fix include_variables bug

When the `include_variables` flag was passed to the plug, any time a
post request was received without variables in the request body, an
error would occur.

I have changed the logic so that variables will only be looked for if
the request has both an `operationName` and `type`. Additionally it will
now only return variables if they exist, whether the request be a
GraphQL one or not. And appropriate regression tests have been added.

lib/uinta/plug.ex

@@ -144,27 +144,24 @@ if Code.ensure_loaded?(Plug) do
     @spec graphql_info(Plug.Conn.t(), map()) :: graphql_info() | nil
     defp graphql_info(%{method: "POST", params: params}, opts) do
       operation = params["operationName"]
-      variables = params["variables"]
-
-      encoded_variables =
-        with true <- opts.include_variables,
-             filtered = filter_variables(variables, opts.filter_variables),
-             {:ok, encoded} <- Jason.encode(filtered) do
-          encoded
-        else
-          _ -> nil
-        end
 
       type =
         params
         |> Map.get("query", "")
         |> String.trim()
         |> query_type()
 
-      if !is_nil(type) && !is_nil(operation) do
-        %{type: type, operation: operation, variables: encoded_variables}
+      info = %{type: type, operation: operation}
+
+      with {:is_nil, false} <- {:is_nil, is_nil(type) || is_nil(operation)},
+           true <- opts.include_variables,
+           variables when is_map(variables) <- params["variables"],
+           filtered = filter_variables(variables, opts.filter_variables),
+           {:ok, encoded} <- Jason.encode(filtered) do
+        Map.put(info, :variables, encoded)
       else
-        nil
+        {:is_nil, true} -> nil
+        _ -> info
       end
     end
 

mix.exs

@@ -8,7 +8,7 @@ defmodule Uinta.MixProject do
       app: :uinta,
       name: "Uinta",
       description: "Simpler structured logs and lower log volume for Elixir apps",
-      version: "0.3.0",
+      version: "0.3.1",
       elixir: "~> 1.8",
       source_url: @project_url,
       homepage_url: @project_url,

test/uinta/plug_test.exs

@@ -158,6 +158,20 @@ defmodule Uinta.PlugTest do
     assert message =~ "with {\"user_uid\":\"b1641ddf-b7b0-445e-bcbb-96ef359eae81\"}"
   end
 
+  test "doesn't try to include variables on non-graphql requests" do
+    message = capture_log(fn -> IncludeVariablesPlug.call(conn(:post, "/", %{}), []) end)
+    refute message =~ "with"
+  end
+
+  test "doesn't try to include variables when none were given" do
+    params = %{"operationName" => "getUser", "query" => "query getUser"}
+
+    message =
+      capture_log(fn -> IncludeVariablesPlug.call(conn(:post, "/graphql", params), []) end)
+
+    refute message =~ "with"
+  end
+
   test "filters variables when applicable" do
     variables = %{
       "user_uid" => "b1641ddf-b7b0-445e-bcbb-96ef359eae81",