ext in buildscript can not be recognised by Gradle Kotlin DSL - gradle

Question

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:
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.
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?

Answer 1

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)
}
}

Answer 2

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)
...

Answer 3

What is working for me is using ext in allprojects instead of buildscript, so in your top-level build.gradle.kts
allprojects {
ext {
set("supportLibraryVersion", "26.0.1")
}
}
then you can use it in build.gradle.kts files in modules like this:
val supportLibraryVersion = ext.get("supportLibraryVersion") as String

Answer 4

None of these answers felt clear to me.
So here's my explanation:
/build.gradle.kts:
buildscript {
extra.apply {
set("compose_version", "1.0.3")
}
...
}
/app/build.gradle.kts:
val composeVersion = rootProject.extra["compose_version"]
implementation("androidx.compose.ui:ui:$composeVersion")
implementation("androidx.compose.material:material:$composeVersion")

Answer 5

There is a new possibility with Kotlin we can use:
object DependencyVersions {
const val JETTY_VERSION = "9.4.12.v20180830"
}
dependencies{
implementation("org.eclipse.jetty:jettyserver:${DependencyVersions.JETTY_VERSION}")
}
Here, DependencyVersions is a name I chose. You can choose another name,
like "MyProjectVariables". This is a way to avoid using the extra or ext properties.

Answer 6

Global properties in kotlin-gradle-dsl:
https://stackoverflow.com/a/53594357/3557894
Kotlin version is embedded into kotlin-gradle-dsl.
You can use dependecies with embedded version as follows:
implementation(embeddedKotlin("stdlib-jdk7"))
classpath(embeddedKotlin("gradle-plugin"))

Answer 7

val junitVersion by extra("4.13.2")
testImplementation("junit:junit:$junitVersion")

Answer 8

In Kotlin, the way to do this is with by extra or an ext block.
With by extra:
val kotlinVersion = "95" by extra
val kotlinCompiler = true by extra
With ext:
ext {
set("kotlinVersion", "95")
set("kotlinCompiler", true)
}

Answer 9

Set it like this:
val kotlinVersion by extra("1.1.4")
Use it like this:
val kotlinVersion: String by rootProject.extra

Answer 10

It's a possibility to define global properties within gradle.properties:
xyzVersion=1.0.0
And then use them in your module's build.gradle.kts:
val xyzVersion: String by project