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Class: RuboCop::Cop::Style::StaticClass

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::AutoCorrector, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
self, ::RuboCop::Cop::VisibilityHelp, ::RuboCop::Cop::RangeHelp, ::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/style/static_class.rb

Overview

Checks for places where classes with only class methods can be replaced with a module. Classes should be used only when it makes sense to create instances out of them.

When AllCops/UseProjectIndex is enabled and the rubydex gem is installed, classes that are subclassed anywhere in the project are not reported, since converting them to modules would break their subclasses.

Examples:

# bad
class SomeClass
  def self.some_method
    # body omitted
  end

  def self.some_other_method
    # body omitted
  end
end

# good
module SomeModule
  module_function

  def some_method
    # body omitted
  end

  def some_other_method
    # body omitted
  end
end

# good - has instance method
class SomeClass
  def instance_method; end
  def self.class_method; end
end

Cop Safety Information:

  • This cop is unsafe, because it is possible that this class is a parent for some other subclass, monkey-patched with instance methods or a dummy instance is instantiated from it somewhere.

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::ProjectIndexHelp - Included

BUILTIN_DOCUMENT_URI, FILE_URI_PREFIX, WINDOWS_DRIVE_PREFIX

::RuboCop::Cop::RangeHelp - Included

BYTE_ORDER_MARK, NOT_GIVEN

::RuboCop::Cop::VisibilityHelp - Included

VISIBILITY_SCOPES

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

support_autocorrect?

::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

::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::VisibilityHelp - Included

#find_visibility_end

Navigate to find the last protected method.
#find_visibility_start, #node_visibility, #node_visibility_from_visibility_block, #node_visibility_from_visibility_inline, #node_visibility_from_visibility_inline_on_def, #node_visibility_from_visibility_inline_on_method_name, #visibility_block?, #visibility_inline_on_def?, #visibility_inline_on_method_name?

::RuboCop::Cop::RangeHelp - Included

#add_range,
#arguments_range

A range containing the first to the last argument of a method call or method definition.
#column_offset_between,
#contents_range

A range containing only the contents of a literal with delimiters (e.g.
#directions,
#effective_column

Returns the column attribute of the range, except if the range is on the first line and there’s a byte order mark at the beginning of that line, in which case 1 is subtracted from the column value.
#final_pos, #move_pos, #move_pos_str, #range_between, #range_by_whole_lines, #range_with_comments, #range_with_comments_and_lines, #range_with_surrounding_comma, #range_with_surrounding_space, #source_range

::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

Instance Method Details

#autocorrect(corrector, class_node) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/static_class.rb', line 85



def autocorrect(corrector, class_node)
  corrector.replace(class_node.loc.keyword, 'module')
  corrector.insert_after(class_node.loc.name, "\nmodule_function\n")

  class_elements(class_node).each do |node|
    if node.defs_type?
      autocorrect_def(corrector, node)
    elsif node.sclass_type?
      autocorrect_sclass(corrector, node)
    end
  end
end


  








  

    #autocorrect_def(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 98



def autocorrect_def(corrector, node)
  corrector.remove(
    range_between(node.receiver.source_range.begin_pos, node.loc.name.begin_pos)
  )
end


  








  

    #autocorrect_sclass(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 104



def autocorrect_sclass(corrector, node)
  corrector.remove(
    range_between(node.loc.keyword.begin_pos, node.identifier.source_range.end_pos)
  )
  corrector.remove(node.loc.end)
end


  








  

    #class_convertible_to_module?(class_node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 111



def class_convertible_to_module?(class_node)
  nodes = class_elements(class_node)
  return false if nodes.empty?

  nodes.all? do |node|
    (node_visibility(node) == :public && node.defs_type?) ||
      sclass_convertible_to_module?(node) ||
      node.equals_asgn? ||
      extend_call?(node)
  end
end


  








  

    #class_elements(class_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 135



def class_elements(class_node)
  class_def = class_node.body

  if !class_def
    []
  elsif class_def.begin_type?
    class_def.children
  else
    [class_def]
  end
end


  








  

    #extend_call?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 123



def extend_call?(node)
  node.send_type? && node.method?(:extend)
end


  








  

    #on_class(class_node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 59



def on_class(class_node)
  return if class_node.parent_class
  return unless class_convertible_to_module?(class_node)
  return if subclassed_in_project?(class_node)

  add_offense(class_node) do |corrector|
    autocorrect(corrector, class_node)
  end
end


  








  

    #sclass_convertible_to_module?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 127



def sclass_convertible_to_module?(node)
  return false unless node.sclass_type?

  class_elements(node).all? do |child|
    node_visibility(child) == :public && (child.def_type? || child.equals_asgn?)
  end
end


  








  

    #subclassed_in_project?(class_node)  ⇒ Boolean  (private)
  



  

    


When AllCops/UseProjectIndex is enabled, a class with descendants
anywhere in the project is not reported: converting it to a module
would break its subclasses.



  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/static_class.rb', line 74



def subclassed_in_project?(class_node)
  return false unless project_index

  declaration = resolve_constant_in_index(class_node.identifier)
  return false unless declaration.is_a?(Rubydex::Class)

  declaration.descendants.any? { |descendant| descendant.name != declaration.name }
rescue StandardError
  false
end