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Class: RuboCop::Cop::Lint::UnusedPrivateMethod

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
self, ::RuboCop::Cop::ProjectIndexHelp, ::RuboCop::Cop::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/lint/unused_private_method.rb

Overview

Checks for private instance methods that are not referenced anywhere in the project.

The check is powered by the project-wide index, so it only runs when AllCops/UseProjectIndex is enabled and the rubydex gem is installed. Without the index the cop does nothing.

A method counts as referenced when a call with its name appears anywhere in the indexed project (regardless of the receiver), when it is the source of an alias, or when its name appears in the same file as a symbol or inside a string literal (covering send(:name) and declarative DSLs like before_action :name). Methods defined in classes or modules with descendants are not checked, since they may be invoked through super or inherited dispatch, and neither are methods whose names are built dynamically (e.g. send("do_#{action}")).

The cop is disabled by default because symbol-based references from other files (e.g. a Rails callback declared in a concern) cannot be detected and would be reported as false positives. It is best suited for occasional dead-code sweeps rather than permanent enforcement.

Examples:

# bad - {helper} is never referenced anywhere in the project
class Service
  def call
    do_something
  end

  private

  def helper
  end
end

# good
class Service
  def call
    do_something(helper)
  end

  private

  def helper
  end
end

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::ProjectIndexHelp - Included

BUILTIN_DOCUMENT_URI, FILE_URI_PREFIX, WINDOWS_DRIVE_PREFIX

Class Attribute Summary

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,
.support_autocorrect?

Returns if class supports autocorrect.
.support_multiple_source?

Override if your cop should be called repeatedly for multiple investigations Between calls to #on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

  • .reference_names_cache

    The reference-name set is derived once per index and shared by the per-file cop instances.

::RuboCop::Cop::Base - Inherited

.autocorrect_incompatible_with

List of cops that should not try to autocorrect at the same time as this cop.
.badge

Naming.
.callbacks_needed, .cop_name, .department,
.documentation_url

Returns a url to view this cops documentation online.
.exclude_from_registry

Call for abstract Cop classes.
.inherited,
.joining_forces

Override and return the Force class(es) you need to join.
.match?

Returns true if the cop name or the cop namespace matches any of the given names.
.new,
.requires_gem

Register a version requirement for the given gem name.
.restrict_on_send

::RuboCop::ExcludeLimit - Extended

exclude_limit

Sets up a configuration option to have an exclude limit tracked.
transform

Instance Attribute Summary

::RuboCop::Cop::Base - Inherited

#active_support_extensions_enabled?, #always_autocorrect?, #config, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #processed_source, #project_index, #string_literals_frozen_by_default?, #target_satisfies_all_gem_version_requirements?

::RuboCop::Cop::AutocorrectLogic - Included

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

Instance Method Summary

::RuboCop::Cop::ProjectIndexHelp - Included

#external_dependency_checksum, #compute_project_index_signature,
#definitions_in_other_files

Returns the definitions among definitions that live in a file other than the one being inspected, ordered by path and line.
#indexed_singleton_member

A namespace without any singleton method has no singleton-class declaration of its own, so the lookup starts from the first ancestor that has one; its find_member covers the rest of the chain.
#indexed_singleton_of

The declaration of `declaration’s singleton class, or nil when no singleton method is defined on it anywhere in the project.
#inherited_index_member?

Whether an ancestor of scope other than scope itself defines member_name.
#lexical_nesting_of

The lexical nesting the node’s constants resolve through, outermost first.
#prior_definition_in_other_file, #project_index_signature,
#resolve_constant_in_index

Resolves a constant node the way Ruby does: the first segment through the lexical nesting and every following segment inside the previous one.
#same_file?

::RuboCop::Cop::Base - Inherited

#add_global_offense

Adds an offense that has no particular location.
#add_offense

Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.
#begin_investigation

Called before any investigation.
#callbacks_needed,
#cop_config

Configuration Helpers.
#cop_name, #excluded_file?,
#external_dependency_checksum

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:
#inspect,
#message

Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.
#name

Alias for Base#cop_name.
#offenses,
#on_investigation_end

Called after all on_…​
#on_new_investigation

Called before all on_…​
#on_other_file

Called instead of all on_…​
#parse

There should be very limited reasons for a Cop to do it’s own parsing.
#parser_engine,
#ready

Called between investigations.
#relevant_file?,
#target_gem_version

Returns a gems locked versions (i.e.
#target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,
#callback_argument

Reserved for Cop::Cop.
#complete_investigation

Called to complete an investigation.
#correct, #current_corrector,
#current_offense_locations

Reserved for Commissioner:
#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #matches_absolute_include_pattern?, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.
#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #eol_comment, #eol_comment_would_be_inside_literal?, #heredoc_range, #line_with_eol_comment_too_long?, #max_line_length, #multiline_ranges, #multiline_string?,
#range_by_lines

Expand the given range to include all of any lines it covers.
#range_of_first_line, #string_continuation?, #surrounding_heredoc?, #surrounding_percent_array?

::RuboCop::Cop::IgnoredNode - Included

#ignore_node, #ignored_node?, #part_of_ignored_node?, #ignored_nodes

Constructor Details

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

Class Method Details

.reference_names_cache

The reference-name set is derived once per index and shared by the per-file cop instances.

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 67



def reference_names_cache
  @reference_names_cache ||= {}.compare_by_identity
end


  







Instance Method Details



  

    #checkable_declaration(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 91



def checkable_declaration(node)
  return nil if IMPLICITLY_INVOKED_METHODS.include?(node.method_name)
  return nil if node.each_ancestor(:any_def, :any_block, :sclass).any?
  return nil unless (namespace_node = node.each_ancestor(:class, :module).first)

  declaration = method_declaration(node, namespace_node)
  declaration if declaration&.private?
end


  








  

    #literal_names   (private)
  



  

    


Symbol literals and identifier-like tokens inside string literals in the
current file, covering send(:name), declarative DSLs like
before_action :name and names embedded in strings (e.g. node-pattern
#helper references).



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 123



def literal_names
  @literal_names ||=
    processed_source.ast.each_descendant(:sym, :str)
                    .with_object(Set.new) do |literal, names|
      if literal.sym_type?
        names << literal.value.to_s
      else
        literal.value.scan(IDENTIFIER_PATTERN) { |token| names << token }
      end
    end
end


  








  

    #method_declaration(node, namespace_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 100



def method_declaration(node, namespace_node)
  namespace = resolve_constant_in_index(namespace_node.identifier)
  return nil unless namespace.is_a?(Rubydex::Namespace)

  namespace.member("#{node.method_name}()")
end


  








  

    #on_def(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 77



def on_def(node)
  return unless project_index

  declaration = checkable_declaration(node)
  return unless declaration
  return if referenced?(node.method_name)
  return if owner_with_descendants?(declaration) || override?(declaration, node.method_name)

  message = format(MSG, method: node.method_name)
  add_offense(node.loc.keyword.join(node.loc.name), message: message)
end


  








  

    #on_new_investigation  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 72



def on_new_investigation
  @literal_names = nil
  super
end


  








  

    #override?(declaration, method_name)  ⇒ Boolean  (private)
  



  

    


An override of an inherited method may be invoked polymorphically
(e.g. a framework hook), even when no direct reference exists.



  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 146



def override?(declaration, method_name)
  owner = declaration.owner
  return false unless owner.is_a?(Rubydex::Namespace)

  owner.ancestors.any? do |ancestor|
    ancestor.name != owner.name && ancestor.member("#{method_name}()")
  end
end


  








  

    #owner_with_descendants?(declaration)  ⇒ Boolean  (private)
  



  

    


A method defined in a class or module with descendants may be invoked
through super or inherited dispatch, which the index does not track.



  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 137



def owner_with_descendants?(declaration)
  owner = declaration.owner
  return false unless owner.is_a?(Rubydex::Namespace)

  owner.descendants.any? { |descendant| descendant.name != owner.name }
end


  








  

    #referenced?(method_name)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 107



def referenced?(method_name)
  name = method_name.to_s

  referenced_names.include?(name) || literal_names.include?(name)
end


  








  

    #referenced_names   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_private_method.rb', line 113



def referenced_names
  self.class.reference_names_cache[project_index] ||=
    project_index.method_references
                 .to_set { |reference| reference.name.delete_suffix('()') }
end