How to merge additional-spring-configuration-metadata.json with kapt when using Kotlin and Gradle?

Question

I have read these documents but I don’t know how to merge additional-spring-configuration-metadata.json with kapt when using Kotlin and Gradle.
https://docs.spring.io/spring-boot/docs/2.2.x/reference/html/appendix-configuration-metadata.html#configuration-metadata-annotation-processor
https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-kotlin-configuration-properties

I managed to merge it this way, but I want to know the official way.

plugins {
    id("org.springframework.boot") version "2.2.2.RELEASE"
    id("io.spring.dependency-management") version "1.0.8.RELEASE"
    kotlin("jvm") version "1.3.61"
    kotlin("plugin.spring") version "1.3.61"
    kotlin("kapt") version "1.3.61"
}

dependencies {
    kapt("org.springframework.boot:spring-boot-configuration-processor")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    …
}

kapt {
    arguments {
        arg(
            "org.springframework.boot.configurationprocessor.additionalMetadataLocations",
            "$projectDir/src/main/resources"
        )
    }
}

tasks.withType<KotlinCompile> {
    kotlinOptions {
        freeCompilerArgs = listOf("-Xjsr305=strict")
        jvmTarget = "1.8"
    }
}

Answer 1

Adding an answer here for better visibility. This is a known issue in the Kapt maven plugin that does not make sure the compilation classpath is available when the annotation processor runs. The implementation can't see the file and therefore won't merge it.

Your workaround works and there is an issue you can vote for in the JetBrains issue tracker.