Handle calendar.txt/calendar_dates.txt entries w/o applicable trips

Ignore rows in calendar.txt and calendar_dates.txt with a service_id
that does not apply to any rows in trips.txt. This is valid GTFS.

partridge/readers.py

@@ -58,17 +58,14 @@ def _service_ids_by_date(feed):
     results = defaultdict(set)
     removals = defaultdict(set)
 
-    calendar = feed.calendar
-    caldates = feed.calendar_dates
-    trips = feed.trips
+    service_ids = set(feed.trips.service_id)
 
-    service_ids = set(trips.service_id)
+    # Only consider calendar.txt/calendar_dates.txt rows with applicable trips
+    calendar = feed.calendar[feed.calendar.service_id.isin(service_ids)].copy()
+    caldates = feed.calendar_dates[feed.calendar_dates.service_id.isin(service_ids)].copy() # noqa E501
 
-    # Process calendar.txt if it exists
     if not calendar.empty:
-        calendar = calendar[calendar.service_id.isin(service_ids)].copy()
-
-        # Ensure dates have been parsed
+        # Parse dates
         calendar.start_date = vparse_date(calendar.start_date)
         calendar.end_date = vparse_date(calendar.end_date)
 
@@ -83,11 +80,8 @@ def _service_ids_by_date(feed):
                 if int(dow[date.weekday()]):
                     results[date].add(cal.service_id)
 
-    # Process calendar_dates.txt if it exists
     if not caldates.empty:
-        caldates = caldates[caldates.service_id.isin(service_ids)].copy()
-
-        # Ensure dates have been parsed
+        # Parse dates
         caldates.date = vparse_date(caldates.date)
 
         # Split out additions and removals

tests/fixtures/trimet-vermont-2018-02-06/agency.txt

@@ -0,0 +1,2 @@
+agency_id,agency_name,agency_url,agency_timezone,agency_lang,agency_phone,agency_fare_url,agency_email,bikes_policy_url
+TRIMET,TriMet,http://trimet.org/,America/Los_Angeles,en,503-238-RIDE,http://trimet.org/fares/,customerservice@trimet.org,http://trimet.org/howtoride/bikes/bikepolicies.htm

tests/fixtures/trimet-vermont-2018-02-06/calendar.txt

@@ -0,0 +1 @@
+service_id,monday,tuesday,wednesday,thursday,friday,saturday,sunday,start_date,end_dateunknown,0,1,1,1,1,0,0,20171120,20180309

tests/fixtures/trimet-vermont-2018-02-06/calendar_dates.txt

@@ -0,0 +1,115 @@
+service_id,date,exception_type
+unknown,20180601,1
+W.504,20180601,1
+W.504,20180531,1
+W.504,20180530,1
+W.504,20180529,1
+W.504,20180528,1
+W.504,20180525,1
+W.504,20180524,1
+W.504,20180523,1
+W.504,20180522,1
+W.504,20180521,1
+W.504,20180518,1
+W.504,20180517,1
+W.504,20180516,1
+W.504,20180515,1
+W.504,20180514,1
+W.504,20180511,1
+W.504,20180510,1
+W.504,20180509,1
+W.504,20180508,1
+W.504,20180507,1
+W.504,20180504,1
+W.504,20180503,1
+W.504,20180502,1
+W.504,20180501,1
+W.504,20180430,1
+W.504,20180427,1
+W.504,20180426,1
+W.504,20180425,1
+W.504,20180424,1
+W.504,20180423,1
+W.504,20180420,1
+W.504,20180419,1
+W.504,20180418,1
+W.504,20180417,1
+W.504,20180416,1
+W.504,20180413,1
+W.504,20180412,1
+W.504,20180411,1
+W.504,20180410,1
+W.504,20180409,1
+W.504,20180406,1
+W.504,20180405,1
+W.504,20180404,1
+W.504,20180403,1
+W.504,20180402,1
+W.504,20180330,1
+W.504,20180329,1
+W.504,20180328,1
+W.504,20180327,1
+W.504,20180326,1
+W.504,20180323,1
+W.504,20180322,1
+W.504,20180321,1
+W.504,20180320,1
+W.504,20180319,1
+W.504,20180316,1
+W.504,20180315,1
+W.504,20180314,1
+W.504,20180313,1
+W.504,20180312,1
+W.504,20180309,1
+W.504,20180308,1
+W.504,20180307,1
+W.504,20180306,1
+W.504,20180305,1
+W.507,20180302,1
+W.507,20180301,1
+W.507,20180228,1
+W.507,20180227,1
+W.507,20180226,1
+W.507,20180223,1
+W.507,20180222,1
+W.507,20180221,1
+W.507,20180220,1
+W.507,20180219,1
+W.507,20180216,1
+W.507,20180215,1
+W.507,20180214,1
+W.507,20180213,1
+W.507,20180212,1
+k.507,20180302,1
+k.507,20180301,1
+k.507,20180228,1
+k.507,20180227,1
+k.507,20180226,1
+k.507,20180223,1
+k.507,20180222,1
+k.507,20180221,1
+k.507,20180220,1
+k.507,20180216,1
+k.507,20180215,1
+k.507,20180214,1
+k.507,20180213,1
+k.507,20180212,1
+W.506,20180209,1
+W.506,20180208,1
+W.506,20180207,1
+W.506,20180206,1
+W.506,20180205,1
+W.506,20180202,1
+W.506,20180201,1
+W.506,20180131,1
+W.506,20180130,1
+W.506,20180129,1
+k.506,20180209,1
+k.506,20180208,1
+k.506,20180207,1
+k.506,20180206,1
+k.506,20180205,1
+k.506,20180202,1
+k.506,20180201,1
+k.506,20180131,1
+k.506,20180130,1

tests/fixtures/trimet-vermont-2018-02-06/feed_info.txt

@@ -0,0 +1,2 @@
+feed_publisher_name,feed_publisher_url,feed_lang,feed_start_date,feed_end_date,feed_version,feed_id,feed_contact_url
+TriMet,http://trimet.org/,en,20180128,20180602,20180128-20180206-0148,TriMet,https://groups.google.com/forum/#!forum/transit-developers-pdx

tests/fixtures/trimet-vermont-2018-02-06/routes.txt

@@ -0,0 +1,2 @@
+route_id,agency_id,route_short_name,route_long_name,route_type,route_url,route_color,route_text_color,route_sort_order
+1,TRIMET,1,Vermont,3,http://trimet.org//schedules/r001.htm,,,400