Adding Table Context to Order Hash

activerecord/CHANGELOG.md

@@ -862,4 +862,34 @@
 
     *Slava Markevich*
 
+*   Prepend original table name to order hash
+
+    With the models
+
+        class Post
+          has_many :comments
+          scope :dewey, -> { order(subject: :desc) }
+        end
+
+        class Comment
+          belongs_to :post
+        end
+
+    And records
+
+        p1 = Post.create(subject: 'Awesomeness')
+        p2 = Post.create(subject: 'Zaniness')
+        c1 = Comment.create(type: 'Cool', post_id: p1.id)
+        c2 = Comment.create(type: 'Cool', post_id: p2.id)
+
+    The call
+
+        Comment.where(type: 'Cool').joins(:post).merge(Post.dewey)
+
+    Should yield
+
+        [c2, c1]
+
+    *Paul Pettengill*
+
 Please check [4-0-stable](https://github.com/rails/rails/blob/4-0-stable/activerecord/CHANGELOG.md) for previous changes.

activerecord/lib/active_record/relation/query_methods.rb

@@ -1012,7 +1012,7 @@ def build_order(arel)
         when Symbol
           table[order].asc
         when Hash
-          order.map { |field, dir| table[field].send(dir) }
+          order.values[0] == :asc ? table[order].asc : table[order].desc
         else
           order
         end
@@ -1037,9 +1037,24 @@ def preprocess_order_args(order_args)
       references.map! { |arg| arg =~ /^([a-zA-Z]\w*)\.(\w+)/ && $1 }.compact!
       references!(references) if references.any?
 
-      # if a symbol is given we prepend the quoted table name
+      # if a symbol or hash is given we prepend the quoted table name
       order_args.map! do |arg|
-        arg.is_a?(Symbol) ? Arel::Nodes::Ascending.new(klass.arel_table[arg]) : arg
+        if arg.is_a?(Symbol)
+          prepend_table_sort(arg, :asc)
+        elsif arg.is_a?(Hash)
+          prepend_table_sort(arg.keys[0], arg.values[0])
+        else
+          arg
+        end
+      end
+    end
+
+    def prepend_table_sort(field, direction)
+      case direction
+      when :asc
+        Arel::Nodes::Ascending.new(klass.arel_table[field])
+      when :desc
+        Arel::Nodes::Descending.new(klass.arel_table[field])
       end
     end
 

activerecord/test/cases/scoping/relation_scoping_test.rb

@@ -206,6 +206,25 @@ def test_merge_inner_scope_has_priority
     end
   end
 
+  def test_merge_order_hash
+    merge_sql = Comment.where(type: "Comment").joins(:post).
+                        merge(Post.ranked_by_comments_hash).to_sql
+    assert_match '"posts"."comments_count" DESC', merge_sql
+
+    merge_results = Comment.where(type: "Comment").joins(:post).
+                            merge(Post.ranked_by_comments_hash).
+                            order("comments.id")
+    c1 = Comment.joins(:post).find(1)
+    c2 = Comment.joins(:post).find(2)
+    c8 = Comment.joins(:post).find(8)
+    c9 = Comment.joins(:post).find(9)
+    assert_equal merge_results.size, 4
+    assert_equal merge_results.first, c8
+    assert_equal merge_results.limit(2).last, c9
+    assert_equal merge_results.limit(3).last, c1
+    assert_equal merge_results.last, c2
+  end
+
   def test_replace_options
     Developer.where(:name => 'David').scoping do
       Developer.unscoped do

activerecord/test/fixtures/posts.yml

@@ -28,13 +28,15 @@ authorless:
 sti_comments:
   id: 4
   author_id: 1
+  comments_count: 4
   title: sti comments
   body: hello
   type: Post
 
 sti_post_and_comments:
   id: 5
   author_id: 1
+  comments_count: 3
   title: sti me
   body: hello
   type: StiPost

activerecord/test/models/post.rb

@@ -19,6 +19,7 @@ def greeting
 
   scope :containing_the_letter_a, -> { where("body LIKE '%a%'") }
   scope :ranked_by_comments,      -> { order("comments_count DESC") }
+  scope :ranked_by_comments_hash, -> { order(comments_count: :desc) }
 
   scope :limit_by, lambda {|l| limit(l) }
 
@@ -40,6 +41,8 @@ def first_comment
   scope :with_comments, -> { preload(:comments) }
   scope :with_tags, -> { preload(:taggings) }
 
+  scope :comment, -> { order(type: :desc) }
+
   has_many   :comments do
     def find_most_recent
       order("id DESC").first