Gradle: manage dependency/plugin versions in multi-project builds - gradle

Question

I was working with Maven before Gradle and Maven has such things like dependencyManagement and pluginManagement what allows to keep all versions "DRY" in one place with help of "properties".
Gradle supports project properties, so I can declare versions like:
buildscript {
ext.kotlin_version = '1.1.61'
repositories {
mavenCentral()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
But this approach cannot be applied to plugins {} DSL. I cannot write something like this:
plugins {
id 'org.jetbrains.kotlin:kotlin-gradle-plugin' version $kotlin_version
}
As according to docs:
values must be literal (e.g. constant strings, not variables)
Is there a way to workaround this limitation?

Answer 1

The latest versions of Gradle allows you to define your versions in a property file, map that version in a pluginManagement block, and then omit the version from all downstream plugin blocks. The pluginManagement block does not have the only-constant restriction.
In fact, once you use this approach, it is a compile time error to even try to declare a version downstream.
After using this approach, there is a good chance you can completely omit your buildscript.
gradle.properties
kotlinVersion=1.3.50
settings.gradle
pluginManagement {
resolutionStrategy {
eachPlugin {
if (requested.id.id == "org.jetbrains.kotlin.jvm") {
useVersion(kotlinVersion)
}
}
}
}
build.gradle
plugins {
id("org.jetbrains.kotlin.jvm")
}
If you are into kotlinscript, get your version from a delegate:
settings.gradle.kts
val kotlinVersion: String by settings
pluginManagement {
resolutionStrategy {
eachPlugin {
if (requested.id.id == "org.jetbrains.kotlin.jvm") {
useVersion(kotlinVersion)
}
}
}
}
Of course, you do not need the properties file. You can just hard code the version in your gradle.settings. But by having the property, you can then declare dependencies to the stdlib using it.

Answer 2

I think you can put the ext closure in a separate properties.gradle, and then reference the properties twice in buildscript as well as project build (buildscript block is evaluated at the very beginning, before any other part of groovy script).
For example, in $projectRoot/gradle/properties.gradle as below:
ext {
kotlinVersion = '1.1.61' // NOTE, the naming convention is better with kotlinVersion instead of kotlin_version
}
And your $projectRoot/build.gradle would look like this:
buildscript {
apply from: "gradle/properties.gradle"
repositories {
jcenter()
}
dependencies {
println "In buildscript, kotlinVersion is $kotlinVersion"
}
}
apply plugin: 'java'
apply from: "gradle/properties.gradle"
repositories {
jcenter()
}
dependencies {
println "In project, kotlinVersion is $kotlinVersion"
}
When you run ./gradlew dependencies, it would show you the populated versions:
> Configure project :
In buildscript, kotlinVersion is 1.1.61
In project, kotlinVersion is 1.1.61