Don't generate exception VEVENTs when there are only invalid/filtered recurrence properties, so that the generated event is non-recurring

Author: rfc2822

lib/src/main/kotlin/at/bitfire/synctools/mapping/calendar/LegacyAndroidEventProcessor.kt

@@ -83,25 +83,27 @@ class LegacyAndroidEventProcessor(
             to = to
         )
 
-        // exceptions of recurring main event
-        for (exception in eventAndExceptions.exceptions) {
-            val exceptionEvent = Event()
+        // Add exceptions of recurring main event
+        if (to.rRules.isNotEmpty() || to.rDates.isNotEmpty()) {
+            for (exception in eventAndExceptions.exceptions) {
+                val exceptionEvent = Event()
 
-            // convert exception to Event
-            populateEvent(
-                entity = exception,
-                main = eventAndExceptions.main,
-                to = exceptionEvent
-            )
+                // convert exception to Event
+                populateEvent(
+                    entity = exception,
+                    main = eventAndExceptions.main,
+                    to = exceptionEvent
+                )
 
-            // make sure that exception has a RECURRENCE-ID
-            val recurrenceId = exceptionEvent.recurrenceId ?: continue
+                // make sure that exception has a RECURRENCE-ID
+                val recurrenceId = exceptionEvent.recurrenceId ?: continue
 
-            // generate EXDATE instead of VEVENT with RECURRENCE-ID for cancelled instances
-            if (exception.entityValues.getAsInteger(Events.STATUS) == Events.STATUS_CANCELED)
-                addAsExDate(exception, recurrenceId, to = to)
-            else
-                to.exceptions += exceptionEvent
+                // generate EXDATE instead of VEVENT with RECURRENCE-ID for cancelled instances
+                if (exception.entityValues.getAsInteger(Events.STATUS) == Events.STATUS_CANCELED)
+                    addAsExDate(exception, recurrenceId, to = to)
+                else
+                    to.exceptions += exceptionEvent
+            }
         }
     }
 

lib/src/test/kotlin/at/bitfire/synctools/mapping/calendar/LegacyAndroidEventProcessorTest.kt

@@ -31,7 +31,7 @@ class LegacyAndroidEventProcessorTest {
     private val tzVienna = tzRegistry.getTimeZone("Europe/Vienna")!!
 
     @Test
-    fun `Populate regular exception`() {
+    fun `Exception is processed`() {
         val result = Event()
         processor.populate(
             eventAndExceptions = EventAndExceptions(
@@ -65,7 +65,38 @@ class LegacyAndroidEventProcessorTest {
     }
 
     @Test
-    fun `Populate cancelled exception as EXDATE`() {
+    fun `Exception is ignored when there's only one invalid RRULE`() {
+        val result = Event()
+        processor.populate(
+            eventAndExceptions = EventAndExceptions(
+                main = Entity(contentValuesOf(
+                    Events.TITLE to "Factically non-recurring non-all-day event with exception",
+                    Events.DTSTART to 1594056600000L,
+                    Events.EVENT_TIMEZONE to tzVienna.id,
+                    Events.ALL_DAY to 0,
+                    Events.RRULE to "FREQ=DAILY;UNTIL=20200706T173000Z"
+                )),
+                exceptions = listOf(
+                    Entity(contentValuesOf(
+                        Events.ORIGINAL_INSTANCE_TIME to 1594143000000L,
+                        Events.ORIGINAL_ALL_DAY to 0,
+                        Events.DTSTART to 1594038600000L,
+                        Events.EVENT_TIMEZONE to tzShanghai.id,
+                        Events.ALL_DAY to 0,
+                        Events.TITLE to "Event moved to one hour later"
+                    ))
+                )
+            ),
+            to = result
+        )
+        assertEquals("Factically non-recurring non-all-day event with exception", result.summary)
+        assertEquals(DtStart("20200706T193000", tzVienna), result.dtStart)
+        assertTrue(result.rRules.isEmpty())
+        assertTrue(result.exceptions.isEmpty())
+    }
+
+    @Test
+    fun `Cancelled exception becomes EXDATE`() {
         val result = Event()
         processor.populate(
             eventAndExceptions = EventAndExceptions(
@@ -97,7 +128,7 @@ class LegacyAndroidEventProcessorTest {
     }
 
     @Test
-    fun `Populate cancelled exception without RECURRENCE-ID`() {
+    fun `Cancelled exception without RECURRENCE-ID is ignored`() {
         val result = Event()
         processor.populate(
             eventAndExceptions = EventAndExceptions(