Improve backward compatibility for #227 - let :if methods and procs…

… ignore additional arguments

In case the method referenced by `:if` does not accept additional
arguments, but the transition action is called with some, avoid
exception "1 argument provided, but 0 were expected" by ignoring
superfluous arguments if needed.

lib/workflow/event.rb

@@ -18,8 +18,18 @@ def initialize(name, transitions_to, condition = nil, meta = {}, &action)
     def condition_applicable?(object, event_arguments)
       if condition
         if condition.is_a?(Symbol)
-          object.send(condition, *event_arguments)
+          m = object.method(condition)
+          # Conditionals can now take the arguments of the trasition action into account #227
+          # But in case the current conditional wants to ignore any event_argument on its decision -
+          # does not accept parameters, also support that.
+          if m.arity == 0 # no additional parameters accepted
+            object.send(condition)
+          else
+            object.send(condition, *event_arguments)
+          end
         else
+          # since blocks can ignore extra arguments without raising an error in Ruby,
+          # no `if` is needed - compare with `arity` switch in above methods handling
           condition.call(object, *event_arguments)
         end
       else

test/conditionals_test.rb

@@ -42,7 +42,7 @@ def sufficient_battery_level?
     assert device.on?
   end
 
-  test 'gh-227 allow event arguments in conditions - test with proc' do
+  test 'gh-227 allow event arguments in conditions - test with a method' do
     c = Class.new do
       include Workflow
       # define more advanced workflow, where event methods allow arguments
@@ -52,26 +52,36 @@ def sufficient_battery_level?
           event :turn_on, :transitions_to => :on, :if => :sufficient_battery_level?
           event :turn_on, :transitions_to => :low_battery # otherwise
         end
-        state :on
+        state :on do
+          event :check, :transitions_to => :low_battery, :if => :check_low_battery?
+          event :check, :transitions_to => :on # stay in on state otherwise
+        end
         state :low_battery
       end
       attr_reader :battery
       def initialize(battery)
         @battery = battery
       end
 
-      def sufficient_battery_level?(power_adapter=false)
+      def sufficient_battery_level?(power_adapter)
         power_adapter || @battery > 10
       end
+
+      def check_low_battery?() # supports no arguments, lets test below, what happens if the action uses addtional args
+        # 'in check_low_battery? method'
+      end
     end
 
     # test for conditions in a proc
     device = c.new 5
     device.turn_on!(true) # case with event arguments to be taken into account
     assert device.on?
+    device.check!('foo') # the conditional in the definition above does not support arguments, but make it work
+    # by ignoring superfluous arguments for compatibility
+    assert device.on?
   end
 
-  test 'gh-227 allow event arguments in conditions - test with a method' do
+  test 'gh-227 allow event arguments in conditions - test with a proc' do
     c = Class.new do
       include Workflow
       # define more advanced workflow, where event methods allow arguments
@@ -81,7 +91,10 @@ def sufficient_battery_level?(power_adapter=false)
           event :turn_on, :transitions_to => :on, :if => proc { |obj, power_adapter| power_adapter || obj.battery > 10 }
           event :turn_on, :transitions_to => :low_battery # otherwise
         end
-        state :on
+        state :on do
+          event :check, :transitions_to => :low_battery, :if => proc { |obj| return false }
+          event :check, :transitions_to => :on # stay in on state otherwise
+        end
         state :low_battery
       end
       attr_reader :battery
@@ -93,6 +106,9 @@ def initialize(battery)
     device = c.new 5
     device.turn_on!(true) # case with event arguments to be taken into account
     assert device.on?
+    device.check!('foo') # also ensure that if conditional in the definition above does not support arguments,
+    # it still works and just ignores superfluous arguments
+    assert device.on?
   end
 
 end