Ensure nil arg is forwarded to callbacks

fixes #404

lib/aasm/core/event.rb

@@ -122,6 +122,8 @@ module AASM::Core
           args.unshift(to_state)
           to_state = nil
         end
+      else
+        args.unshift(nil) if args.blank? # If single arg given which is nil, push it back to args
       end
 
       transitions.each do |transition|

spec/models/guard_with_params.rb

@@ -10,7 +10,7 @@ class GuardWithParams
 
   def user_is_manager?(user)
     ok = false
-    if user.has_role? :manager
+    if user && user.has_role?(:manager)
       ok = true
     end
     return ok

spec/models/parametrised_event.rb

@@ -11,6 +11,10 @@ class ParametrisedEvent
       transitions :from => :sleeping, :to => [:showering, :working]
     end
 
+    event :shower do
+      transitions :from => :sleeping, :to => :showering, :after => :wet_hair, :success => :wear_clothes
+    end
+
     event :dress do
       transitions :from => :sleeping, :to => :working, :after => :wear_clothes, :success => :wear_makeup
       transitions :from => :showering, :to => [:working, :dating], :after => Proc.new { |*args| wear_clothes(*args) }, :success => proc { |*args| wear_makeup(*args) }
@@ -24,6 +28,9 @@ class ParametrisedEvent
   def wear_makeup(makeup, moisturizer)
   end
 
+  def wet_hair(dryer)
+  end
+
   def condition_hair
   end
 

spec/unit/event_spec.rb

@@ -325,6 +325,12 @@ describe 'parametrised events' do
     pe.dress!(:working, 'blue', 'jeans')
   end
 
+  it 'should call :after transition method if arg is nil' do
+    dryer = nil
+    expect(pe).to receive(:wet_hair).with(dryer)
+    pe.shower!(dryer)
+  end
+
   it 'should call :after transition proc' do
     pe.wakeup!(:showering)
     expect(pe).to receive(:wear_clothes).with('purple', 'slacks')
@@ -344,6 +350,12 @@ describe 'parametrised events' do
     pe.dress!(:working, 'foundation', 'SPF')
   end
 
+  it 'should call :success transition method if arg is nil' do
+    shirt_color = nil
+    expect(pe).to receive(:wear_clothes).with(shirt_color)
+    pe.shower!(shirt_color)
+  end
+
   it 'should call :success transition proc' do
     pe.wakeup!(:showering)
     expect(pe).to receive(:wear_makeup).with('purple', 'slacks')

spec/unit/guard_with_params_spec.rb

@@ -7,4 +7,8 @@ describe "guards with params" do
   it "list permitted states" do
     expect(guard.aasm.states({:permitted => true}, user).map(&:name)).to eql [:reviewed]
   end
+
+  it "list no states if user is blank" do
+    expect(guard.aasm.states({:permitted => true}, nil).map(&:name)).to eql []
+  end
 end