fix(ics): export a series' deleted occurrences (#225)

Import learned to read EXDATE, but the export side never wrote it: an in-app
backup and restore brought back every occurrence the user had deleted. EXDATE
lives on the master row, so the export query's ORIGINAL_ID IS NULL filter never
hid it — it just wasn't in the projection.

An all-day series' exclusions are written VALUE=DATE, since RFC 5545 ties
EXDATE's value type to DTSTART's and a bare day code without it reads as a
malformed DATE-TIME. Sync adapters disagree on whether an all-day exclusion is
yyyyMMdd or a padded midnight stamp, so the time part is dropped on the way out.

CHANGELOG.md

@@ -42,6 +42,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   imported without complaint and then appeared nowhere. Any all-day event that
   ends where it starts, or carries no end at all, is now a one-day event
   ([#225]).
+- **A backup no longer brings back occurrences you had deleted.** Remove a single
+  occurrence of a repeating event, back up, restore — and it was there again,
+  because the removals never made it into the file. They travel with the series
+  now, so a restored calendar looks the way you left it ([#225]).
 
 ### Added
 - **More of an imported `.ics` survives the trip**: tasks come across as events

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt

@@ -308,7 +308,6 @@ class CalendarRepositoryImpl @Inject constructor(
         dataSource.deleteEventFromOccurrence(eventId, beginMillis)
     }
 
-
     private companion object {
         const val TAG = "CalendarRepository"
     }

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapper.kt

@@ -56,6 +56,11 @@ internal fun ColumnReader.toIcsEvent(
         zoneId = getString(EventExportProjection.IDX_EVENT_TIMEZONE)?.takeIf { it.isNotBlank() }
             ?: "UTC",
         recurrenceRule = rrule,
+        exDates = if (rrule == null) {
+            emptyList()
+        } else {
+            exportExDates(getString(EventExportProjection.IDX_EXDATE), isAllDay)
+        },
         location = getString(EventExportProjection.IDX_LOCATION),
         description = getString(EventExportProjection.IDX_DESCRIPTION),
         reminderMinutes = if (isAllDay) {
@@ -72,3 +77,19 @@ internal fun ColumnReader.toIcsEvent(
     )
 }
 
+/**
+ * The row's `EXDATE` as the writer wants it: one stamp per entry, empties
+ * dropped.
+ *
+ * An all-day exclusion names a calendar day, and sync adapters are inconsistent
+ * about whether they write it as a bare `yyyyMMdd` or pad it to a midnight
+ * stamp; the time part is dropped so the exported value is the day either way.
+ * Calendula's own writes ([buildOccurrenceExdateValues]) are already bare.
+ */
+internal fun exportExDates(exdate: String?, isAllDay: Boolean): List<String> = exdate
+    ?.split(',')
+    ?.map { it.trim() }
+    ?.filter { it.isNotEmpty() }
+    ?.map { if (isAllDay) it.substringBefore('T') else it }
+    ?.distinct()
+    .orEmpty()

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/Projections.kt

@@ -121,10 +121,12 @@ internal object EventDetailProjection {
 /**
  * Master/one-off Events rows for a whole-calendar backup. Unlike
  * [EventDetailProjection] this reads `UID_2445` (to keep a row's identity across
- * backups) and `DURATION` (recurring rows carry it instead of DTEND). Modified-
+ * backups) and `DURATION` (recurring rows carry it instead of DTEND), plus
+ * `EXDATE` so a series exports the occurrences deleted from it. Modified-
  * occurrence and cancelled-exception rows are filtered out by the query
- * (`ORIGINAL_ID IS NULL`), so RECURRENCE-ID overrides and EXDATEs aren't
+ * (`ORIGINAL_ID IS NULL`), so RECURRENCE-ID overrides aren't exported — a
- * exported yet — a documented v1 limit (import skips them too).
+ * documented v1 limit (import skips them too). EXDATE is unaffected by that
+ * filter: it lives on the master row, not on an exception of its own.
  */
 internal object EventExportProjection {
     val COLUMNS: Array<String> = arrayOf(
@@ -137,6 +139,7 @@ internal object EventExportProjection {
         CalendarContract.Events.ALL_DAY,
         CalendarContract.Events.EVENT_TIMEZONE,
         CalendarContract.Events.RRULE,
+        CalendarContract.Events.EXDATE,
         CalendarContract.Events.EVENT_LOCATION,
         CalendarContract.Events.DESCRIPTION,
         CalendarContract.Events.STATUS,
@@ -153,11 +156,12 @@ internal object EventExportProjection {
     const val IDX_ALL_DAY = 6
     const val IDX_EVENT_TIMEZONE = 7
     const val IDX_RRULE = 8
-    const val IDX_LOCATION = 9
+    const val IDX_EXDATE = 9
-    const val IDX_DESCRIPTION = 10
+    const val IDX_LOCATION = 10
-    const val IDX_STATUS = 11
+    const val IDX_DESCRIPTION = 11
-    const val IDX_AVAILABILITY = 12
+    const val IDX_STATUS = 12
-    const val IDX_CALENDAR_ID = 13
+    const val IDX_AVAILABILITY = 13
+    const val IDX_CALENDAR_ID = 14
 }
 
 /**

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsEvent.kt

@@ -22,6 +22,12 @@ data class IcsEvent(
     val zoneId: String,
     /** Bare RRULE value (no `RRULE:` prefix), or null for a one-off event. */
     val recurrenceRule: String? = null,
+    /**
+     * Occurrences deleted from the series, in the provider's `EXDATE` shape —
+     * `yyyyMMdd` for an all-day series, a UTC `yyyyMMddTHHmmssZ` stamp
+     * otherwise. Empty for a one-off event.
+     */
+    val exDates: List<String> = emptyList(),
     val location: String? = null,
     val description: String? = null,
     /** Reminder lead times in minutes before start (raw provider offsets). */

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsWriter.kt

@@ -46,6 +46,7 @@ class IcsWriter(private val prodId: String = ICS_PROD_ID) {
         appendTimes(event)
         event.recurrenceRule?.takeIf { it.isNotBlank() }
             ?.let { add("RRULE:${it.removePrefix("RRULE:")}") }
+        appendExDates(event)
         event.location?.takeIf { it.isNotBlank() }
             ?.let { add("LOCATION:${escapeText(it)}") }
         event.description?.takeIf { it.isNotBlank() }
@@ -83,6 +84,20 @@ class IcsWriter(private val prodId: String = ICS_PROD_ID) {
         }
     }
 
+    /**
+     * The series' deleted occurrences. RFC 5545 ties `EXDATE`'s value type to
+     * `DTSTART`'s, so an all-day series needs the explicit `VALUE=DATE` — without
+     * it the bare day codes read as an invalid DATE-TIME. Only written for a
+     * recurring event: an exclusion names an occurrence, and a one-off has none.
+     */
+    private fun MutableList<String>.appendExDates(event: IcsEvent) {
+        if (event.recurrenceRule.isNullOrBlank()) return
+        val stamps = event.exDates.filter { it.isNotBlank() }.distinct()
+        if (stamps.isEmpty()) return
+        val prefix = if (event.isAllDay) "EXDATE;VALUE=DATE:" else "EXDATE:"
+        add(prefix + stamps.joinToString(","))
+    }
+
     private fun MutableList<String>.appendAlarm(minutes: Int, summary: String) {
         add("BEGIN:VALARM")
         add("ACTION:DISPLAY")

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapperTest.kt

@@ -102,4 +102,70 @@ class IcsExportMapperTest {
         const val NINE_AM = 9 * 60
         val BERLIN: ZoneId = ZoneId.of("Europe/Berlin")
     }
+
+    @Test
+    fun `a recurring row carries its EXDATE exclusions`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 7L,
+            EventExportProjection.IDX_TITLE to "Weekly",
+            EventExportProjection.IDX_DTSTART to 1_000_000L,
+            EventExportProjection.IDX_DURATION to "P3600S",
+            EventExportProjection.IDX_ALL_DAY to 0,
+            EventExportProjection.IDX_RRULE to "FREQ=WEEKLY",
+            EventExportProjection.IDX_EXDATE to "20260901T080000Z,20260908T080000Z",
+            EventExportProjection.IDX_EVENT_TIMEZONE to "UTC",
+        )
+
+        val event = reader.toIcsEvent(
+            reminderMinutes = emptyList(),
+            calendarName = null,
+            allDayReminderTimeMinutes = NINE_AM,
+        )
+
+        assertThat(event.exDates)
+            .containsExactly("20260901T080000Z", "20260908T080000Z").inOrder()
+    }
+
+    @Test
+    fun `an all-day EXDATE keeps only the day, however the adapter padded it`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 8L,
+            EventExportProjection.IDX_TITLE to "Holiday",
+            EventExportProjection.IDX_DTSTART to 0L,
+            EventExportProjection.IDX_DURATION to "P1D",
+            EventExportProjection.IDX_ALL_DAY to 1,
+            EventExportProjection.IDX_RRULE to "FREQ=YEARLY",
+            EventExportProjection.IDX_EXDATE to "20260901,20270901T000000Z",
+            EventExportProjection.IDX_EVENT_TIMEZONE to "UTC",
+        )
+
+        val event = reader.toIcsEvent(
+            reminderMinutes = emptyList(),
+            calendarName = null,
+            allDayReminderTimeMinutes = NINE_AM,
+        )
+
+        assertThat(event.exDates).containsExactly("20260901", "20270901").inOrder()
+    }
+
+    @Test
+    fun `a one-off row exports no exclusions even if the column is set`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 9L,
+            EventExportProjection.IDX_TITLE to "Standup",
+            EventExportProjection.IDX_DTSTART to 1_000_000L,
+            EventExportProjection.IDX_DTEND to 1_900_000L,
+            EventExportProjection.IDX_ALL_DAY to 0,
+            EventExportProjection.IDX_EXDATE to "20260901T080000Z",
+            EventExportProjection.IDX_EVENT_TIMEZONE to "UTC",
+        )
+
+        val event = reader.toIcsEvent(
+            reminderMinutes = emptyList(),
+            calendarName = null,
+            allDayReminderTimeMinutes = NINE_AM,
+        )
+
+        assertThat(event.exDates).isEmpty()
+    }
 }

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsParserTest.kt

@@ -165,4 +165,36 @@ class IcsParserTest {
         assertThat(result.events.map { it.uid }).containsExactly("good")
         assertThat(result.warnings).contains(IcsParseWarning.EventWithoutStartSkipped)
     }
+
+    @Test
+    fun `round-trips a timed series' deleted occurrences`() {
+        val event = IcsEvent(
+            uid = "u20@calendula",
+            summary = "Weekly",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 13, 30),
+            isAllDay = false,
+            zoneId = "UTC",
+            recurrenceRule = "FREQ=WEEKLY",
+            exDates = listOf("20260625T130000Z"),
+        )
+
+        assertThat(roundTrip(event).exDates).containsExactly("20260625T130000Z")
+    }
+
+    @Test
+    fun `round-trips an all-day series' deleted occurrences`() {
+        val event = IcsEvent(
+            uid = "u21@calendula",
+            summary = "Holiday",
+            start = LocalDate(2026, 6, 18).atStartOfDayIn(TimeZone.UTC),
+            end = LocalDate(2026, 6, 19).atStartOfDayIn(TimeZone.UTC),
+            isAllDay = true,
+            zoneId = "UTC",
+            recurrenceRule = "FREQ=YEARLY",
+            exDates = listOf("20270618"),
+        )
+
+        assertThat(roundTrip(event).exDates).containsExactly("20270618")
+    }
 }

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsWriterTest.kt

@@ -149,4 +149,55 @@ class IcsWriterTest {
         // Stable across calls — a re-export of the same row yields the same UID.
         assertThat(deriveIcsUid(null, 7, 1000)).isEqualTo(deriveIcsUid(null, 7, 1000))
     }
+
+    @Test
+    fun `a timed series writes its exclusions as UTC stamps`() {
+        val event = IcsEvent(
+            uid = "u9@calendula",
+            summary = "Weekly",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 13, 30),
+            isAllDay = false,
+            zoneId = "UTC",
+            recurrenceRule = "FREQ=WEEKLY",
+            exDates = listOf("20260625T130000Z", "20260702T130000Z"),
+        )
+
+        assertThat(lines(listOf(event)))
+            .contains("EXDATE:20260625T130000Z,20260702T130000Z")
+    }
+
+    @Test
+    fun `an all-day series marks its exclusions VALUE=DATE`() {
+        val start = LocalDate(2026, 6, 18).atStartOfDayIn(TimeZone.UTC)
+        val event = IcsEvent(
+            uid = "u10@calendula",
+            summary = "Holiday",
+            start = start,
+            end = LocalDate(2026, 6, 19).atStartOfDayIn(TimeZone.UTC),
+            isAllDay = true,
+            zoneId = "UTC",
+            recurrenceRule = "FREQ=YEARLY",
+            exDates = listOf("20270618"),
+        )
+
+        // RFC 5545 ties EXDATE's value type to DTSTART's; a bare day code
+        // without VALUE=DATE reads as a malformed DATE-TIME.
+        assertThat(lines(listOf(event))).contains("EXDATE;VALUE=DATE:20270618")
+    }
+
+    @Test
+    fun `a one-off event never writes an EXDATE`() {
+        val event = IcsEvent(
+            uid = "u11@calendula",
+            summary = "Standup",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 13, 30),
+            isAllDay = false,
+            zoneId = "UTC",
+            exDates = listOf("20260625T130000Z"),
+        )
+
+        assertThat(lines(listOf(event)).none { it.startsWith("EXDATE") }).isTrue()
+    }
 }