DateUtils.parseVTimeZone: return null instead of throwing a RuntimeException on parsing error

Author: rfc2822

lib/src/androidTest/kotlin/at/bitfire/ical4android/util/DateUtilsTest.kt

@@ -63,4 +63,23 @@ class DateUtilsTest {
         assertFalse(DateUtils.isDateTime(null))
     }
 
+
+    @Test
+    fun testParseVTimeZone() {
+        val vtz = """
+            BEGIN:VCALENDAR
+            VERSION:2.0
+            PRODID:DAVx5
+            BEGIN:VTIMEZONE
+            TZID:Asia/Shanghai
+            END:VTIMEZONE
+            END:VCALENDAR""".trimIndent()
+        assertEquals("Asia/Shanghai", DateUtils.parseVTimeZone(vtz)?.timeZoneId?.value)
+    }
+
+    @Test
+    fun testParseVTimeZone_Invalid() {
+        assertNull(DateUtils.parseVTimeZone("Invalid"))
+    }
+
 }

lib/src/main/kotlin/at/bitfire/ical4android/util/DateUtils.kt

@@ -123,20 +123,22 @@ object DateUtils {
     fun isDateTime(date: DateProperty?) = date != null && date.date is DateTime
 
     /**
-     * Parses a VTIMEZONE definition to a VTimeZone object.
-     * @param timezoneDef VTIMEZONE definition
-     * @return parsed VTimeZone
-     * @throws IllegalArgumentException when the timezone definition can't be parsed
+     * Parses an iCalendar that only contains a `VTIMEZONE` definition to a VTimeZone object.
+     *
+     * @param timezoneDef iCalendar with only a `VTIMEZONE` definition
+     *
+     * @return parsed [VTimeZone], or `null` when the timezone definition can't be parsed
      */
-    fun parseVTimeZone(timezoneDef: String): VTimeZone {
+    fun parseVTimeZone(timezoneDef: String): VTimeZone? {
         Ical4Android.checkThreadContextClassLoader()
 
         val builder = CalendarBuilder(tzRegistry)
         try {
             val cal = builder.build(StringReader(timezoneDef))
             return cal.getComponent(VTimeZone.VTIMEZONE) as VTimeZone
-        } catch (e: Exception) {
-            throw IllegalArgumentException("Couldn't parse timezone definition")
+        } catch (_: Exception) {
+            // Couldn't parse timezone definition
+            return null
         }
     }