# frozen_string_literal: true
module RuboCop
module Cop
module Style
# Checks for redundant argument forwarding when calling super with arguments identical to
# the method definition.
#
# Using zero arity `super` within a `define_method` block results in `RuntimeError`:
#
# [source,ruby]
# ----
# def m
# define_method(:foo) { super() } # => OK
# end
#
# def m
# define_method(:foo) { super } # => RuntimeError
# end
# ----
#
# Furthermore, any arguments accompanied by a block may potentially be delegating to
# `define_method`, therefore, `super` used within these blocks will be allowed.
# This approach might result in false negatives, yet ensuring safe detection takes precedence.
#
# NOTE: When forwarding the same arguments but replacing the block argument with a new inline
# block, it is not necessary to explicitly list the non-block arguments. As such, an offense
# will be registered in this case.
#
# @example
# # bad
# def method(*args, **kwargs)
# super(*args, **kwargs)
# end
#
# # good - implicitly passing all arguments
# def method(*args, **kwargs)
# super
# end
#
# # good - forwarding a subset of the arguments
# def method(*args, **kwargs)
# super(*args)
# end
#
# # good - forwarding no arguments
# def method(*args, **kwargs)
# super()
# end
#
# # bad - forwarding with overridden block
# def method(*args, **kwargs, &block)
# super(*args, **kwargs) { do_something }
# end
#
# # good - implicitly passing all non-block arguments
# def method(*args, **kwargs, &block)
# super { do_something }
# end
#
# # good - assigning to the block variable before calling super
# def method(&block)
# # Assigning to the block variable would pass the old value to super,
# # under this circumstance the block must be referenced explicitly.
# block ||= proc { 'fallback behavior' }
# super(&block)
# end
class SuperArguments < Base
extend AutoCorrector
DEF_TYPES = %i[def defs].freeze
ASSIGN_TYPES = %i[or_asgn lvasgn].freeze
MSG = 'Call `super` without arguments and parentheses when the signature is identical.'
MSG_INLINE_BLOCK = 'Call `super` without arguments and parentheses when all positional ' \
'and keyword arguments are forwarded.'
def on_super(super_node)
return unless (def_node = find_def_node(super_node))
def_node_args = def_node.arguments.argument_list
super_args = preprocess_super_args(super_node.arguments)
return unless arguments_identical?(def_node, super_node, def_node_args, super_args)
# If the number of arguments to the def node and super node are different here,
# it's because the block argument is not forwarded.
message = def_node_args.size == super_args.size ? MSG : MSG_INLINE_BLOCK
add_offense(super_node, message: message) do |corrector|
corrector.replace(super_node, 'super')
end
end
private
def find_def_node(super_node)
super_node.ancestors.find do |node|
# When defining dynamic methods, implicitly calling `super` is not possible.
# Since there is a possibility of delegation to `define_method`,
# `super` used within the block is always allowed.
break if node.any_block_type? && !block_sends_to_super?(super_node, node)
break node if DEF_TYPES.include?(node.type)
end
end
# rubocop:disable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
def arguments_identical?(def_node, super_node, def_args, super_args)
return false if argument_list_size_differs?(def_args, super_args, super_node)
def_args.zip(super_args).each do |def_arg, super_arg|
next if positional_arg_same?(def_arg, super_arg)
next if positional_rest_arg_same(def_arg, super_arg)
next if keyword_arg_same?(def_arg, super_arg)
next if keyword_rest_arg_same?(def_arg, super_arg)
next if block_arg_same?(def_node, super_node, def_arg, super_arg)
next if forward_arg_same?(def_arg, super_arg)
return false
end
true
end
# rubocop:enable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
def argument_list_size_differs?(def_args, super_args, super_node)
# If the def node has a block argument and the super node has an explicit block,
# the number of arguments is the same, so ignore the def node block arg.
def_args_size = def_args.size
def_args_size -= 1 if def_args.any?(&:blockarg_type?) && block_sends_to_super?(super_node)
def_args_size != super_args.size
end
def block_sends_to_super?(super_node, parent_node = super_node.parent)
# Checks if the send node of a block is the given super node,
# or a method chain containing it.
return false unless parent_node
return false unless parent_node.any_block_type?
parent_node.send_node.each_node(:super).any?(super_node)
end
def positional_arg_same?(def_arg, super_arg)
return false unless def_arg.type?(:arg, :optarg)
return false unless super_arg.lvar_type?
def_arg.name == super_arg.children.first
end
def positional_rest_arg_same(def_arg, super_arg)
return false unless def_arg.restarg_type?
# anonymous forwarding
return true if def_arg.name.nil? && super_arg.forwarded_restarg_type?
return false unless super_arg.splat_type?
return false unless (lvar_node = super_arg.children.first).lvar_type?
def_arg.name == lvar_node.children.first
end
def keyword_arg_same?(def_arg, super_arg)
return false unless def_arg.type?(:kwarg, :kwoptarg)
return false unless (pair_node = super_arg).pair_type?
return false unless (sym_node = pair_node.key).sym_type?
return false unless (lvar_node = pair_node.value).lvar_type?
return false unless sym_node.source == lvar_node.source
def_arg.name == sym_node.value
end
def keyword_rest_arg_same?(def_arg, super_arg)
return false unless def_arg.kwrestarg_type?
# anonymous forwarding
return true if def_arg.name.nil? && super_arg.forwarded_kwrestarg_type?
return false unless super_arg.kwsplat_type?
return false unless (lvar_node = super_arg.children.first).lvar_type?
def_arg.name == lvar_node.children.first
end
def block_arg_same?(def_node, super_node, def_arg, super_arg)
return false unless def_arg.blockarg_type?
return true if block_sends_to_super?(super_node)
return false unless super_arg.block_pass_type?
# anonymous forwarding
return true if (block_pass_child = super_arg.children.first).nil? && def_arg.name.nil?
block_arg_name = block_pass_child.children.first
def_arg.name == block_arg_name && !block_reassigned?(def_node, block_arg_name)
end
# Reassigning the block argument will still pass along the original block to super
# https://bugs.ruby-lang.org/issues/20505
def block_reassigned?(def_node, block_arg_name)
def_node.each_node(*ASSIGN_TYPES).any? do |assign_node|
# TODO: Since `Symbol#name` is supported from Ruby 3.0, the inheritance check for
# `AST::Node` can be removed when requiring Ruby 3.0+.
lhs = assign_node.node_parts[0]
next if lhs.is_a?(AST::Node) && !lhs.respond_to?(:name)
assign_node.name == block_arg_name
end
end
def forward_arg_same?(def_arg, super_arg)
def_arg.forward_arg_type? && super_arg.forwarded_args_type?
end
def preprocess_super_args(super_args)
super_args.flat_map do |node|
if node.hash_type? && !node.braces?
node.children
else
node
end
end
end
end
end
end
end