Add config to control boldening of radio labels

The original behaviour of the form builder followed the examples in the
Design System documentation at the time and emboldened any radio button
labels when hints were present.

These examples were dropped in 2020[0] and the guidance changed. In the
referenced PR I said I'd look into changing the behaviour in the form
builder but never did.

As it would be a breaking change we're just adding a new configuration
option, `default_collection_radio_buttons_auto_bold_labels`, to allow
the behaviour to be modified.

[0] alphagov/govuk-design-system#1284

guide/content/form-elements/radios.slim

@@ -39,9 +39,11 @@ p.govuk-body
       null or empty no hint will be rendered.
 
   p.govuk-body
-    | When descriptions are enabled in a radio button collection the labels are
-      made <strong>bold</strong> by default. This provides additional contrast
-      and makes the labels stand out from the hint.
+    | When descriptions are enabled in a radio button collection the labels are made
+      <strong>bold</strong> by default. This makes the labels stand out from the hints.
+      The auto bolding behaviour can be disabled by changing the
+      <code>default_collection_radio_buttons_auto_bold_labels</code>
+      configuration flag to <code>false</code>.
 
 == render('/partials/example.*',
   caption: 'Small radios',

lib/govuk_design_system_formbuilder.rb

@@ -43,6 +43,11 @@ module GOVUKDesignSystemFormBuilder
   # * +:default_collection_radio_buttons_include_hidden+ controls whether or not
   #   a hidden field is added when rendering a collection of radio buttons
   #
+  # * +:default_collection_radio_buttons_auto_bold_labels+ will automatically
+  #   make labels on {#govuk_collection_radio_buttons} bold when a +:hint_method+
+  #   is present. The default can be overridden using the +bold_labels:+ argument.
+  #   The default value is 'true'.
+  #
   # * +:default_error_summary_title+ sets the text used in error summary
   #   blocks. As per the GOV.UK Design System spec, it defaults to
   #   'There is a problem'.
@@ -91,6 +96,7 @@ module GOVUKDesignSystemFormBuilder
     default_error_summary_turbo_prefix: 'turbo',
     default_collection_check_boxes_include_hidden: true,
     default_collection_radio_buttons_include_hidden: true,
+    default_collection_radio_buttons_auto_bold_labels: true,
     default_submit_validate: false,
 
     localisation_schema_fallback: %i(helpers __context__),

lib/govuk_design_system_formbuilder/elements/radios/collection.rb

@@ -21,11 +21,7 @@ def initialize(builder, object_name, attribute_name, collection, value_method:,
           @classes        = classes
           @form_group     = form_group
           @include_hidden = include_hidden
-          @bold_labels    = if bold_labels.nil?
-                              hint_method.present?
-                            else
-                              bold_labels
-                            end
+          @bold_labels    = (bold_labels.nil? && auto_bold_labels?) || bold_labels
         end
 
         def html
@@ -38,6 +34,11 @@ def html
 
       private
 
+        def auto_bold_labels?
+          (config.default_collection_radio_buttons_auto_bold_labels &&
+            @hint_method.present?)
+        end
+
         def fieldset_options
           {
             legend: @legend,

spec/govuk_design_system_formbuilder/builder/configuration/radio_auto_embolden_label_spec.rb

@@ -0,0 +1,69 @@
+describe GOVUKDesignSystemFormBuilder::FormBuilder do
+  include_context 'setup builder'
+  include_context 'setup examples'
+
+  describe 'labels auto bolding config' do
+    specify %(the default should be to bold labels when hints are present) do
+      expect(GOVUKDesignSystemFormBuilder.config.default_collection_radio_buttons_auto_bold_labels).to be(true)
+    end
+
+    let(:label_selector) { 'label.govuk-label' }
+    let(:bold_label_selector) { label_selector + '--s' }
+    let(:method) { :govuk_collection_radio_buttons }
+    let(:attribute) { :favourite_shape }
+
+    let(:shapes) do
+      [
+        OpenStruct.new(id: 't', name: 'Triangle', description: 'A three-edged polygon'),
+        OpenStruct.new(id: 's', name: 'Square', description: 'A regular quadrilateral'),
+        OpenStruct.new(id: 'p', name: 'Pentagon'),
+        OpenStruct.new(id: 'h', name: 'Hexagon'),
+      ]
+    end
+
+    let(:args) { [method, attribute, shapes, :id, :name, :description] }
+    let(:kwargs) { {} }
+
+    subject { builder.send(*args, **kwargs) }
+
+    context 'when default_collection_radio_buttons_auto_bold_labels is set to true' do
+      specify 'all of the labels are bold' do
+        expect(subject).to have_tag(label_selector, count: shapes.size)
+        expect(subject).to have_tag(bold_label_selector, count: shapes.size)
+      end
+
+      context %(when the default is overriden with the 'bold_labels' argument) do
+        let(:kwargs) { { bold_labels: false } }
+
+        specify 'none of the labels are bold' do
+          expect(subject).to have_tag(label_selector, count: shapes.size)
+          expect(subject).not_to have_tag(bold_label_selector)
+        end
+      end
+    end
+
+    context 'when default_collection_radio_buttons_auto_bold_labels is set to false' do
+      before do
+        GOVUKDesignSystemFormBuilder.configure do |conf|
+          conf.default_collection_radio_buttons_auto_bold_labels = false
+        end
+      end
+
+      after { GOVUKDesignSystemFormBuilder.reset! }
+
+      specify 'none of the labels are bold' do
+        expect(subject).to have_tag(label_selector, count: shapes.size)
+        expect(subject).not_to have_tag(bold_label_selector)
+      end
+
+      context %(when the default is overriden with the 'bold_labels' argument) do
+        let(:kwargs) { { bold_labels: true } }
+
+        specify 'all of the labels are bold' do
+          expect(subject).to have_tag(label_selector, count: shapes.size)
+          expect(subject).to have_tag(bold_label_selector, count: shapes.size)
+        end
+      end
+    end
+  end
+end

spec/support/examples.rb

@@ -24,6 +24,7 @@ class Being
     :stationery,
     :stationery_choice,
     :hairstyle,
+    :favourite_shape,
   )
 
   def initialize(_args = nil)