UtcOffset serialization (as a string primitive)

Author: ilya-g

core/common/src/UtcOffset.kt

@@ -5,6 +5,10 @@
 
 package kotlinx.datetime
 
+import kotlinx.datetime.serializers.UtcOffsetSerializer
+import kotlinx.serialization.Serializable
+
+@Serializable(with = UtcOffsetSerializer::class)
 public expect class UtcOffset {
     public val totalSeconds: Int
 

core/common/src/serializers/TimeZoneSerializers.kt

@@ -7,6 +7,7 @@ package kotlinx.datetime.serializers
 
 import kotlinx.datetime.FixedOffsetTimeZone
 import kotlinx.datetime.TimeZone
+import kotlinx.datetime.UtcOffset
 import kotlinx.serialization.*
 import kotlinx.serialization.descriptors.*
 import kotlinx.serialization.encoding.*
@@ -25,7 +26,7 @@ public object TimeZoneSerializer: KSerializer<TimeZone> {
 
 public object FixedOffsetTimeZoneSerializer: KSerializer<FixedOffsetTimeZone> {
 
-    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("ZoneOffset", PrimitiveKind.STRING)
+    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("FixedOffsetTimeZone", PrimitiveKind.STRING)
 
     override fun deserialize(decoder: Decoder): FixedOffsetTimeZone {
         val zone = TimeZone.of(decoder.decodeString())
@@ -41,3 +42,17 @@ public object FixedOffsetTimeZoneSerializer: KSerializer<FixedOffsetTimeZone> {
     }
 
 }
+
+public object UtcOffsetSerializer: KSerializer<UtcOffset> {
+
+    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("UtcOffset", PrimitiveKind.STRING)
+
+    override fun deserialize(decoder: Decoder): UtcOffset {
+        return UtcOffset.parse(decoder.decodeString())
+    }
+
+    override fun serialize(encoder: Encoder, value: UtcOffset) {
+        encoder.encodeString(value.toString())
+    }
+
+}

core/js/src/UtcOffset.kt

@@ -6,7 +6,10 @@
 package kotlinx.datetime
 
 import kotlinx.datetime.internal.JSJoda.ZoneOffset
+import kotlinx.datetime.serializers.UtcOffsetSerializer
+import kotlinx.serialization.Serializable
 
+@Serializable(with = UtcOffsetSerializer::class)
 public actual class UtcOffset(internal val zoneOffset: ZoneOffset) {
     public actual val totalSeconds: Int get() = zoneOffset.totalSeconds().toInt()
 

core/jvm/src/UtcOffsetJvm.kt

@@ -5,9 +5,12 @@
 
 package kotlinx.datetime
 
+import kotlinx.datetime.serializers.UtcOffsetSerializer
+import kotlinx.serialization.Serializable
 import java.time.DateTimeException
 import java.time.ZoneOffset
 
+@Serializable(with = UtcOffsetSerializer::class)
 public actual class UtcOffset(internal val zoneOffset: ZoneOffset) {
     public actual val totalSeconds: Int get() = zoneOffset.totalSeconds
 

core/native/src/UtcOffset.kt

@@ -5,9 +5,12 @@
 
 package kotlinx.datetime
 
+import kotlinx.datetime.serializers.UtcOffsetSerializer
+import kotlinx.serialization.Serializable
 import kotlin.math.abs
 import kotlin.native.concurrent.ThreadLocal
 
+@Serializable(with = UtcOffsetSerializer::class)
 public actual class UtcOffset internal constructor(public actual val totalSeconds: Int) {
     private val id: String = zoneIdByOffset(totalSeconds)
 

serialization/common/test/UtcOffsetSerializationTest.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2019-2021 JetBrains s.r.o.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.datetime.serialization.test
+
+import kotlinx.datetime.*
+import kotlinx.datetime.serializers.*
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.json.*
+import kotlinx.serialization.serializer
+import kotlin.test.*
+
+class UtcOffsetSerializationTest {
+
+    private fun testSerializationAsPrimitive(serializer: KSerializer<UtcOffset>) {
+        val offset2h = UtcOffset.parse("+2")
+        assertEquals("\"+02:00\"", Json.encodeToString(serializer, offset2h))
+        assertEquals(offset2h, Json.decodeFromString(serializer, "\"+02:00\""))
+        assertEquals(offset2h, Json.decodeFromString(serializer, "\"+02\""))
+        assertEquals(offset2h, Json.decodeFromString(serializer, "\"+2\""))
+
+        assertFailsWith<IllegalArgumentException> {
+            Json.decodeFromString(serializer, "\"UTC+02:00\"") // not an offset
+        }
+    }
+
+    @Test
+    fun defaultSerializer() {
+        testSerializationAsPrimitive(Json.serializersModule.serializer())
+    }
+
+    @Test
+    fun stringPrimitiveSerializer() {
+        testSerializationAsPrimitive(UtcOffsetSerializer)
+        testSerializationAsPrimitive(UtcOffset.serializer())
+    }
+}