Builder supports action hooks

lib/vagrant/action/builder.rb

@@ -17,6 +17,12 @@ module Vagrant
     #     Vagrant::Action.run(app)
     #
     class Builder
+      # This is the stack of middlewares added. This should NOT be used
+      # directly.
+      #
+      # @return [Array]
+      attr_reader :stack
+
       # This is a shortcut for a middleware sequence with only one item
       # in it. For a description of the arguments and the documentation, please
       # see {#use} instead.
@@ -26,6 +32,18 @@ module Vagrant
         new.use(middleware, *args, &block)
       end
 
+      def initialize
+        @stack = []
+      end
+
+      # Implement a custom copy that copies the stack variable over so that
+      # we don't clobber that.
+      def initialize_copy(original)
+        super
+
+        @stack = original.stack.dup
+      end
+
       # Returns a mergeable version of the builder. If `use` is called with
       # the return value of this method, then the stack will merge, instead
       # of being treated as a separate single middleware.
@@ -109,19 +127,27 @@ module Vagrant
       # @param [Vagrant::Action::Environment] env The action environment
       # @return [Object] A callable object
       def to_app(env)
-        # Wrap the middleware stack with the Warden to provide a consistent
-        # and predictable behavior upon exceptions.
-        Warden.new(stack.dup, env)
+        app_stack = nil
+
+        # If we have action hooks, then we apply them
+        if env[:action_hooks]
+          builder = self.dup
+
+          # Apply all the hooks to the new builder instance
+          env[:action_hooks].each do |hook|
+            hook.apply(builder)
           end
 
-      protected
+          # The stack is now the result of the new builder
+          app_stack = builder.stack.dup
+        end
 
-      # Returns the current stack of middlewares. You probably won't
-      # need to use this directly, and it's recommended that you don't.
-      #
-      # @return [Array]
-      def stack
-        @stack ||= []
+        # If we don't have a stack then default to using our own
+        app_stack ||= stack.dup
+
+        # Wrap the middleware stack with the Warden to provide a consistent
+        # and predictable behavior upon exceptions.
+        Warden.new(app_stack, env)
       end
     end
   end

test/unit/vagrant/action/builder_test.rb

@@ -9,6 +9,13 @@ describe Vagrant::Action::Builder do
     Proc.new { |env| env[:data] << data }
   end
 
+  context "copying" do
+    it "should copy the stack" do
+      copy = subject.dup
+      copy.stack.object_id.should_not == subject.stack.object_id
+    end
+  end
+
   context "build" do
     it "should provide build as a shortcut for basic sequences" do
       data = {}
@@ -170,4 +177,20 @@ describe Vagrant::Action::Builder do
       data[:data].should == [2]
     end
   end
+
+  describe "action hooks" do
+    it "applies them properly" do
+      hook = double("hook")
+      hook.stub(:apply) do |builder|
+        builder.use appender_proc(2)
+      end
+
+      data[:action_hooks] = [hook]
+
+      subject.use appender_proc(1)
+      subject.call(data)
+
+      data[:data].should == [1, 2]
+    end
+  end
 end