Additional warning: calendar_dates for everything

[AntoineAugusti]

From etalab/transport-site#2331

The file only uses overrides and not regular schedules + overrides

[antoine-de]

hum, I'm not sure about this one 🤔

I think it's a common practice to do this isn't it @Tristramg ?

It is explicitly stated as an alternative strategy by the spec:

Alternate: Omit calendar.txt, and specify each date of service in calendar_dates.txt. This allows for considerable service variation and accommodates service without normal weekly schedules. In this case service_id is an ID.

It sure is more troublesome to some reuses, but I'm not sure it should be added in a validator (even as information).

What do you think about this @Tristramg @AntoineAugusti ?

[Tristramg]

There can’t be a general rule. If some bus runs on weird patterns like only on a public holiday, using dates makes sens.
If the schedule is very regular, a calendar is nicer.

We could imagine a metric trying to tell which approach would be better, but it’s not an easy task and probably not worth it.

Maybe something like « if there are more than N calendar_dates for a trip, and no calendar » add an information ?
We’d need to see an example file where people are annoyed