@valerio.bozzolan F267558 in the task description is not attached, thus it cannot be seen by others.

Fixed thanks aklapper

I'm quite sure we have to set PhabricatorApplicationTransaction.php::setIgnoreOnNoEffect(bool) somewhere but I don't know where ihih

Historical references: rP69eab4196de462e42b07b60e2b52071631f4a3c8 and rP4041a7e0f66406dbaa31faa3807d50833b7c7efd (which didn't help much).

We perform two transactions: $xaction->getTransactionType(): status and $xaction->getTransactionType(): reassign.
Looking at the latter:

Step1: Expand "Change Status" field (setting the Resolved status by default):

'type: reassign' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:717]
'oldValue: ' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:718]
'newValue: PHID-USER-....' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:719]

Step2: Also expand the "Assign / Claim" field (prepopulated with my username):

Same result as in Step1

Step3: Manually remove my username from the "Assign / Claim" field:

'type: reassign' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:717]
'oldValue: ' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:718]
'newValue: ' at [/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:719]

The reassign action is not special-cased in transactionHasEffect() or parent transactionHasEffect(), so we end up calling generic getTransactionHasEffect() which simply compares if $old !== $new. The result is false (as the actor manually removes themselves from being automatically set as owner), though IMO it should be true (no owner was set before either).

Obviously, any fixes should be in ManiphestTransactionEditor and not spill into generic parent PhabricatorApplicationTransactionEditor.

I looked into adding a case in transactionHasEffect(). That is not possible as it handles one single transaction (e.g. reassign) while our situation depends on a second condition (status change transaction).

I also looked into adjusting/expanding the code which silently sets the actor as owner. This code handles only setting up the "hidden" reassign transaction but it is entirely unrelated to any UI dialogs. Still it provides some pointers / conditions to look into.

I failed to "locate" the PhabricatorApplicationTransaction that we're about to perform after manually opening the "Add Field > Assign / Claim" dropdown in a scope limited to Maniphest && also allowing to check for the other transaction condition (status change transaction), to try setIgnoreOnNoEffect mentioned above.