Add mapping for pathnames

plugins/commands/serve/mappers.rb

@@ -208,6 +208,7 @@ require Vagrant.source_root.join("plugins/commands/serve/mappers/environment.rb"
 require Vagrant.source_root.join("plugins/commands/serve/mappers/guest.rb").to_s
 require Vagrant.source_root.join("plugins/commands/serve/mappers/known_types.rb").to_s
 require Vagrant.source_root.join("plugins/commands/serve/mappers/machine.rb").to_s
+require Vagrant.source_root.join("plugins/commands/serve/mappers/pathname.rb").to_s
 require Vagrant.source_root.join("plugins/commands/serve/mappers/project.rb").to_s
 require Vagrant.source_root.join("plugins/commands/serve/mappers/state_bag.rb").to_s
 require Vagrant.source_root.join("plugins/commands/serve/mappers/target.rb").to_s

plugins/commands/serve/mappers/pathname.rb

@@ -0,0 +1,33 @@
+module VagrantPlugins
+  module CommandServe
+    class Mappers
+      class PathnameToProto < Mapper
+        def initialize
+          super(
+            inputs: [Input.new(type: Pathname)],
+            output: SDK::Args::Path,
+            func: method(:converter),
+          )
+        end
+
+        def converter(path)
+          SDK::Args::Path.new(path: path.to_s)
+        end
+      end
+
+      class PathnameFromProto < Mapper
+        def initialize
+          super(
+            inputs: [Input.new(type: SDK::Args::Path)],
+            output: Pathname,
+            func: method(:converter),
+          )
+        end
+
+        def converter(path)
+          Pathname.new(path.path)
+        end
+      end
+    end
+  end
+end