123456789_123456789_123456789_123456789_123456789_

Class: RuboCop::Cop::Style::HashLookupMethod

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::ConfigurableEnforcedStyle, ::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_lookup_method.rb

Overview

Enforces the use of either Hash#[] or Hash#fetch for hash lookup.

This cop can be configured to prefer either bracket-style ([]) or fetch-style lookup. It is disabled by default.

When enforcing fetch style, only single-argument bracket access is flagged. When enforcing brackets style, only fetch calls with a single key argument are flagged (not those with default values or blocks).

Examples:

EnforcedStyle: brackets (default)

# bad
hash.fetch(key)

# good
hash[key]

# good - fetch with default value is allowed
hash.fetch(key, default)

# good - fetch with block is allowed
hash.fetch(key) { default }

EnforcedStyle: fetch

# bad
hash[key]

# good
hash.fetch(key)

Cop Safety Information:

  • This cop is unsafe because Hash#[] and Hash#fetch have different semantics. Hash#[] returns nil for missing keys, while Hash#fetch raises a KeyError. Replacing one with the other can change program behavior in cases where the key is missing.

    Additionally, it cannot be guaranteed that the receiver is a Hash or responds to the replacement method.

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::ConfigurableEnforcedStyle - Included

SYMBOL_TO_STRING_CACHE

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::ConfigurableEnforcedStyle - Included

#detected_style, #detected_style=, #no_acceptable_style?, #style_configured?

::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::ConfigurableEnforcedStyle - Included

#alternative_style, #alternative_styles, #ambiguous_style_detected,
#conflicting_styles_detected

Alias for ConfigurableEnforcedStyle#no_acceptable_style!.
#correct_style_detected, #no_acceptable_style!, #opposite_style_detected, #style, #style_detected, #style_parameter_name, #supported_styles, #unexpected_style_detected,
#unrecognized_style_detected

Alias for ConfigurableEnforcedStyle#no_acceptable_style!.

::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

#correct_brackets_to_fetch(corrector, node) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 85



def correct_brackets_to_fetch(corrector, node)
  receiver = node.receiver.source
  key = node.first_argument.source
  operator = node.csend_type? ? '&.' : '.'
  corrector.replace(node, "#{receiver}#{operator}fetch(#{key})")
end


  








  

    #correct_fetch_to_brackets(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 77



def correct_fetch_to_brackets(corrector, node)
  receiver = node.receiver.source
  key = node.first_argument.source
  replacement = "#{receiver}[#{key}]"
  replacement = "(#{replacement})" if node.csend_type?
  corrector.replace(node, replacement)
end


  








  

    #offense_for_brackets?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 68



def offense_for_brackets?(node)
  style == :brackets && node.receiver && node.method?(:fetch) && node.arguments.one? &&
    !node.block_literal?
end


  








  

    #offense_for_fetch?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 73



def offense_for_fetch?(node)
  style == :fetch && node.method?(:[]) && node.arguments.one?
end


  








  

    #on_csend(node)  
  



  

    


Alias for #on_send.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 64



alias on_csend on_send


  








  

    #on_send(node)  
    Also known as: #on_csend
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/hash_lookup_method.rb', line 53



def on_send(node)
  if offense_for_brackets?(node)
    add_offense(node.loc.selector, message: BRACKET_MSG) do |corrector|
      correct_fetch_to_brackets(corrector, node)
    end
  elsif offense_for_fetch?(node)
    add_offense(node, message: FETCH_MSG) do |corrector|
      correct_brackets_to_fetch(corrector, node)
    end
  end
end