)
  if @delegate.respond_to?(name)
    @delegate.send(name, *args)
  else
    super
  end
end

# good
def respond_to_missing?(name, include_private)
  @delegate.respond_to?(name) || super
end

def method_missing(name, *args)
  if @delegate.respond_to?(name)
    @delegate.send(name, *args)
  else
    super
  end
end

Constant Summary collapse

MSG = 
'When using `method_missing`, define `respond_to_missing?`.'

Constants inherited from Base

Base::RESTRICT_ON_SEND

Instance Attribute Summary

Attributes inherited from Base

#config, #processed_source

Instance Method Summary collapse

Methods inherited from Base

#active_support_extensions_enabled?, #add_global_offense, #add_offense, #always_autocorrect?, autocorrect_incompatible_with, badge, #begin_investigation, #callbacks_needed, callbacks_needed, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #cop_config, cop_name, #cop_name, department, documentation_url, exclude_from_registry, #excluded_file?, #external_dependency_checksum, inherited, #initialize, #inspect, joining_forces, lint?, match?, #message, #offenses, #on_investigation_end, #on_new_investigation, #on_other_file, #parse, #parser_engine, #ready, #relevant_file?, requires_gem, #string_literals_frozen_by_default?, support_autocorrect?, support_multiple_source?, #target_rails_version, #target_ruby_version

Methods included from ExcludeLimit

#exclude_limit

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

silence_warnings

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#on_def(node) ⇒ Object Also known as: on_defs 



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# File 'lib/rubocop/cop/style/missing_respond_to_missing.rb', line 57

def on_def(node)
  return unless node.method?(:method_missing)
  return if implements_respond_to_missing?(node)

  add_offense(node)
end