Guest#capability? for testing for capabilities

lib/vagrant/guest.rb

@@ -19,11 +19,19 @@ module Vagrant
   class Guest
     attr_reader :chain
 
-    def initialize(machine, guests)
+    # The name of the guest OS. This is available after {#detect!} is
+    # called.
+    #
+    # @return [Symbol]
+    attr_reader :name
+
+    def initialize(machine, guests, capabilities)
       @logger       = Log4r::Logger.new("vagrant::guest")
+      @capabilities = capabilities
       @chain        = []
       @guests       = guests
       @machine      = machine
+      @name         = nil
     end
 
     # This will detect the proper guest OS for the machine and set up
@@ -63,15 +71,18 @@ module Vagrant
 
             if guest.detect?(@machine)
               @logger.info("Detected: #{name}!")
-              @chain << guest
+              @chain << [name, guest]
+              @name = name
 
               # Build the proper chain of parents if there are any.
               # This allows us to do "inheritence" of capabilities later
               if guest_info[1]
-                parent_info = @guests[guest_info[1]]
+                parent_name = guest_info[1]
+                parent_info = @guests[parent_name]
                 while parent_info
-                  @chain << parent_info[0].new
-                  parent_info = @guests[parent_info[1]]
+                  @chain << [parent_name, parent_info[0].new]
+                  parent_name = parent_info[1]
+                  parent_info = @guests[parent_name]
                 end
               end
 
@@ -89,6 +100,18 @@ module Vagrant
       raise Errors::GuestNotDetected if @chain.empty?
     end
 
+    # Tests whether the guest has the named capability.
+    #
+    # @return [Boolean]
+    def capability?(cap_name)
+      @chain.each do |guest_name, guest|
+        caps = @capabilities[guest_name]
+        return true if caps && caps.has_key?(cap_name)
+      end
+
+      false
+    end
+
     # This returns whether the guest is ready to work. If this returns
     # `false`, then {#detect!} should be called in order to detect the
     # guest OS.

test/unit/vagrant/guest_test.rb

@@ -5,10 +5,22 @@ require File.expand_path("../../base", __FILE__)
 describe Vagrant::Guest do
   include_context "unit"
 
+  let(:capabilities) { {} }
   let(:guests)  { {} }
   let(:machine) { double("machine") }
 
-  subject { described_class.new(machine, guests) }
+  subject { described_class.new(machine, guests, capabilities) }
+
+  # This registers a capability with a specific guest
+  def register_capability(guest, capability)
+    cap = Class.new do
+      define_method(capability) do
+      end
+    end
+
+    capabilities[guest] ||= {}
+    capabilities[guest][capability] = cap.new
+  end
 
   # This registers a guest with the class.
   #
@@ -29,6 +41,37 @@ describe Vagrant::Guest do
     guests[name] = [guest, parent]
   end
 
+  describe "#capability?" do
+    before :each do
+      register_guest(:foo, nil, true)
+      register_guest(:bar, :foo, true)
+
+      subject.detect!
+    end
+
+    it "doesn't have unknown capabilities" do
+      subject.capability?(:what_is_this_i_dont_even).should_not be
+    end
+
+    it "doesn't have capabilities registered to other guests" do
+      register_capability(:baz, :test)
+
+      subject.capability?(:test).should_not be
+    end
+
+    it "has capability of detected guest" do
+      register_capability(:bar, :test)
+
+      subject.capability?(:test).should be
+    end
+
+    it "has capability of parent guests" do
+      register_capability(:foo, :test)
+
+      subject.capability?(:test).should be
+    end
+  end
+
   describe "#detect!" do
     it "detects the first match" do
       register_guest(:foo, nil, false)
@@ -36,8 +79,10 @@ describe Vagrant::Guest do
       register_guest(:baz, nil, false)
 
       subject.detect!
+      subject.name.should == :bar
       subject.chain.length.should == 1
-      subject.chain[0].name.should == :bar
+      subject.chain[0][0].should == :bar
+      subject.chain[0][1].name.should == :bar
     end
 
     it "detects those with the most parents first" do
@@ -48,8 +93,10 @@ describe Vagrant::Guest do
       register_guest(:bar2, :foo2, true)
 
       subject.detect!
+      subject.name.should == :baz
       subject.chain.length.should == 3
-      subject.chain.map(&:name).should == [:baz, :bar, :foo]
+      subject.chain.map(&:first).should == [:baz, :bar, :foo]
+      subject.chain.map { |x| x[1] }.map(&:name).should == [:baz, :bar, :foo]
     end
 
     it "raises an exception if no guest can be detected" do