Fix explicit names on multiple file fields

If a file field tag is passed the multiple option, it is turned into an
array field (appending "[]"), but if the file field is passed an
explicit name as an option, leave the name alone (do not append "[]").

Fixes #9830

1 files changed, 10 insertions, 0 deletions

diff --git a/actionpack/test/template/form_helper_test.rb b/actionpack/test/template/form_helper_test.rb
index dff0b8bdc2..1ff320224d 100644
--- a/actionpack/test/template/form_helper_test.rb
+++ b/actionpack/test/template/form_helper_test.rb
@@ -361,6 +361,16 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, file_field("user", "avatar")
   end
 
+  def test_file_field_with_multiple_behavior
+    expected = '<input id="import_file" multiple="multiple" name="import[file][]" type="file" />'
+    assert_dom_equal expected, file_field("import", "file", :multiple => true)
+  end
+
+  def test_file_field_with_multiple_behavior_and_explicit_name
+    expected = '<input id="import_file" multiple="multiple" name="custom" type="file" />'
+    assert_dom_equal expected, file_field("import", "file", :multiple => true, :name => "custom")
+  end
+
   def test_hidden_field
     assert_dom_equal(
       '<input id="post_title" name="post[title]" type="hidden" value="Hello World" />',