handle case of nil inside array value for in in_order_of

activerecord/lib/active_record/relation/query_methods.rb

@@ -733,11 +733,13 @@ def in_order_of(column, values, filter: true)
       scope = spawn.order!(build_case_for_value_position(arel_column, values, filter: filter))
 
       if filter
+        values = values.flatten(1)
+
         where_clause =
           if values.include?(nil)
-            arel_column.in(values.compact.flatten(1)).or(arel_column.eq(nil))
+            arel_column.in(values.compact).or(arel_column.eq(nil))
           else
-            arel_column.in(values.flatten(1))
+            arel_column.in(values)
           end
 
         scope = scope.where!(where_clause)
@@ -2142,7 +2144,11 @@ def build_case_for_value_position(column, values, filter: true)
         node = Arel::Nodes::Case.new
         values.each.with_index(1) do |value, order|
           if value.is_a?(Array)
-            node.when(column.in(value)).then(order)
+            if value.include?(nil)
+              node.when(column.in(value.compact).or(column.eq(nil))).then(order)
+            else
+              node.when(column.in(value)).then(order)
+            end
           else
             node.when(column.eq(value)).then(order)
           end

activerecord/test/cases/relation/field_ordered_values_test.rb

@@ -124,4 +124,17 @@ def test_in_order_of_with_array_values
 
     assert_equal([3, 2, 5, 4, 7, 1], posts.map(&:id))
   end
+
+  def test_in_order_of_with_array_values_with_nil
+    Book.destroy_all
+    Book.create!(format: "paperback")
+    Book.create!(format: "ebook")
+    Book.create!(format: nil)
+    Book.create!(format: "letter")
+    Book.create!(format: "digital")
+
+    order = ["ebook", ["paperback", nil, "digital"], "letter"]
+    books = Book.in_order_of(:format, order).order(format: :desc)
+    assert_equal(["ebook", "paperback", "digital", nil, "letter"], books.map(&:format))
+  end
 end