class RuboCop::Cop::Rails::RedundantForeignKey

end
belongs_to :author, foreign_key: ‘user_id’
class Comment
end
has_many :comments
class Post
# good
end
belongs_to :post, foreign_key: ‘post_id’
class Comment
end
has_many :comments, foreign_key: ‘post_id’
class Post
# bad
@example
is redundant.
Detects cases where the ‘:foreign_key` option on associations

def default_foreign_key(node, association_type, association_name, options) 

def default_foreign_key(node, association_type, association_name, options)
  if association_type == :belongs_to
    "#{association_name}_id"
  elsif (as = find_as_option(options))
    "#{as}_id"
  else
    node.parent_module_name&.foreign_key
  end
end

def find_as_option(options) 

def find_as_option(options)
  options.pairs.find do |pair|
    pair.key.sym_type? && pair.key.value == :as
  end&.value&.value
end

def on_send(node) 

def on_send(node)
  association_with_foreign_key(node) do |type, name, options, foreign_key_pair, foreign_key|
    if redundant?(node, type, name, options, foreign_key)
      add_offense(foreign_key_pair) do |corrector|
        range = range_with_surrounding_space(foreign_key_pair.source_range, side: :left)
        range = range_with_surrounding_comma(range, :left)
        corrector.remove(range)
      end
    end
  end
end

def redundant?(node, association_type, association_name, options, foreign_key) 

def redundant?(node, association_type, association_name, options, foreign_key)
  foreign_key.to_s == default_foreign_key(node, association_type, association_name, options)
end