Gradle optional @Input

Question

How can I provide an optional property for task?

class CustomTask extends DefaultTask {

    @Input
    Closure preconfig

    // ...    
}

This way obligates user to provide preconfig closure as parameter when defining task with CustomTask type.

How can I achieve declarative way other than defining methods to set properties?

class CustomTask extends DefaultTask {

    @Input
    Closure preconfig

    def preconfig(Closure c){
        this.preconfig = c
    }

    // ...   
}

Answer 1

Actually, I found a solution in assigning default value to the @Input fields.

Example:

class CustomTask extends DefaultTask {

    @Input
    Closure preconfig = null // or { } <- empty closure

    // ...    
}

And then check if the @Input variable is not null:

// ...

@TaskAction
def action(){
    if (preconfig) { preconfig() }
}

// ...

Also there is useful annotation @Optional:

class CustomTask extends DefaultTask {

    @Input @Optional
    Closure preconfig

    // ...    
}