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Class: RuboCop::Cop::Lint::ConstantReassignment

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::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/lint/constant_reassignment.rb

Overview

Checks for constant reassignments.

Emulates Ruby’s runtime warning "already initialized constant X" when a constant is reassigned in the same file and namespace using the NAME = value syntax.

The cop cannot catch all offenses, like, for example, when a constant is reassigned in another file, or when using metaprogramming (Module#const_set).

The cop only takes into account constants assigned in a "simple" way: directly inside class/module definition, or within another constant. Other type of assignments (e.g., inside a conditional) are disregarded.

The cop also tracks constant removal using Module#remove_const with symbol or string argument.

Examples:

# bad
X = :foo
X = :bar

# bad
class A
  X = :foo
  X = :bar
end

# bad
module A
  X = :foo
  X = :bar
end

# good - keep only one assignment
X = :bar

class A
  X = :bar
end

module A
  X = :bar
end

# good - use OR assignment
X = :foo
X ||= :bar

# good - use conditional assignment
X = :foo
X = :bar unless defined?(X)

# good - remove the assigned constant first
class A
  X = :foo
  remove_const :X
  X = :bar
end

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

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

::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, #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::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, #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, #heredoc_range, #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, #range_overlaps_offense?, #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

#ancestor_namespaces(node) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 139



def ancestor_namespaces(node)
  node
    .each_ancestor(:class, :module)
    .map { |ancestor| ancestor.identifier.short_name }
    .reverse
end


  








  

    #constant_names   (private)
  

  [ GitHub ]


  

  


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



def constant_names
  @constant_names ||= Set.new
end


  








  

    #constant_namespaces(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 135



def constant_namespaces(node)
  node.each_path.select(&:const_type?).map(&:short_name)
end


  








  

    #fixed_constant_path?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 98



def fixed_constant_path?(node)
  node.each_path.all? { |path| path.cbase_type? || path.const_type? || path.self_type? }
end


  








  

    #freeze_method?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 115



def freeze_method?(node)
  node.send_type? && node.method?(:freeze)
end


  








  

    #fully_qualified_constant_name(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 119



def fully_qualified_constant_name(node)
  if node.absolute?
    namespace = node.namespace.const_type? ? node.namespace.source : nil

    "#{namespace}::#{node.name}"
  else
    constant_namespaces = ancestor_namespaces(node) + constant_namespaces(node)

    fully_qualified_name_for(constant_namespaces, node.name)
  end
end


  








  

    #fully_qualified_name_for(namespaces, constant)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 131



def fully_qualified_name_for(namespaces, constant)
  ['', *namespaces, constant].join('::')
end


  








  

    #namespace_definition?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 111



def namespace_definition?(node)
  node.module_type? || node.class_type?
end


  








  

    #on_casgn(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 76



def on_casgn(node)
  return unless fixed_constant_path?(node)
  return unless simple_assignment?(node)
  return if constant_names.add?(fully_qualified_constant_name(node))

  add_offense(node, message: format(MSG, constant: node.name))
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 84



def on_send(node)
  constant = remove_constant(node)

  return unless constant

  namespaces = ancestor_namespaces(node)

  return if namespaces.none?

  constant_names.delete(fully_qualified_name_for(namespaces, constant))
end


  








  

    #remove_constant(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 71



def_node_matcher :remove_constant, <<~PATTERN
  (send _ :remove_const
    ({sym str} $_))
PATTERN


  








  

    #simple_assignment?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/constant_reassignment.rb', line 102



def simple_assignment?(node)
  node.ancestors.all? do |ancestor|
    return true if namespace_definition?(ancestor)

    ancestor.begin_type? || ancestor.literal? || ancestor.casgn_type? ||
      freeze_method?(ancestor)
  end
end