From 38ed6f40017a104077b614a14c32ac4e257b6f55 Mon Sep 17 00:00:00 2001
From: Paul Swartz <paul@paulswartz.net>
Date: Mon, 2 Apr 2018 11:49:15 -0400
Subject: [PATCH] don't fetch relationships twice

For some implementations of `relationships/2`, it can be expensive to calculate.
For the top level, we've already calculated the relationships as a part of the
`%ResourceObject{}` so we don't need to do it again.
---
 lib/ja_serializer/builder/included.ex        | 8 ++++++--
 test/ja_serializer/builder/included_test.exs | 9 +++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/ja_serializer/builder/included.ex b/lib/ja_serializer/builder/included.ex
index 75d1ef9..dcca6cc 100644
--- a/lib/ja_serializer/builder/included.ex
+++ b/lib/ja_serializer/builder/included.ex
@@ -36,6 +36,7 @@ defmodule JaSerializer.Builder.Included do
   end
 
   defp resource_objects_for(structs, conn, serializer, opts) do
+    structs = Enum.filter(structs, &is_map/1)
     %{data: structs, conn: conn, serializer: serializer, opts: opts}
     |> ResourceObject.build
     |> List.wrap
@@ -43,8 +44,11 @@ defmodule JaSerializer.Builder.Included do
 
   # Find relationships that should be included.
   defp relationships_with_include(context) do
-    context.data
-    |> context.serializer.relationships(context.conn)
+    context
+    |> case do
+         %{relationships: relationships} -> relationships
+         %{data: data} -> context.serializer.relationships(data, context.conn)
+       end
     |> Enum.filter(fn({rel_name, rel_definition}) ->
       case context[:opts][:include] do
         # if `include` param is not present only return 'default' includes
diff --git a/test/ja_serializer/builder/included_test.exs b/test/ja_serializer/builder/included_test.exs
index cfa2de3..0ce66c3 100644
--- a/test/ja_serializer/builder/included_test.exs
+++ b/test/ja_serializer/builder/included_test.exs
@@ -315,4 +315,13 @@ defmodule JaSerializer.Builder.IncludedTest do
     ids = Enum.map(json["included"], &(Map.get(&1, "id")))
     assert not "p1" in ids
   end
+
+  test "non-existent include that is serialized into resource identifier results in no includes being added" do
+    a1 = %TestModel.Article{id: "a1", title: "a1", author: "p1"}
+
+    json = JaSerializer.format(ArticleSerializer, a1, %{}, include: "author")
+    keys = Map.keys(json)
+    assert not "included" in keys
+    assert json["data"]["relationships"]["author"]["data"]["id"] == "p1"
+  end
 end