Class: RuboCop::Cop::Naming::MemoizedInstanceVariableName

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 Object RuboCop::Cop::Base RuboCop::Cop::Naming::MemoizedInstanceVariableName
Defined in:	lib/rubocop/cop/naming/memoized_instance_variable_name.rb

Overview

Checks for memoized methods whose instance variable name does not match the method name. Applies to both regular methods (defined with def) and dynamic methods (defined with define_method or define_singleton_method).

This cop can be configured with the EnforcedStyleForLeadingUnderscores directive. It can be configured to allow for memoized instance variables prefixed with an underscore. Prefixing ivars with an underscore is a convention that is used to implicitly indicate that an ivar should not be set or referenced outside of the memoization method.

Examples:

EnforcedStyleForLeadingUnderscores: disallowed (default)

# bad
# Method foo is memoized using an instance variable that is
# not {@foo}. This can cause confusion and bugs.
def foo
  @something ||= calculate_expensive_thing
end

def foo
  return @something if defined?(@something)
  @something = calculate_expensive_thing
end

# good
def _foo
  @foo ||= calculate_expensive_thing
end

# good
def foo
  @foo ||= calculate_expensive_thing
end

# good
def foo
  @foo ||= begin
    calculate_expensive_thing
  end
end

# good
def foo
  helper_variable = something_we_need_to_calculate_foo
  @foo ||= calculate_expensive_thing(helper_variable)
end

# good
define_method(:foo) do
  @foo ||= calculate_expensive_thing
end

# good
define_method(:foo) do
  return @foo if defined?(@foo)
  @foo = calculate_expensive_thing
end

EnforcedStyleForLeadingUnderscores: required

# bad
def foo
  @something ||= calculate_expensive_thing
end

# bad
def foo
  @foo ||= calculate_expensive_thing
end

def foo
  return @foo if defined?(@foo)
  @foo = calculate_expensive_thing
end

# good
def foo
  @_foo ||= calculate_expensive_thing
end

# good
def _foo
  @_foo ||= calculate_expensive_thing
end

def foo
  return @_foo if defined?(@_foo)
  @_foo = calculate_expensive_thing
end

# good
define_method(:foo) do
  @_foo ||= calculate_expensive_thing
end

# good
define_method(:foo) do
  return @_foo if defined?(@_foo)
  @_foo = calculate_expensive_thing
end

EnforcedStyleForLeadingUnderscores :optional

# bad
def foo
  @something ||= calculate_expensive_thing
end

# good
def foo
  @foo ||= calculate_expensive_thing
end

# good
def foo
  @_foo ||= calculate_expensive_thing
end

# good
def _foo
  @_foo ||= calculate_expensive_thing
end

# good
def foo
  return @_foo if defined?(@_foo)
  @_foo = calculate_expensive_thing
end

# good
define_method(:foo) do
  @foo ||= calculate_expensive_thing
end

# good
define_method(:foo) do
  @_foo ||= calculate_expensive_thing
end

Cop Safety Information:

This cop relies on the pattern @instance_var ||= …, but this is sometimes used for other purposes than memoization so this cop is considered unsafe. Also, its autocorrection is unsafe because it may conflict with instance variable names already in use.

Constant Summary

DYNAMIC_DEFINE_METHODS =
# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 157
```
%i[define_method define_singleton_method].to_set.freeze
```
INITIALIZE_METHODS =
# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 158
```
%i[initialize initialize_clone initialize_copy initialize_dup].freeze
```

MSG =
# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 153

'Memoized variable `%<var>s` does not match ' \
'method name `%<method>s`. Use `@%<suggested_var>s` instead.'

UNDERSCORE_REQUIRED =
# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 155
```
'Memoized variable `%<var>s` does not start ' \
'with `_`. Use `@%<suggested_var>s` instead.'
```

`::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

Instance Method Summary

#defined_memoized?(node, ivar)
#method_definition?(node)
#on_defined?(node) ⇒ Boolean

Metrics/MethodLength.
#on_or_asgn(node)

rubocop:disable Metrics/MethodLength.
#find_definition(node) private
#matches?(method_name, ivar_assign) ⇒ Boolean private
#message(variable) private
#style_parameter_name private
#suggested_var(method_name) private
#variable_name_candidates(method_name) private

`::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_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

#defined_memoized?(node, ivar)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 198


def_node_matcher :defined_memoized?, <<~PATTERN
  (begin
    (if (defined $(ivar %1)) (return $(ivar %1)) nil?)
    ...
    $(ivasgn %1 _))
PATTERN

#find_definition(node) (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 243


def find_definition(node)
  # Methods can be defined in a `def` or `defs`,
  # or dynamically via a `block` node.
  node.each_ancestor(:def, :defs, :block).each do |ancestor|
    method_node, method_name = method_definition?(ancestor)
    return [method_node, method_name] if method_node
  end

  nil
end

#matches?(method_name, ivar_assign) ⇒ `Boolean` (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 254


def matches?(method_name, ivar_assign)
  return true if ivar_assign.nil? || INITIALIZE_METHODS.include?(method_name)

  method_name = method_name.to_s.delete('!?=')
  variable = ivar_assign.children.first
  variable_name = variable.to_s.sub('@', '')

  variable_name_candidates(method_name).include?(variable_name)
end

#message(variable) (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 264


def message(variable)
  variable_name = variable.to_s.sub('@', '')

  return UNDERSCORE_REQUIRED if style == :required && !variable_name.start_with?('_')

  MSG
end

#method_definition?(node)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 161


def_node_matcher :method_definition?, <<~PATTERN
  ${
    (block (send _ %DYNAMIC_DEFINE_METHODS ({sym str} $_)) ...)
    (def $_ ...)
    (defs _ $_ ...)
  }
PATTERN

#on_defined?(node) ⇒ `Boolean`

Metrics/MethodLength

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 206


def on_defined?(node)
  arg = node.first_argument
  return false unless arg.ivar_type?

  method_node, method_name = find_definition(node)
  return false unless method_node

  var_name = arg.children.first
  defined_memoized?(method_node.body, var_name) do |defined_ivar, return_ivar, ivar_assign|
    return false if matches?(method_name, ivar_assign)

    suggested_var = suggested_var(method_name)
    msg = format(
      message(var_name.to_s),
      var: var_name.to_s,
      suggested_var: suggested_var,
      method: method_name
    )
    add_offense(defined_ivar, message: msg) do |corrector|
      corrector.replace(defined_ivar, "@#{suggested_var}")
    end
    add_offense(return_ivar, message: msg) do |corrector|
      corrector.replace(return_ivar, "@#{suggested_var}")
    end
    add_offense(ivar_assign.loc.name, message: msg) do |corrector|
      corrector.replace(ivar_assign.loc.name, "@#{suggested_var}")
    end
  end
end

#on_or_asgn(node)

rubocop:disable Metrics/MethodLength

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 171


def on_or_asgn(node)
  lhs, _value = *node
  return unless lhs.ivasgn_type?

  method_node, method_name = find_definition(node)
  return unless method_node

  body = method_node.body
  return unless body == node || body.children.last == node

  return if matches?(method_name, lhs)

  suggested_var = suggested_var(method_name)
  msg = format(
    message(lhs.children.first.to_s),
    var: lhs.children.first.to_s,
    suggested_var: suggested_var,
    method: method_name
  )
  add_offense(lhs, message: msg) do |corrector|
    corrector.replace(lhs.loc.name, "@#{suggested_var}")
  end
end

#style_parameter_name (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 239


def style_parameter_name
  'EnforcedStyleForLeadingUnderscores'
end

#suggested_var(method_name) (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 272


def suggested_var(method_name)
  suggestion = method_name.to_s.delete('!?=')

  style == :required ? "_#{suggestion}" : suggestion
end

#variable_name_candidates(method_name) (private)

[ GitHub ]

# File 'lib/rubocop/cop/naming/memoized_instance_variable_name.rb', line 278


def variable_name_candidates(method_name)
  no_underscore = method_name.delete_prefix('_')
  with_underscore = "_#{method_name}"
  case style
  when :required
    [with_underscore,
     method_name.start_with?('_') ? method_name : nil].compact
  when :disallowed
    [method_name, no_underscore]
  when :optional
    [method_name, with_underscore, no_underscore]
  else
    raise 'Unreachable'
  end
end

Class: RuboCop::Cop::Naming::MemoizedInstanceVariableName

Overview

Constant Summary

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::ConfigurableEnforcedStyle - Included

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

Class Method Summary

::RuboCop::Cop::Base - Inherited

::RuboCop::ExcludeLimit - Extended

Instance Attribute Summary

::RuboCop::Cop::ConfigurableEnforcedStyle - Included

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::AutocorrectLogic - Included

Instance Method Summary

::RuboCop::Cop::ConfigurableEnforcedStyle - Included

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

Instance Method Details

#defined_memoized?(node, ivar)

#find_definition(node) (private)

#matches?(method_name, ivar_assign) ⇒ Boolean (private)

#message(variable) (private)

#method_definition?(node)

#on_defined?(node) ⇒ Boolean

#on_or_asgn(node)

#style_parameter_name (private)

#suggested_var(method_name) (private)

#variable_name_candidates(method_name) (private)

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::ConfigurableEnforcedStyle` - Included

`::RuboCop::Cop::AutoCorrector` - Extended

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::ExcludeLimit` - Extended

`::RuboCop::Cop::ConfigurableEnforcedStyle` - Included

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::AutocorrectLogic` - Included

`::RuboCop::Cop::ConfigurableEnforcedStyle` - Included

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::AutocorrectLogic` - Included

`::RuboCop::Cop::IgnoredNode` - Included

#matches?(method_name, ivar_assign) ⇒ `Boolean` (private)

#on_defined?(node) ⇒ `Boolean`