Add failed callback(s) into InvalidTransition exception

lib/aasm/aasm.rb

@@ -91,10 +91,10 @@ def aasm_fire_event(state_machine_name, event_name, options, *args, &block)
         if new_state_name = event.fire(self, {:may_fire => may_fire_to}, *args)
           aasm_fired(state_machine_name, event, old_state, new_state_name, options, *args, &block)
         else
-          aasm_failed(state_machine_name, event_name, old_state)
+          aasm_failed(state_machine_name, event_name, old_state, event.failed_callbacks)
         end
       else
-        aasm_failed(state_machine_name, event_name, old_state)
+        aasm_failed(state_machine_name, event_name, old_state, event.failed_callbacks)
       end
     rescue StandardError => e
       event.fire_callbacks(:error, self, e, *process_args(event, aasm(state_machine_name).current_state, *args)) || raise(e)
@@ -143,13 +143,13 @@ def aasm_fired(state_machine_name, event, old_state, new_state_name, options, *a
     persist_successful
   end
 
-  def aasm_failed(state_machine_name, event_name, old_state)
+  def aasm_failed(state_machine_name, event_name, old_state, failures = [])
     if self.respond_to?(:aasm_event_failed)
       self.aasm_event_failed(event_name, old_state.name)
     end
 
     if AASM::StateMachine[self.class][state_machine_name].config.whiny_transitions
-      raise AASM::InvalidTransition.new(self, event_name, state_machine_name)
+      raise AASM::InvalidTransition.new(self, event_name, state_machine_name, failures)
     else
       false
     end

lib/aasm/core/event.rb

@@ -72,6 +72,10 @@ def transitions(definitions=nil, &block)
       @transitions
     end
 
+    def failed_callbacks
+      @transitions.flat_map(&:failures)
+    end
+
   private
 
     def attach_event_guards(definitions)

lib/aasm/core/transition.rb

@@ -2,12 +2,13 @@ module AASM::Core
   class Transition
     include DslHelper
 
-    attr_reader :from, :to, :event, :opts
+    attr_reader :from, :to, :event, :opts, :failures
     alias_method :options, :opts
 
     def initialize(event, opts, &block)
       add_options_from_dsl(opts, [:on_transition, :guard, :after], &block) if block
 
+      @failures = []
       @event = event
       @from = opts[:from]
       @to = opts[:to]
@@ -52,7 +53,9 @@ def invoke_callbacks_compatible_with_guard(code, record, args, options={})
       case code
       when Symbol, String
         arity = record.send(:method, code.to_sym).arity
-        arity == 0 ? record.send(code) : record.send(code, *args)
+        result = (arity == 0 ? record.send(code) : result = record.send(code, *args))
+        failures << code unless result
+        result
       when Proc
         code.arity == 0 ? record.instance_exec(&code) : record.instance_exec(*args, &code)
       when Array

lib/aasm/errors.rb

@@ -3,14 +3,18 @@ module AASM
   class UnknownStateMachineError < RuntimeError; end
 
   class InvalidTransition < RuntimeError
-    attr_reader :object, :event_name, :state_machine_name
+    attr_reader :object, :event_name, :state_machine_name, :failures
 
-    def initialize(object, event_name, state_machine_name)
-      @object, @event_name, @state_machine_name = object, event_name, state_machine_name
+    def initialize(object, event_name, state_machine_name, failures = [])
+      @object, @event_name, @state_machine_name, @failures = object, event_name, state_machine_name, failures
     end
 
     def message
-      "Event '#{event_name}' cannot transition from '#{object.aasm(state_machine_name).current_state}'"
+      "Event '#{event_name}' cannot transition from '#{object.aasm(state_machine_name).current_state}'#{reasoning}"
+    end
+
+    def reasoning
+      ". Failed callback(s): #{@failures}." unless failures.empty?
     end
   end