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Class: RuboCop::Cop::Lint::UnreachablePatternBranch

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::TargetRubyVersion, ::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/unreachable_pattern_branch.rb

Overview

Checks for unreachable in pattern branches in case…​in statements.

An in branch is unreachable when a previous branch uses an unguarded catch-all pattern that matches any value unconditionally. Any in branches (and else) that follow such a catch-all are dead code.

A catch-all pattern is one of:

  • A bare variable capture (in x)

  • An underscore (in _)

  • A pattern alias where the left side is a catch-all (in _ ⇒ y)

  • An alternation pattern where at least one alternative is a catch-all (in _ | Integer)

Note
 A catch-all pattern with a guard clause (e.g., in _ if condition) does NOT make subsequent branches unreachable because the guard might not be satisfied.

Examples:

# bad
case value
in Integer
  handle_integer
in x
  handle_other
in String
  handle_string
else
  handle_else
end

# good
case value
in Integer
  handle_integer
in String
  handle_string
in x
  handle_other
end

# bad - else is unreachable after catch-all
case value
in Integer
  handle_integer
in _
  handle_other
else
  handle_else
end

# good - guard clause means catch-all might not match
case value
in x if x.positive?
  handle_positive
in Integer
  handle_integer
else
  handle_other
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::TargetRubyVersion - Extended

maximum_target_ruby_version, minimum_target_ruby_version, required_maximum_ruby_version, required_minimum_ruby_version, support_target_ruby_version?

::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, #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

#catch_all_pattern?(pattern) ⇒ Boolean (private)

[ GitHub ] 

  


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



def catch_all_pattern?(pattern)
  case pattern.type
  when :match_var
    true
  when :match_as, :begin
    catch_all_pattern?(pattern.children[0])
  when :match_alt
    pattern.children.any? { |child| catch_all_pattern?(child) }
  else
    false
  end
end


  








  

    #on_case_match(case_node)  
  

  [ GitHub ]


  

  


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



def on_case_match(case_node)
  catch_all_found = false

  case_node.in_pattern_branches.each do |in_pattern_node|
    if catch_all_found
      add_offense(in_pattern_node)
      next
    end

    pattern = in_pattern_node.pattern
    guard = in_pattern_node.children[1]

    catch_all_found = true if catch_all_pattern?(pattern) && guard.nil?
  end

  return unless catch_all_found && case_node.else?

  add_offense(case_node.loc.else, message: MSG_ELSE)
end