From 326e6527497126b2ea3627e377b6a4b5c9191bef Mon Sep 17 00:00:00 2001
From: Hincu Petru <hincupetru@gmail.com>
Date: Mon, 3 Feb 2014 09:51:05 +0000
Subject: [PATCH] Fixed "Hash#to_param confused by empty hash values #13892"

---
 .../lib/active_support/core_ext/object/to_param.rb    |  1 +
 activesupport/test/core_ext/object/to_param_test.rb   | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/activesupport/lib/active_support/core_ext/object/to_param.rb b/activesupport/lib/active_support/core_ext/object/to_param.rb
index 3b137ce6ae..e40846e7d6 100644
--- a/activesupport/lib/active_support/core_ext/object/to_param.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_param.rb
@@ -51,6 +51,7 @@ class Hash
   #
   # This method is also aliased as +to_query+.
   def to_param(namespace = nil)
+    return (namespace ? nil.to_query(namespace) : '') if empty?
     collect do |key, value|
       value.to_query(namespace ? "#{namespace}[#{key}]" : key)
     end.sort! * '&'
diff --git a/activesupport/test/core_ext/object/to_param_test.rb b/activesupport/test/core_ext/object/to_param_test.rb
index bd7c6c422a..eae68ed184 100644
--- a/activesupport/test/core_ext/object/to_param_test.rb
+++ b/activesupport/test/core_ext/object/to_param_test.rb
@@ -1,5 +1,6 @@
 require 'abstract_unit'
 require 'active_support/core_ext/object/to_param'
+require 'active_support/core_ext/object/to_query'
 
 class ToParamTest < ActiveSupport::TestCase
   def test_object
@@ -16,4 +17,14 @@ def test_boolean
     assert_equal true, true.to_param
     assert_equal false, false.to_param
   end
+
+  def test_nested_empty_hash
+    hash1 = {a: 1, b: {c: 3, d: {}}}.to_param
+    hash2 = {p: 12, b: {c: 3, e: nil, f: ''}}.to_param
+    hash3 = {b: {c: 3, k: {}, f: '' }}.to_param
+
+    assert_equal 'a=1&b[c]=3&b[d]=', CGI::unescape(hash1)
+    assert_equal 'b[c]=3&b[e]=&b[f]=&p=12', CGI::unescape(hash2)
+    assert_equal 'b[c]=3&b[f]=&b[k]=', CGI::unescape(hash3)
+  end
 end
-- 
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