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Class: RuboCop::Cop::Lint::RedundantSafeNavigation

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

Overview

Checks for redundant safe navigation calls. Use cases where a constant, named in camel case for classes and modules is nil are rare, and an offense is not detected when the receiver is a constant. The detection also applies to self, and to literal receivers, except for nil.

For all receivers, the instance_of?, kind_of?, is_a?, eql?, respond_to?, and equal? methods are checked by default. These are customizable with ::RuboCop::Cop::AllowedMethods option.

The ::RuboCop::Cop::AllowedMethods option specifies nil-safe methods, in other words, it is a method that is allowed to skip safe navigation. Note that the AllowedMethod option is not an option that specifies methods for which to suppress (allow) this cop’s check.

In the example below, the safe navigation operator (&.) is unnecessary because NilClass has methods like respond_to? and is_a?.

The InferNonNilReceiver option specifies whether to look into previous code paths to infer if the receiver can’t be nil. This check is unsafe because the receiver can be redefined between the safe navigation call and previous regular method call. It does the inference only in the current scope, e.g. within the same method definition etc.

The AdditionalNilMethods option specifies additional custom methods which are defined on NilClass. When InferNonNilReceiver is set, they are used to determine whether the receiver can be nil.

Examples:

# bad
CamelCaseConst&.do_something

# good
CamelCaseConst.do_something

# bad
foo.to_s&.strip
foo.to_i&.zero?
foo.to_f&.zero?
foo.to_a&.size
foo.to_h&.size

# good
foo.to_s.strip
foo.to_i.zero?
foo.to_f.zero?
foo.to_a.size
foo.to_h.size

# bad
do_something if attrs&.respond_to?(:[])

# good
do_something if attrs.respond_to?(:[])

# bad
foo&.bar ? foo&.bar.baz : qux

# good
foo&.bar ? foo.bar.baz : qux

# bad
if foo&.bar
  foo&.bar.baz
end

# good
if foo&.bar
  foo.bar.baz
end

# bad
while node&.is_a?(BeginNode)
  node = node.parent
end

# good
while node.is_a?(BeginNode)
  node = node.parent
end

# good - without {&.} this changes the return value for {nil}
foo&.respond_to?(:to_a)
foo&.respond_to?(:class)

# bad - for `nil`s conversion methods return default values for the type
foo&.to_h || {}
foo&.to_h { |k, v| [k, v] } || {}
foo&.to_a || []
foo&.to_i || 0
foo&.to_f || 0.0
foo&.to_s || ''

# good
foo.to_h
foo.to_h { |k, v| [k, v] }
foo.to_a
foo.to_i
foo.to_f
foo.to_s

# bad
self&.foo

# good
self.foo

AllowedMethods: [nil_safe_method]

# bad
do_something if attrs&.nil_safe_method(:[])

# good
do_something if attrs.nil_safe_method(:[])
do_something if attrs&.not_nil_safe_method(:[])

InferNonNilReceiver: false (default)

# good
foo.bar
foo&.baz

InferNonNilReceiver: true

# bad
foo.bar
foo&.baz # would raise on previous line if {foo} is nil

# good
foo.bar
foo.baz

# bad
if foo.condition?
  foo&.bar
end

# good
if foo.condition?
  foo.bar
end

# good (different scopes)
def method1
  foo.bar
end

def method2
  foo&.bar
end

AdditionalNilMethods: [present?]

# good
foo.present?
foo&.bar

Cop Safety Information:

  • This cop is unsafe, because autocorrection can change the return type of the expression. An offending expression that previously could return nil will be autocorrected to never return nil.

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

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::AllowedMethods - Included

#ignored_method?

::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::AllowedMethods - Included

#allowed_method?, #allowed_methods, #cop_config_allowed_methods, #cop_config_deprecated_values

::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 Attribute Details

#infer_non_nil_receiver? ⇒ Boolean (readonly, private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 272



def infer_non_nil_receiver?
  cop_config['InferNonNilReceiver']
end


  







Instance Method Details



  

    #additional_nil_methods   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 276



def additional_nil_methods
  @additional_nil_methods ||=
    Array(cop_config.fetch('AdditionalNilMethods', []).map(&:to_sym))
end


  








  

    #assume_receiver_instance_exists?(receiver)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 240



def assume_receiver_instance_exists?(receiver)
  return true if receiver.const_type? && !receiver.short_name.match?(SNAKE_CASE)

  receiver.self_type? || (receiver.literal? && !receiver.nil_type?)
end


  








  

    #check?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 257



def check?(node)
  return false unless allowed_method?(node.method_name)

  parent = node.parent
  return false unless parent

  condition?(parent, node) ||
    parent.operator_keyword? ||
    (parent.send_type? && parent.negation_method?)
end


  








  

    #condition?(parent, node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 268



def condition?(parent, node)
  (parent.conditional? || parent.post_condition_loop?) && parent.condition == node
end


  








  

    #conversion_with_default?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 183



def_node_matcher :conversion_with_default?, <<~PATTERN
  {
    (or $(csend _ :to_h) (hash))
    (or (any_block $(csend _ :to_h) ...) (hash))
    (or $(csend _ :to_a) (array))
    (or $(csend _ :to_i) (int 0))
    (or $(csend _ :to_f) (float 0.0))
    (or $(csend _ :to_s) (str empty?))
  }
PATTERN


  








  

    #guaranteed_instance?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 246



def guaranteed_instance?(node)
  receiver = if node.any_block_type?
               node.send_node
             else
               node
             end
  return false unless receiver.send_type?

  GUARANTEED_INSTANCE_METHODS.include?(receiver.method_name)
end


  








  

    #guarded_by_nil_receiver?(node)  ⇒ Boolean  (private)
  



  

    


Returns true when the &. is meaningful because the receiver may actually be nil.



  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 229



def guarded_by_nil_receiver?(node)
  return false if assume_receiver_instance_exists?(node.receiver)

  guaranteed_instance = guaranteed_instance?(node.receiver)
  return true if !guaranteed_instance && !check?(node)

  # `nil.respond_to?(<nil method>)` is `true`, so `&.` is meaningful when the receiver
  # may be nil. A guaranteed instance can never be nil, so `&.` is still redundant there.
  respond_to_nil_method?(node) && !guaranteed_instance
end


  








  

    #on_csend(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 194



def on_csend(node)
  range = node.loc.dot

  if infer_non_nil_receiver?
    checker = Lint::Utils::NilReceiverChecker.new(node.receiver, additional_nil_methods)

    if checker.cant_be_nil?
      add_offense(range, message: MSG_NON_NIL) { |corrector| corrector.replace(range, '.') }
      return
    end
  end

  return if guarded_by_nil_receiver?(node)

  add_offense(range) { |corrector| corrector.replace(range, '.') }
end


  








  

    #on_or(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 212



def on_or(node)
  conversion_with_default?(node) do |send_node|
    range = send_node.loc.dot.begin.join(node.source_range.end)

    add_offense(range, message: MSG_LITERAL) do |corrector|
      corrector.replace(send_node.loc.dot, '.')

      range_with_default = node.lhs.source_range.end.begin.join(node.source_range.end)
      corrector.remove(range_with_default)
    end
  end
end


  








  

    #respond_to_nil_method?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/redundant_safe_navigation.rb', line 178



def_node_matcher :respond_to_nil_method?, <<~PATTERN
  (csend _ :respond_to? (sym %NIL_METHODS))
PATTERN