Add compact_blank shortcut for reject(&:blank?)

I frequently find myself having to .compact but for blank. which means
on an array reject(&:blank?) (this is fine), or,
on a hash `.reject { |_k, v| v.blank? }` which is slightly more
frustrating and i usually write it as .reject(&:blank?) first and am
confused when it's trying to check if the keys are blank.

I've added the analagous .compact_blank! where there's a reject! to
build on (there's also a reject! in Set, but there's no other core_ext
touching Set so i've left that alone)

2 files changed, 30 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 6a07a73d94..27c2a8db36 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -744,6 +744,18 @@ module ActionController
     end
     alias_method :delete_if, :reject!
 
+    # Returns a new instance of <tt>ActionController::Parameters</tt> without the blank values.
+    # Uses Object#blank? for determining if a value is blank.
+    def compact_blank
+      reject { |_k, v| v.blank? }
+    end
+
+    # Removes all blank values in place and returns self.
+    # Uses Object#blank? for determining if a value is blank.
+    def compact_blank!
+      reject! { |_k, v| v.blank? }
+    end
+
     # Returns values that were assigned to the given +keys+. Note that all the
     # +Hash+ objects will be converted to <tt>ActionController::Parameters</tt>.
     def values_at(*keys)
diff --git a/actionpack/test/controller/parameters/mutators_test.rb b/actionpack/test/controller/parameters/mutators_test.rb
index 31ee7964f5..ffffd2996f 100644
--- a/actionpack/test/controller/parameters/mutators_test.rb
+++ b/actionpack/test/controller/parameters/mutators_test.rb
@@ -127,4 +127,22 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
   test "deep_transform_keys! retains unpermitted status" do
     assert_not_predicate @params.deep_transform_keys! { |k| k }, :permitted?
   end
+
+  test "compact_blank retains permitted status" do
+    @params.permit!
+    assert_predicate @params.compact_blank, :permitted?
+  end
+
+  test "compact_blank retains unpermitted status" do
+    assert_not_predicate @params.compact_blank, :permitted?
+  end
+
+  test "compact_blank! retains permitted status" do
+    @params.permit!
+    assert_predicate @params.compact_blank!, :permitted?
+  end
+
+  test "compact_blank! retains unpermitted status" do
+    assert_not_predicate @params.compact_blank!, :permitted?
+  end
 end