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Class: RuboCop::Cop::Lint::UnreachableLoop

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

Overview

Checks for loops that will have at most one iteration.

A loop that can never reach the second iteration is a possible error in the code. In rare cases where only one iteration (or at most one iteration) is intended behavior, the code should be refactored to use if conditionals.

Note
 Block methods that are used with Enumerables are considered to be loops.

AllowedPatterns can be used to match against the block receiver in order to allow code that would otherwise be registered as an offense (eg. times used not in an Enumerable context).

Examples:

# bad
while node
  do_something(node)
  node = node.parent
  break
end

# good
while node
  do_something(node)
  node = node.parent
end

# bad
def verify_list(head)
  item = head
  begin
    if verify(item)
      return true
    else
      return false
    end
  end while(item)
end

# good
def verify_list(head)
  item = head
  begin
    if verify(item)
      item = item.next
    else
      return false
    end
  end while(item)

  true
end

# bad
def find_something(items)
  items.each do |item|
    if something?(item)
      return item
    else
      raise NotFoundError
    end
  end
end

# good
def find_something(items)
  items.each do |item|
    if something?(item)
      return item
    end
  end
  raise NotFoundError
end

# bad
2.times { raise ArgumentError }

AllowedPatterns: ['(exactly|at_least|at_most)\(\d+\)\.times'] (default)

# good
exactly(2).times { raise StandardError }

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::AllowedPattern - Included

#ignored_line?, #matches_ignored_pattern?

::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::AllowedPattern - Included

#allowed_line?, #allowed_patterns, #cop_config_deprecated_methods_values, #cop_config_patterns_values, #matches_allowed_pattern?

::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_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, #max_line_length,
#range_by_lines

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

#break_command?(node) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 143



def_node_matcher :break_command?, <<~PATTERN
  {
    return break
    (send
     {nil? (const {nil? cbase} :Kernel)}
     {:raise :fail :throw :exit :exit! :abort}
     ...)
  }
PATTERN


  








  

    #break_statement?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 153



def break_statement?(node)
  return true if break_command?(node)

  case node.type
  when :begin, :kwbegin
    statements = *node
    break_statement = statements.find { |statement| break_statement?(statement) }
    break_statement && !preceded_by_continue_statement?(break_statement)
  when :if
    check_if(node)
  when :case, :case_match
    check_case(node)
  else
    false
  end
end


  








  

    #check(node)   (private)
  

  [ GitHub ]


  

  


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



def check(node)
  statements = statements(node)
  break_statement = statements.find { |statement| break_statement?(statement) }
  return unless break_statement

  unless preceded_by_continue_statement?(break_statement) ||
         conditional_continue_keyword?(break_statement)
    add_offense(node)
  end
end


  








  

    #check_case(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 176



def check_case(node)
  else_branch = node.else_branch
  return false unless else_branch
  return false unless break_statement?(else_branch)

  branches = if node.case_type?
               node.when_branches
             else
               node.in_pattern_branches
             end

  branches.all? { |branch| branch.body && break_statement?(branch.body) }
end


  








  

    #check_if(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 170



def check_if(node)
  if_branch = node.if_branch
  else_branch = node.else_branch
  if_branch && else_branch && break_statement?(if_branch) && break_statement?(else_branch)
end


  








  

    #conditional_continue_keyword?(break_statement)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 200



def conditional_continue_keyword?(break_statement)
  or_node = break_statement.each_descendant(:or).to_a.last

  or_node && CONTINUE_KEYWORDS.include?(or_node.rhs.type)
end


  








  

    #loop_method?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 110



def loop_method?(node)
  return false unless node.block_type? || node.numblock_type?

  send_node = node.send_node
  loopable = send_node.enumerable_method? || send_node.enumerator_method? ||
             send_node.method?(:loop)
  loopable && !matches_allowed_pattern?(send_node.source)
end


  








  

    #on_block(node)  
  

  [ GitHub ]


  

  


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



def on_block(node)
  check(node) if loop_method?(node)
end


  








  

    #on_for(node)  
  



  

    


Alias for #on_while.



  



  [ GitHub ]


  

  


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



alias on_for on_while


  








  

    #on_numblock(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 104



def on_numblock(node)
  check(node) if loop_method?(node)
end


  








  

    #on_until(node)  
  



  

    


Alias for #on_while.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 95



alias on_until on_while


  








  

    #on_until_post(node)  
  



  

    


Alias for #on_while.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 97



alias on_until_post on_while


  








  

    #on_while(node)  
    Also known as: #on_until, #on_while_post, #on_until_post, #on_for
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 92



def on_while(node)
  check(node)
end


  








  

    #on_while_post(node)  
  



  

    


Alias for #on_while.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 96



alias on_while_post on_while


  








  

    #preceded_by_continue_statement?(break_statement)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 190



def preceded_by_continue_statement?(break_statement)
  break_statement.left_siblings.any? do |sibling|
    # Numblocks have the arguments count as a number in the AST.
    next if sibling.is_a?(Integer)
    next if sibling.loop_keyword? || loop_method?(sibling)

    sibling.each_descendant(*CONTINUE_KEYWORDS).any?
  end
end


  








  

    #statements(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unreachable_loop.rb', line 130



def statements(node)
  body = node.body

  if body.nil?
    []
  elsif body.begin_type?
    body.children
  else
    [body]
  end
end