core: Configurable communicator

lib/vagrant/errors.rb

@@ -300,6 +300,10 @@ module Vagrant
       error_key(:command_unavailable_windows)
     end
 
+    class CommunicatorNotFound < VagrantError
+      error_key(:communicator_not_found)
+    end
+
     class ConfigInvalid < VagrantError
       error_key(:config_invalid)
     end

lib/vagrant/machine.rb

@@ -173,9 +173,10 @@ module Vagrant
     # @return [Object]
     def communicate
       if !@communicator
-        # For now, we always return SSH. In the future, we'll abstract
+        requested  = @config.vm.communicator
-        # this and allow plugins to define new methods of communication.
+        requested ||= :ssh
-        klass = Vagrant.plugin("2").manager.communicators[:ssh]
+        klass = Vagrant.plugin("2").manager.communicators[requested]
+        raise Errors::CommunicatorNotFound, comm: requested.to_s if !klass
         @communicator = klass.new(self)
       end
 

templates/locales/en.yml

@@ -579,6 +579,9 @@ en:
         The executable '%{file}' Vagrant is trying to run was not
         found in the %PATH% variable. This is an error. Please verify
         this software is installed and on the path.
+      communicator_not_found: |-
+        The requested communicator '%{comm}' could not be found.
+        Please verify the name is correct and try again.
       config_invalid: |-
         There are errors in the configuration of this machine. Please fix
         the following errors and try again:

test/unit/vagrant/machine_test.rb

@@ -240,14 +240,27 @@ describe Vagrant::Machine do
     end
   end
 
-  describe "communicator" do
+  describe "#communicate" do
-    it "should always return the SSH communicator" do
+    it "should return the SSH communicator by default" do
-      expect(instance.communicate).to be_kind_of(VagrantPlugins::CommunicatorSSH::Communicator)
+      expect(subject.communicate).
+        to be_kind_of(VagrantPlugins::CommunicatorSSH::Communicator)
+    end
+
+    it "should return the specified communicator if given" do
+      subject.config.vm.communicator = :winrm
+      expect(subject.communicate).
+        to be_kind_of(VagrantPlugins::CommunicatorWinRM::Communicator)
     end
 
     it "should memoize the result" do
-      obj = instance.communicate
+      obj = subject.communicate
-      expect(instance.communicate).to eql(obj)
+      expect(subject.communicate).to equal(obj)
+    end
+
+    it "raises an exception if an invalid communicator is given" do
+      subject.config.vm.communicator = :foo
+      expect { subject.communicate }.
+        to raise_error(Vagrant::Errors::CommunicatorNotFound)
     end
   end