fix(dav): strip DTSTAMP only from etag, preserve in stored data

DTSTAMP is a required property per RFC 5545 and must not be removed
from stored calendar data. Strip it only from the serialized string
used for etag computation via preg_replace, leaving the data passed
to createCalendarObject/updateCalendarObject unchanged.

Signed-off-by: Olen <regopa@gmail.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: olen <ola@nytt.no>

Author: Olen

apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php

@@ -110,20 +110,15 @@ public function refreshSubscription(string $principalUri, string $uri) {
 					}
 				}
 
-				// Strip DTSTAMP to prevent false positives during change detection.
+				$sObject = $vObject->serialize();
+				$uid = $vBase->UID->getValue();
+				// Strip DTSTAMP lines for etag computation only.
 				// Many providers (Google Calendar, Outlook, itslearning) set DTSTAMP
 				// to the current time on every feed request per RFC 5545, causing
 				// every event to appear modified on every refresh.
-				foreach ($vObject->getComponents() as $component) {
-					if ($component->name === 'VTIMEZONE') {
-						continue;
-					}
-					$component->remove('DTSTAMP');
-				}
-
-				$sObject = $vObject->serialize();
-				$uid = $vBase->UID->getValue();
-				$etag = md5($sObject);
+				// DTSTAMP is kept in the stored data as it is a required property.
+				$sObjectForEtag = preg_replace('/^DTSTAMP:.*\r?\n/m', '', $sObject);
+				$etag = md5($sObjectForEtag);
 
 				// No existing object with this UID, create it
 				if (!isset($existingObjects[$uid])) {

apps/dav/tests/unit/CalDAV/WebcalCaching/RefreshWebcalServiceTest.php

@@ -460,69 +460,6 @@ public function testRunCreateCalendarBadRequest(string $body, string $format, st
 		$refreshWebcalService->refreshSubscription('principals/users/testuser', 'sub123');
 	}
 
-	public function testDtstampIsStrippedFromOutput(): void {
-		$refreshWebcalService = new RefreshWebcalService(
-			$this->caldavBackend,
-			$this->logger,
-			$this->connection,
-			$this->timeFactory,
-			$this->importService
-		);
-
-		$this->caldavBackend->expects(self::once())
-			->method('getSubscriptionsForUser')
-			->with('principals/users/testuser')
-			->willReturn([
-				[
-					'id' => '42',
-					'uri' => 'sub123',
-					RefreshWebcalService::STRIP_TODOS => '1',
-					RefreshWebcalService::STRIP_ALARMS => '1',
-					RefreshWebcalService::STRIP_ATTACHMENTS => '1',
-					'source' => 'webcal://foo.bar/bla2',
-					'lastmodified' => 0,
-				],
-			]);
-
-		// Input has DTSTAMP
-		$body = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Test//Test//EN\r\nBEGIN:VEVENT\r\nUID:strip-test\r\nDTSTAMP:20260209T120000Z\r\nDTSTART:20260301T100000Z\r\nSUMMARY:Test Event\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
-		$stream = $this->createStreamFromString($body);
-
-		$this->connection->expects(self::once())
-			->method('queryWebcalFeed')
-			->willReturn(['data' => $stream, 'format' => 'ical']);
-
-		$this->caldavBackend->expects(self::once())
-			->method('getLimitedCalendarObjects')
-			->willReturn([]);
-
-		// Feed the VCalendar with DTSTAMP into the service
-		$vCalendar = VObject\Reader::read($body);
-		$generator = function () use ($vCalendar) {
-			yield $vCalendar;
-		};
-
-		$this->importService->expects(self::once())
-			->method('importText')
-			->willReturn($generator());
-
-		// Verify DTSTAMP is absent from the data passed to createCalendarObject
-		$this->caldavBackend->expects(self::once())
-			->method('createCalendarObject')
-			->with(
-				'42',
-				self::matchesRegularExpression('/^[a-f0-9-]+\.ics$/'),
-				self::callback(function (string $calendarData): bool {
-					self::assertStringContainsString('DTSTART', $calendarData);
-					self::assertStringNotContainsString('DTSTAMP', $calendarData);
-					return true;
-				}),
-				CalDavBackend::CALENDAR_TYPE_SUBSCRIPTION
-			);
-
-		$refreshWebcalService->refreshSubscription('principals/users/testuser', 'sub123');
-	}
-
 	public function testDtstampChangeDoesNotTriggerUpdate(): void {
 		$refreshWebcalService = new RefreshWebcalService(
 			$this->caldavBackend,
@@ -555,10 +492,8 @@ public function testDtstampChangeDoesNotTriggerUpdate(): void {
 			->method('queryWebcalFeed')
 			->willReturn(['data' => $stream, 'format' => 'ical']);
 
-		// The stored etag was computed from the DTSTAMP-stripped serialization.
-		// Reader::read() preserves the original PRODID and does not add CALSCALE.
-		$strippedBody = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Test//Test//EN\r\nBEGIN:VEVENT\r\nUID:dtstamp-test\r\nDTSTART:20260301T100000Z\r\nSUMMARY:Test Event\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
-		$existingEtag = md5($strippedBody);
+		// The stored etag was computed from the DTSTAMP-stripped serialization
+		$existingEtag = md5(preg_replace('/^DTSTAMP:.*\r?\n/m', '', $body));
 
 		$this->caldavBackend->expects(self::once())
 			->method('getLimitedCalendarObjects')
@@ -591,9 +526,9 @@ public function testDtstampChangeDoesNotTriggerUpdate(): void {
 	}
 
 	public static function identicalDataProvider(): array {
-		// DTSTAMP is stripped before etag computation, so the etag body must not contain it
-		$icalBody = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject " . VObject\Version::VERSION . "//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
-		$etag = md5($icalBody);
+		$icalBody = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject " . VObject\Version::VERSION . "//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTAMP:20160218T133704Z\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
+		// Etag is computed from DTSTAMP-stripped serialization
+		$etag = md5(preg_replace('/^DTSTAMP:.*\r?\n/m', '', $icalBody));
 
 		return [
 			[
@@ -617,8 +552,7 @@ public static function runDataProvider(): array {
 			[
 				"BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTAMP:20160218T133704Z\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n",
 				'ical',
-				// DTSTAMP is stripped before serialization, so the expected result must not contain it
-				"BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject " . VObject\Version::VERSION . "//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n",
+				"BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject " . VObject\Version::VERSION . "//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTAMP:20160218T133704Z\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n",
 			],
 		];
 	}