API Consumers need a way to track when candidates are merged together

[jarofgreen]

There needs to be one consistent rule that always holds true that API Consumers can use to pick this up. They may be tracking data against IDs.

eg http://yournextmp.popit.mysociety.org/api/v0.1/persons/5895 and http://yournextmp.popit.mysociety.org/api/v0.1/persons/5239

At present, you can look through all version records and look in the ID field. If you see a different ID, then you know a merge happened.

• Can this be guaranteed to always be the case?
• If so, should this be documented somewhere?
• If not, what is?
• Would someone ever get de-merged?

[mhl]

@jarofgreen Thanks for raising this - I've created a ticket for what I think is the ideal solution: https://github.com/mysociety/popit-api/issues/132

In the mean time, to answer your questions:

• Yes - it's guaranteed that if any versions[].data.id is different from id then that other ID was merged into this one
• Yes, it should be documented, but currently isn't
• That's the best way at the moment, although I think returning 3xx redirections from the PopIt API woudl be better
• I don't have any plans for allowing people to be de-merged (i.e. merges to be reverted)

TODO:

• [ ] Document the current hacky way of finding where merges have occurred