Make boolean input tag generate valid html5 when using nested style

This keeps Rails functionality by adding the required hidden checkbox
which will send an "unchecked value" when checkbox is not checked.

CHANGELOG.md

@@ -28,7 +28,8 @@
     to generate custom label and input structure. It is used internally with the :nested
     option for `:boolean_style`, and is useful to allow some more customization if required.
   * Do not generate hidden check box field when using nested boolean style, as it is considered
-    invalid markup in HTML5. This will only work in Rails > 3.2.1 (not released at this time).
+    invalid markup in HTML5. This will work by default in Rails > 3.2.1 (not released at this time),
+    and is backported inside SimpleForm builder extensions.
     More info in [#215](https://github.com/plataformatec/simple_form/issues/215)
   * Add `item_wrapper_class` configuration option for collection radio buttons / check boxes inputs.
 

lib/generators/simple_form/templates/config/initializers/simple_form.rb.tt

@@ -84,7 +84,6 @@ SimpleForm.setup do |config|
   # to learn about the different styles for forms and inputs,
   # buttons and other elements.
   config.default_wrapper = :bootstrap
-
 <% else %>
   # The default wrapper to be used by the FormBuilder.
   config.default_wrapper = :default

lib/simple_form/inputs/boolean_input.rb

@@ -3,7 +3,8 @@ module Inputs
     class BooleanInput < Base
       def input
         if nested_boolean_style?
-          template.label_tag(nil, :class => "checkbox") { build_check_box(nil) }
+          build_hidden_field_for_checkbox +
+            template.label_tag(nil, :class => "checkbox") { build_check_box_without_hidden_field }
         else
           build_check_box
         end
@@ -13,7 +14,8 @@ def label_input
         if options[:label] == false
           input
         elsif nested_boolean_style?
-          @builder.label(label_target, label_html_options) { build_check_box(nil) + label_text }
+          build_hidden_field_for_checkbox +
+            @builder.label(label_target, label_html_options) { build_check_box_without_hidden_field + label_text }
         else
           input + label
         end
@@ -22,12 +24,27 @@ def label_input
       private
 
       # Build a checkbox tag using default unchecked value. This allows us to
-      # reuse the method for nested boolean style, but with nil unchecked value,
-      # which won't generate the hidden checkbox (only in Rails > 3.2.1).
+      # reuse the method for nested boolean style, but with no unchecked value,
+      # which won't generate the hidden checkbox. This is the default functionality
+      # in Rails > 3.2.1, and is backported in SimpleForm AV helpers.
       def build_check_box(unchecked_value='0')
         @builder.check_box(attribute_name, input_html_options, '1', unchecked_value)
       end
 
+      # Build a checkbox without generating the hidden field. See
+      # #build_hidden_field_for_checkbox for more info.
+      def build_check_box_without_hidden_field
+        build_check_box(nil)
+      end
+
+      # Create a hidden field for the current checkbox, so we can simulate Rails
+      # functionality with hidden + checkbox, but under a nested context, where
+      # we need the hidden field to be *outside* the label (otherwise it
+      # generates invalid html - html5 only).
+      def build_hidden_field_for_checkbox
+        @builder.hidden_field(attribute_name, :value => '0', :id => nil)
+      end
+
       # Booleans are not required by default because in most of the cases
       # it makes no sense marking them as required. The only exception is
       # Terms of Use usually presented at most sites sign up screen.

test/inputs/boolean_input_test.rb

@@ -20,20 +20,29 @@ class BooleanInputTest < ActionView::TestCase
     assert_no_select 'label > input'
   end
 
-  test 'input allows changing default boolean style config to nested, generating a default label' do
+  test 'input allows changing default boolean style config to nested, generating a default label and a manual hidden field for checkbox' do
     swap SimpleForm, :boolean_style => :nested do
       with_input_for @user, :active, :boolean
       assert_select 'label[for=user_active]', 'Active'
       assert_select 'label.boolean > input.boolean'
-      assert_no_select 'input + label'
+      assert_no_select 'input[type=checkbox] + label'
+    end
+  end
+
+  test 'input boolean generates a manual hidden field for checkbox outside the label, to recreate Rails functionality with valid html5' do
+    swap SimpleForm, :boolean_style => :nested do
+      with_input_for @user, :active, :boolean
+
+      assert_select "input[type=hidden][name='user[active]'] + label.boolean > input.boolean"
+      assert_no_select 'input[type=checkbox] + label'
     end
   end
 
   test 'input accepts changing boolean style to nested through given options' do
     with_input_for @user, :active, :boolean, :boolean_style => :nested
     assert_select 'label[for=user_active]', 'Active'
     assert_select 'label.boolean > input.boolean'
-    assert_no_select 'input + label'
+    assert_no_select 'input[type=checkbox] + label'
   end
 
   test 'input accepts changing boolean style to inline through given options, when default is nested' do
@@ -67,7 +76,7 @@ class BooleanInputTest < ActionView::TestCase
       swap SimpleForm, :boolean_style => :nested do
         with_input_for @user, :active, :boolean
 
-        assert_select 'label.boolean + label.checkbox > input.boolean'
+        assert_select 'label.boolean + input[type=hidden] + label.checkbox > input.boolean'
       end
     end
   end