How can I use parameters in gradle tasks?

Question

There are many tasks that come with gradle which use parameters.

gradle test --tests *Test
gradle dependencyInsight --dependency junit

How can I access parameters in my own custom tasks?

Answer 1

I recently stumbled upon @Option in some internal Gradle task (JavaExec, I think). The JavaDoc of the annotation reads exactly like what you are looking for, but it was 'internal' API. The functionality is part of the public API starting with Gradle 4.6: See release notes and user guide.

Just tested this:

import org.gradle.api.tasks.options.Option

class MyTask extends DefaultTask {
    @Option(option="funky", description="test")
    String myOption

    @TaskAction
    void echoOption() {
        logger.lifecycle("Value of 'myOption': ${myOption}")
    }
}

task myTask(type: MyTask) {
}

Result:

$ gradle myTask --funky=foo
:myTask
Value of 'myOption': foo

BUILD SUCCESSFUL

Total time: 0.845 secs