Gradle Kotlin DSL Replace Token

Question

In my code there is const val VERSION = $version.
I want to replace $version with real version string which is in my build.gradle.kts.
How can I do this?

Answer 1

Working example here.

One way is to use a template file (stored outside of src tree). Let's call it TemplateVersion.kt:

class Version() {
    val version = "__VERSION";
}

and then in build.gradle.kts, as initial part of the compileKotlin task, we generate Version.kt from TemplateVersion.kt:

val sourceFile = File(rootDir.absolutePath + "/resources/TemplateVersion.kt")
val propFile = File(rootDir.absolutePath + "/gradle.properties")
val destFile = File(rootDir.absolutePath + "/src/main/kotlin/${targetPackage}/Version.kt")

tasks.register("generateVersion") {
    inputs.file(sourceFile)
    inputs.file(propFile)
    outputs.file(destFile)

    doFirst {
        generateVersion()
    }
}

tasks.named("compileKotlin") {
    dependsOn("generateVersion") 
}

fun generateVersion() {
    val version: String by project
    val rootDir: File by project

    val inputStream: InputStream = sourceFile.inputStream()

    destFile.printWriter().use { out -> 
        inputStream.bufferedReader().forEachLine { inputLine ->
            val newLine = inputLine.replace("__VERSION", version)
            out.println(newLine) 
        }
    }

    inputStream.close()
}

where gradle.properties is:

version=5.1.50

It is trivially easy to add more fields to Version.kt, such as a build-timestamp.

(Edit: This has been updated with a proper generateVersion task that will detect changes to gradle.properties. The compileKotlin task will invoke this task).