Merge pull request #285 from Kuniwak/care-nil-instance

Fix a bug can be occurred when `instance` returns `nil`

lib/kitchen/driver/vagrant.rb

@@ -469,10 +469,13 @@ def local_kitchen_cache
       #   instance's Vagrantfile
       # @api private
       def vagrant_root
-        root = File.join(config[:kitchen_root], %w{.kitchen kitchen-vagrant},
-          "kitchen-#{File.basename(config[:kitchen_root])}-#{instance.name}"
-        )
-        @vagrant_root ||= instance.nil? ? nil : root
+        if !@vagrant_root && !instance.nil?
+          @vagrant_root = File.join(
+            config[:kitchen_root], %w{.kitchen kitchen-vagrant},
+            "kitchen-#{File.basename(config[:kitchen_root])}-#{instance.name}"
+          )
+        end
+        @vagrant_root
       end
 
       # @param type [Symbol] either `:ssh` or `:winrm`

spec/kitchen/driver/vagrant_spec.rb

@@ -48,6 +48,10 @@
     d
   end
 
+  let(:driver_with_no_instance) do
+    driver_object
+  end
+
   let(:instance) do
     Kitchen::Instance.new(
       :verifier => verifier,
@@ -540,6 +544,12 @@ def run_command(_cmd, options = {})
       driver.verify_dependencies
     end
 
+    it "passes for supported versions of Vagrant when it has no instances" do
+      with_modern_vagrant
+
+      driver_with_no_instance.verify_dependencies
+    end
+
     it "raises a UserError for unsupported versions of Vagrant" do
       with_unsupported_vagrant