kotlin-power-assert

Introduction: Kotlin compiler plugin to enable power assertions in the Kotlin programming language
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Kotlin Compiler Plugin which high-jacks Kotlin assert function calls and transforms them similar to Groovy's Power Assert feature. This plugin uses the new IR backend for the Kotlin compiler.

Example

Given following code:

val hello = "Hello"
assert(hello.length == "World".substring(1, 4).length)

Normally the assertion message would look like:

java.lang.AssertionError: Assertion failed
    at <stacktrace>

A custom assertion message can be provided:

val hello = "Hello"
assert(hello.length == "World".substring(1, 4).length) { "Incorrect length" }

But this just replaces the message:

java.lang.AssertionError: Incorrect length
    at <stacktrace>

With kotlin-power-assert included, the error message for the previous example will be transformed:

java.lang.AssertionError: Incorrect length
assert(hello.length == "World".substring(1, 4).length)
       |     |      |          |               |
       |     |      |          |               3
       |     |      |          orl
       |     |      false
       |     5
       Hello
    at <stacktrace>

Complex, multi-line, boolean expression are also supported:

Assertion failed
assert(
  (text != null && text.toLowerCase() == text) ||
   |    |
   |    false
   null
      text == "Hello"
      |    |
      |    false
      null
)

Gradle Plugin

Builds of the Gradle plugin are available through the Gradle Plugin Portal.

plugins {
  kotlin("jvm") version "1.3.70"
  id("com.bnorm.power.kotlin-power-assert") version "0.3.0"
}

The plugin by default will transform assert function call but can also transform other functions like require, check, and/or assertTrue. The function needs to validate the Boolean expression evaluates to true and has a form which also takes a String or String producing lambda.

configure<com.bnorm.power.PowerAssertGradleExtension> {
  functions = listOf("kotlin.test.assertTrue", "kotlin.require")
}

Kotlin IR

Using this compiler plugin only works if the code is compiled using Kotlin 1.3.70 and IR is enabled. IR can be enabled only when compiling the test SourceSet if desired. As Kotlin IR is still experimental, mileage may vary.

compileTestKotlin {
    kotlinOptions {
        useIR = true
    }
}
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