core: Vagrant::Environment uses new host settings

lib/vagrant/environment.rb

@@ -487,22 +487,33 @@ module Vagrant
     def host
       return @host if defined?(@host)
 
-      # Attempt to figure out the host class. Note that the order
-      # matters here, so please don't touch. Specifically: The symbol
-      # check is done after the detect check because the symbol check
-      # will return nil, and we don't want to trigger a detect load.
+      # Determine the host class to use. ":detect" is an old Vagrant config
+      # that shouldn't be valid anymore, but we respect it here by assuming
+      # its old behavior. No need to deprecate this because I thin it is
+      # fairly harmless.
       host_klass = config_global.vagrant.host
-      if host_klass.nil? || host_klass == :detect
-        hosts = Vagrant.plugin("2").manager.hosts.to_hash
+      host_klass = nil if host_klass == :detect
 
-        # Get the flattened list of available hosts
-        host_klass = Hosts.detect(hosts)
+      begin
+        @host = Host.new(
+          host_klass,
+          Vagrant.plugin("2").manager.hosts,
+          Vagrant.plugin("2").manager.host_capabilities)
+      rescue Errors::CapabilityHostNotDetected
+        # If the auto-detect failed, then we create a brand new host
+        # with no capabilities and use that. This should almost never happen
+        # since Vagrant works on most host OS's now, so this is a "slow path"
+        klass     = Class.new(Vagrant.plugin("2", :host)) do
+          def detect?; true; end
+        end
+
+        hosts     = { generic: [klass, nil] }
+        host_caps = {}
+
+        @host = Host.new(:generic, hosts, host_caps)
+      rescue Errors::CapabilityHostExplicitNotDetected => e
+        raise Errors::HostExplicitNotDetected, e.extra_data
       end
-
-      # If no host class is detected, we use the base class.
-      host_klass ||= Vagrant.plugin("2", :host)
-
-      @host ||= host_klass.new(@ui)
     end
 
     # Action runner for executing actions in the context of this environment.

lib/vagrant/errors.rb

@@ -333,6 +333,10 @@ module Vagrant
       error_key(:guest_not_detected)
     end
 
+    class HostExplicitNotDetected < VagrantError
+      error_key(:host_explicit_not_detected)
+    end
+
     class LinuxMountFailed < VagrantError
       error_key(:linux_mount_failed)
     end

lib/vagrant/plugin/v2/host.rb

@@ -14,16 +14,6 @@ module Vagrant
           false
         end
 
-        # Initializes a new host class.
-        #
-        # The only required parameter is a UI object so that the host
-        # objects have some way to communicate with the outside world.
-        #
-        # @param [UI] ui UI for the hosts to output to.
-        def initialize(ui)
-          @ui = ui
-        end
-
         # Returns true of false denoting whether or not this host supports
         # NFS shared folder setup. This method ideally should verify that
         # NFS is installed.

plugins/kernel_v2/config/vagrant.rb

@@ -5,6 +5,15 @@ module VagrantPlugins
     class VagrantConfig < Vagrant.plugin("2", :config)
       attr_accessor :host
 
+      def initialize
+        @host = UNSET_VALUE
+      end
+
+      def finalize!
+        @host = nil if @host == UNSET_VALUE
+        @host = @host.to_sym if @host
+      end
+
       def to_s
         "Vagrant"
       end

templates/locales/en.yml

@@ -412,6 +412,11 @@ en:
         directory that Vagrant uses must be both readable and writable.
 
         You specified: %{home_path}
+      host_explicit_not_detected: |-
+        The host implementation explicitly specified in your Vagrantfile
+        ("%{value}") could not be found. Please verify that the plugin is
+        installed which implements this host and that the value you used
+        for `config.vagrant.host` is correct.
       interrupted: |-
         Vagrant exited after cleanup due to external interrupt.
       local_data_dir_not_accessible: |-

test/unit/vagrant/environment_test.rb

@@ -8,6 +8,7 @@ require "vagrant/util/file_mode"
 
 describe Vagrant::Environment do
   include_context "unit"
+  include_context "capability_helpers"
 
   let(:env) do
     isolated_environment.tap do |e|
@@ -21,9 +22,83 @@ describe Vagrant::Environment do
   end
 
   let(:instance)  { env.create_vagrant_env }
-
   subject { instance }
 
+  describe "#host" do
+    let(:plugin_hosts) { {} }
+    let(:plugin_host_caps) { {} }
+
+    before do
+      m = Vagrant.plugin("2").manager
+      m.stub(hosts: plugin_hosts)
+      m.stub(host_capabilities: plugin_host_caps)
+    end
+
+    it "should default to some host even if there are none" do
+      env.vagrantfile <<-VF
+      Vagrant.configure("2") do |config|
+        config.vagrant.host = nil
+      end
+      VF
+
+      expect(subject.host).to be
+    end
+
+    it "should attempt to detect a host if no host is set" do
+      env.vagrantfile <<-VF
+      Vagrant.configure("2") do |config|
+        config.vagrant.host = nil
+      end
+      VF
+
+      plugin_hosts[:foo] = [detect_class(true), nil]
+      plugin_host_caps[:foo] = { bar: Class }
+
+      result = subject.host
+      expect(result.capability?(:bar)).to be_true
+    end
+
+    it "should attempt to detect a host if host is :detect" do
+      env.vagrantfile <<-VF
+      Vagrant.configure("2") do |config|
+        config.vagrant.host = :detect
+      end
+      VF
+
+      plugin_hosts[:foo] = [detect_class(true), nil]
+      plugin_host_caps[:foo] = { bar: Class }
+
+      result = subject.host
+      expect(result.capability?(:bar)).to be_true
+    end
+
+    it "should use an exact host if specified" do
+      env.vagrantfile <<-VF
+      Vagrant.configure("2") do |config|
+        config.vagrant.host = "foo"
+      end
+      VF
+
+      plugin_hosts[:foo] = [detect_class(false), nil]
+      plugin_hosts[:bar] = [detect_class(true), nil]
+      plugin_host_caps[:foo] = { bar: Class }
+
+      result = subject.host
+      expect(result.capability?(:bar)).to be_true
+    end
+
+    it "should raise an error if an exact match was specified but not found" do
+      env.vagrantfile <<-VF
+      Vagrant.configure("2") do |config|
+        config.vagrant.host = "bar"
+      end
+      VF
+
+      expect { subject.host }.
+        to raise_error(Vagrant::Errors::HostExplicitNotDetected)
+    end
+  end
+
   describe "active machines" do
     it "should be empty if the machines folder doesn't exist" do
       folder = instance.local_data_path.join("machines")