fix: Double agency prefix on IDs from consolidated/merged GTFS feeds

[Ahmedhossamdev]

Problem

When using a consolidated/merged GTFS feed (e.g. Puget Sound Consolidated GTFS), some IDs in
the feed already include the agency prefix for example a stop with raw ID 40_1121 in the DB.
When our code calls utils.FormCombinedID("40", "40_1121") it produces 40_40_1121, which is
wrong.

https://www.soundtransit.org/help-contacts/business-information/open-transit-data-otd/otd-downloads

[Mady356]

Hey Ahmed,

I saw the consolidated GTFS ID issue and wanted to ask before I dig into it further.

The bug makes sense, but I’m curious about the intended scope of the fix: would you want this handled directly inside FormCombinedID, or would you prefer keeping that helper simple and handling consolidated-feed IDs closer to the specific callers that need it?

I’m also wondering whether the safe rule is specifically “if rawID starts with agencyID + '_' then return it as-is,” or whether there are edge cases across feeds that make the normalization logic more subtle than that. I’m not sure if you’re planning to implement it yourself, but I’d be happy to take a pass at it or explore a solution if that would be helpful.