Cosmetics in Flattenable

lib/estructura/flattenable.ex

@@ -36,7 +36,11 @@ defimpl Estructura.Flattenable, for: Any do
     quote do
       defimpl Estructura.Flattenable, for: unquote(module) do
         def flatten(input, options) do
-          options = Keyword.merge(unquote(options), options)
+          options =
+            unquote(options)
+            |> Keyword.merge(options)
+            |> Keyword.update(:only, [], fn only -> Enum.map(only, &to_string/1) end)
+            |> Keyword.update(:except, [], fn except -> Enum.map(except, &to_string/1) end)
 
           input
           |> Map.from_struct()

lib/estructura/tree.ex

@@ -26,13 +26,16 @@ defmodule Estructura.Tree do
               ]
             ]}
          ]},
-      content: {StreamData, :tree, [{StreamData, :fixed_list, [[]]}, &Estructura.Tree.child_gen/1]}
+      content:
+        {StreamData, :tree, [{StreamData, :fixed_list, [[]]}, &Estructura.Tree.child_gen/1]}
     ]
 
   if {:module, Jason} == Code.ensure_compiled(Jason) do
-    @derive {Jason.Encoder, only: [:name, :attributes, :content]}
+    @derive {Jason.Encoder, only: ~w|name attributes content|a}
   end
 
+  @derive {Estructura.Flattenable, only: ~w|name attributes content|a}
+
   defstruct name: nil, attributes: %{}, content: []
 
   @type t :: %{
@@ -190,7 +193,8 @@ defmodule Estructura.Tree do
         {1, nil},
         {2, StreamData.string(:alphanumeric)},
         {7, Estructura.Tree.__generator__()}
-        ]),
-    max_length: @max_children)
+      ]),
+      max_length: @max_children
+    )
   end
 end

mix.exs

@@ -2,7 +2,7 @@ defmodule Estructura.MixProject do
   use Mix.Project
 
   @app :estructura
-  @version "1.2.3"
+  @version "1.2.4"
 
   def project do
     [