Gradle: Use a sibling subproject as plugin - gradle

Question

I have a project with two subprobjects: gradle-plugin and plugin-consumer. I want to apply the plugin from gradle-plugin to plugin-consumer. I tried to do this:
// plugin-consumer/build.gradle
buildscript {
dependencies {
classpath project(':gradle-plugin')
}
}
apply plugin: 'my.plugin.id'
But I was greeted with the following error:
A problem occurred configuring project ':plugin-consumer'.
> Cannot use project dependencies in a script classpath definition.
I assume this is not supported because it'd require fully building gradle-plugin before plugin-consumer can be configured.
Fortunately I can use a fileTree dependency to accomplish my goal:
// plugin-consumer/build.gradle
buildscript {
dependencies {
classpath fileTree(includes: ['*.jar'], dir: '../gradle-plugin/build/libs')
}
}
apply plugin: 'my.plugin.id'
This works, but it feels like a massive hack and leads to "bootstrapping problems".
For example, I can't clean gradle-plugin because the (deleted) jar file is necessary for configuring plugin-consumer, which must be done to (re)build gradle-plugin.
Fortunately this can be avoided by always running build immediately after clean (in the same 'run' so to speak). This can be done manually (gradle clean build) or automatically (with clean.finalizedBy(build)). Again, this works, but feels like a hack.
At last, my actual question: is there a better way to do this?
Please note that gradle-plugin is an independent plugin that's not only used by plugin-consumer, therefore buildSrc is unfortunately not an appropriate solution here.

Answer 1

You can publish the plugin to your local Maven repository with the Maven Publish plugin. Then simply consume it like any other artifact.
Assuming you have something similar in your plugin project:
plugins {
`maven-publish`
`java-gradle-plugin`
}
Simply publish it locally:
./gradlew :my-plugin-project:publishToMavenLocal
Then in your consuming project, something like:
buildscript {
repositories {
mavenLocal()
}
dependencies {
"classpath"("com.example:my-plugin-gav:1.0.0-SNAPSHOT")
}
}
// apply plugin