1.7.1

This is a bugfix release that aims to fix missing kotlinx-serialization-hocon artifact.
It also contains experimental integration with kotlinx-io library.
Kotlin 2.0.0 is used by default.

Fixed HOCON publication

Sadly, 1.7.0 release was published incomplete: kotlinx-serialization-hocon artifact is missing from 1.7.0 and 1.7.0-RC releases.
This release fixes this problem and now kotlinx-serialization-hocon is available again with 1.7.1 version.
No other changes were made to this artifact. Related ticket: #2717.

Add integration with a kotlinx-io library

kotlinx-io is an official multiplatform library that provides basic IO primitives, similar to Okio.
kotlinx.serialization integration is now available in a separate artifact, located at the kotlinx-serialization-json-io coordinates. Integration artifact provides functions similar to existing Okio integration: encodeToSink, decodeFromSource, and decodeSourceToSequence. Check out the PR for more details.

Other bugfixes

• Prohibited use of elements other than JsonObject in JsonTransformingSerializer with polymorphic serialization (#2715)

1.7.0

This release contains all of the changes from 1.7.0-RC and is compatible with Kotlin 2.0.
Please note that for reasons explained in the 1.7.0-RC changelog, it may not be possible to use it with the Kotlin 1.9.x
compiler plugin. Yet, it is still fully backward compatible with previous versions.

The only difference with 1.7.0-RC is that the classDiscriminatorMode property in JsonBuilder is marked as experimental,
as it should have been when it was introduced (#2680).

1.7.0-RC

This is a release candidate for the next version. It is based on Kotlin 2.0.0-RC3 and is fully compatible with a stable Kotlin 2.0 release.
Due to a potential breaking change (see below), it requires a compiler plugin with a version at least of 2.0.0-RC1.

Important change: priority of PolymorphicSerializer for interfaces during call to serializer() function

Non-sealed interfaces in kotlinx.serialization are always serializable with a polymorphic serializer,
even if they do not have @Serializable annotation. This also means that serializersModule.serializer<SomeInterface>() call will return you a serializer capable of polymorphism. This function was written in a way that it unconditionally returns a PolymorphicSerializer if type argument is a non-sealed interface. This caused problems with SerializersModule functionality, because actual module was not taken into consideration, and therefore it was impossible to override serializer for interface using 'contextual serialization' feature. The problem is described in detail here. To overcome these problems, we had to change the behavior of this function regarding interfaces. It now looks into SerializersModule first if T is a non-sealed interface, and only if there is no registered contextual serializer for T, it returns a polymorphic serializer.

Behavior before 1.7.0-RC:

interface SomeInterface

val module = SerializersModule {
    contextual(SomeInterface::class, CustomSomeInterfaceSerializer)
}

// Prints PolymorphicSerializer<SomeInterface>:
println(module.serializer<SomeInterface>())

Behavior in 1.7.0-RC, 1.7.0, and higher:

interface SomeInterface

val module = SerializersModule {
    contextual(SomeInterface::class, CustomSomeInterfaceSerializer)
}

// Prints CustomSomeInterfaceSerializer:
println(module.serializer<SomeInterface>())

We expect minimal impact from this change, but be aware of it anyway.
Implementation details are available in this PR.

Due to the serializer() function being also a compiler intrinsic, code
of kotlinx.serialization compiler plugin also accommodates this change in the 2.0 branch. To get a consistent result from both plugin and runtime, kotlinx.serialization compiler plugin should be at least of 2.0.0-RC1 version.
To verify so, 1.7.0-RC runtime will be rejected by older plugins.

Json configuration flag to allow commentaries

While JSON standard does not allow any kind of commentaries, they are one of the most popular extensions — for example, commentaries are widely used in configuration files. To support this use-case, we added a new configuration flag, allowComments. This flag allows the parser to skip over C/Java-style commentaries in JSON input. Note that commentaries cannot affect decoding or encoding in any way and are not stored anywhere. See details in the PR.

Promote JsonConfiguration.explicitNulls to a stable API

This configuration flag has been around for a long time and got positive feedback. Therefore, we are promoting it to a stable state. It also received functionality enhancements when used with JsonConfiguration.coerceInputValues (#2586). See related PR for details.

oneof support in ProtoBuf

oneof fields in protobuf messages represent a set of optional fields, where the only one of them is present. With the help of the new @ProtoOneOf annotation, you can naturally map them to Kotlin's sealed class hierarchy. Check out the comprehensive guide for this feature here.

This functionality was contributed to us by xzk.

Other improvements and bugfixes

• Update okio to 3.9.0 version (#2671)
• Add extension to access original descriptor from one made with SerialDescriptor.nullable (#2633) (thanks to Chuckame)
• Use @SerialName of inline polymorphic children in Json (#2601) (thanks to Tad Fisher)
• Fix serializing nulls for a property of a parameterized type with a nullable upper bound with Protobuf (#2561) (thanks to Shreck Ye)
• Fixed type discriminator value for custom serializer that uses encodeJsonElement (#2628)
• Refine exception messages in case of deserializing data from JsonElement. (#2648)

1.6.3

This release provides a couple of new features and uses Kotlin 1.9.22 as default.

Class discriminator output mode

Class discriminator provides information for serializing and deserializing polymorphic class hierarchies.
In case you want to encode more or less information for various third party APIs about types in the output, it is possible to control
addition of the class discriminator with the JsonBuilder.classDiscriminatorMode property.
For example, ClassDiscriminatorMode.NONE does not add class discriminator at all, in case the receiving party is not interested in Kotlin types.
You can learn more about this feature in the documentation and corresponding PR.

Other features

• Add kebab-case naming strategy (#2531) (thanks to Emil Kantis)
• Add value class support to the ProtoBufSchemaGenerator (#2542) (thanks to Felipe Rotilho)

Bugfixes and improvements

• Fix: Hocon polymorphic serialization in containers (#2151) (thanks to LichtHund)
• Actualize lenient mode documentation (#2568)
• Slightly improve error messages thrown from serializer() function (#2533)
• Do not try to coerce input values for properties (#2530)
• Make empty objects and arrays collapsed in pretty print mode (#2506)
• Update Gradle dokka configuration to make sure "source" button is visible in all API docs (#2518, #2524)

1.6.2

This is a patch release accompanying Kotlin 1.9.21. It also provides additional targets that were not available in 1.6.1: wasm-wasi and (deprecated) linuxArm32Hfp.

• Add Wasm WASI target (#2510)
• Bring back linuxArm32Hfp target because it is deprecated, but not removed yet. (#2505)

1.6.1

This release uses Kotlin 1.9.20 by default, while upcoming 1.9.21 is also supported.

Trailing commas in Json

Trailing commas are one of the most popular non-spec Json variations. A new configuration flag, allowTrailingComma, makes Json parser accept them instead of throwing an exception. Note that it does not affect encoding, so kotlinx.serialization always produces Json without trailing commas. See details in the corresponding PR.

Support of WasmJs target

Kotlin/Wasm has been experimental for some time and gained enough maturity to be added to the kotlinx libraries. Starting with 1.6.1, kotlinx.serialization provides a wasm-js flavor, so your projects with Kotlin/Wasm can have even more functionality. As usual, just add serialization dependencies to your build and declare wasmJs target. Please remember that Kotlin/Wasm is still experimental, so changes are expected.

Bugfixes and improvements

• Fix TaggedDecoder nullable decoding (#2456) (thanks to Phillip Schichtel)
• Fix IllegalAccessException for some JPMS boundaries (#2469)
• Cbor: check if inline value classes are marked as @ByteString (#2466) (thanks to eater)
• Improve polymorphic deserialization optimization (#2481)
• Update Okio dependency to 3.6.0 (#2473)
• Add protobuf conformance tests (#2404) (thanks to Doğaç Eldenk)
• Support decoding maps with boolean keys (#2440)

1.6.0

This release contains all features and bugfixes from 1.6.0-RC plus some bugfixes on its own (see below).
Kotlin 1.9.0 is used as a default, while 1.9.10 is also supported.

Bugfixes

• Improve error messages from Json parser (#2406)
• Mark @SerialName, @Required and @Transient with @MustBeDocumented (#2407)
• Ensure that no additional files except java compiler output get into multi-release jar (#2405)
• Fix enums with negative numbers in protobuf not serializing & de-serializing (#2400) (thanks to Doğaç Eldenk)

1.6.0-RC

This release is based on the Kotlin 1.9.0.

Removal of Legacy JS target

Some time ago, in Kotlin 1.8, JS IR compiler was promoted to stable and old JS compiler was deprecated.
Kotlin 1.9 promotes the usage of deprecated JS compiler to an error. As a result, kotlinx.serialization no longer builds with the legacy compiler and does not distribute artifacts for it. You can read the migration guide for JS IR compiler here.

Also pay attention to the fact that Kotlin/Native also has some deprecated targets that are going to be removed in the Kotlin 1.9.20. Therefore, kotlinx.serialization 1.6.0-RC and 1.6.0 are likely the last releases that support these targets.

Case insensitivity for enums in Json

This release features a new configuration flag for Json: decodeEnumsCaseInsensitive that allows you to decode enum values in a case-insensitive manner.
For example, when decoding enum class Foo { VALUE_A , VALUE_B} both inputs "value_a" and "value_A" will yield Foo.VALUE_A. You can read more about this feature in the documentation and corresponding PR.

Other bugfixes and enhancements

• Add support to decode numeric literals containing an exponent (#2227) (thanks to Roberto Blázquez)
• Fix NoSuchMethodError related to Java 8 API compatibility (#2328, #2350) (thanks to Björn Kautler)
• Changed actual FormatLanguage annotation for JS and Native to avoid problems with duplicating org.intellij.lang.annotations.Language (#2390, #2379)
• Fix error triggered by 'consume leading class discriminator' polymorphic parsing optimization (#2362)
• Fix runtime error with Serializer for Nothing on the JS target (#2330) (thanks to Shreck Ye)
• Fix beginStructure in JsonTreeDecoder when inner structure descriptor is same as outer (#2346) (thanks to Ugljesa Jovanovic)
• Actualize 'serializer not found' platform-specific message (#2339)
• Fixed regression with serialization using a list parametrized with contextual types (#2331)

1.5.1

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)

1.5.0

This release contains all features and bugfixes from 1.5.0-RC plus some experimental features and bugfixes on its own (see below).
Kotlin 1.8.10 is used as a default.

HoconEncoder and HoconDecoder interfaces and HOCON-specific serializers

These interfaces work in a way similar to JsonEncoder and JsonDecoder: they allow intercepting (de)serialization process,
making writing if custom HOCON-specific serializers easier. New ConfigMemorySizeSerializer and JavaDurationSerializer already make use of them.
See more details in the PR.
Big thanks to Alexander Mikhailov for contributing this!

Ability to read buffered huge strings in custom Json deserializers

New interface ChunkedDecoder allows you to read huge strings that may not fit in memory by chunks.
Currently, this interface is only implemented by Json decoder that works with strings and streams,
but we may expand it later, if there's a demand for it.
See more details in the PR authored by Alexey Sviridov.

Bugfixes

• Improve runtime exceptions messages (#2180)
• Added support for null values for nullable enums in lenient mode (#2176)
• Prevent class loaders from leaking when using ClassValue cache (#2175)