Strip associations from user struct

When preparing the user for serialization the associations
are now stripped given that the associations preloading might
not be required.

lib/addict/interactors/create_session.ex

@@ -6,10 +6,10 @@ defmodule Addict.Interactors.CreateSession do
 
   Returns `{:ok, conn}`
   """
-  def call(conn, user) do
+  def call(conn, user, schema \\ Addict.Configs.user_schema) do
     conn = conn
     |> fetch_session
-    |> put_session(:current_user, Addict.Presenter.strip_all(user))
+    |> put_session(:current_user, Addict.Presenter.strip_all(user, schema))
     {:ok, conn}
   end
 end

lib/addict/presenter.ex

@@ -4,10 +4,17 @@ Normalized structure presentation
 """
 
   @doc """
-  Strips `:__struct__`, `:__meta__` and `:encrypted_password` from the structure
+  Strips all associations, `:__struct__`, `:__meta__` and `:encrypted_password` from the structure
+
+  Returns the stripped structure
   """
-  def strip_all(model) do
-    model |> Map.drop([:__struct__, :__meta__, :encrypted_password])
+  def strip_all(model, schema \\ Addict.Configs.user_schema) do
+    model |> drop_keys(schema)
+  end
+
+  defp drop_keys(model, schema) do
+    associations = schema.__schema__(:associations)
+    Map.drop model, associations ++ [:__struct__, :__meta__, :encrypted_password]
   end
 
 end

test/interactors/create_session_test.exs

@@ -19,7 +19,7 @@ defmodule CreateSessionTest do
 
     assert Plug.Conn.get_session(conn, :current_user) == nil
 
-    {:ok, conn} = CreateSession.call(conn, fake_user)
+    {:ok, conn} = CreateSession.call(conn, fake_user, TestAddictSchema)
 
     assert Plug.Conn.get_session(conn, :current_user) == fake_user
   end

test/interactors/destroy_session_test.exs

@@ -16,7 +16,7 @@ defmodule DestroySessionTest do
     conn = conn(:get, "/")
            |> Plug.Session.call(@session_opts)
            |> fetch_session
-    {:ok, conn} = CreateSession.call(conn, fake_user)
+    {:ok, conn} = CreateSession.call(conn, fake_user, TestAddictSchema)
 
     {:ok, conn} = DestroySession.call(conn)
 

test/presenter_test.exs

@@ -0,0 +1,38 @@
+defmodule PresenterTest do
+  alias Addict.Presenter
+  use ExUnit.Case, async: true
+
+  test "it strips associations" do
+    user = struct(
+      TestAddictUserAssociationsSchema,
+      %{
+        name: "Joe Doe",
+        email: "joe.doe@example.com",
+        encrypted_password: "what a hash!"
+      })
+
+    model = Presenter.strip_all(user, TestAddictUserAssociationsSchema)
+
+    assert Map.has_key?(model, :__struct__) == false
+    assert Map.has_key?(model, :__meta__) == false
+    assert Map.has_key?(model, :drugs) == false
+  end
+end
+
+defmodule TestAddictDrugsSchema do
+  use Ecto.Schema
+  schema "drugs" do
+    field :name, :string
+  end
+end
+
+defmodule TestAddictUserAssociationsSchema do
+  use Ecto.Schema
+
+  schema "users" do
+    field :name, :string
+    field :email, :string
+    field :encrypted_password, :string
+    has_many :drugs, TestAddictDrugsSchema
+  end
+end