Add hoc sequences in create_list

lib/factory_bot.rb

@@ -47,6 +47,7 @@
 require "factory_bot/decorator/new_constructor"
 require "factory_bot/linter"
 require "factory_bot/version"
+require "factory_bot/attribute_sequence"
 
 module FactoryBot
   Deprecation = ActiveSupport::Deprecation.new("7.0", "factory_bot")

lib/factory_bot/attribute_sequence.rb

@@ -0,0 +1,24 @@
+module FactoryBot
+  # @api private
+  class AttributeSequence
+    attr_reader :expression
+
+    def initialize(&block)
+      @expression = block
+    end
+
+    def evaluate(index)
+      expression.call(index)
+    end
+
+    def self.evaluate_attributes(traits_and_overrides, i)
+      traits_and_overrides.map do |attribute|
+        next attribute unless attribute.is_a?(Hash)
+
+        attribute.transform_values do |value|
+          value.is_a?(self) ? value.evaluate(i) : value
+        end
+      end    
+    end
+  end
+end

lib/factory_bot/strategy_syntax_method_registrar.rb

@@ -39,7 +39,9 @@ def define_list_strategy_method
 
         Array.new(amount) do |i|
           block_with_index = StrategySyntaxMethodRegistrar.with_index(block, i)
-          send(strategy_name, name, *traits_and_overrides, &block_with_index)
+          traits_and_evaluated_overrides =
+            FactoryBot::AttributeSequence.evaluate_attributes(traits_and_overrides, i)
+          send(strategy_name, name, *traits_and_evaluated_overrides, &block_with_index)
         end
       end
     end

lib/factory_bot/syntax/methods.rb

@@ -129,6 +129,10 @@ def generate_list(name, count)
           Internal.sequence_by_name(name).next
         end
       end
+
+      def build_sequence(&block)
+        FactoryBot::AttributeSequence.new(&block)
+      end
     end
   end
 end

spec/acceptance/create_list_spec.rb

@@ -38,6 +38,16 @@
     end
   end
 
+  context "with sequencial attributes" do
+    subject { FactoryBot.create_list(:post, 20, title: FactoryBot.build_sequence{ |n| "title_#{n}" }) }
+
+    it "create sequencial attribute values" do
+      subject.each_with_index do |record, i|
+        expect(record.title).to eq "title_#{i}"
+      end
+    end
+  end
+
   context "with a block" do
     subject do
       FactoryBot.create_list(:post, 20, title: "The Listing of the Block") do |post|