What does it mean when a revision number is missing?

Question

I've noticed in the API docs for revisions that revision_number may be absent. Yet all examples, e.g. /posts/{ids}/revisions include a revision number for all responses.

I have a colleague who swears they've seen missing revision numbers in the wild, but we cannot come up with examples to speculate about what would trigger this.

In what circumstances would a revision number be omitted? What does it signify? And, given that absent fields should be inferred to be null, if a given revision has no revision number today, might it have one later on, after more revisions?

Answer 1

There are several events which count as a revision but do not have a number; only edits (to the body, title or tags) have a revision number. Roughly speaking, everything which is listed on a posts revision history page (example) counts as a revision. You can compare that with the API results, and you'll see the revision number is missing for events like

• (un)protecting the question
• closing/reopening the question
• (un)locking the question
• making the question community wiki
• posting a bounty

Those events will never get a revision number in the future (unless the API somehow changes, I guess, but that's not likely) and you'll need another way to sort them: on creation date or activity date.