YashRE42 be76d7592a reload: Manually save draft and preserve id when triggering reload. ...

We received a complaint about the generation of multiple duplicate
drafts for a single message. It was discovered that the likely cause
of this was how we were handling clients that were frequently
suspending/unsuspending, we would initiate a reload when we discovered
this, and expect the `beforeunload` handler to save the draft. This
behaved correctly, however, we would also save the compose state and
fill it in via `preserve_state` in reload.js. The important detail
here is that `preserve_state` would not encode and preserve the
`draft_id` for the current message, partly because it had no way of
knowing the `draft_id` of the draft... since we have not saved it yet,
the `beforeunload` event happens after `preserve_state`. As such,
performing any action that would trigger a draft to be saved, eg
pressing Esc to close the compose box, would save a duplicate draft of
the same message.

To resolve the above bug, we (1) ensure that we call
`drafts.update_draft()` in `preserve_state`, this returns a draft_id
to us, which we (2) ensure that we encode as part of the url and (3)
set on the `#composebox-textarea` as a `draft-id` data attribute,
which we check the next time we try to save the draft, post reload.

Note that this causes us to save the draft twice, once from
preserve_state and then again from the `beforeunload` handler, but we
do not add two drafts since the second update_draft call just edits
the timestamp because it finds the `draft-id` data attribute on the
`#composebox-textarea` set by the first call.

2021-12-01 12:03:20 -08:00

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