Superform vs Rails form helpers: complex select tags with groups

The Rails form helpers make working with grouped select tags extremely cumbersome because it doesn’t expose the <option> and <optgroup> tags in a way that gives developers the control they need over the HTML. Consider the following example:

grouped_options = [
  [['United States','US'], 'Canada'],
  ['Denmark','Germany','France']
]
grouped_options_for_select(grouped_options, nil, divider: '---------')

It emits the following HTML.

<optgroup label="---------">
  <option value="US">United States</option>
  <option value="Canada">Canada</option>
</optgroup>
<optgroup label="---------">
  <option value="Denmark">Denmark</option>
  <option value="Germany">Germany</option>
  <option value="France">France</option>
</optgroup>

Things get even more convoluted when working with ActiveRecord and groups

class Continent < ActiveRecord::Base
  has_many :countries
  # attribs: id, name
end

class Country < ActiveRecord::Base
  belongs_to :continent
  # attribs: id, name, continent_id
end

Rails requires calling a completely different method to generate grouped select tags.

option_groups_from_collection_for_select(@continents, :countries, :name, :id, :name, 3)

It emits the following HTML.

<optgroup label="Africa">
  <option value="1">Egypt</option>
  <option value="4">Rwanda</option>
  ...
</optgroup>
<optgroup label="Asia">
  <option value="3" selected="selected">China</option>
  <option value="12">India</option>
  <option value="5">Japan</option>
  ...
</optgroup>

Want to do that in Superform?

render field(:countries).select do |s|
  # Pretend WebSources is an ActiveRecord scope with a "Social" category that has "Facebook, X, etc"
  # and a "Search" category with "AltaVista, Yahoo, etc."
  Country.select(:id, :name).group_by(:continent) do |continent, countries|
    s.optgroup(label: continent.name) do
      s.options countries
    end
  end
end