Your autosave snapshot changed after you took it

transcript

You take a snapshot of a draft. Then you edit the draft. And the snapshot changes. How?

The draft has biryani, two, with the note, no onion. The autosave copies the list of lines. Then the host adds a note, extra gravy.

The shallow snapshot shows extra gravy. A new list, but the same line objects inside it. A deep copy makes new lines with new notes. The snapshot still says no onion.

You need two copies. One when you save, so later edits can't reach the snapshot. And one when you restore, so a restored draft can't change the snapshot either.

The autosave holds the snapshots and hands them back. Only the draft opens one. So the draft can change what it stores, and the autosave never notices.

A snapshot that shares state with the draft is just a window. Copy in when you save, copy out when you restore.

Full breakdown in the lecture.