TRAN-7530: Add none checks and similar defenses against exceptions (#56)

* TRAN-7530: default return value

* TRAN-7530: check none

* TRAN-7530: default value

* TRAN-7530: avoids index error

* TRAN-7530: avoid nonetype ref

* TRAN-7530: return empty array

* TRAN-7530: handle nonexistent keys

Author: joshverma

gtfs_realtime_translators/translators/mbta.py

@@ -11,10 +11,12 @@ class MbtaGtfsRealtimeTranslator:
 
     def __call__(self, data):
         json_data = json.loads(data)
-        predictions = json_data['data']
-        static_relationships = json_data['included']
-        static_data = self.__get_static_data(static_relationships)
-        entities = self.__make_trip_updates(predictions, static_data)
+        entities = []
+        predictions = json_data.get('data')
+        static_relationships = json_data.get('included')
+        if predictions and static_relationships:
+            static_data = self.__get_static_data(static_relationships)
+            entities = self.__make_trip_updates(predictions, static_data)
         return FeedMessage.create(entities=entities)
 
     @classmethod

gtfs_realtime_translators/translators/njt_bus.py

@@ -35,7 +35,8 @@ def __skip_processing(cls, stop_id, filtered_stops):
     @classmethod
     def __make_trip_updates(cls, data, filtered_stops):
         trip_updates = []
-        trips = data['SCHEDULEROWSET'].values()
+        schedule_row_set = data.get('SCHEDULEROWSET', {})
+        trips = schedule_row_set.values()
 
         for value in trips:
             for idx, item_entry in enumerate(value):

gtfs_realtime_translators/translators/septa_regional_rail.py

@@ -41,8 +41,8 @@ def __call__(self, data):
             raise ValueError('root_key: unexpected format')
 
         arrivals_body = json_data[root_key]
-        northbound = [ direction_list['Northbound'] for direction_list in arrivals_body if [*direction_list][0] == 'Northbound' ][0]
-        southbound = [ direction_list['Southbound'] for direction_list in arrivals_body if [*direction_list][0] == 'Southbound' ][0]
+        northbound = self.get_arrivals_from_direction_list('Northbound', arrivals_body)
+        southbound = self.get_arrivals_from_direction_list('Southbound', arrivals_body)
         arrivals = northbound + southbound
 
         transformed_arrivals = [ self.transform_arrival(arrival) for arrival in arrivals ]
@@ -51,6 +51,19 @@ def __call__(self, data):
         entities = [ self.__make_trip_update(idx, self.stop_id, arrival) for idx, arrival in enumerate(filtered_arrivals) ]
         return FeedMessage.create(entities=entities)
 
+    @classmethod
+    def get_arrivals_from_direction_list(cls, direction_string, arrivals_body):
+        arrivals = []
+        for direction_list in arrivals_body:
+            # When there are no arrivals, the API gives us an empty list instead
+            # of a dictionary
+            if isinstance(direction_list, dict) \
+                    and [*direction_list][0] == direction_string:
+                arrivals.append(direction_list[direction_string])
+        if arrivals:
+            return arrivals[0]
+        return []
+
     @classmethod
     def calculate_time_at(cls, **kwargs):
         now = pendulum.now()

gtfs_realtime_translators/translators/wcdot_bus.py

@@ -31,8 +31,12 @@ def generate_trip_updates(self, entities):
                 arrival = update.get("arrival")
                 departure = update.get("departure")
                 if stop_id == self.stop_id:
-                    arrival_delay = arrival.get('delay',None)
-                    departure_delay = departure.get('delay',None)
+                    arrival_delay = None
+                    departure_delay = None
+                    if arrival:
+                        arrival_delay = arrival.get('delay',None)
+                    if departure:
+                        departure_delay = departure.get('delay',None)
                     trip_update = TripUpdate.create(
                         entity_id=entity_id,
                         arrival_delay=arrival_delay,