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A library is more robust if it plays well with the rest of the ecosystem surrounding it. Arrow integrates with many useful libraries in the Kotlin ecosystem. This is a non-exhaustive list, and we're happy to hear about support for Arrow from other libraries.

We'd love to hear from you!

Do you maintain or know of a library with support for Arrow? Feel free to open an issue in the repository, and we'll add it to this list. Thanks in advance! 🤩

tip

There's a custom set of rules for Detekt that can help you refine your style when using Arrow.

Testing​

Kotest​

If you want to test the result of a function that uses a type defined in Arrow, like Either, you can use the matchers extension library. If you're using property-based testing (you should!), you can use generators for Arrow types.

AssertJ​

Assertions covering Either and Option are provided by this library.

Serialization​

See the corresponding section.

Configuration​

Hoplite​

Hoplite is a great library for handling configurations and supporting various sources, formats, and cascading setups. The library supports most Arrow types for decoding.

Validation​

Akkurate​

Akkurate provides a language to describe complex validation code. It provides integration with Arrow's typed error mechanism.

HTTP​

Retrofit​

If Retrofit is your library of choice for querying HTTP services, this small integration module may come in quite handy.

Ktor​

Serialization​

If you're using kotlinx.serialization, you need no further changes other than importing the serializers with @UseSerializers. If you want to use Arrow Core types directly as your request or response models, you will need to include the ArrowModule in your serializers module:

install(ContentNegotiation) {
  json(Json {
    serializersModule = ArrowModule
  })
}

If you're using Jackson, you can use a custom mapper, and pass it to the ContentNegotiation configuration.

object JsonMapper {
  val mapper: ObjectMapper = ObjectMapper()
    .registerModule(KotlinModule(singletonSupport = SingletonSupport.CANONICALIZE))
    .registerArrowModule()
    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
    .disable(JsonParser.Feature.INCLUDE_SOURCE_IN_LOCATION)
    .setSerializationInclusion(JsonInclude.Include.NON_ABSENT)
}

install(ContentNegotiation) {
  register(ContentType.Application.Json, JacksonConverter(JsonMapper.mapper))
}

Resilience​

The arrow-resilience-ktor-client module provides Ktor client plug-ins for retry/repeat and circuit breakers based on Arrow's.

kJWT​

This library adds support for JSON Web Signatures and JSON Web Tokens to the Kotlin and Arrow ecosystems.

Caching​

cache4k​

You can easily integrate cache4k as caching mechanism for memoization.