import org.gradle.api.*

            open class MyExtension<T>

            class FooPlugin : Plugin<Project> {
                override fun apply(project: Project): Unit = project.run {
                    // Using add() without specifying the public type causes type erasure
                    extensions.add("mine", MyExtension<String>())
                }
            }
            """
        )

        and:
        fixture.assertStateLoaded()

        when:
        file("a/build.gradle") << """
            myExtension.message = 'this is project a'
        """
        file("b/build.gradle") << """
            myExtension.message = 'this is project b'
        """

        server.expect("configure-root")
        server.expectConcurrent("configure-a", "configure-b")

        model2[1].message == "It works from project :a"

        and:
        fixture.assertStateLoaded()
        outputDoesNotContain("creating model")

        when:
        buildFile << """
            myExtension.message = 'this is the root project'
        """

        executer.withArguments(ENABLE_CLI)
        def model3 = runBuildAction(new FetchCustomModelForEachProject())

        then:
        model3.size() == 2

        model2.message == "It works from project :"

        and:
        fixture.assertStateLoaded()
        outputDoesNotContain("creating model")

        when:
        buildFile << """
            myExtension.message = 'this is the root project'
        """

        executer.withArguments(ENABLE_CLI)
        def model3 = fetchModel()

        then:
        model3.message == "this is the root project"

include::sample[dir="snippets/plugins/mappingExtensions/groovy",files="app/build.gradle[tags=snippet]"]
====

In this example, the `MyExtension` class defines an `inputParameter` property that can be set in the build script.
The `MyPlugin` class configures this extension and uses its `inputParameter` value to configure the `MyCustomTask` task.