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# frozen_string_literal: true
module RuboCop
module Cop
module Gitlab
# This cop looks for delegations to predicate methods with `allow_nil: true` option.
# This construct results in three possible results: true, false and nil.
# In other words, it does not preserve the strict Boolean nature of predicate method return value.
# This cop suggests creating a method to handle `nil` delegator and ensure only Boolean type is returned.
#
# @example
# # bad
# delegate :is_foo?, to: :bar, allow_nil: true
#
# # good
# def is_foo?
# return false unless bar
# bar.is_foo?
# end
#
# def is_foo?
# !!bar&.is_foo?
# end
class DelegatePredicateMethods < RuboCop::Cop::Base
MSG = "Using `delegate` with `allow_nil` on the following predicate methods is discouraged: %s."
RESTRICT_ON_SEND = %i[delegate].freeze
def_node_matcher :predicate_allow_nil_option, <<~PATTERN
(send nil? :delegate
(sym $_)*
(hash <$(pair (sym :allow_nil) true) ...>)
)
PATTERN
def on_send(node)
predicate_allow_nil_option(node) do |delegated_methods, _options|
offensive_methods = delegated_methods.select { |method| method.end_with?('?') }
next if offensive_methods.empty?
add_offense(node, message: format(MSG, offensive_methods.join(', ')))
end
end
end
end
end
end
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