Handle added trips in finder_api

FinderApi.departures implicitly assumed that all trips have associated
schedules, which is not true of added trips. This assumption led to a
nil creeping into an unexpected place, leading ultimately to an
UndefinedFunctionError. This case is now accounted for.

apps/site/lib/site_web/controllers/schedule/finder_api.ex

@@ -161,12 +161,11 @@ defmodule SiteWeb.ScheduleController.FinderApi do
   @spec enhance_journeys(Journey.t()) :: map
   defp enhance_journeys(%{departure: departure} = journey) do
     now = Timex.now()
-    diff = DateTime.diff(Timex.now(), departure.schedule.time)
 
     time_map =
       departure
       |> TransitNearMe.build_time_map(now: now)
-      |> recent_departure(departure.prediction, diff)
+      |> recent_departure(departure, now)
 
     Map.put(journey, :realtime, time_map)
   end
@@ -177,13 +176,23 @@ defmodule SiteWeb.ScheduleController.FinderApi do
   # a prediction's status and limit recent trips to a certain time range.
   # NOTE: Only works for N/S Station and Back Bay, and predictions will
   # drop off (become nil) anytime during the duration of the trip.
-  defp recent_departure({_, details}, %{status: "Departed"} = prediction, time_elapsed)
-       when time_elapsed <= @recent_departure_max_age do
-    Map.put(details, :prediction, %{
-      time: details.scheduled_time,
-      track: prediction.track,
-      status: "Departed"
-    })
+  defp recent_departure(
+         {_, details},
+         %{schedule: schedule, prediction: %{status: "Departed"} = prediction},
+         now
+       )
+       when not is_nil(schedule) do
+    time_elapsed = DateTime.diff(now, schedule.time)
+
+    if time_elapsed <= @recent_departure_max_age do
+      Map.put(details, :prediction, %{
+        time: details.scheduled_time,
+        track: prediction.track,
+        status: "Departed"
+      })
+    else
+      details
+    end
   end
 
   defp recent_departure({_, details}, _, _), do: details

apps/site/test/site_web/controllers/schedule/finder_api_test.exs

@@ -153,6 +153,26 @@ defmodule SiteWeb.ScheduleController.FinderApiTest do
                }
              ] = response
     end
+
+    test "can handle added trips", %{conn: conn} do
+      added_prediction = %Prediction{@prediction | schedule_relationship: :added}
+
+      path =
+        finder_api_path(conn, :departures, %{
+          id: "CR-Providence",
+          direction: "0",
+          stop: "place-sstat"
+        })
+
+      response =
+        conn
+        |> assign(:schedules_fn, fn _, _ -> [] end)
+        |> assign(:predictions_fn, fn _ -> [added_prediction] end)
+        |> get(path)
+        |> json_response(200)
+
+      assert [%{"departure" => %{"prediction" => added_prediction, "schedule" => nil}}] = response
+    end
   end
 
   describe "trip/2" do