I have a multi-module Gradle build using Gradle Ko...

# build-tools

[diesieben07]

I have a multi-module Gradle build using Gradle Kotlin DSL. I would like to share a common configuration for the Kotlin plugin across the modules, for example the "used experimental annotations".
For example I have this snippet:

kotlin {
    sourceSets.all {
        languageSettings.useExperimentalAnnotation("kotlin.RequiresOptIn")
    }
}

I would like to move this into buildSrc so in the modules I can just do:

kotlin {
    configureExperimentalAnnotations()
}

To do this, I'd want to do this as an extension function on KotlinProjectExtension, but I have no idea which dependency I need in the buildSrc Gradle script for that. kotlin-gradle-plugin doesn't have it.

Any advice?

[tapchicoma]

KotlinPluginExtension should be available when you will add kotlin-gradle-plugin as a buildSrc module dependency.

[tapchicoma]

could you past here you dependency declaration line?

[diesieben07]

dependencies {
    implementation(kotlin("gradle-plugin"))
}

in the build.gradle.kts in buildSrc. I do have the jar as a dependency now, but the package that contains KotlinPluginExtension is empty in the jar file

[tapchicoma]

which version? 1.4.31?

[diesieben07]

Yes

[diesieben07]

This is the whole build.gradle.kts file in buildSrc:

plugins {
    kotlin("jvm") version "1.4.31"
}

repositories {
    mavenCentral()
}

dependencies {
    implementation(kotlin("gradle-plugin"))
}

[diesieben07]

import org.jetbrains.kotlin.gradle.dsl.KotlinJvmProjectExtension
This import doesn't work in the buildSrc code (it works in the build.gradle.kts file)

[tapchicoma]

Plugins block should be:

plugins {
    `kotlin-dsl`
}

[tapchicoma]

and then dependency will have implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.31") notation

[diesieben07]

Now its telling me my kotlin("jvm") plugin on the main build.gradle.kts must not include a version. But if I remove that version, I am not specifying a version anywhere, which one will it use?

[diesieben07]

Okay, I've made those changes (and removed the version from the plugin application in my main build.gradle.kts).
The situation however is unfortunately unchanged

[diesieben07]

I'll make a minimal reproduction project

[tapchicoma]

probably even this dependency notation will be better to use (it will pull all plugin ids from Gradle plugin portal):

implementation("org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin:1.4.31")

and you need to add gradlePluginPortal() to the repositories { }

Also I've checked plugin jar file and KotlinJvmProjectExtension class file is there 🤔

[diesieben07]

Here is my sample project:
https://github.com/diesieben07/kotlin-dsl-buildsrc-bug
https://github.com/diesieben07/kotlin-dsl-buildsrc-bug/blob/master/buildSrc/build.gradle.kts
https://github.com/diesieben07/kotlin-dsl-buildsrc-bug/blob/master/buildSrc/src/main/kotlin/buildUtil.kt

[tapchicoma]

I see KotlinProjectExtension in your sample project:

[tapchicoma]

probably try to invalidate caches and restart

[diesieben07]

... the hell? Well, thanks for confirming that for me. I'll try to invalidate all the things

[diesieben07]

invalidating intellij caches didn't help. Time to bring out the big guns: rm -rf ~/.gradle

[diesieben07]

God bless the brute force, it worked.

[diesieben07]

Thanks for helping me debug it.

[diesieben07]

Okay, coming back to this thread, because this has stopped working when I updated to Kotlin 1.5.0.
I have always had warnings to the following extend when doing this:

Runtime JAR files in the classpath should have the same version. These files were found in the classpath:

With it then listing the Kotin stdlib that is shipped with Gradle (1.3.72) and my version (1.4.31, now 1.5.0).
Now with Kotlin 1.5.0 this breaks completely:

Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.5.1, expected version is 1.1.16.

I have reinstated my test-repository here: https://github.com/diesieben07/kotlin-dsl-buildsrc-bug

Any advice?

[diesieben07]

Updating to Gradle 7 "fixes" this, because Gradle 7 ships Kotlin 1.4.31 internally (no idea why Kotlin 1.4 accepts the 1.5 jars, but 1.3 doesn't?). But I still have that warning because in buildSrc I have 1.4.31 and 1.5.0 jars on the classpath... How to do this properly?

[tapchicoma]

warning should be fixed with 1.5.10 release, see this issue

[tapchicoma]

Gradle has updated Kotlin to 1.4 in 6.8 release

[diesieben07]

Okay, but just to be clear, that only removes the warning, right? It won't fix the hard crash with Kotlin 1.5 on Gradle < 6.8?

[tapchicoma]

it may fix it as well 🤔

[diesieben07]

well, I'll stay tuned for 1.5.10 then. At least my build runs again with updated Gradle and I'll trust that those warnings are nothing bad 😄

[diesieben07]

Thank you!

[udalov]

(no idea why Kotlin 1.4 accepts the 1.5 jars, but 1.3 doesn’t?)

Thanks for bringing this up, it is indeed unclear and we should document this. Since Kotlin 1.3, Kotlin/JVM metadata has “up to 1 version” forward-compatibility policy. So 1.3 can read metadata of classes compiled with Kotlin from 1.0 to 1.4.255; 1.4 can read metadata from 1.0 to 1.5.255, and so on.

[diesieben07]

Ahhh, that would explain it and that is indeed what I am seeing. With Gradle < 6.8 (so shipping with 1.3) I could use Kotlin 1.4 fine. Now with Gradle >= 6.8 (shipping with 1.4) I can also use 1.5

[diesieben07]

Unfortunately the 1.5.10 update has broken buildSrc in the IDE completely (works fine when building, it's just an IDE bug):
😞 Let me make a YouTrack issue

[diesieben07]

https://youtrack.jetbrains.com/issue/KT-47006

[diesieben07]

Duplicate of: https://youtrack.jetbrains.com/issue/KT-46939