From 1f6095f912cb95e3fd0edb22823a4fb9aba20ce6 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 7 Jan 2014 16:12:12 -0800
Subject: [PATCH 1/5] core: Vagrant::CapabilityHost is a module for adding
 capabilities to things

---
 lib/vagrant/capability_host.rb            | 175 ++++++++++++++++++++++
 lib/vagrant/errors.rb                     |  16 ++
 templates/locales/en.yml                  |  16 ++
 test/unit/vagrant/capability_host_test.rb | 166 ++++++++++++++++++++
 test/unit/vagrant/guest_test.rb           | 118 ---------------
 5 files changed, 373 insertions(+), 118 deletions(-)
 create mode 100644 lib/vagrant/capability_host.rb
 create mode 100644 test/unit/vagrant/capability_host_test.rb

diff --git a/lib/vagrant/capability_host.rb b/lib/vagrant/capability_host.rb
new file mode 100644
index 000000000..4c77930fa
--- /dev/null
+++ b/lib/vagrant/capability_host.rb
@@ -0,0 +1,175 @@
+module Vagrant
+  # This module enables a class to host capabilities. Prior to being able
+  # to use any capabilities, the `initialize_capabilities!` method must be
+  # called.
+  #
+  # Capabilities allow small pieces of functionality to be plugged in using
+  # the Vagrant plugin model. Capabilities even allow for a certain amount
+  # of inheritence, where only a subset of capabilities may be implemented but
+  # a parent implements the rest.
+  #
+  # Capabilities are used heavily in Vagrant for host/guest interactions. For
+  # example, "mount_nfs_folder" is a guest-OS specific operation, so capabilities
+  # defer these operations to the guest.
+  module CapabilityHost
+    # Initializes the capability system by detecting the proper capability
+    # host to execute on and building the chain of capabilities to execute.
+    #
+    # @param [Symbol] host The host to use for the capabilities, or nil if
+    #   we should auto-detect it.
+    # @param [Hash<Symbol, Array<Class, Symbol>>] hosts Potential capability
+    #   hosts. The key is the name of the host, value[0] is a class that
+    #   implements `#detect?` and value[1] is a parent host (if any).
+    # @param [Hash<Symbol, Hash<Symbol, Class>>] capabilities The capabilities
+    #   that are supported. The key is the host of the capability. Within that
+    #   is a hash where the key is the name of the capability and the value
+    #   is the class/module implementing it.
+    def initialize_capabilities!(host, hosts, capabilities, *args)
+      @cap_logger = Log4r::Logger.new("vagrant::capability_host::#{self.class}")
+
+      if host && !hosts[host]
+        raise Errors::CapabilityHostExplicitNotDetected, value: host.to_s
+      end
+
+      if !host
+        host = autodetect_capability_host(hosts) if !host
+        raise Errors::CapabilityHostNotDetected if !host
+      end
+
+      if !hosts[host]
+        # This should never happen because the autodetect above uses the
+        # hosts hash to look up hosts. And if an explicit host is specified,
+        # we do another check higher up.
+        raise "Internal error. Host not found: #{host}"
+      end
+
+      name      = host
+      host_info = hosts[name]
+      host      = host_info[0].new
+      chain     = []
+      chain << [name, host]
+
+      # Build the proper chain of parents if there are any.
+      # This allows us to do "inheritance" of capabilities later
+      if host_info[1]
+        parent_name = host_info[1]
+        parent_info = hosts[parent_name]
+        while parent_info
+          chain << [parent_name, parent_info[0].new]
+          parent_name = parent_info[1]
+          parent_info = hosts[parent_name]
+        end
+      end
+
+      @cap_host_chain = chain
+      @cap_args       = args
+      @cap_caps       = capabilities
+      true
+    end
+
+    # Returns the chain of hosts that will be checked for capabilities.
+    #
+    # @return [Array<Array<Symbol, Class>>]
+    def capability_host_chain
+      @cap_host_chain
+    end
+
+    # Tests whether the given capability is possible.
+    #
+    # @param [Symbol] cap_name Capability name
+    # @return [Boolean]
+    def capability?(cap_name)
+      !capability_module(cap_name.to_sym).nil?
+    end
+
+    # Executes the capability with the given name, optionally passing more
+    # arguments onwards to the capability. If the capability returns a value,
+    # it will be returned.
+    #
+    # @param [Symbol] cap_name Name of the capability
+    def capability(cap_name, *args)
+      @cap_logger.info("Execute capability: #{cap_name} (#{@cap_host_chain[0][0]})")
+      cap_mod = capability_module(cap_name.to_sym)
+      if !cap_mod
+        raise Errors::CapabilityNotFound,
+          :cap  => cap_name.to_s,
+          :host => @cap_host_chain[0][0].to_s
+      end
+
+      cap_method = nil
+      begin
+        cap_method = cap_mod.method(cap_name)
+      rescue NameError
+        raise Errors::CapabilityInvalid,
+          :cap => cap_name.to_s,
+          :host => @cap_host_chain[0][0].to_s
+      end
+
+      args = @cap_args + args
+      cap_method.call(*args)
+    end
+
+    protected
+
+    def autodetect_capability_host(hosts, *args)
+      @cap_logger.info("Autodetecting guest for machine: #{@machine}")
+
+      # Get the mapping of hosts with the most parents. We start searching
+      # with the hosts with the most parents first.
+      parent_count = {}
+      hosts.each do |name, parts|
+        parent_count[name] = 0
+
+        parent = parts[1]
+        while parent
+          parent_count[name] += 1
+          parent = hosts[parent]
+          parent = parent[1] if parent
+        end
+      end
+
+      # Now swap around the mapping so that it is a mapping of
+      # count to the actual list of host names
+      parent_count_to_hosts = {}
+      parent_count.each do |name, count|
+        parent_count_to_hosts[count] ||= []
+        parent_count_to_hosts[count] << name
+      end
+
+      sorted_counts = parent_count_to_hosts.keys.sort.reverse
+      sorted_counts.each do |count|
+        parent_count_to_hosts[count].each do |name|
+          @cap_logger.debug("Trying: #{name}")
+          host_info = hosts[name]
+          host      = host_info[0].new
+
+          if host.detect?(*args)
+            @cap_logger.info("Detected: #{name}!")
+            return name
+          end
+        end
+      end
+
+      return nil
+    end
+
+    # Returns the registered module for a capability with the given name.
+    #
+    # @param [Symbol] cap_name
+    # @return [Module]
+    def capability_module(cap_name)
+      @cap_logger.debug("Searching for cap: #{cap_name}")
+      @cap_host_chain.each do |host_name, host|
+        @cap_logger.debug("Checking in: #{host_name}")
+        caps = @cap_caps[host_name]
+
+        if caps && caps.has_key?(cap_name)
+          @cap_logger.debug("Found cap: #{cap_name} in #{host_name}")
+          return caps[cap_name]
+        end
+      end
+
+      nil
+    end
+  end
+end
diff --git a/lib/vagrant/errors.rb b/lib/vagrant/errors.rb
index ce21aef7b..fc30dfe1a 100644
--- a/lib/vagrant/errors.rb
+++ b/lib/vagrant/errors.rb
@@ -172,6 +172,22 @@ module Vagrant
       error_key(:bundler_error)
     end
 
+    class CapabilityHostExplicitNotDetected < VagrantError
+      error_key(:capability_host_explicit_not_detected)
+    end
+
+    class CapabilityHostNotDetected < VagrantError
+      error_key(:capability_host_not_detected)
+    end
+
+    class CapabilityInvalid < VagrantError
+      error_key(:capability_invalid)
+    end
+
+    class CapabilityNotFound < VagrantError
+      error_key(:capability_not_found)
+    end
+
     class CFEngineBootstrapFailed < VagrantError
       error_key(:cfengine_bootstrap_failed)
     end
diff --git a/templates/locales/en.yml b/templates/locales/en.yml
index 384d1220d..6ca7b8e0b 100644
--- a/templates/locales/en.yml
+++ b/templates/locales/en.yml
@@ -261,6 +261,22 @@ en:
         issues. The error from Bundler is:
 
         %{message}
+      capability_host_explicit_not_detected: |-
+        The explicit capability host specified of '%{value}' could not be
+        found.
+
+        This is an internal error that users should never see. Please report
+        a bug.
+      capability_host_not_detected: |-
+        The capability host could not be detected. This is an internal error
+        that users should never see. Please report a bug.
+      capability_invalid: |-
+        The capability '%{cap}' is invalid. This is an internal error that
+        users should never see. Please report a bug.
+      capability_not_found: |-
+        The capability '%{cap}' could not be found. This is an internal error
+        that users should never see. Please report a bug.
+
       cfengine_bootstrap_failed: |-
         Failed to bootstrap CFEngine. Please see the output above to
         see what went wrong and address the issue.
diff --git a/test/unit/vagrant/capability_host_test.rb b/test/unit/vagrant/capability_host_test.rb
new file mode 100644
index 000000000..d35e81afb
--- /dev/null
+++ b/test/unit/vagrant/capability_host_test.rb
@@ -0,0 +1,166 @@
+require File.expand_path("../../base", __FILE__)
+
+require "vagrant/capability_host"
+
+describe Vagrant::CapabilityHost do
+  subject do
+    Class.new do
+      extend Vagrant::CapabilityHost
+    end
+  end
+
+  def detect_class(result)
+    Class.new do
+      define_method(:detect?) do
+        result
+      end
+    end
+  end
+
+  def cap_instance(name, options=nil)
+    options ||= {}
+
+    Class.new do
+      if !options[:corrupt]
+        define_method(name) do |*args|
+          raise "cap: #{name} #{args.inspect}"
+        end
+      end
+    end.new
+  end
+
+  describe "#initialize_capabilities! and #capability_host_chain" do
+    it "raises an error if an explicit host is not found" do
+      expect { subject.initialize_capabilities!(:foo, {}, {}) }.
+        to raise_error(Vagrant::Errors::CapabilityHostExplicitNotDetected)
+    end
+
+    it "raises an error if a host can't be detected" do
+      hosts = {
+        foo: [detect_class(false), nil],
+        bar: [detect_class(false), :foo],
+      }
+
+      expect { subject.initialize_capabilities!(nil, hosts, {}) }.
+        to raise_error(Vagrant::Errors::CapabilityHostNotDetected)
+    end
+
+    it "detects a basic child" do
+      hosts = {
+        foo: [detect_class(false), nil],
+        bar: [detect_class(true), nil],
+        baz: [detect_class(false), nil],
+      }
+
+      subject.initialize_capabilities!(nil, hosts, {})
+
+      chain = subject.capability_host_chain
+      expect(chain.length).to eql(1)
+      expect(chain[0][0]).to eql(:bar)
+    end
+
+    it "detects the host with the most parents (deepest) first" do
+      hosts = {
+        foo: [detect_class(true), nil],
+        bar: [detect_class(true), :foo],
+        baz: [detect_class(true), :bar],
+        foo2: [detect_class(true), nil],
+        bar2: [detect_class(true), :foo2],
+      }
+
+      subject.initialize_capabilities!(nil, hosts, {})
+
+      chain = subject.capability_host_chain
+      expect(chain.length).to eql(3)
+      expect(chain.map(&:first)).to eql([:baz, :bar, :foo])
+    end
+
+    it "detects a forced host" do
+      hosts = {
+        foo: [detect_class(false), nil],
+        bar: [detect_class(false), nil],
+        baz: [detect_class(false), nil],
+      }
+
+      subject.initialize_capabilities!(:bar, hosts, {})
+
+      chain = subject.capability_host_chain
+      expect(chain.length).to eql(1)
+      expect(chain[0][0]).to eql(:bar)
+    end
+  end
+
+  describe "#capability?" do
+    before do
+      host  = nil
+      hosts = {
+        foo: [detect_class(true), nil],
+        bar: [detect_class(true), :foo],
+      }
+
+      caps = {
+        foo: { parent: Class.new },
+        bar: { self: Class.new },
+      }
+
+      subject.initialize_capabilities!(host, hosts, caps)
+    end
+
+    it "does not have a non-existent capability" do
+      expect(subject.capability?(:foo)).to be_false
+    end
+
+    it "has capabilities of itself" do
+      expect(subject.capability?(:self)).to be_true
+    end
+
+    it "has capabilities of parent" do
+      expect(subject.capability?(:parent)).to be_true
+    end
+  end
+
+  describe "capability" do
+    let(:caps) { {} }
+
+    def init
+      host  = nil
+      hosts = {
+        foo: [detect_class(true), nil],
+        bar: [detect_class(true), :foo],
+      }
+
+      subject.initialize_capabilities!(host, hosts, caps)
+    end
+
+    it "executes the capability" do
+      caps[:bar] = { test: cap_instance(:test) }
+      init
+
+      expect { subject.capability(:test) }.
+        to raise_error(RuntimeError, "cap: test []")
+    end
+
+    it "executes the capability with arguments" do
+      caps[:bar] = { test: cap_instance(:test) }
+      init
+
+      expect { subject.capability(:test, 1) }.
+        to raise_error(RuntimeError, "cap: test [1]")
+    end
+
+    it "raises an exception if the capability doesn't exist" do
+      init
+
+      expect { subject.capability(:what_is_this_i_dont_even) }.
+        to raise_error(Vagrant::Errors::CapabilityNotFound)
+    end
+
+    it "raises an exception if the method doesn't exist on the module" do
+      caps[:bar] = { test_is_corrupt: cap_instance(:test_is_corrupt, corrupt: true) }
+      init
+
+      expect { subject.capability(:test_is_corrupt) }.
+        to raise_error(Vagrant::Errors::CapabilityInvalid)
+    end
+  end
+end
diff --git a/test/unit/vagrant/guest_test.rb b/test/unit/vagrant/guest_test.rb
index 4dcaab414..6dd9cbf8c 100644
--- a/test/unit/vagrant/guest_test.rb
+++ b/test/unit/vagrant/guest_test.rb
@@ -53,124 +53,6 @@ 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 "executes the capability" do
-      register_capability(:bar, :test)
-
-      expect { subject.capability(:test) }.
-        to raise_error(RuntimeError, "cap: test [machine]")
-    end
-
-    it "executes the capability with arguments" do
-      register_capability(:bar, :test)
-
-      expect { subject.capability(:test, 1) }.
-        to raise_error(RuntimeError, "cap: test [machine, 1]")
-    end
-
-    it "raises an exception if the capability doesn't exist" do
-      expect { subject.capability(:what_is_this_i_dont_even) }.
-        to raise_error(Vagrant::Errors::GuestCapabilityNotFound)
-    end
-
-    it "raises an exception if the method doesn't exist on the module" do
-      register_capability(:bar, :test_is_corrupt, corrupt: true)
-
-      expect { subject.capability(:test_is_corrupt) }.
-        to raise_error(Vagrant::Errors::GuestCapabilityInvalid)
-    end
-  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)
-      register_guest(:bar, nil, true)
-      register_guest(:baz, nil, false)
-
-      subject.detect!
-      subject.name.should == :bar
-      subject.chain.length.should == 1
-      subject.chain[0][0].should == :bar
-      subject.chain[0][1].name.should == :bar
-    end
-
-    it "detects those with the most parents first" do
-      register_guest(:foo, nil, true)
-      register_guest(:bar, :foo, true)
-      register_guest(:baz, :bar, true)
-      register_guest(:foo2, nil, true)
-      register_guest(:bar2, :foo2, true)
-
-      subject.detect!
-      subject.name.should == :baz
-      subject.chain.length.should == 3
-      subject.chain.map(&:first).should == [:baz, :bar, :foo]
-      subject.chain.map { |x| x[1] }.map(&:name).should == [:baz, :bar, :foo]
-    end
-
-    it "detects the forced guest setting" do
-      register_guest(:foo, nil, false)
-      register_guest(:bar, nil, false)
-
-      machine.config.vm.stub(:guest => :bar)
-
-      subject.detect!
-      subject.name.should == :bar
-    end
-
-    it "raises an exception if the forced guest can't be found" do
-      register_guest(:foo, nil, true)
-
-      machine.config.vm.stub(:guest => :bar)
-
-      expect { subject.detect! }.
-        to raise_error(Vagrant::Errors::GuestExplicitNotDetected)
-    end
-
-    it "raises an exception if no guest can be detected" do
-      expect { subject.detect! }.
-        to raise_error(Vagrant::Errors::GuestNotDetected)
-    end
-  end
-
   describe "#ready?" do
     before(:each) do
       register_guest(:foo, nil, true)

From b15cb22e3e96b940a10a4053ac257039831b4b02 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 7 Jan 2014 16:14:16 -0800
Subject: [PATCH 2/5] core: errors expose their extra data

---
 lib/vagrant/errors.rb            | 5 +++++
 test/unit/vagrant/errors_test.rb | 8 +++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/vagrant/errors.rb b/lib/vagrant/errors.rb
index fc30dfe1a..8654ac752 100644
--- a/lib/vagrant/errors.rb
+++ b/lib/vagrant/errors.rb
@@ -43,6 +43,9 @@ module Vagrant
     # error code, and the error key is used as a default message from
     # I18n.
     class VagrantError < StandardError
+      # This is extra data passed into the message for translation.
+      attr_accessor :extra_data
+
       def self.error_key(key=nil, namespace=nil)
         define_method(:error_key) { key }
         error_namespace(namespace) if namespace
@@ -57,6 +60,8 @@ module Vagrant
       end
 
       def initialize(message=nil, *args)
+        message ||= {}
+        @extra_data = message.dup
         message = { :_key => message } if message && !message.is_a?(Hash)
         message = { :_key => error_key, :_namespace => error_namespace }.merge(message || {})
 
diff --git a/test/unit/vagrant/errors_test.rb b/test/unit/vagrant/errors_test.rb
index 66a2d1ea7..3c00b39c9 100644
--- a/test/unit/vagrant/errors_test.rb
+++ b/test/unit/vagrant/errors_test.rb
@@ -32,10 +32,16 @@ describe Vagrant::Errors::VagrantError do
       end
     end
 
-    subject { klass.new }
+    subject { klass.new(data: "yep") }
 
     it "should use the translation for the message" do
       subject.to_s.should == "foo"
     end
+
+    it "should expose translation keys to the user" do
+      expect(subject.extra_data.length).to eql(1)
+      expect(subject.extra_data).to have_key(:data)
+      expect(subject.extra_data[:data]).to eql("yep")
+    end
   end
 end

From 1f760b2c481f2f1305e90a0d50496114f147b3e2 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 7 Jan 2014 16:26:58 -0800
Subject: [PATCH 3/5] core: pass extra args to detect? when detecting
 capability host

---
 lib/vagrant/capability_host.rb                |  2 +-
 test/unit/base.rb                             |  1 +
 .../shared/capability_helpers_context.rb      | 21 +++++++++++
 test/unit/vagrant/capability_host_test.rb     | 37 +++++++++----------
 4 files changed, 40 insertions(+), 21 deletions(-)
 create mode 100644 test/unit/support/shared/capability_helpers_context.rb

diff --git a/lib/vagrant/capability_host.rb b/lib/vagrant/capability_host.rb
index 4c77930fa..c75f3c980 100644
--- a/lib/vagrant/capability_host.rb
+++ b/lib/vagrant/capability_host.rb
@@ -32,7 +32,7 @@ module Vagrant
       end
 
       if !host
-        host = autodetect_capability_host(hosts) if !host
+        host = autodetect_capability_host(hosts, *args) if !host
         raise Errors::CapabilityHostNotDetected if !host
       end
 
diff --git a/test/unit/base.rb b/test/unit/base.rb
index 4218abcbf..db530c2e4 100644
--- a/test/unit/base.rb
+++ b/test/unit/base.rb
@@ -14,6 +14,7 @@ require "unit/support/dummy_communicator"
 require "unit/support/dummy_provider"
 require "unit/support/shared/base_context"
 require "unit/support/shared/action_synced_folders_context"
+require "unit/support/shared/capability_helpers_context"
 require "unit/support/shared/virtualbox_context"
 
 # Do not buffer output
diff --git a/test/unit/support/shared/capability_helpers_context.rb b/test/unit/support/shared/capability_helpers_context.rb
new file mode 100644
index 000000000..f336cc7c3
--- /dev/null
+++ b/test/unit/support/shared/capability_helpers_context.rb
@@ -0,0 +1,21 @@
+shared_context "capability_helpers" do
+  def detect_class(result)
+    Class.new do
+      define_method(:detect?) do
+        result
+      end
+    end
+  end
+
+  def cap_instance(name, options=nil)
+    options ||= {}
+
+    Class.new do
+      if !options[:corrupt]
+        define_method(name) do |*args|
+          raise "cap: #{name} #{args.inspect}"
+        end
+      end
+    end.new
+  end
+end
diff --git a/test/unit/vagrant/capability_host_test.rb b/test/unit/vagrant/capability_host_test.rb
index d35e81afb..d460a649b 100644
--- a/test/unit/vagrant/capability_host_test.rb
+++ b/test/unit/vagrant/capability_host_test.rb
@@ -3,32 +3,14 @@ require File.expand_path("../../base", __FILE__)
 require "vagrant/capability_host"
 
 describe Vagrant::CapabilityHost do
+  include_context "capability_helpers"
+
   subject do
     Class.new do
       extend Vagrant::CapabilityHost
     end
   end
 
-  def detect_class(result)
-    Class.new do
-      define_method(:detect?) do
-        result
-      end
-    end
-  end
-
-  def cap_instance(name, options=nil)
-    options ||= {}
-
-    Class.new do
-      if !options[:corrupt]
-        define_method(name) do |*args|
-          raise "cap: #{name} #{args.inspect}"
-        end
-      end
-    end.new
-  end
-
   describe "#initialize_capabilities! and #capability_host_chain" do
     it "raises an error if an explicit host is not found" do
       expect { subject.initialize_capabilities!(:foo, {}, {}) }.
@@ -45,6 +27,21 @@ describe Vagrant::CapabilityHost do
         to raise_error(Vagrant::Errors::CapabilityHostNotDetected)
     end
 
+    it "passes on extra args to the detect method" do
+      klass = Class.new do
+        def detect?(*args)
+          raise "detect: #{args.inspect}"
+        end
+      end
+
+      hosts = {
+        foo: [klass, nil],
+      }
+
+      expect { subject.initialize_capabilities!(nil, hosts, {}, 1, 2) }.
+        to raise_error(RuntimeError, "detect: [1, 2]")
+    end
+
     it "detects a basic child" do
       hosts = {
         foo: [detect_class(false), nil],

From 40babfc3f7cbbe9a0a0b4d95db833bd96f7c3a39 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 7 Jan 2014 16:27:12 -0800
Subject: [PATCH 4/5] core: modify Guest to use new CapabilityHost mixin

---
 lib/vagrant/guest.rb            | 152 ++------------------------------
 test/unit/vagrant/guest_test.rb |  43 +++------
 2 files changed, 18 insertions(+), 177 deletions(-)

diff --git a/lib/vagrant/guest.rb b/lib/vagrant/guest.rb
index 4cd719400..85a6eb8da 100644
--- a/lib/vagrant/guest.rb
+++ b/lib/vagrant/guest.rb
@@ -1,5 +1,7 @@
 require "log4r"
 
+require "vagrant/capability_host"
+
 module Vagrant
   # This class handles guest-OS specific interactions with a machine.
   # It is primarily responsible for detecting the proper guest OS
@@ -17,21 +19,13 @@ module Vagrant
   # This system allows for maximum flexibility and pluginability for doing
   # guest OS specific operations.
   class Guest
-    attr_reader :chain
-
-    # The name of the guest OS. This is available after {#detect!} is
-    # called.
-    #
-    # @return [Symbol]
-    attr_reader :name
+    include CapabilityHost
 
     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
@@ -40,52 +34,7 @@ module Vagrant
       @logger.info("Detect guest for machine: #{@machine}")
 
       guest_name = @machine.config.vm.guest
-      if guest_name
-        @logger.info("Using explicit config.vm.guest value: #{guest_name}")
-      else
-        # No explicit guest was specified, so autodetect it.
-        guest_name = autodetect_guest
-        raise Errors::GuestNotDetected if !guest_name
-      end
-
-      if !@guests[guest_name]
-        # This can happen if config.vm.guest was specified with a value
-        # that doesn't exist.
-        raise Errors::GuestExplicitNotDetected, value: guest_name.to_s
-      end
-
-      @name  = guest_name
-      @chain = guest_chain(@name)
-    end
-
-    # Tests whether the guest has the named capability.
-    #
-    # @return [Boolean]
-    def capability?(cap_name)
-      !capability_module(cap_name.to_sym).nil?
-    end
-
-    # Executes the capability with the given name, optionally passing
-    # more arguments onwards to the capability.
-    def capability(cap_name, *args)
-      @logger.info("Execute capability: #{cap_name} (#{@chain[0][0]})")
-      cap_mod = capability_module(cap_name.to_sym)
-      if !cap_mod
-        raise Errors::GuestCapabilityNotFound,
-          :cap => cap_name.to_s,
-          :guest => @chain[0][0].to_s
-      end
-
-      cap_method = nil
-      begin
-        cap_method = cap_mod.method(cap_name)
-      rescue NameError
-        raise Errors::GuestCapabilityInvalid,
-          :cap => cap_name.to_s,
-          :guest => @chain[0][0].to_s
-      end
-
-      cap_method.call(@machine, *args)
+      initialize_capabilities!(guest_name, @guests, @capabilities, @machine)
     end
 
     # This returns whether the guest is ready to work. If this returns
@@ -94,98 +43,7 @@ module Vagrant
     #
     # @return [Boolean]
     def ready?
-      !@chain.empty?
-    end
-
-    protected
-
-    # Returns the registered module for a capability with the given name.
-    #
-    # @param [Symbol] cap_name
-    # @return [Module]
-    def capability_module(cap_name)
-      @logger.debug("Searching for cap: #{cap_name}")
-      @chain.each do |guest_name, guest|
-        @logger.debug("Checking in: #{guest_name}")
-        caps = @capabilities[guest_name]
-
-        if caps && caps.has_key?(cap_name)
-          @logger.debug("Found cap: #{cap_name} in #{guest_name}")
-          return caps[cap_name]
-        end
-      end
-
-      nil
-    end
-
-    # This autodetects the guest to use and returns the name of the guest.
-    # This returns nil if the guest type could not be autodetected.
-    #
-    # @return [Symbol]
-    def autodetect_guest
-      @logger.info("Autodetecting guest for machine: #{@machine}")
-
-      # Get the mapping of guests with the most parents. We start searching
-      # with the guests with the most parents first.
-      parent_count = {}
-      @guests.each do |name, parts|
-        parent_count[name] = 0
-
-        parent = parts[1]
-        while parent
-          parent_count[name] += 1
-          parent = @guests[parent]
-          parent = parent[1] if parent
-        end
-      end
-
-      # Now swap around the mapping so that it is a mapping of
-      # count to the actual list of guest names
-      parent_count_to_guests = {}
-      parent_count.each do |name, count|
-        parent_count_to_guests[count] ||= []
-        parent_count_to_guests[count] << name
-      end
-
-      sorted_counts = parent_count_to_guests.keys.sort.reverse
-      sorted_counts.each do |count|
-        parent_count_to_guests[count].each do |name|
-          @logger.debug("Trying: #{name}")
-          guest_info = @guests[name]
-          guest      = guest_info[0].new
-
-          if guest.detect?(@machine)
-            @logger.info("Detected: #{name}!")
-            return name
-          end
-        end
-      end
-
-      return nil
-    end
-
-    # This returns the complete chain for the given guest.
-    #
-    # @return [Array]
-    def guest_chain(name)
-      guest_info = @guests[name]
-      guest      = guest_info[0].new
-      chain      = []
-      chain << [name, guest]
-
-      # Build the proper chain of parents if there are any.
-      # This allows us to do "inheritance" of capabilities later
-      if guest_info[1]
-        parent_name = guest_info[1]
-        parent_info = @guests[parent_name]
-        while parent_info
-          chain << [parent_name, parent_info[0].new]
-          parent_name = parent_info[1]
-          parent_info = @guests[parent_name]
-        end
-      end
-
-      return chain
+      !!capability_host_chain
     end
   end
 end
diff --git a/test/unit/vagrant/guest_test.rb b/test/unit/vagrant/guest_test.rb
index 6dd9cbf8c..0a7d76001 100644
--- a/test/unit/vagrant/guest_test.rb
+++ b/test/unit/vagrant/guest_test.rb
@@ -3,7 +3,7 @@ require "pathname"
 require File.expand_path("../../base", __FILE__)
 
 describe Vagrant::Guest do
-  include_context "unit"
+  include_context "capability_helpers"
 
   let(:capabilities) { {} }
   let(:guests)  { {} }
@@ -18,44 +18,27 @@ describe Vagrant::Guest do
 
   subject { described_class.new(machine, guests, capabilities) }
 
-  # This registers a capability with a specific guest
-  def register_capability(guest, capability, options=nil)
-    options ||= {}
+  describe "#detect!" do
+    it "auto-detects if no explicit guest name given" do
+      machine.config.vm.stub(guest: nil)
+      subject.should_receive(:initialize_capabilities!).
+        with(nil, guests, capabilities, machine)
 
-    cap = Class.new do
-      if !options[:corrupt]
-        define_method(capability) do |*args|
-          raise "cap: #{capability} #{args.inspect}"
-        end
-      end
+      subject.detect!
     end
 
-    capabilities[guest] ||= {}
-    capabilities[guest][capability] = cap.new
-  end
+    it "uses the explicit guest name if specified" do
+      machine.config.vm.stub(guest: :foo)
+      subject.should_receive(:initialize_capabilities!).
+        with(:foo, guests, capabilities, machine)
 
-  # This registers a guest with the class.
-  #
-  # @param [Symbol] name Name of the guest
-  # @param [Symbol] parent Name of the parent
-  # @param [Boolean] detect Whether or not to detect properly
-  def register_guest(name, parent, detect)
-    guest = Class.new(Vagrant.plugin("2", "guest")) do
-      define_method(:name) do
-        name
-      end
-
-      define_method(:detect?) do |m|
-        detect
-      end
+      subject.detect!
     end
-
-    guests[name] = [guest, parent]
   end
 
   describe "#ready?" do
     before(:each) do
-      register_guest(:foo, nil, true)
+      guests[:foo] = [detect_class(true), nil]
     end
 
     it "should not be ready by default" do

From c1d56da1ca9e55bb12755d3c1f2e6607aedc6f6d Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 7 Jan 2014 16:29:05 -0800
Subject: [PATCH 5/5] core: get tests passing for changes

---
 test/unit/support/shared/capability_helpers_context.rb | 2 +-
 test/unit/vagrant/machine_test.rb                      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/test/unit/support/shared/capability_helpers_context.rb b/test/unit/support/shared/capability_helpers_context.rb
index f336cc7c3..7db62d161 100644
--- a/test/unit/support/shared/capability_helpers_context.rb
+++ b/test/unit/support/shared/capability_helpers_context.rb
@@ -1,7 +1,7 @@
 shared_context "capability_helpers" do
   def detect_class(result)
     Class.new do
-      define_method(:detect?) do
+      define_method(:detect?) do |*args|
         result
       end
     end
diff --git a/test/unit/vagrant/machine_test.rb b/test/unit/vagrant/machine_test.rb
index 9cb6fe6b8..ca60f078b 100644
--- a/test/unit/vagrant/machine_test.rb
+++ b/test/unit/vagrant/machine_test.rb
@@ -225,8 +225,8 @@ describe Vagrant::Machine do
     it "should return the configured guest" do
       result = instance.guest
       result.should be_kind_of(Vagrant::Guest)
-      result.ready?.should be
-      result.chain[0][0].should == :test
+      expect(result).to be_ready
+      expect(result.capability_host_chain[0][0]).to eql(:test)
     end
   end