This release contains an important Native targets overhaul, as well as numerous enhancements and bugfixes. Kotlin 1.8.21 is used by default.

New set of Native targets

The official Kotlin target support policy has recently been published describing new target policy: each target belongs to a certain tier, and different tiers have different stability guarantees. The official recommendation for library authors is to support targets up to Tier 3, and kotlinx.serialization now follows it. It means that in this release, there are a lot of new targets added from this tier, such as androidNativeX86 or watchosDeviceArm64. Note that since they belong to Tier 3, they're not auto-tested on CI.

kotlinx.serialization also ships some deprecated Kotlin/Native targets that do not belong to any tier (e.g. iosArm32, mingwX86). We'll continue to release them, but we do not provide support for them, nor do we plan to add new targets from the deprecated list.

Improvements in Json elements

There are two new function sets that should make creating raw Json elements easier. First one contains overloads for JsonPrimitive constructor-like function that accept unsigned types: JsonPrimitive(1u). Second one adds new addAll functions to JsonArrayBuilder to be used with collections of numbers, booleans or strings: buildJsonArray { addAll(listOf(1, 2, 3)) }. Both were contributed to us by aSemy.

Other enhancements

• Potential source-breaking change: Rename json-okio target variables to sink (#2226)
• Function to retrieve KSerializer by KClass and type arguments serializers (#2291)
• Added FormatLanguage annotation to Json methods (#2234)
• Properties Format: Support sealed/polymorphic classes as class properties (#2255)

Bugfixes

• KeyValueSerializer: Fix missing call to endStructure() (#2272)
• ObjectSerializer: Respect sequential decoding (#2273)
• Fix value class encoding in various corner cases (#2242)
• Fix incorrect json decoding iterator's .hasNext() behavior on array-wrapped inputs (#2268)
• Fix memory leak caused by invalid KTypeWrapper's equals method (#2274)
• Fixed NoSuchMethodError when parsing a JSON stream on Java 8 (#2219)
• Fix MissingFieldException duplication (#2213)