Merge pull request #9616 from exviva/multiple_select_name_double_square_brackets

Fix incorrectly appended square brackets to a multiple select box

Before:

    select(:category, [], {}, {:multiple => true, :name => "post[category][]"})
    # => <select name="post[category][][]" ...>

After:

    select(:category, [], {}, {:multiple => true, :name => "post[category][]"})
    # => <select name="post[category][]" ...>

Conflicts:
	actionpack/CHANGELOG.md
	actionpack/lib/action_view/helpers/tags/base.rb
	actionpack/test/template/form_options_helper_test.rb

3 files changed, 27 insertions, 2 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index e5facdb5a2..0682593666 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,12 +1,29 @@
 ## unreleased ##
 
+*   Fix incorrectly appended square brackets to a multiple select box
+    if an explicit name has been given and it already ends with "[]".
+
+    Before:
+
+        select(:category, [], {}, multiple: true, name: "post[category][]")
+        # => <select name="post[category][][]" ...>
+
+    After:
+
+        select(:category, [], {}, multiple: true, name: "post[category][]")
+        # => <select name="post[category][]" ...>
+
+    Backport #9616.
+
+    *Olek Janiszewski*
+
 *   Fix `ActionDispatch::Request#formats` when the Accept request-header is an
     empty string. Fix #7774 [Backport #8977, #9541]
 
     *Soylent + Maxime Réty*
 
 ## Rails 3.2.13.rc1 (Feb 17, 2013) ##
-    
+
 *   Determine the controller#action from only the matched path when using the
     shorthand syntax. Previously the complete path was used, which led
     to problems with nesting (scopes and namespaces).
diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index 7df74d96fb..920dc3f794 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -1207,7 +1207,7 @@ module ActionView
             options["id"] = options.fetch("id"){ tag_id }
           end
 
-          options["name"] += "[]" if options["multiple"]
+          options["name"] += "[]" if options["multiple"] && !options["name"].ends_with?("[]")
           options["id"] = [options.delete('namespace'), options["id"]].compact.join("_").presence
         end
 
diff --git a/actionpack/test/template/form_options_helper_test.rb b/actionpack/test/template/form_options_helper_test.rb
index 3009fa5330..72c2609a48 100644
--- a/actionpack/test/template/form_options_helper_test.rb
+++ b/actionpack/test/template/form_options_helper_test.rb
@@ -515,6 +515,14 @@ class FormOptionsHelperTest < ActionView::TestCase
     )
   end
 
+  def test_select_with_multiple_and_with_explicit_name_ending_with_brackets
+    output_buffer =  select(:post, :category, "", {}, :multiple => true, :name => 'post[category][]')
+    assert_dom_equal(
+      "<input type=\"hidden\" name=\"post[category][]\" value=\"\"/><select multiple=\"multiple\" id=\"post_category\" name=\"post[category][]\"></select>",
+      output_buffer
+    )
+  end
+
   def test_select_with_multiple_and_disabled_to_add_disabled_hidden_input
     output_buffer =  select(:post, :category, "", {}, :multiple => true, :disabled => true)
     assert_dom_equal(