feat: modernize ActiveModel integration with backward compatibility

lib/state_machines/integrations/active_model.rb

@@ -353,12 +353,22 @@ def around_validation(object)
 
       def define_state_initializer
         define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1
-          def initialize(**params)
-            params.transform_keys! do |key|
+          def initialize(params = nil, **kwargs)
+            # Support both positional hash and keyword arguments
+            attrs = params.nil? ? kwargs : params
+          #{'  '}
+            attrs.transform_keys! do |key|
               self.class.attribute_aliases[key.to_s] || key.to_s
             end if self.class.respond_to?(:attribute_aliases)
 
-            self.class.state_machines.initialize_states(self, {}, params) { super }
+            # Call super with the appropriate arguments based on what we received
+            self.class.state_machines.initialize_states(self, {}, attrs) do
+              if params
+                super(params)
+              else
+                super(**kwargs)
+              end
+            end
           end
         end_eval
       end

test/machine_initialization_compatibility_test.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require_relative 'test_helper'
+
+class MachineInitializationCompatibilityTest < BaseTestCase
+  def setup
+    @model = new_model do
+      include ActiveModel::Validations
+      attr_accessor :state
+    end
+
+    @machine = StateMachines::Machine.new(@model, initial: :parked)
+    @machine.state :parked, :idling
+    @machine.event :ignite
+  end
+
+  def test_should_accept_positional_hash_argument
+    record = @model.new({ state: 'idling' })
+    assert_equal 'idling', record.state
+  end
+
+  def test_should_accept_keyword_arguments
+    record = @model.new(state: 'idling')
+    assert_equal 'idling', record.state
+  end
+
+  def test_should_accept_empty_initialization
+    record = @model.new
+    assert_equal 'parked', record.state
+  end
+
+  def test_should_handle_attribute_aliases
+    @model.class_eval do
+      def self.attribute_aliases
+        { 'status' => 'state' }
+      end
+    end
+
+    record = @model.new(status: 'idling')
+    assert_equal 'idling', record.state
+  end
+
+  def test_should_prefer_positional_hash_over_keywords_when_both_present
+    # If someone accidentally provides both, positional takes precedence
+    record = @model.new({ state: 'idling' }, state: 'parked')
+    assert_equal 'idling', record.state
+  end
+
+  def test_should_handle_empty_positional_hash
+    # Empty hash should still be treated as positional argument
+    record = @model.new({})
+    assert_equal 'parked', record.state # Gets default initial state
+  end
+
+  def test_should_use_keywords_when_empty_hash_and_keywords_present
+    # With the fix, keywords are ignored even with empty positional hash
+    record = @model.new({}, state: 'idling')
+    assert_equal 'parked', record.state # Empty hash takes precedence
+  end
+end