Adding Hash#compact and Hash#compact! methods

  * Adding Hash#compact and Hash#compact! methods
  * Using Ruby 1.9 syntax on documentation
  * Updating guides for `Hash#compact` and `Hash#compact!` methods
  * Updating CHANGELOG for ActiveSupport
  * Removing unecessary protected method and lambda for `Hash#compact` implementations
  * Performing `Hash#compact` implementation - https://gist.github.com/tinogomes/8332883
  * fixing order position
  * Fixing typo

5 files changed, 63 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2cb1e79365..adaeb99c87 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Added `Hash#compact` and `Hash#compact!` for removing items with nil value from hash.
+
+    *Celestino Gomes*
+
 *   Maintain proleptic gregorian in Time#advance
 
     `Time#advance` uses `Time#to_date` and `Date#advance` to calculate a new date.
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index 686f12c6da..f68e1662f9 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,3 +1,4 @@
+require 'active_support/core_ext/hash/compact'
 require 'active_support/core_ext/hash/conversions'
 require 'active_support/core_ext/hash/deep_merge'
 require 'active_support/core_ext/hash/except'
diff --git a/activesupport/lib/active_support/core_ext/hash/compact.rb b/activesupport/lib/active_support/core_ext/hash/compact.rb
new file mode 100644
index 0000000000..6566215a4d
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/compact.rb
@@ -0,0 +1,20 @@
+class Hash
+  # Returns a hash with non +nil+ values.
+  # 
+  #   hash = { a: true, b: false, c: nil}
+  #   hash.compact # => { a: true, b: false}
+  #   hash # => { a: true, b: false, c: nil}
+  #   { c: nil }.compact # => {}
+  def compact
+    self.select { |_, value| !value.nil? }
+  end
+  
+  # Replaces current hash with non +nil+ values.
+  # 
+  #   hash = { a: true, b: false, c: nil}
+  #   hash.compact! # => { a: true, b: false}
+  #   hash # => { a: true, b: false}
+  def compact!
+    self.reject! { |_, value| value.nil? }
+  end
+end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 1ee9fbf46e..40c8f03374 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -54,6 +54,8 @@ class HashExtTest < ActiveSupport::TestCase
     assert_respond_to h, :deep_stringify_keys!
     assert_respond_to h, :to_options
     assert_respond_to h, :to_options!
+    assert_respond_to h, :compact
+    assert_respond_to h, :compact!
   end
 
   def test_transform_keys
@@ -865,6 +867,32 @@ class HashExtTest < ActiveSupport::TestCase
     original.expects(:delete).never
     original.except(:a)
   end
+
+  def test_compact
+    hash_contain_nil_value = @symbols.merge(z: nil)
+    hash_with_only_nil_values = { a: nil, b: nil }
+    
+    h = hash_contain_nil_value.dup
+    assert_equal(@symbols, h.compact)
+    assert_equal(hash_contain_nil_value, h)
+    
+    h = hash_with_only_nil_values.dup
+    assert_equal({}, h.compact)
+    assert_equal(hash_with_only_nil_values, h)
+  end
+
+  def test_compact!
+    hash_contain_nil_value = @symbols.merge(z: nil)
+    hash_with_only_nil_values = { a: nil, b: nil }
+    
+    h = hash_contain_nil_value.dup
+    assert_equal(@symbols, h.compact!)
+    assert_equal(@symbols, h)
+    
+    h = hash_with_only_nil_values.dup
+    assert_equal({}, h.compact!)
+    assert_equal({}, h)
+  end
 end
 
 class IWriteMyOwnXML
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 1a43bd206e..59dfefd22f 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -2907,6 +2907,16 @@ The method `with_indifferent_access` returns an `ActiveSupport::HashWithIndiffer
 
 NOTE: Defined in `active_support/core_ext/hash/indifferent_access.rb`.
 
+### Compacting
+
+The methods `compact` and `compact!` return a Hash without items with `nil` value. 
+
+```ruby
+{a: 1, b: 2, c: nil}.compact # => {a: 1, b: 2}
+```
+
+NOTE: Defined in `active_support/core_ext/hash/compact.rb`.
+
 Extensions to `Regexp`
 ----------------------