Make Guard implementation of :task_has_failed simple.

This change makes sure that Guard implementation can just
`throw :task_has_failed` without knowing whether the enclosing
group has enabled :halt_on_fail.

The problem with throw/catch is, that when you throw a :symbol,
you'll have to catch it, otherwise you get a 'uncatched throw' error.

When the Guard group has not enabled :halt_on_fail, we catch the throw
when execute the supervised task.

lib/guard.rb

@@ -192,14 +192,14 @@ module Guard
     # Loop through all groups and run the given task for each Guard.
     #
     # Stop the task run for the all Guards within a group if one Guard
-    # throws `:task_has_failed` and the group has its `:halt_on_fail` option to `true`.
+    # throws `:task_has_failed`.
     #
     # @param [Symbol] task the task to run
     # @param [Array<String>] files the list of files to pass to the task
     #
     def run_guard_task(task, files = nil)
       groups.each do |group|
-        catch group.options[:halt_on_fail] == true ? :task_has_failed : :no_catch do
+        catch :task_has_failed do
           guards(:group => group.name).each do |guard|
             if task == :run_on_change
               run_on_change_task(files, guard, task)
@@ -262,17 +262,22 @@ module Guard
 
     # Run a Guard task, but remove the Guard when his work leads to a system failure.
     #
+    # When the Group has `:halt_on_fail` disabled, we've to catch `:task_has_failed`
+    # here in order to avoid an uncaught throw error.
+    #
     # @param [Guard::Guard] guard the Guard to execute
     # @param [Symbol] task the task to run
     # @param [Array] args the arguments for the task
     # @raise [:task_has_failed] when task has failed
     #
     def run_supervised_task(guard, task, *args)
+      catch guard_symbol(guard) do
         guard.hook("#{ task }_begin", *args)
         result = guard.send(task, *args)
         guard.hook("#{ task }_end", result)
 
         result
+      end
 
     rescue Exception => ex
       UI.error("#{ guard.class.name } failed to achieve its <#{ task.to_s }>, exception was:" +
@@ -284,6 +289,25 @@ module Guard
       ex
     end
 
+    # Get the symbol we have to catch when running a supervised task.
+    # If we are within a Guard group that has the `:halt_on_fail`
+    # option set, we do NOT catch it here, it will be catched at the
+    # group level.
+    #
+    # @see .run_guard_task
+    #
+    # @param [Guard::Guard] guard the Guard to execute
+    # @return [Symbol] the symbol to catch
+    #
+    def guard_symbol(guard)
+      if guard.group.class == Symbol
+        group = groups(guard.group)
+        group.options[:halt_on_fail] ? :no_catch : :task_has_failed
+      else
+        :task_has_failed
+      end
+    end
+
     # Add a Guard to use.
     #
     # @param [String] name the Guard name

spec/guard_spec.rb

@@ -369,7 +369,7 @@ describe Guard do
       end
     end
 
-    context "one guard fails (by returning false)" do
+    context "one guard fails" do
       before do
         subject.guards.each_with_index do |g, i|
           g.stub!(:task) do
@@ -437,6 +437,7 @@ describe Guard do
       @g = mock(Guard::Guard).as_null_object
       subject.guards.push(@g)
       subject.add_group(:foo, { :halt_on_fail => true })
+      subject.add_group(:bar, { :halt_on_fail => false })
     end
 
     context "with a task that succeed" do
@@ -486,7 +487,8 @@ describe Guard do
       end
     end
 
-    context "with a task that return false and guard's group has the :halt_on_fail option == true" do
+    context "with a task that throw :task_has_failed" do
+      context "for a guard's group has the :halt_on_fail option == true" do
         before(:each) { @g.stub!(:group) { :foo }; @g.stub!(:failing) { throw :task_has_failed } }
 
         it "throws :task_has_failed" do
@@ -494,8 +496,17 @@ describe Guard do
         end
       end
 
+      context "for a guard's group has the :halt_on_fail option == false" do
+        before(:each) { @g.stub!(:group) { :bar }; @g.stub!(:failing) { throw :task_has_failed } }
+
+        it "catches :task_has_failed" do
+          expect { subject.run_supervised_task(@g, :failing) }.to_not throw_symbol(:task_has_failed)
+        end
+      end
+    end
+
     context "with a task that raises an exception" do
-      before(:each) { @g.stub!(:failing) { raise "I break your system" } }
+      before(:each) { @g.stub!(:group) { :foo }; @g.stub!(:failing) { raise "I break your system" } }
 
       it "fires the Guard" do
         lambda { subject.run_supervised_task(@g, :failing) }.should change(subject.guards, :size).by(-1)
@@ -510,6 +521,42 @@ describe Guard do
     end
   end
 
+  describe '.guard_symbol' do
+    let(:guard) { mock(Guard::Guard).as_null_object }
+
+    it 'returns :task_has_failed when the group is missing' do
+      subject.guard_symbol(guard).should eql :task_has_failed
+    end
+
+    context 'for a group with :halt_on_fail' do
+      let(:group) { mock(Guard::Group) }
+
+      before do
+        guard.stub(:group).and_return :foo
+        group.stub(:options).and_return({ :halt_on_fail => true })
+      end
+
+      it 'returns :task_has_failed when the group is missing' do
+        subject.should_receive(:groups).with(:foo).and_return group
+        subject.guard_symbol(guard).should eql :no_catch
+      end
+    end
+
+    context 'for a group without :halt_on_fail' do
+      let(:group) { mock(Guard::Group) }
+
+      before do
+        guard.stub(:group).and_return :foo
+        group.stub(:options).and_return({ :halt_on_fail => false })
+      end
+
+      it 'returns :task_has_failed when the group is missing' do
+        subject.should_receive(:groups).with(:foo).and_return group
+        subject.guard_symbol(guard).should eql :task_has_failed
+      end
+    end
+  end
+
   describe ".debug_command_execution" do
     subject { ::Guard.setup }