At a guess, this happens when

1. person A opens the task for editing
2. person B adds himself to the CC field
3. person A saves the form (which in his verson does not have person A in the CC list).

Hah! So we now miss the dreaded mid-air collisions. ;-)

Lets upstream this then?

In T78236#945574, @Krenair wrote:

Lets upstream this then?

I'd imagine this is a known issue, but I haven't dug up a Phabricator.org task yet.

In T78236#945580, @MZMcBride wrote:

I'd imagine this is a known issue, but I haven't dug up a Phabricator.org task yet.

Surprisingly, I actually can't find any. The only vaguely relevant thing is https://secure.phabricator.com/T4768, but this is about Phriction (the wiki app) rather than Maniphest (the bug filing app). The issue itself is known (for example, on https://secure.phabricator.com/T6205 it's mentioned as one of the reasons for why you can only "Associate Projects" when adding a comment, but not "Edit Projects" – no potential for race conditions this way).

We might be the only Phabricator instance where this actually matters, given how much traffic we have, even in comparison to upstream. And it does matter, I keep seeing task edits that were clearly edit conflicts in my inbox (many of them mentioned above, T75901 is another particularly funny example).

In T78236#966583, @matmarex wrote:

In T78236#945580, @MZMcBride wrote:

I'd imagine this is a known issue, but I haven't dug up a Phabricator.org task yet.

Surprisingly, I actually can't find any. The only vaguely relevant thing is https://secure.phabricator.com/T4768, but this is about Phriction (the wiki app) rather than Maniphest (the bug filing app). The issue itself is known (for example, on https://secure.phabricator.com/T6205 it's mentioned as one of the reasons for why you can only "Associate Projects" when adding a comment, but not "Edit Projects" – no potential for race conditions this way).

We might be the only Phabricator instance where this actually matters, given how much traffic we have, even in comparison to upstream. And it does matter, I keep seeing task edits that were clearly edit conflicts in my inbox (many of them mentioned above, T75901 is another particularly funny example).

Yes, this usually happens when we're monitoring tasks modifications on IRC, where the original poster may change something later while other person does a triage or assigns projects, etc.

The funny thing is that it happened there for another task that affects Wikimedia :) https://secure.phabricator.com/T6905#90576

I think this matters for all instances, we just happen to be the ones that experience it more often due to relatively high traffic.

Yes, we're the only known very active user of maniphest.

Cc

In T93510#1140031, @Nikerabbit wrote:

PS: Phabricator doesn't handle edit conflicts at all it seems.

In T100276#1309360, @Jdforrester-WMF wrote:

This is upstream at https://secure.phabricator.com/T4768 – do we want to make this an 'official' Wikimedia upstream request?

Yes.

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