active_support/indifferent_hash: fix cloning default_proc on dup

3 files changed, 30 insertions, 1 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 6ebbdbc3db..e2eb539353 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Fix setting `default_proc` on `HashWithIndifferentAccess#dup`
+
+    *Simon Eskildsen*
+
 *   Fix a range of values for parameters of the Time#change
 
     *Nikolay Kondratyev*
diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 4f71f13971..bf34a4ef32 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -188,7 +188,7 @@ module ActiveSupport
     #   dup[:a][:c]  # => "c"
     def dup
       self.class.new(self).tap do |new_hash|
-        new_hash.default = default
+        set_defaults(new_hash)
       end
     end
 
@@ -275,6 +275,14 @@ module ActiveSupport
           value
         end
       end
+
+      def set_defaults(target)
+        if default_proc
+          target.default_proc = default_proc.dup
+        else
+          target.default = default
+        end
+      end
   end
 end
 
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index e10bee5e00..137a03873e 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -998,6 +998,23 @@ class HashExtTest < ActiveSupport::TestCase
     assert hash.key?('a')
     assert_equal 1, hash[:a]
   end
+
+  def test_dup_with_default_proc
+    hash = HashWithIndifferentAccess.new
+    hash.default_proc = proc { |h, v| raise "walrus" }
+    assert_nothing_raised { hash.dup }
+  end
+
+  def test_dup_with_default_proc_sets_proc
+    hash = HashWithIndifferentAccess.new
+    hash.default_proc = proc { |h, k| k + 1 }
+    new_hash = hash.dup
+
+    assert_equal 3, new_hash[2]
+
+    new_hash.default = 2
+    assert_equal 2, new_hash[:non_existant]
+  end
 end
 
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