`ActiveRecord::Relation#order` supports hash like `ActiveRecord::Relation#where` (#50000)

* relation#order supports hash like relation#where

This allows for an ActiveRecord::Relation to take a hash such as
`Topic.includes(:posts).order(posts: { created_at: :desc })`

* use is_a? to support subclasses of each

Co-authored-by: Rafael Mendonça França <rafael@rubyonrails.org>

activerecord/CHANGELOG.md

@@ -505,4 +505,12 @@
 
     *Tristan Fellows*
 
+*   Allow for more complex hash arguments for `order` which mimics `where` in `ActiveRecord::Relation`.
+
+    ```ruby
+    Topic.includes(:posts).order(posts: { created_at: :desc })
+    ```
+
+    *Myles Boone*
+
 Please check [7-1-stable](https://github.com/rails/rails/blob/7-1-stable/activerecord/CHANGELOG.md) for previous changes.

activerecord/lib/active_record/relation/query_methods.rb

@@ -1918,7 +1918,9 @@ module ActiveRecord
         args.each do |arg|
           next unless arg.is_a?(Hash)
           arg.each do |_key, value|
-            unless VALID_DIRECTIONS.include?(value)
+            if value.is_a?(Hash)
+              validate_order_args([value])
+            elsif VALID_DIRECTIONS.exclude?(value)
               raise ArgumentError,
                 "Direction \"#{value}\" is invalid. Valid directions are: #{VALID_DIRECTIONS.to_a.inspect}"
             end
@@ -1926,9 +1928,13 @@ module ActiveRecord
         end
       end
 
+      def flattened_args(order_args)
+        order_args.flat_map { |e| (e.is_a?(Hash) || e.is_a?(Array)) ? flattened_args(e.to_a) : e }
+      end
+
       def preprocess_order_args(order_args)
         @klass.disallow_raw_sql!(
-          order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a },
+          flattened_args(order_args),
           permit: connection.column_name_with_order_matcher
         )
 
@@ -1943,14 +1949,20 @@ module ActiveRecord
           when Symbol
             order_column(arg.to_s).asc
           when Hash
-            arg.map { |field, dir|
-              case field
-              when Arel::Nodes::SqlLiteral, Arel::Nodes::Node, Arel::Attribute
-                field.public_send(dir.downcase)
+            arg.map do |key, value|
+              if value.is_a?(Hash)
+                value.map do |field, dir|
+                  order_column([key.to_s, field.to_s].join(".")).public_send(dir.downcase)
+                end
               else
-                order_column(field.to_s).public_send(dir.downcase)
+                case key
+                when Arel::Nodes::SqlLiteral, Arel::Nodes::Node, Arel::Attribute
+                  key.public_send(value.downcase)
+                else
+                  order_column(key.to_s).public_send(value.downcase)
+                end
               end
-            }
+            end
           else
             arg
           end
@@ -1964,18 +1976,20 @@ module ActiveRecord
       end
 
       def column_references(order_args)
-        references = order_args.flat_map do |arg|
+        order_args.flat_map do |arg|
           case arg
           when String, Symbol
             arg
           when Hash
-            arg.keys.map do |key|
-              key if key.is_a?(String) || key.is_a?(Symbol)
-            end
+            arg.keys.select { |e| e.is_a?(String) || e.is_a?(Symbol) }
           end
-        end
-        references.map! { |arg| arg =~ /^\W?(\w+)\W?\./ && $1 }.compact!
-        references
+        end.filter_map do |arg|
+          arg =~ /^\W?(\w+)\W?\./ && $1
+        end +
+        order_args
+          .select { |e| e.is_a?(Hash) }
+          .flat_map { |e| e.map { |k, v| k if v.is_a?(Hash) } }
+          .compact
       end
 
       def order_column(field)

activerecord/test/cases/relation/order_test.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/author"
+require "models/book"
+
+class OrderTest < ActiveRecord::TestCase
+  fixtures :authors
+
+  def test_order_asc
+    Book.destroy_all
+    z = Book.create!(name: "Zulu", author: authors(:david))
+    y = Book.create!(name: "Yankee", author: authors(:mary))
+    x = Book.create!(name: "X-Ray", author: authors(:david))
+
+    alphabetical = [x, y, z]
+
+    assert_equal(alphabetical, Book.order(name: :asc))
+    assert_equal(alphabetical, Book.order(name: :ASC))
+    assert_equal(alphabetical, Book.order(name: "asc"))
+    assert_equal(alphabetical, Book.order(:name))
+    assert_equal(alphabetical, Book.order("name"))
+    assert_equal(alphabetical, Book.order("books.name"))
+    assert_equal(alphabetical, Book.order(Book.arel_table["name"]))
+    assert_equal(alphabetical, Book.order(books: { name: :asc }))
+  end
+
+  def test_order_desc
+    Book.destroy_all
+    z = Book.create!(name: "Zulu", author: authors(:david))
+    y = Book.create!(name: "Yankee", author: authors(:mary))
+    x = Book.create!(name: "X-Ray", author: authors(:david))
+
+    reverse_alphabetical = [z, y, x]
+
+    assert_equal(reverse_alphabetical, Book.order(name: :desc))
+    assert_equal(reverse_alphabetical, Book.order(name: :DESC))
+    assert_equal(reverse_alphabetical, Book.order(name: "desc"))
+    assert_equal(reverse_alphabetical, Book.order(:name).reverse_order)
+    assert_equal(reverse_alphabetical, Book.order("name desc"))
+    assert_equal(reverse_alphabetical, Book.order("books.name desc"))
+    assert_equal(reverse_alphabetical, Book.order(Book.arel_table["name"].desc))
+    assert_equal(reverse_alphabetical, Book.order(books: { name: :desc }))
+  end
+
+  def test_order_with_association
+    Book.destroy_all
+    z = Book.create!(name: "Zulu", author: authors(:david))
+    y = Book.create!(name: "Yankee", author: authors(:mary))
+    x = Book.create!(name: "X-Ray", author: authors(:david))
+
+    author_then_book_name = [x, z, y]
+
+    assert_equal(author_then_book_name, Book.includes(:author).order(authors: { name: :asc }, books: { name: :asc }))
+    assert_equal(author_then_book_name, Book.includes(:author).order("authors.name", books: { name: :asc }))
+    assert_equal(author_then_book_name, Book.includes(:author).order("authors.name", "books.name"))
+    assert_equal(author_then_book_name, Book.includes(:author).order({ authors: { name: :asc } }, Book.arel_table[:name]))
+
+    author_desc_then_book_name = [y, x, z]
+
+    assert_equal(author_desc_then_book_name, Book.includes(:author).order(authors: { name: :desc }, books: { name: :asc }))
+    assert_equal(author_desc_then_book_name, Book.includes(:author).order("authors.name desc", books: { name: :asc }))
+    assert_equal(author_desc_then_book_name, Book.includes(:author).order({ authors: { name: :desc } }, :name))
+  end
+end

guides/source/active_record_querying.md

@@ -912,6 +912,14 @@ irb> Book.order("title ASC").order("created_at DESC")
 SELECT * FROM books ORDER BY title ASC, created_at DESC
 ```
 
+You can also order from a joined table
+
+```ruby
+Book.includes(:author).order(books: { print_year: :desc }, authors: { name: :asc })
+# OR
+Book.includes(:author).order('books.print_year desc', 'authors.name asc')
+```
+
 WARNING: In most database systems, on selecting fields with `distinct` from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set.
 
 Selecting Specific Fields