lib/rubocop/cop/style/struct_inheritance.rb
# frozen_string_literal: true
module RuboCop
module Cop
module Style
# Checks for inheritance from Struct.new.
#
# @safety
# Autocorrection is unsafe because it will change the inheritance
# tree (e.g. return value of `Module#ancestors`) of the constant.
#
# @example
# # bad
# class Person < Struct.new(:first_name, :last_name)
# def age
# 42
# end
# end
#
# # good
# Person = Struct.new(:first_name, :last_name) do
# def age
# 42
# end
# end
class StructInheritance < Base
include RangeHelp
extend AutoCorrector
MSG = "Don't extend an instance initialized by `Struct.new`. " \
'Use a block to customize the struct.'
def on_class(node)
return unless struct_constructor?(node.parent_class)
add_offense(node.parent_class.source_range) do |corrector|
corrector.remove(range_with_surrounding_space(node.loc.keyword, newlines: false))
corrector.replace(node.loc.operator, '=')
correct_parent(node.parent_class, corrector)
end
end
# @!method struct_constructor?(node)
def_node_matcher :struct_constructor?, <<~PATTERN
{(send (const {nil? cbase} :Struct) :new ...)
(block (send (const {nil? cbase} :Struct) :new ...) ...)}
PATTERN
private
def correct_parent(parent, corrector)
if parent.block_type?
corrector.remove(range_with_surrounding_space(parent.loc.end, newlines: false))
elsif (class_node = parent.parent).body.nil?
corrector.remove(range_for_empty_class_body(class_node, parent))
else
corrector.insert_after(parent, ' do')
end
end
def range_for_empty_class_body(class_node, struct_new)
if class_node.single_line?
range_between(struct_new.source_range.end_pos, class_node.source_range.end_pos)
else
range_by_whole_lines(class_node.loc.end, include_final_newline: true)
end
end
end
end
end
end