Require ID for PATCH

lib/jsonapi/error_view.ex

@@ -40,6 +40,12 @@ defmodule JSONAPI.ErrorView do
     |> serialize_error
   end
 
+  def missing_data_id_param do
+    "Missing id in data parameter"
+    |> build_error(400, @crud_message, "/data/id")
+    |> serialize_error
+  end
+
   def missing_data_type_param do
     "Missing type in data parameter"
     |> build_error(400, @crud_message, "/data/type")

lib/jsonapi/plugs/format_required.ex

@@ -25,6 +25,10 @@ defmodule JSONAPI.FormatRequired do
 
   def call(%{params: %{"data" => %{"type" => _, "id" => _}}} = conn, _), do: conn
 
+  def call(%{method: "PATCH", params: %{"data" => %{"attributes" => _}}} = conn, _) do
+    send_error(conn, missing_data_id_param())
+  end
+
   def call(%{params: %{"data" => %{"attributes" => _}}} = conn, _),
     do: send_error(conn, missing_data_type_param())
 

test/jsonapi/plugs/format_required_test.exs

@@ -61,13 +61,21 @@ defmodule JSONAPI.FormatRequiredTest do
     refute conn.halted
   end
 
-  test "halts if only type member is present on a patch" do
+  test "halts and returns an error for missing id in data param on a patch" do
     conn =
       :patch
-      |> conn("/example", Jason.encode!(%{data: %{type: "something"}}))
+      |> conn("/example", Jason.encode!(%{data: %{attributes: %{}, type: "something"}}))
       |> call_plug
 
     assert conn.halted
+    assert 400 == conn.status
+
+    %{"errors" => [error]} = Jason.decode!(conn.resp_body)
+
+    assert %{
+             "source" => %{"pointer" => "/data/id"},
+             "title" => "Missing id in data parameter"
+           } = error
   end
 
   test "does not halt if type and id members are present on a patch" do