Revert silent discard of NoMethodError from plugins introduced by 95d…

…9cd1 (fixes #413)

Rather than silently discarding all NoMethodErrors, we just check
whether the plugin implements the task and only execute it if it does.

lib/guard/runner.rb

@@ -51,7 +51,7 @@ def deprecation_warning
     def run(task, scopes = {})
       Lumberjack.unit_of_work do
         scoped_guards(scopes) do |guard|
-          run_supervised_task(guard, task)
+          run_supervised_task(guard, task) if guard.respond_to?(task)
         end
       end
     end
@@ -101,8 +101,6 @@ def run_supervised_task(guard, task, *args)
           result
         end
 
-      rescue NoMethodError
-        # Do nothing
       rescue Exception => ex
         ::Guard::UI.error("#{ guard.class.name } failed to achieve its <#{ task.to_s }>, exception was:" +
                  "\n#{ ex.class }: #{ ex.message }\n#{ ex.backtrace.join("\n") }")

spec/guard/runner_spec.rb

@@ -68,8 +68,9 @@
   describe '#run' do
     let(:scopes) { { :group => foo_group } }
 
-    it 'executes a supervised task on all registered guards' do
-      [foo_guard, bar1_guard, bar2_guard].each do |g|
+    it 'executes a supervised task on all registered guards implementing that task' do
+      [foo_guard, bar1_guard].each do |g|
+        g.stub(:my_task)
         subject.should_receive(:run_supervised_task).with(g, :my_task)
       end
       subject.run(:my_task)
@@ -94,6 +95,7 @@
       let(:scopes) { { :plugins => [bar1_guard] } }
 
       it 'executes the supervised task on the specified guard only' do
+        bar1_guard.stub(:my_task)
         subject.should_receive(:run_supervised_task).with(bar1_guard, :my_task)
 
         subject.should_not_receive(:run_supervised_task).with(foo_guard, :my_task)
@@ -107,6 +109,7 @@
       let(:scopes) { { :groups => [foo_group] } }
 
       it 'executes the task on each guard in the specified group only' do
+        foo_guard.stub(:my_task)
         subject.should_receive(:run_supervised_task).with(foo_guard, :my_task)
 
         subject.should_not_receive(:run_supervised_task).with(bar1_guard, :my_task)