Add ActiveSupport::ArrayInquirer and Array#inquiry

Wrapping an array in an `ArrayInquirer` gives a friendlier way to check its
string-like contents. For example, `request.variant` returns an `ArrayInquirer`
object. To check a request's variants, you can call:

    request.variant.phone?
    request.variant.any?(:phone, :tablet)

...instead of:

    request.variant.include?(:phone)
    request.variant.any? { |v| v.in?([:phone, :tablet]) }

`Array#inquiry` is a shortcut for wrapping the receiving array in an
`ArrayInquirer`:

    pets = [:cat, :dog]
    pets.cat?    # => true
    pets.ferret? # => false
    pets.any?(:cat, :ferret} # => true

6 files changed, 110 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 49088527ae..7eaad6340f 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,23 @@
+*   Added `ActiveSupport::ArrayInquirer` and `Array#inquiry`.
+
+    Wrapping an array in an `ArrayInquirer` gives a friendlier way to check its
+    contents:
+
+        variants = ActiveSupport::ArrayInquirer.new([:phone, :tablet])
+
+        variants.phone?    # => true
+        variants.tablet?   # => true
+        variants.desktop?  # => false
+
+        variants.any?(:phone, :tablet)   # => true
+        variants.any?(:phone, :desktop)  # => true
+        variants.any?(:desktop, :watch)  # => false
+
+    `Array#inquiry` is a shortcut for wrapping the receiving array in an
+    `ArrayInquirer`.
+
+    *George Claghorn*
+
 *   Deprecate `alias_method_chain` in favour of `Module#prepend` introduced in Ruby 2.0
 
     *Kir Shatrov*
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index 290920dbf8..9af3f8b447 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -59,6 +59,7 @@ module ActiveSupport
     autoload :StringInquirer
     autoload :TaggedLogging
     autoload :XmlMini
+    autoload :ArrayInquirer
   end
 
   autoload :Rescuable
diff --git a/activesupport/lib/active_support/array_inquirer.rb b/activesupport/lib/active_support/array_inquirer.rb
new file mode 100644
index 0000000000..0ae534da00
--- /dev/null
+++ b/activesupport/lib/active_support/array_inquirer.rb
@@ -0,0 +1,38 @@
+module ActiveSupport
+  # Wrapping an array in an +ArrayInquirer+ gives a friendlier way to check
+  # its string-like contents:
+  #
+  #   variants = ActiveSupport::ArrayInquirer.new([:phone, :tablet])
+  #
+  #   variants.phone?    # => true
+  #   variants.tablet?   # => true
+  #   variants.desktop?  # => false
+  #
+  #   variants.any?(:phone, :tablet)   # => true
+  #   variants.any?(:phone, :desktop)  # => true
+  #   variants.any?(:desktop, :watch)  # => false
+  class ArrayInquirer < Array
+    def any?(*candidates, &block)
+      if candidates.none?
+        super
+      else
+        candidates.any? do |candidate|
+          include?(candidate) || include?(candidate.to_sym)
+        end
+      end
+    end
+
+    private
+      def respond_to_missing?(name, include_private = false)
+        name[-1] == '?'
+      end
+
+      def method_missing(name, *args)
+        if name[-1] == '?'
+          any?(name[0..-2])
+        else
+          super
+        end
+      end
+  end
+end
diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index 7d0c1e4c8d..7551551bd7 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -4,3 +4,4 @@ require 'active_support/core_ext/array/conversions'
 require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/array/grouping'
 require 'active_support/core_ext/array/prepend_and_append'
+require 'active_support/core_ext/array/inquiry'
diff --git a/activesupport/lib/active_support/core_ext/array/inquiry.rb b/activesupport/lib/active_support/core_ext/array/inquiry.rb
new file mode 100644
index 0000000000..de623c466c
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/array/inquiry.rb
@@ -0,0 +1,15 @@
+class Array
+  # Wraps the array in an +ArrayInquirer+ object, which gives a friendlier way
+  # to check its string-like contents.
+  #
+  #   pets = [:cat, :dog].inquiry
+  #
+  #   pets.cat?     # => true
+  #   pets.ferret?  # => false
+  #
+  #   pets.any?(:cat, :ferret)  # => true
+  #   pets.any?(:ferret, :alligator)  # => false
+  def inquiry
+    ActiveSupport::ArrayInquirer.new(self)
+  end
+end
diff --git a/activesupport/test/array_inquirer_test.rb b/activesupport/test/array_inquirer_test.rb
new file mode 100644
index 0000000000..488e0d34a9
--- /dev/null
+++ b/activesupport/test/array_inquirer_test.rb
@@ -0,0 +1,35 @@
+require 'abstract_unit'
+
+class ArrayInquirerTest < ActiveSupport::TestCase
+  def setup
+    @array_inquirer = ActiveSupport::ArrayInquirer.new([:mobile, :tablet])
+  end
+
+  def test_individual
+    assert @array_inquirer.mobile?
+    assert @array_inquirer.tablet?
+    assert_not @array_inquirer.desktop?
+  end
+
+  def test_any
+    assert @array_inquirer.any?(:mobile, :desktop)
+    assert @array_inquirer.any?(:watch, :tablet)
+    assert_not @array_inquirer.any?(:desktop, :watch)
+  end
+
+  def test_any_with_block
+    assert @array_inquirer.any? { |v| v == :mobile }
+    assert_not @array_inquirer.any? { |v| v == :desktop }
+  end
+
+  def test_respond_to
+    assert_respond_to @array_inquirer, :development?
+  end
+
+  def test_inquiry
+    result = [:mobile, :tablet].inquiry
+
+    assert_instance_of ActiveSupport::ArrayInquirer, result
+    assert_equal @array_inquirer, result
+  end
+end