Poko

Poko is a Kotlin compiler plugin that makes writing and maintaining data model classes for public APIs easy. Like with normal Kotlin data classes, all you have to do is provide properties in your class's primary constructor. With the @Poko annotation, this compiler plugin automatically generates toString, equals, and hashCode functions. Poko is compatible with all Kotlin Multiplatform targets.

Use

Mark your class as a @Poko class instead of a data class:

@Poko class MyData(
    val int: Int,
    val requiredString: String,
    val optionalString: String?,
)

And reap the benefits of a readable toString and working equals and hashCode. Unlike normal data classes, no copy or componentN functions are generated.

Like normal data classes, Poko classes must have at least one property in their primary constructor. Non-property parameters in the primary constructor are ignored, as are non-constructor properties. Any of the three generated functions can be overridden manually, in which case Poko will not generate that function but will still generate the non-overridden functions. Using array properties is not recommended, and if they are used, it is recommended to override equals and hashCode manually.

Annotation

By default, the dev.drewhamilton.poko.Poko annotation is used to mark classes for Poko generation. If you prefer, you can create a different annotation and supply it to the Gradle plugin.

apply plugin: "dev.drewhamilton.poko"
poko {
  pokoAnnotation.set "com/example/MyData"
}

Nested annotations mentioned below can optionally be added with the same name to the base annotation and used for their respective features. For example, @MyData.ReadArrayContent will cause the annotated property's contents to be used in the Poko-generated functions.

Arrays

By default, Poko does nothing to inspect the contents of array properties. This aligns with the behavior of data classes.

Poko consumers can change this behavior on a per-property basis with the @Poko.ReadArrayContent annotation. On properties of a typed array type, this annotation will generate a contentDeepEquals check. On properties of a primitive array type, this annotation will generate a contentEquals check. And on properties of type Any or of a generic type, this annotation will generate a when statement that disambiguates the many array types at runtime and uses the appropriate contentDeepEquals or contentEquals check. In all cases, the corresponding content-based hashCode and toString are generated for the property as well.

Using arrays as properties in data types is not generally recommended: arrays are mutable, and mutating data can affect the results of equals and hashCode over time, which is generally unexpected. For this reason, @Poko.ReadArrayContent should only be used in very performance-sensitive APIs.

Skipping properties

It is sometimes useful to omit some properties from consideration when generating the Poko functions. This can be done with the experimental @Poko.Skip annotation. Properties with this annotation will be excluded from all three generated functions. For example:

@Poko class Data(
    val id: String,
    @Poko.Skip val callback: () -> Unit,
) : CircuitUiState

Data("a", { println("a") }) == Data("a", { println("not a") }) // yields `true`

Download

Poko is available on Maven Central. It is experimental, and the API may undergo breaking changes before version 1.0.0. Kotlin compiler plugins in general are experimental and new versions of Kotlin might break something in this compiler plugin.

Since the Kotlin compiler has frequent breaking changes, different versions of Kotlin are exclusively compatible with specific versions of Poko.

Kotlin version	Poko version
2.1.0	0.18.2
2.0.0 – 2.0.21	0.17.2
1.9.0 – 1.9.24	0.15.3
1.8.20 – 1.8.22	0.13.1
1.8.0 – 1.8.10	0.12.0
1.7.0 – 1.7.21	0.11.0
1.6.20 – 1.6.21	0.10.0
1.6.0 – 1.6.10	0.9.0
1.5.0 – 1.5.31	0.8.1
1.4.30 – 1.4.32	0.7.4
1.4.20 – 1.4.21	0.5.0*
1.4.0 – 1.4.10	0.3.1*
1.3.72	0.2.4*

Snapshots of the development version are available in Sonatype's Snapshots repository.

Releases are signed with this key.

pub   rsa4096 2020-02-02
      09939C73246B4BA7444CAA453D002DBC5EA9615F
uid   Drew Hamilton <drew.hamilton.0@gmail.com>
sig   3D002DBC5EA9615F 2020-02-02

To use Poko, apply the Gradle plugin in your project:

// Root project:
plugins {
    id("dev.drewhamilton.poko") apply false
}

// Per module:
plugins {
    id("dev.drewhamilton.poko")
}

*Versions prior to 0.7.0 use plugin name dev.drewhamilton.extracare.

License

Copyright 2020 Drew Hamilton

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.