simple_form の association メソッドで collection を未指定な場合に警告する rubocop

simple_form_association_collection.rb

module RuboCop
  module Cop
    module FooBar
      class SimpleFormAssociationCollection < Base
        MSG = 'Specify the `collection` option'.freeze

        def_node_matcher :has_association_call?, <<~PATTERN
          (block
            (send _ :simple_form_for ...)
            (args (arg _f))
            `$(send (lvar _f) :association $...))
        PATTERN

        def_node_matcher :has_collection_option?, <<~PATTERN
          (hash <(pair (sym :collection) _) ...>)
        PATTERN

        def on_block(node)
          match = has_association_call?(node)
          return if match.nil?

          send_node, args_node = match
          return if args_node.any? { |nd| has_collection_option?(nd) }

          add_offense(send_node)
        end
      end
    end
  end
end

simple_form_association_collection_spec.rb

RSpec.describe RuboCop::Cop::FooBar::SimpleFormAssociationCollection, :config do
  let(:config) { RuboCop::Config.new }

  it 'bad' do
    expect_offense(<<~RUBY)
      simple_form_for user do |f|
        f.association :group
        ^^^^^^^^^^^^^^^^^^^^ Specify the `collection` option
      end
    RUBY
  end

  it 'good' do
    expect_no_offenses(<<~RUBY)
      simple_form_for user do |f|
        f.association :group, collection: current_company.groups
      end
    RUBY
  end
end