Class: RuboCop::Cop::Style::EmptyClassDefinition

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Includes:
ConfigurableEnforcedStyle
Defined in:
lib/rubocop/cop/style/empty_class_definition.rb

Overview

Enforces consistent style for empty class definitions.

This cop can enforce either a standard class definition or ‘Class.new` for classes with no body.

The supported styles are:

  • class_keyword (default) - prefer standard class definition over ‘Class.new`

  • class_new - prefer ‘Class.new` over class definition

One difference between the two styles is that the ‘Class.new` form does not make the subclass name available to the base class’s ‘inherited` callback. For this reason, `EnforcedStyle: class_keyword` is set as the default style. Class definitions without a superclass, which are not involved in inheritance, are not detected. This ensures safe detection regardless of the applied style. This avoids overlapping responsibilities with the `Lint/EmptyClass` cop.

Use ‘AllowedParentClasses` to permit both styles for specific parent classes. For example, adding `StandardError` allows both `Error = Class.new(StandardError)` and `class Error < StandardError; end` regardless of the enforced style.

Examples:

EnforcedStyle: class_keyword (default)

# bad
FooError = Class.new(StandardError)

# okish
class FooError < StandardError; end

# good
class FooError < StandardError
end

EnforcedStyle: class_new

# bad
class FooError < StandardError
end

# bad
class FooError < StandardError; end

# good
FooError = Class.new(StandardError)

AllowedParentClasses: [‘StandardError’]

# good - allowed regardless of EnforcedStyle
FooError = Class.new(StandardError)

# good - allowed regardless of EnforcedStyle
class FooError < StandardError
end

Constant Summary collapse

MSG_CLASS_KEYWORD = 
'Use the `class` keyword instead of `Class.new` to define an empty class.'
MSG_CLASS_NEW = 
'Use `Class.new` instead of the `class` keyword to define an empty class.'

Constants inherited from Base

Base::RESTRICT_ON_SEND

Instance Attribute Summary

Attributes inherited from Base

#config, #processed_source

Instance Method Summary collapse

Methods included from AutoCorrector

support_autocorrect?

Methods included from ConfigurableEnforcedStyle

#alternative_style, #alternative_styles, #ambiguous_style_detected, #correct_style_detected, #detected_style, #detected_style=, #no_acceptable_style!, #no_acceptable_style?, #opposite_style_detected, #style, #style_configured?, #style_detected, #style_parameter_name, #supported_styles, #unexpected_style_detected

Methods inherited from Base

#active_support_extensions_enabled?, #add_global_offense, #add_offense, #always_autocorrect?, autocorrect_incompatible_with, badge, #begin_investigation, #callbacks_needed, callbacks_needed, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #cop_config, cop_name, #cop_name, department, documentation_url, exclude_from_registry, #excluded_file?, #external_dependency_checksum, inherited, #initialize, #inspect, joining_forces, lint?, match?, #message, #offenses, #on_investigation_end, #on_new_investigation, #on_other_file, #parse, #parser_engine, #ready, #relevant_file?, requires_gem, #string_literals_frozen_by_default?, support_autocorrect?, support_multiple_source?, #target_gem_version, #target_rails_version, #target_ruby_version

Methods included from ExcludeLimit

cop_dir_for, #exclude_limit, read_limits

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

silence_warnings

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#class_new_assignment(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/empty_class_definition.rb', line 66

def_node_matcher :class_new_assignment, <<~PATTERN
  (casgn _ _ $(send (const _ :Class) :new _))
PATTERN

#on_casgn(node) ⇒ Object 



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

def on_casgn(node)
  return unless %i[class_keyword class_definition].include?(style)
  return unless (class_new_node = class_new_assignment(node))
  return if (arg = class_new_node.first_argument) && !arg.const_type?
  return if allowed_parent_class?(class_new_node.first_argument.source)

  add_offense(node, message: MSG_CLASS_KEYWORD) do |corrector|
    autocorrect_class_new(corrector, node, class_new_node)
  end
end

#on_class(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/empty_class_definition.rb', line 81

def on_class(node)
  return unless style == :class_new
  return unless node.parent_class
  return if (body = node.body) && !body.children.empty?
  return if allowed_parent_class?(node.parent_class.source)

  add_offense(node, message: MSG_CLASS_NEW) do |corrector|
    autocorrect_class_definition(corrector, node)
  end
end