Why isn't the latest version of Kotlin being found in this case?

[xenomachina]

The snippets below are pared down from a gradle plugin we have that in turn
relies on the kotlin-gradle-plugin. For some reason dependencyUpdates isn't
detecting when the kotlin dependency is out of date. I found a workaround, but
I don't really understand why it works or why it's necessary.

gradle.properties contains:

kotlin_version = 1.6.0

and build.gradle contains:

buildscript {
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

plugins {
    id 'com.github.ben-manes.versions' version '0.50.0'
    id 'java-gradle-plugin'
}

repositories {
    mavenCentral()
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}

If I run ./gradlew dependencyUpdates, it says:

The following dependencies are using the latest milestone version:
 - com.github.ben-manes.versions:com.github.ben-manes.versions.gradle.plugin:0.50.0
 - org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.0

However, if I add the following to the plugins block in build.gradle:

id 'org.jetbrains.kotlin.jvm' version "$kotlin_version"

and then run ./gradlew dependencyUpdates, it says:

The following dependencies have later milestone versions:
 - org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin [1.6.0 -> 2.0.0-Beta2]
     https://kotlinlang.org/

So addiing the plugin dependency "fixes" the issue, but why is this necessary
for dependencyUpdates to see that there are newer versions of Kotlin?
The code builds and functions correctly without it.

(I'm using Gradle 8.1.1, in case it matters.)

[ben-manes]

I'm not sure. If I drop down a few plugin versions, e.g. compare v46 and v47, then it shows up. Can you confirm?

If so, then the only change that looks relevant came from the Gradle team (#768)

[xenomachina]

What is "dependabot for Caffeine"?

Our code is on GitLab, not Github, and as far as I can tell, dependabot doesn't work on GitLab. We have our own in-house tool that relies on gradle-versions-plugin and gradle-use-latest-versions-plugin for our Gradle dependencies.

[ben-manes]

Oh sorry, I just meant my other open-source project which is on github.

[xenomachina]

Ah, gotcha! I totally mis-parsed that as something like "Windows Subsystem for Linux". 😆

[tresat]

This issue certainly seems related to that linked change, and how the plugin isn't building a query dependency for the Kotlin plugin. I'll take a closer look next week.