Allow string hash values on AR order method

This behavior has almost no performance impact:

String not allowed  66.910000   0.030000  66.940000 ( 67.024976)
String allowed      69.360000   0.030000  69.390000 ( 69.503096)

Benchmarked with http://git.io/Y0YuRw.

activerecord/CHANGELOG.md

+*   Allow strings to specify the `#order` value.
+
+    Example:
+
+        Model.order(id: 'asc').to_sql == Model.order(id: :asc).to_sql
+
+    Fixes #10732.
+
+    *Marcelo Casiraghi*
+
 *   Dynamically register PostgreSQL enum OIDs. This prevents "unknown OID"
     warnings on enum columns.
 

activerecord/lib/active_record/relation/query_methods.rb

@@ -1030,10 +1030,13 @@ def build_order(arel)
       arel.order(*orders) unless orders.empty?
     end
 
+    VALID_DIRECTIONS = [:asc, :desc, 'asc', 'desc'] # :nodoc:
+
     def validate_order_args(args)
       args.grep(Hash) do |h|
-        unless (h.values - [:asc, :desc]).empty?
-          raise ArgumentError, 'Direction should be :asc or :desc'
+        h.values.map(&:downcase).each do |value|
+          raise ArgumentError, "Direction '#{value}' is invalid. Valid " \
+                               "directions are asc and desc." unless VALID_DIRECTIONS.include?(value)
         end
       end
     end
@@ -1055,7 +1058,7 @@ def preprocess_order_args(order_args)
         when Hash
           arg.map { |field, dir|
             field = klass.attribute_alias(field) if klass.attribute_alias?(field)
-            table[field].send(dir)
+            table[field].send(dir.downcase)
           }
         else
           arg

activerecord/test/cases/relations_test.rb

@@ -171,7 +171,6 @@ def test_finding_with_order
     assert_equal topics(:first).title, topics.first.title
   end
 
-
   def test_finding_with_arel_order
     topics = Topic.order(Topic.arel_table[:id].asc)
     assert_equal 5, topics.to_a.size
@@ -194,8 +193,43 @@ def test_order_with_hash_and_symbol_generates_the_same_sql
     assert_equal Topic.order(:id).to_sql, Topic.order(:id => :asc).to_sql
   end
 
+  def test_finding_with_desc_order_with_string
+    topics = Topic.order(id: "desc")
+    assert_equal 5, topics.to_a.size
+    assert_equal [topics(:fifth), topics(:fourth), topics(:third), topics(:second), topics(:first)], topics.to_a
+  end
+
+  def test_finding_with_asc_order_with_string
+    topics = Topic.order(id: 'asc')
+    assert_equal 5, topics.to_a.size
+    assert_equal [topics(:first), topics(:second), topics(:third), topics(:fourth), topics(:fifth)], topics.to_a
+  end
+
+  def test_nothing_raises_on_upcase_desc_arg
+    Topic.order(id: "DESC")
+  end
+
+  def test_nothing_raises_on_downcase_desc_arg
+    Topic.order(id: "desc")
+  end
+
+  def test_nothing_raises_on_upcase_asc_arg
+    Topic.order(id: "ASC")
+  end
+
+  def test_nothing_raises_on_downcase_asc_arg
+    Topic.order(id: "asc")
+  end
+
+  def test_nothing_raises_on_case_insensitive_args
+    Topic.order(id: "DeSc")
+    Topic.order(id: :DeSc)
+    Topic.order(id: "aSc")
+    Topic.order(id: :aSc)
+  end
+
   def test_raising_exception_on_invalid_hash_params
-    assert_raise(ArgumentError) { Topic.order(:name, "id DESC", :id => :DeSc) }
+    assert_raise(ArgumentError) { Topic.order(:name, "id DESC", id: :asfsdf) }
   end
 
   def test_finding_last_with_arel_order