fix(proposal): avoid UID collision when converting a proposal without…

lib/Service/Proposal/ProposalService.php

@@ -341,7 +341,9 @@ public function convertProposal(IUser $user, int $proposalId, int $dateId, array
 		$vObject = new VCalendar();
 		/** @var \Sabre\VObject\Component\VEvent $vEvent */
 		$vEvent = $vObject->add('VEVENT', []);
-		$vEvent->UID->setValue($proposal->getUuid() ?? Uuid::v4()->toRfc4122());
+		// UID is assigned below depending on whether an existing blocker is reused (PUT in place)
+		// or a fresh calendar object is created. Reusing the proposal UUID for a fresh INSERT
+		// would collide with an orphan blocker held by oc_calendarobjects.calobjects_by_uid_index.
 		$vEvent->add('DTSTART', $eventTimezone ? $selectedDate->getDate()->setTimezone($eventTimezone) : $selectedDate->getDate());
 		$vEvent->add('DTEND', (clone $vEvent->DTSTART->getDateTime())->add(new \DateInterval("PT{$proposal->getDuration()}M")));
 		$vEvent->add('SEQUENCE', 1);
@@ -368,8 +370,16 @@ public function convertProposal(IUser $user, int $proposalId, int $dateId, array
 		// convert existing calendar blocker to event if it exists, otherwise create a new event in the user's calendar
 		$result = $this->findCalendarBlocker($user, $proposal);
 		if ($result !== null) {
+			// blocker found in the user's calendars: reuse the proposal UUID so iCal threading
+			// is preserved. applyCalendarBlockersOrganizer issues a PUT against the same URI,
+			// which updates the existing row rather than inserting a new one.
+			$vEvent->UID->setValue($proposal->getUuid() ?? Uuid::v4()->toRfc4122());
 			$this->applyCalendarBlockersOrganizer($user, $result['calendarUri'], $result['eventUri'], $vObject);
 		} else {
+			// blocker was not surfaced by the search (calendar not in the principal listing,
+			// search backend lag, etc.) but may still hold the proposal UID in oc_calendarobjects.
+			// Use a fresh UUID so the INSERT below cannot collide on calobjects_by_uid_index.
+			$vEvent->UID->setValue(Uuid::v4()->toRfc4122());
 			$userCalendar->createFromString(
 				Uuid::v4()->toRfc4122() . '.ics',
 				$vObject->serialize()

tests/php/unit/Service/Proposal/ProposalServiceTest.php

@@ -585,6 +585,61 @@ public function testConvertProposalSuccess(): void {
 		$this->addToAssertionCount(1); // If we reached this point, the test is successfully completed
 	}
 
+	/**
+	 * Regression: when no calendar blocker is found by the search, the converted event must not
+	 * reuse the proposal's UUID. Otherwise an INSERT into oc_calendarobjects collides with a
+	 * possibly-orphaned blocker holding the same UID and triggers SQLSTATE[23505] (#7941).
+	 */
+	public function testConvertProposalUsesFreshUuidWhenBlockerNotFound(): void {
+		$proposalEntry = $this->createProposalEntry(1, 'Convert Proposal');
+		$proposalEntry->setDuration(60);
+		$proposalEntry->setUuid('9d8aa045-d371-49c1-9f70-aaaaaaaaaaaa');
+		$dateEntry = new ProposalDateEntry();
+		$dateEntry->setId(10);
+		$dateEntry->setPid(1);
+		$dateEntry->setUid('testuser');
+		$dateEntry->setDate((new \DateTimeImmutable('+1 day'))->getTimestamp());
+
+		$this->proposalMapper->expects($this->once())
+			->method('fetchById')
+			->with('testuser', 1)
+			->willReturn($proposalEntry);
+		$this->proposalParticipantMapper->expects($this->once())
+			->method('fetchByProposalId')
+			->with('testuser', 1)
+			->willReturn([]);
+		$this->proposalDateMapper->expects($this->once())
+			->method('fetchByProposalId')
+			->with('testuser', 1)
+			->willReturn([$dateEntry]);
+		$this->proposalVoteMapper->expects($this->once())
+			->method('fetchByProposalId')
+			->with('testuser', 1)
+			->willReturn([]);
+
+		// Simulate the bug condition: search across the user's calendars surfaces no blocker
+		// (even though one may still exist in oc_calendarobjects with the proposal's UID).
+		$this->calendarManager->method('getCalendarsForPrincipal')->willReturn([]);
+
+		$calendar = $this->createMock(\OCP\Calendar\ICreateFromString::class);
+		$calendar->method('isDeleted')->willReturn(false);
+		$calendar->expects($this->once())
+			->method('createFromString')
+			->with(
+				$this->callback(fn ($name) => str_ends_with($name, '.ics')),
+				$this->callback(fn ($data) => !str_contains($data, 'UID:' . $proposalEntry->getUuid())),
+			);
+		$this->calendarManager->method('getPrimaryCalendar')->with('testuser')->willReturn($calendar);
+
+		$this->proposalVoteMapper->expects($this->once())->method('deleteByProposalId')->with('testuser', 1);
+		$this->proposalParticipantMapper->expects($this->once())->method('deleteByProposalId')->with('testuser', 1);
+		$this->proposalDateMapper->expects($this->once())->method('deleteByProposalId')->with('testuser', 1);
+		$this->proposalMapper->expects($this->once())->method('deleteById')->with('testuser', 1);
+
+		$this->service->convertProposal($this->user, 1, 10);
+		$this->addToAssertionCount(1);
+	}
+
 	public function testConvertProposalDateNotFound(): void {
 		// mock objects
 		// proposal entry