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Class: RuboCop::Cop::Style::HashFetchChain

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

Overview

Use Hash#dig instead of chaining potentially null fetch calls.

When fetch(identifier, nil) calls are chained on a hash, the expectation is that each step in the chain returns either nil or another hash, and in both cases, these can be simplified with a single call to dig with multiple arguments.

If the 2nd parameter is {} or Hash.new, an offense will also be registered, as long as the final call in the chain is a nil value. If a non-nil value is given, the chain will not be registered as an offense, as the default value cannot be safely given with dig.

Note
 See Style/DigChain for replacing chains of dig calls with a single method call.

Examples:

# bad
hash.fetch('foo', nil)&.fetch('bar', nil)

# bad
# earlier members of the chain can return `{}` as long as the final {fetch}
# has {nil} as a default value
hash.fetch('foo', {}).fetch('bar', nil)

# good
hash.dig('foo', 'bar')

# ok - not handled by the cop since the final {fetch} value is non-nil
hash.fetch('foo', {}).fetch('bar', {})

Cop Safety Information:

  • This cop is unsafe because it cannot be guaranteed that the receiver is a Hash or that fetch or dig have the expected standard implementation.

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::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, #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

#diggable?(node)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/hash_fetch_chain.rb', line 50



def_node_matcher :diggable?, <<~PATTERN
  (call _ :fetch $_arg {nil (hash) (send (const {nil? cbase} :Hash) :new)})
PATTERN


  








  

    #inspect_chain(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_fetch_chain.rb', line 84



def inspect_chain(node)
  arguments = []

  while (arg = diggable?(node))
    arguments.unshift(arg)
    ignore_node(node)
    last_replaceable_node = node
    node = node.receiver
  end

  [last_replaceable_node, arguments]
end


  








  

    #last_fetch_non_nil?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


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



def last_fetch_non_nil?(node)
  # When chaining `fetch` methods, `fetch(x, {})` is acceptable within
  # the chain, as long as the last method in the chain has a `nil`
  # default value.

  return false unless node.method?(:fetch)

  !node.last_argument&.nil_type?
end


  








  

    #on_csend(node)  
  



  

    


Alias for #on_send.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_fetch_chain.rb', line 70



alias on_csend on_send


  








  

    #on_send(node)  
    Also known as: #on_csend
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_fetch_chain.rb', line 54



def on_send(node)
  return if ignored_node?(node)
  return if last_fetch_non_nil?(node)

  last_replaceable_node, arguments = inspect_chain(node)
  return unless last_replaceable_node
  return unless arguments.size > 1

  range = last_replaceable_node.selector.join(node.loc.end)
  replacement = replacement(arguments)
  message = format(MSG, replacement: replacement)

  add_offense(range, message: message) do |corrector|
    corrector.replace(range, replacement)
  end
end


  








  

    #replacement(arguments)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_fetch_chain.rb', line 97



def replacement(arguments)
  values = arguments.map(&:source).join(', ')
  "dig(#{values})"
end