Fix ActiveRecord::QueryMethods#in_order_of to work with nils

activerecord/CHANGELOG.md

@@ -1,3 +1,11 @@
+*   Fix `ActiveRecord::QueryMethods#in_order_of` to include `nil`s, to match the
+    behavior of `Enumerable#in_order_of`.
+
+    For example, `Post.in_order_of(:title, [nil, "foo"])` will now include posts
+    with `nil` titles, the same as `Post.all.to_a.in_order_of(:title, [nil, "foo"])`.
+
+    *fatkodima*
+
 *   Revert "Fix autosave associations with validations added on `:base` of the associated objects."
 
     This change intended to remove the :base attribute from the message,

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -657,15 +657,6 @@ def schema_version
         migration_context.current_version
       end
 
-      def field_ordered_value(column, values) # :nodoc:
-        node = Arel::Nodes::Case.new(column)
-        values.each.with_index(1) do |value, order|
-          node.when(value).then(order)
-        end
-
-        Arel::Nodes::Ascending.new(node.else(values.length + 1))
-      end
-
       class << self
         private
           def initialize_type_map(m)

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -138,11 +138,6 @@ def supports_insert_on_duplicate_update?
         true
       end
 
-      def field_ordered_value(column, values) # :nodoc:
-        field = Arel::Nodes::NamedFunction.new("FIELD", [column, values.reverse.map { |value| Arel::Nodes.build_quoted(value) }])
-        Arel::Nodes::Descending.new(field)
-      end
-
       def get_advisory_lock(lock_name, timeout = 0) # :nodoc:
         query_value("SELECT GET_LOCK(#{quote(lock_name.to_s)}, #{timeout})") == 1
       end

activerecord/lib/active_record/relation/query_methods.rb

@@ -444,13 +444,16 @@ def order!(*args) # :nodoc:
       self
     end
 
-    # Allows to specify an order by a specific set of values. Depending on your
-    # adapter this will either use a CASE statement or a built-in function.
+    # Allows to specify an order by a specific set of values.
     #
     #   User.in_order_of(:id, [1, 5, 3])
     #   # SELECT "users".* FROM "users"
-    #   #   ORDER BY FIELD("users"."id", 1, 5, 3)
     #   #   WHERE "users"."id" IN (1, 5, 3)
+    #   #   ORDER BY CASE
+    #   #     WHEN "users"."id" = 1 THEN 1
+    #   #     WHEN "users"."id" = 5 THEN 2
+    #   #     WHEN "users"."id" = 3 THEN 3
+    #   #   END ASC
     #
     def in_order_of(column, values)
       klass.disallow_raw_sql!([column], permit: connection.column_name_with_order_matcher)
@@ -462,9 +465,16 @@ def in_order_of(column, values)
       values = values.map { |value| type_caster.type_cast_for_database(column, value) }
       arel_column = column.is_a?(Symbol) ? order_column(column.to_s) : column
 
+      where_clause =
+        if values.include?(nil)
+          arel_column.in(values.compact).or(arel_column.eq(nil))
+        else
+          arel_column.in(values)
+        end
+
       spawn
-        .order!(connection.field_ordered_value(arel_column, values))
-        .where!(arel_column.in(values))
+        .order!(build_case_for_value_position(arel_column, values))
+        .where!(where_clause)
     end
 
     # Replaces any existing order defined on the relation with the specified order.
@@ -1669,6 +1679,15 @@ def order_column(field)
         end
       end
 
+      def build_case_for_value_position(column, values)
+        node = Arel::Nodes::Case.new
+        values.each.with_index(1) do |value, order|
+          node.when(column.eq(value)).then(order)
+        end
+
+        Arel::Nodes::Ascending.new(node)
+      end
+
       def resolve_arel_attributes(attrs)
         attrs.flat_map do |attr|
           case attr

activerecord/test/cases/relation/field_ordered_values_test.rb

@@ -69,4 +69,16 @@ def test_in_order_of_after_regular_order
 
     assert_equal(order, posts.map(&:id))
   end
+
+  def test_in_order_of_with_nil
+    Book.destroy_all
+    Book.create!(format: "paperback")
+    Book.create!(format: "ebook")
+    Book.create!(format: nil)
+
+    order = ["ebook", nil, "paperback"]
+    books = Book.in_order_of(:format, order)
+
+    assert_equal(order, books.map(&:format))
+  end
 end