Add a hidden field on the collection_radio_buttons

This will avoid a error be raised when the only input on the form is the
`collection_radio_buttons`.

7 files changed, 96 insertions, 36 deletions

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index 9ea250643a..82a88952c3 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Add a `hidden_field` on the `collection_radio_buttons` to avoid raising a error
+    when the only input on the form is the `collection_radio_buttons`.
+
+    *Mauro George*
+
 *   `url_for` does not modify its arguments when generating polymorphic URLs.
 
     *Bernerd Schaefer*
diff --git a/actionview/lib/action_view/helpers/form_options_helper.rb b/actionview/lib/action_view/helpers/form_options_helper.rb
index 728e633bbf..f6dd179bb7 100644
--- a/actionview/lib/action_view/helpers/form_options_helper.rb
+++ b/actionview/lib/action_view/helpers/form_options_helper.rb
@@ -644,6 +644,24 @@ module ActionView
       #   collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial) do |b|
       #      b.label(:"data-value" => b.value) { b.radio_button + b.text }
       #   end
+      #
+      # ==== Gotcha
+      #
+      # The HTML specification says when nothing is select on a collection of radio buttons
+      # web browsers do not send any value to server.
+      # Unfortunately this introduces a gotcha:
+      # if a +User+ model has a +category_id+ field, and in the form none category is selected no +category_id+ parameter is sent. So,
+      # any strong parameters idiom like
+      #
+      #   params.require(:user).permit(...)
+      #
+      # will raise a error since no +{user: ...}+ will be present.
+      #
+      # To prevent this the helper generates an auxiliary hidden field before
+      # every collection of radio buttons. The hidden field has the same name as collection radio button and blank value.
+      #
+      # In case if you don't want the helper to generate this hidden field you can specify
+      # <tt>include_hidden: false</tt> option.
       def collection_radio_buttons(object, method, collection, value_method, text_method, options = {}, html_options = {}, &block)
         Tags::CollectionRadioButtons.new(object, method, self, collection, value_method, text_method, options, html_options).render(&block)
       end
diff --git a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
index 1765fa6558..3256d44e18 100644
--- a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
@@ -9,29 +9,13 @@ module ActionView
         class CheckBoxBuilder < Builder # :nodoc:
           def check_box(extra_html_options={})
             html_options = extra_html_options.merge(@input_html_options)
+            html_options[:multiple] = true
             @template_object.check_box(@object_name, @method_name, html_options, @value, nil)
           end
         end
 
         def render(&block)
-          rendered_collection = render_collection do |item, value, text, default_html_options|
-            default_html_options[:multiple] = true
-            builder = instantiate_builder(CheckBoxBuilder, item, value, text, default_html_options)
-
-            if block_given?
-              @template_object.capture(builder, &block)
-            else
-              render_component(builder)
-            end
-          end
-
-          # Append a hidden field to make sure something will be sent back to the
-          # server if all check boxes are unchecked.
-          if @options.fetch(:include_hidden, true)
-            rendered_collection + hidden_field
-          else
-            rendered_collection
-          end
+          render_collection_for(CheckBoxBuilder, &block)
         end
 
         private
@@ -39,11 +23,6 @@ module ActionView
         def render_component(builder)
           builder.check_box + builder.label
         end
-
-        def hidden_field
-          hidden_name = @html_options[:name] || "#{tag_name(false, @options[:index])}[]"
-          @template_object.hidden_field_tag(hidden_name, "", id: nil)
-        end
       end
     end
   end
diff --git a/actionview/lib/action_view/helpers/tags/collection_helpers.rb b/actionview/lib/action_view/helpers/tags/collection_helpers.rb
index 8050638363..fea4c8d4ec 100644
--- a/actionview/lib/action_view/helpers/tags/collection_helpers.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_helpers.rb
@@ -79,6 +79,32 @@ module ActionView
             yield item, value, text, default_html_options.merge(additional_html_options)
           end.join.html_safe
         end
+
+        def render_collection_for(builder_class, &block) #:nodoc:
+          options = @options.stringify_keys
+          rendered_collection = render_collection do |item, value, text, default_html_options|
+            builder = instantiate_builder(builder_class, item, value, text, default_html_options)
+
+            if block_given?
+              @template_object.capture(builder, &block)
+            else
+              render_component(builder)
+            end
+          end
+
+          # Append a hidden field to make sure something will be sent back to the
+          # server if all radio buttons are unchecked.
+          if options.fetch('include_hidden', true)
+            rendered_collection + hidden_field
+          else
+            rendered_collection
+          end
+        end
+
+        def hidden_field #:nodoc:
+          hidden_name = @html_options[:name] || "#{tag_name(false, @options[:index])}[]"
+          @template_object.hidden_field_tag(hidden_name, "", id: nil)
+        end
       end
     end
   end
diff --git a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
index 20be34c1f2..21aaf122f8 100644
--- a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
@@ -14,15 +14,7 @@ module ActionView
         end
 
         def render(&block)
-          render_collection do |item, value, text, default_html_options|
-            builder = instantiate_builder(RadioButtonBuilder, item, value, text, default_html_options)
-
-            if block_given?
-              @template_object.capture(builder, &block)
-            else
-              render_component(builder)
-            end
-          end
+          render_collection_for(RadioButtonBuilder, &block)
         end
 
         private
diff --git a/actionview/test/template/form_collections_helper_test.rb b/actionview/test/template/form_collections_helper_test.rb
index b193d387c3..32471b1640 100644
--- a/actionview/test/template/form_collections_helper_test.rb
+++ b/actionview/test/template/form_collections_helper_test.rb
@@ -198,6 +198,41 @@ class FormCollectionsHelperTest < ActionView::TestCase
     assert_select 'input[type=radio][value=false][checked=checked]'
   end
 
+  test 'collection radio buttons generates only one hidden field for the entire collection, to ensure something will be sent back to the server when posting an empty collection' do
+    collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
+    with_collection_radio_buttons :user, :category_ids, collection, :id, :name
+
+    assert_select "input[type=hidden][name='user[category_ids][]'][value='']", count: 1
+  end
+
+  test 'collection radio buttons generates a hidden field using the given :name in :html_options' do
+    collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
+    with_collection_radio_buttons :user, :category_ids, collection, :id, :name, {}, { name: "user[other_category_ids][]" }
+
+    assert_select "input[type=hidden][name='user[other_category_ids][]'][value='']", count: 1
+  end
+
+  test 'collection radio buttons generates a hidden field with index if it was provided' do
+    collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
+    with_collection_radio_buttons :user, :category_ids, collection, :id, :name, { index: 322 }
+
+    assert_select "input[type=hidden][name='user[322][category_ids][]'][value='']", count: 1
+  end
+
+  test 'collection radio buttons does not generate a hidden field if include_hidden option is false' do
+    collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
+    with_collection_radio_buttons :user, :category_ids, collection, :id, :name, include_hidden: false
+
+    assert_select "input[type=hidden][name='user[category_ids][]'][value='']", count: 0
+  end
+
+  test 'collection radio buttons does not generate a hidden field if include_hidden option is false with key as string' do
+    collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
+    with_collection_radio_buttons :user, :category_ids, collection, :id, :name, 'include_hidden' => false
+
+    assert_select "input[type=hidden][name='user[category_ids][]'][value='']", count: 0
+  end
+
   # COLLECTION CHECK BOXES
   test 'collection check boxes accepts a collection and generate a series of checkboxes for value method' do
     collection = [Category.new(1, 'Category 1'), Category.new(2, 'Category 2')]
diff --git a/actionview/test/template/form_helper_test.rb b/actionview/test/template/form_helper_test.rb
index 77c660d450..2fc381c93d 100644
--- a/actionview/test/template/form_helper_test.rb
+++ b/actionview/test/template/form_helper_test.rb
@@ -1596,7 +1596,8 @@ class FormHelperTest < ActionView::TestCase
       "<input id='post_active_true' name='post[active]' type='radio' value='true' />" +
       "<label for='post_active_true'>true</label>" +
       "<input checked='checked' id='post_active_false' name='post[active]' type='radio' value='false' />" +
-      "<label for='post_active_false'>false</label>"
+      "<label for='post_active_false'>false</label>" +
+      "<input type='hidden' name='post[active][]' value='' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1619,7 +1620,8 @@ class FormHelperTest < ActionView::TestCase
       "true</label>" +
       "<label for='post_active_false'>"+
       "<input checked='checked' id='post_active_false' name='post[active]' type='radio' value='false' />" +
-      "false</label>"
+      "false</label>" +
+      "<input type='hidden' name='post[active][]' value='' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1645,6 +1647,7 @@ class FormHelperTest < ActionView::TestCase
       "<label for='post_active_false'>"+
       "<input checked='checked' id='post_active_false' name='post[active]' type='radio' value='false' />" +
       "false</label>"+
+      "<input type='hidden' name='post[active][]' value='' />" +
       "<input id='post_id' name='post[id]' type='hidden' value='1' />"
     end
 
@@ -1663,7 +1666,8 @@ class FormHelperTest < ActionView::TestCase
       "<input id='foo_post_active_true' name='post[active]' type='radio' value='true' />" +
       "<label for='foo_post_active_true'>true</label>" +
       "<input checked='checked' id='foo_post_active_false' name='post[active]' type='radio' value='false' />" +
-      "<label for='foo_post_active_false'>false</label>"
+      "<label for='foo_post_active_false'>false</label>" +
+      "<input type='hidden' name='post[active][]' value='' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1681,7 +1685,8 @@ class FormHelperTest < ActionView::TestCase
       "<input id='post_1_active_true' name='post[1][active]' type='radio' value='true' />" +
       "<label for='post_1_active_true'>true</label>" +
       "<input checked='checked' id='post_1_active_false' name='post[1][active]' type='radio' value='false' />" +
-      "<label for='post_1_active_false'>false</label>"
+      "<label for='post_1_active_false'>false</label>" +
+      "<input type='hidden' name='post[1][active][]' value='' />"
     end
 
     assert_dom_equal expected, output_buffer