Autocorrect for Rails/StrongParametersExpect fails for accepts_nested_attributes_for params

[chaadow]

---

Expected behavior

I expect this :

    params.require(:company_tool).permit(
      :salary,
      :employees_count,
      rows_prices: {
        row_total_one_employee: [
          :price,
          :cell_id
        ],
        row_total_all_employees: [
          :price,
          :cell_id
        ]
      }

to be autocorrected with :

# Note the double array `[[ ...]]`
    params.expect(
      company_tool: [:salary,
                     :employees_count,
                     rows_prices: [
                        row_total_one_employee: [[ # double array
                         :price,
                         :cell_id
                        ]],
                        row_total_all_employees: [[
                           :price,
                           :cell_id
                        ]]
                     ]
           ]
    )

Actual behavior

it gets autocorrected to this :

    params.expect(
      company_tool: [:salary,
                     :employees_count,
                     {  # unnecessary opening of hash
                        rows_prices: { # Here it's better to open with `[` than `{` according to docs
                           row_total_one_employee: [ # no double array
                              :price,
                              :cell_id
                       ],
                       row_total_all_employees: [ # no double array
                         :price,
                         :cell_id
                       ]
                     }
               }
     ]
    )

which is false, and make row_prices empty when provided with an array

Steps to reproduce the problem

To reproduce you can put the examples above in any controller and you will get the same result

Example can also be found here

• https://edgeguides.rubyonrails.org/action_controller_overview.html#nested-parameters
• also example 2 and 3 here can be valuable : https://edgeguides.rubyonrails.org/action_controller_overview.html#examples

RuboCop version

$ [bundle exec] rubocop -V
1.71.0 (using Prism 1.3.0, rubocop-ast 1.37.0, analyzing as Ruby 3.4, running on ruby 3.4.1) [arm64-darwin24]
  - rubocop-capybara 2.21.0
  - rubocop-factory_bot 2.26.1
  - rubocop-graphql 1.5.4
  - rubocop-performance 1.23.1
  - rubocop-rails 2.29.1
  - rubocop-rspec 3.4.0
  - rubocop-rspec_rails 2.30.0

[chaadow]

I also feel that using hashes in autocorrect is most of the time not necessary except for this case :

Example 4: Imagine a scenario where you have parameters representing a product name, and a hash of arbitrary data associated with that product, and you want to permit the product name attribute and also the whole data hash:

def product_params
  params.expect(product: [ :name, data: {} ])
end