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ext in buildscript can not be recognised by Gradle Kotlin DSL

In these days, I am trying to write some codes to experience the Spring reactive features and kotlin extension in Spring 5, and I also prepared a gradle Kotlin DSL build.gradle.kt to configure the gradle build.

The build.gradle.kt is converted from Spring Boot template codes generated by http://start.spring.io.

But the ext in the buildscript can not be detected by Gradle.

buildscript {
  ext { }
}

The ext will cause Gradle build error.

To make the variables in classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion") and compile("org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlinVersion") work, I added the variables in the hard way.

val kotlinVersion = "1.1.4"
val springBootVersion = "2.0.0.M3"

But I have to declare them in global top location and duplicate them in the buildscript.

Code: https://github.com/hantsy/spring-reactive-sample/blob/master/kotlin-gradle/build.gradle.kts

Is there a graceful approach to make ext work?

Update: There are some ugly approaches:

  1. From Gradle Kotlin DSL example, https://github.com/gradle/kotlin-dsl/tree/master/samples/project-properties, declares the properties in gradel.properties.

    kotlinVersion = 1.1.4
    springBootVersion = 2.0.0.M3
    

    And use it in build.gradle.kts.

    buildScript{
       val kotlinVersion by project
    
    }
     val kotlinVersion by project //another declare out of buildscript block.
    
  2. Similar with above declare them in buildScript block:

    buildScript{
       extra["kotlinVersion"] = "1.1.4"
       extra["springBootVersion"] = "2.0.0.M3"
       val kotlinVersion: String by extra
    
    }
     val kotlinVersion: String by extra//another declare out of buildscript block.
    

How can I avoid the duplication of val kotlinVersion: String by extra?

like image 233
Hantsy Avatar asked Aug 18 '17 09:08

Hantsy


2 Answers

With Kotlin DSL ext has been changed to extra and it can be used under buildscript.

Eg :-

buildscript {
    // Define versions in a single place
    extra.apply{
        set("minSdkVersion", 26)
        set("targetSdkVersion", 27)
    }
}
like image 200
Shashi Bhushan Avatar answered Oct 17 '22 18:10

Shashi Bhushan


It is possible to use constants defined in .kt file in .gradle.kts files.

create buildSrc folder in root folder of your project

create buildSrc/build.gradle.kts file with the following content

plugins {
    `kotlin-dsl`
}

repositories {
    mavenCentral()
}

create file buildSrc/src/main/kotlin/Constants.kt with the following content

object Constants {
    const val kotlinVersion = "1.3.70"
    const val targetSdkVersion = 28
}

Synchronize. Now you may reference created constants in various .gradle.kts files like this

...
classpath(kotlin("gradle-plugin", version = Constants.kotlinVersion))
...

...
targetSdkVersion(Constants.targetSdkVersion)
...
like image 24
Eugene Popovich Avatar answered Oct 17 '22 18:10

Eugene Popovich