GTFS lib warns on missing calendar.txt

[mattwigway]

[main] INFO com.conveyal.gtfs.GTFSFeed - GTFSError: calendar line 0: This table is required by the GTFS specification but is missing.

This is actually perfectly legal.

[blackmad]

I was looking into using gtfs-lib to do gtfs feed validation, since I think it's what OTP uses internally, and I was surprised how many feeds give me this calendar missing error, which doesn't seem to actually be an error.

Any updates on this?

[timlod]

Still an issue. See https://gtfs.org/schedule/reference/#calendar_datestxt for the official documentation describing how this is okay:

Alternate: Omit [calendar.txt](https://gtfs.org/schedule/reference/#calendartxt), and specify each date of service in [calendar_dates.txt](https://gtfs.org/schedule/reference/#calendardatestxt). This allows for considerable service variation and accommodates service without normal weekly schedules. In this case service_id is an ID.