make Hash#extract! more symmetric with Hash#slice

3 files changed, 31 insertions, 3 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 0a12ba6cdd..82752b6776 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,5 +1,16 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Hash#extract! returns only those keys that present in the reciever.
+
+        {:a => 1, :b => 2}.extract!(:a, :x) # => {:a => 1}
+
+    *Mikhail Dieterle*
+
+*   Hash#extract! returns the same subclass, that the reciever is. I.e.
+    HashWithIndifferentAccess#extract! returns HashWithIndifferentAccess instance.
+
+    *Mikhail Dieterle*
+
 *   Optimize ActiveSupport::Cache::Entry to reduce memory and processing overhead. *Brian Durand*
 
 *   Tests tag the Rails log with the current test class and test case:
diff --git a/activesupport/lib/active_support/core_ext/hash/slice.rb b/activesupport/lib/active_support/core_ext/hash/slice.rb
index 45fec57009..de09f26f3d 100644
--- a/activesupport/lib/active_support/core_ext/hash/slice.rb
+++ b/activesupport/lib/active_support/core_ext/hash/slice.rb
@@ -32,9 +32,9 @@ class Hash
 
   # Removes and returns the key/value pairs matching the given keys.
   #
-  #   { a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b)
-  #   # => {:a => 1, :b => 2}
+  #   { a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b) # => { a: 1, b: 2 }
+  #   { a: 1, b: 2 }.extract!(:a, :x) # => { a: 1 }
   def extract!(*keys)
-    keys.each_with_object({}) { |key, result| result[key] = delete(key) }
+    keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
   end
 end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 01934dd2c3..5ba8e822b3 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -725,6 +725,23 @@ class HashExtTest < ActiveSupport::TestCase
     original = {:a => 1, :b => 2, :c => 3, :d => 4}
     expected = {:a => 1, :b => 2}
 
+    assert_equal expected, original.extract!(:a, :b, :x)
+  end
+
+  def test_extract_nils
+    original = {:a => nil, :b => nil}
+    expected = {:a => nil}
+    extracted = original.extract!(:a, :x)
+
+    assert_equal expected, extracted
+    assert_equal nil, extracted[:a]
+    assert_equal nil, extracted[:x]
+  end
+
+  def test_indifferent_extract
+    original = {:a => 1, :b => 2, :c => 3, :d => 4}.with_indifferent_access
+    expected = {:a => 1, :b => 2}.with_indifferent_access
+
     assert_equal expected, original.extract!(:a, :b)
   end