Task and plugin conflict in Gradle (Failed to apply plugin [class 'org.gradle.langu...)

Question

I tried to run a task from build.gradle using the following command:

gradle footype

However the build failed and displayed these two error messages that I want to fix:

> Configure project : 
The Task.leftShift(Closure) method has been deprecated and is scheduled to 
be removed in Gradle 5.0. Please use Task.doLast(Action) instead.

And this message as well:

* What went wrong:
An exception occurred applying plugin request [id: 'java']
> Failed to apply plugin [class         
'org.gradle.language.base.plugins.LifecycleBasePlugin']
   > Declaring custom 'assemble' task when using the standard Gradle 
lifecycle plugins is not allowed.

Here is the code of the build.gradle file:

plugins{
  id "com.gradle.build-scan" version "1.10.2"
  id "org.arquillian.spacelift" version "1.0.0-alpha-17"
  id "java"
}

group 'k'
version '1.0-SNAPSHOT'

sourceCompatibility = 1.8

repositories {
  mavenCentral()
}

task fooType {
  doLast {
    def foo = "bar"
    println "$foo + foo = ${foo + "foo"}"
  }
}

I searched on other posts and they all seem to mention a task called clean() which doesn't appear in my code, so I'd like to know what's the problem.

Thank you muchly for reading this post.

Answer 1

When it comes to this message:

Configure project : The Task.leftShift(Closure) method has been deprecated and is scheduled to be removed in Gradle 5.0. Please use Task.doLast(Action) instead.

it is just a warning. It states that one (possibly more) plugin you applied uses << which will be removed in version 5.0 of gradle in favour of doLast. You are not using << directly in your script and that's ok. To eliminate this warning first of all you need to know which plugin uses it, then raise an issue on plugin's site asking for deprecated code elimination.

When it comes to the second message it's an error and in single build script nothing can be done about it. Two plugins java and org.arquillian.spacelift have declared a task with the same name (it's assemble) - this is a conflict. Maybe you can split you project into a multimodule?