Collection check boxes propagates input's id to the label's for attribute.

actionview/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Collection input propagates input's `id` to the label's `for` attribute when
+    using html options as the last element of collection.
+
+    *Vasiliy Ermolovich*
+
 *   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`.
 

actionview/lib/action_view/helpers/tags/collection_helpers.rb

@@ -19,6 +19,8 @@ module ActionView
 
           def label(label_html_options={}, &block)
             html_options = @input_html_options.slice(:index, :namespace).merge(label_html_options)
+            html_options[:for] ||= @input_html_options[:id] if @input_html_options[:id]
+
             @template_object.label(@object_name, @sanitized_attribute_name, @text, html_options, &block)
           end
         end

actionview/test/template/form_collections_helper_test.rb

@@ -306,6 +306,17 @@ class FormCollectionsHelperTest < ActionView::TestCase
     assert_select 'input[type=checkbox][value="2"].bar'
   end
 
+  test 'collection check boxes propagates input id to the label for attribute' do
+    collection = [[1, 'Category 1', {id: 'foo'}], [2, 'Category 2', {id: 'bar'}]]
+    with_collection_check_boxes :user, :active, collection, :first, :second
+
+    assert_select 'input[type=checkbox][value="1"]#foo'
+    assert_select 'input[type=checkbox][value="2"]#bar'
+
+    assert_select 'label[for=foo]'
+    assert_select 'label[for=bar]'
+  end
+
   test 'collection check boxes sets the label class defined inside the block' do
     collection = [[1, 'Category 1', {class: 'foo'}], [2, 'Category 2', {class: 'bar'}]]
     with_collection_check_boxes :user, :active, collection, :second, :first do |b|